Self-assemblies of positional isomeric linear bis-urea ligands with

Subscriber access provided by University of South Dakota

Article

Self-assemblies of positional isomeric linear bis-urea ligands with oxyanions/hydrated oxyanions: Evidences of F- and OH- induced atmospheric CO2 fixation Utsab Manna, Asesh Das, and Gopal Das Cryst. Growth Des., Just Accepted Manuscript • DOI: 10.1021/acs.cgd.8b01044 • Publication Date (Web): 04 Sep 2018 Downloaded from http://pubs.acs.org on September 13, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 35 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Crystal Growth & Design

Self-assemblies of positional isomeric linear bis-urea ligands with oxyanions/hydrated oxyanions: Evidences of F- and OH- induced atmospheric CO2 fixation Utsab Manna, Asesh Das and Gopal Das* Department of Chemistry, Indian Institute of Technology Guwahati, Assam-781039, Fax: +91-361-2582349; Tel: +91-361-2582313; E-mail: [email protected].

1 ACS Paragon Plus Environment

Crystal Growth & Design 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ABSTRACT. A set of three positional isomeric nitro-phenyl functionalized linear bis-urea scaffolds has been purposefully synthesized from p-phenylenediamine, basically for investigating the extensive anion-coordination behavior in their neutral form. The para-isomer (L1) and meta-isomer (L2) can readily form bicarbonate dimer (HCO3)2 entrapped neutral selfassemblies in the solid state by either fluoride or hydroxide induced atmospheric CO2 fixation and. In the bulk scale and based on the isolated yield of (HCO3)2 entrapped complexes of L1 and L2, it has been found that 6.7, 7.3 and 6.2 mmol of CO2 can be fixed respectively by 1 mmol of linear bis-urea derivatives. The another planar acetate anions in their bare and hydrated form [(OCOCH3)(H2O)]2 are coordinated by hydrogen-bonding interactions in non-cooperative fashions with L1 and L2 respectively. Interestingly, the para-isomer L1 entraps bisulfate dimer (HSO4)2, while the meta-isomer L2 has been found to self-assemble with divalent sulphate (SO42) and polymeric dihydrogen-phosphate (H2PO4)n by non-cooperative hydrogen-bonding interactions also. However, successful crystallization of any anion complexes with ortho-isomer (L3) was not fruitful, instead free L3 ligand structure has been attained in most of the cases. This phenomena occurs owing to the steric hindrance provided by the nitro group at the orthoposition, which probably hampers the facile inclusion via coordination of an anion due to electrostatic factor, as observed and confirmed by the presence of intramolecular hydrogenbonding interactions in the crystal structures of free ligand L3.


Page 2 of 35

Page 3 of 35 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1. Introduction Anion coordination by hydrogen-bonding scaffold within the self-assembled architectures of neutral host molecules is a key area of supramolecular recognition chemistry due to the critical relevance of anions in a range of chemical, biological, medical and environmental routes.1-7 The hydrogen-bonding environment of several anion binding proteins in natural system such as phosphate binding proteins in Escherichia Coli8 or sulphate binding proteins in Salmonella typhimurium bacteria9, have inspired the researchers for developing numerous hydrogen-bond accessible abiotic receptors that offer specific binding sites from functionalities like amine, amide, urea/thiourea, pyrrole/indole and imidazolium for the recognition of anionic guests on suitable frameworks.10-21 As anions usually have very high free solvation energies (e.g., ∆Ghydration of CO32- , SO42- and H2PO4- are -1315, -1080 and -465 kJ mol-1 respectively), hence for effective recognition of one or more higher coordinating oxyanions, more than one receptor molecules are obviously required in the entire host-guest system with interior anion binding components and very large standard Gibbs energy of hydration must be compensated by the host molecules22-24. Increasing concentration of CO2 due to consumption of fossil fuels, the growing number of automobiles, industries, etc.in the atmosphere is a major environmental concern and these demands efficient fixation25-26 and activation of aerial CO2 as carbonate/bicarbonate by artificial receptors. Among tetrahedral oxyanions, high phosphate concentration in aquatic ecosystems is accountable for eutrophication; the harmful effect of sulfate has been recognized as a prominent species of concern in cleanup processes of hard water, nuclear waste and it may destruct the vitrification process also. Besides among planar oxyanions, carbonate is one of the major anions in biomineralized materials as well as it also works as a buffer in the blood and acetate anion is used by organisms in the form of acetyl coenzyme A8-9,27-29. As a consequence, the design and synthesis of proper and sophisticated three-dimensional polytopic receptors for full entrapment or encapsulation of monomeric, dimeric or polymeric oxyanions or hydrated oxyanions become the contemporary aspect to the researchers. The number of tren-based or benzene based tripodal acyclic podands with several -NH functionalities have been well-known as an established area for binding and recognition anions via formation of molecular capsules with topological complementarity, as they can readily offer flexible and structurally preorganized cavity30-32. In contrast, recognition of anionic guests by entrapment or encapsulation within the self-assembled architectures of aromatic dipodal urea/thiourea based neutral receptors are very 3 ACS Paragon Plus Environment


Scheme 1. Schematic diagram of synthetic route and molecular structure of aromatic 1,4-diamine based nitrophenyl-functionalized dipodal isomeric bis-urea receptors L1-L3, by advancement from rigid aromatic 1,2- and 1,3-diamine based nitrophenyl-functionalized dipodal isomeric bis-urea receptors.

few in literature due to the less flexible and less coordinating binding sites containing rigid scaffolds compared to the tripodal ligands. Several bisurea/thiourea derivatives of ophenylenediamine were reported previously as anion receptor or anion sensor in solid or solution states by Gale et. al.33-36, Wu et. al.37, A. Das et. al.38, Molina et. al.39, Tarr et. al.40 and from our group41-42 also, as the amine groups of o-phenylenenediamine become most converging among ortho, meta and para-phenylenedimine and hence aromatic 1,2-diamine based receptors have much more tendencies to form cooperative anion complexes compared to other isomeric rigid diamines. Very recently, we reported a class of meta-phenynenediamine based neutral bis-urea receptors with one or more terminal aryl substituents and their self-assembled anion/hydratredanion bound architectures have been studied extensively in solid and solution states, where the complexation phenomena are heavily governed by the anion dimension or substituent effect.43-45 Continuing our group’s pursuit in the field of substituent driven anionic/hydrated anionic supramolecular self-assemblies of acyclic receptors46-56, herein we develop a class of nitro4 ACS Paragon Plus Environment

Page 4 of 35

Page 5 of 35 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


phenyl functionalized comparatively less cooperative and more challenging positional isomeric linear bis-urea receptors L1-L3 (scheme-1), derived from least converging aromatic diamine (para-phenylenediamine) to investigate the coordination behavior with anions/hydrated anions in neutral form. Structural studies reveal that both para-isomer (L1) and meta-isomer (L1) are capable of (HCO3)2-dimer entrapment either by fluoride or hydroxide induced fixation of atmospheric CO2 in complexes 1a, 2a and 2b. The acetate anions in their bare and hydrated form are also trapped by hydrogen-bonding interactions with L1 and L2 in complexes 1b and 2c respectively. Subsequently, the para-isomer entraps (HSO4)2-dimer in complex 1c, while the meta-isomer has been found to self-assemble with SO42- and linear polymeric (H2PO4)n in respective complexes 2d and 2e, by non-cooperative hydrogen-bonding interactions also. In contrast to L1 and L2, the complex formation was not fruitful in the presence of different anions in case of ortho-isomer (L3), instead free ligand structures from DMF or DMSO solvent has been obtained in most of the cases, which occurs due to the steric hindrance provided by the nitro group at the ortho-position and existence of strong intramolecular H⋯O interactions in free L3 structures. 2. Results and Discussion: The isomeric bis-urea receptors L1-L3 were obtained in quantitative yield by the reaction of pphenylenediamine with 2.0 equiv of the respective 4-nitrophenyl isocyanate, 3-nitrophenyl isocyanate and 2-nitrophenyl isocyante in dry acetonitrile and recrystallized also from either DMF or DMSO medium. Structural evidences acquired from the single crystal X-ray analyses of the anion complexes can deliver a clear vision into the binding variances of a particular anion with the particular isomeric receptor. Custelcean et. al. in 2013 reported one of the rare examples of p-phenylenediamine based tetra-urea receptors with aliphatic terminals57, which demonstrated the trapping of H2PO4- tetramer and hexamer by hydrogen bonding connectivities with the receptors via co-crystallization. It was quite expected that this kinds of p-phenylenediamine based symmetrical electron deficient isomeric dipodal urea receptors can form neutral host-guest self-assemblies with anions of various dimensionalities including phosphate. Basically the larger oxyanions like sulphate, hydrogensulphate, phosphate, hydrogenphosphate, carbonate, hydrogencarbonate obviously require a greater number of hydrogen bonding sites to form stable complexes and herein two or more rigid dipodal p-nitro and m-nitrophenyl functionalized dipodal receptors also readily produce stable complexes with (HCO3)2-dimer, (HSO4)2-dimer, 5 ACS Paragon Plus Environment


Page 6 of 35

Table 1 Key observation on systematic oxyanion binding of positional isomeric receptors: Anions with size Planar hydrogencarbonate (HCO3 ) Planar acetate (OCOCH3 ) Tetrahedral hydrogensulphate (HSO4 ) 2Tetrahedral sulphate (SO4 ) Tetrahedral Dihyrogenphosphate (H2PO4 )

Anion-salt added n-TBAF n-TBAOH n-TBAOAc nTBAHSO4 (nTBA)2SO4 nTBAH2PO4

Bound anion assembly -

Cyclic (HCO3 )2 dimer Cyclic (HCO3 )2 dimer Single acetate (OAc ) [(OAc)(H2O)]2 cluster Cyclic (HSO4 )2 dimer 2-

Neutral host-guest Complexes Non-cooperative complexes with L1 (1a) and L2 (2a) Non-cooperative complexes with L2 (2b) Non-cooperative complexes with L1 (1b) Non-cooperative complexes with L2 (2c) Non-cooperative complexes with L1 (1c)

Single sulphate (SO4 )

Non-cooperative complexes with L2 (2d)

Polymeric (H2PO4)n

Non-cooperative complexes with L2 (2e)

(H2PO4)n linear polymer or hydrated [(OCOCH3)(H2O)]2 cluster, irrespective of less receptor flexibility or less number of anion coordinating site compared to flexible tripodal receptors. The crystallization turns out to be the traditional road realizing the structural perceptions of anion complexes from the perspective of anion receptor chemistry, which are then correlated to the observed selectivity in solution. Description of single crystal X-ray analyses study of neutral isomeric bisurea receptors L1-L3 and their hydrated/non-hydrated oxyanion complexes has been depicted in the figures 1-4 and tabulated in table 1. 2.1. Single crystal X-ray structural analysis studies: 2.1.1. Structure of the free and DMSO solvated host molecules L1-L3: Single crystals of all the three isomeric receptors L1-L3 for XRD analysis were attained from DMSO solvent as L1·DMSO, L2.DMSO and L3.DMSO with identical molecular formula, where L1 and L2 both crystallize in the triclinic space group P -1 (Z = 1) and L3 crystallize in the monoclinic space group P 21/c (Z = 2). Structural elucidation of each DMSO solvated receptor structures clearly reveals that the existence of half-unit of C2v-symmetric L1/L2/L3 ligand molecules with single DMSO unit in the respective asymmetric units. In addition, the single crystals of free L2 and L3 ligands were also obtained from the DMF solvent, although they didn’t contain any solvated DMF molecule in respective C2v-symmetric receptor units of unit cell and they crystallize from the monoclinic space group P 21/n (Z = 2) and triclinic space group P -1 (Z = 1) respectively with identical molecular formulas. The X-ray analysis of all the free linear ligand structures obtained from either DMSO/DMF solution reveals the almost planar architectures as well as the anti-orientation of two adjacent urea groups in each of the nitrofunctionalized isomeric bisurea receptors (Figure 1). In the DMSO solvated free receptors L1-L3, each urea group is H-bonded to one solvent DMSO molecule by two N−H···O hydrogen 6 ACS Paragon Plus Environment

Page 7 of 35 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 1. X-ray structures (partial) of the free ligands obtained from DMF/DMSO solvents depicting non-covalent interactions within the array of (a) L1.DMSO, (b) L2.DMSO, (c) L2, (d) L3.DMSO and (e) L3.

bonding interactions, although each of them (L1·DMSO, L2.DMSO and L3.DMSO) selfassemble to form different kinds of cyclic H-bonded network by number of weak C−H···O or C−H···π interactions (Figure 1a, 1b, 1d). Figure 1a describes the formation of two different kinds of cyclic architectures by N−Hurea···ODMSO, C−HDMSO···Onitro and C−Haryl···Ocarbonyl interactions in L1.DMSO. Figure 1b describes more than two types of cyclic H-bonded structure N−Hurea···ODMSO, C−HDMSO···Onitro, C−Haryl···Onitro and C−HDMSO···Ocarbonyl interactions in L2.DMSO. While figure 1d describes the three kinds of cyclic network with the aid of strong intramolecular N−Hurea···Onitro interactions followed by N−Hurea···ODMSO, C−HDMSO···Onitro, C−HDMSO···πaryl interactions in L3.DMSO. On the other hand, the free ligand structures of meta7 ACS Paragon Plus Environment


Page 8 of 35

isomer L2 and ortho-isomer L3 achieved from DMF solution mixture reveals the construction of parallel β-sheet type architectures with the help of few cyclic H-bonded networks formed by strong N−Hurea···Ocarbonyl and weak N−Hurea···πaryl or πaryl···πaryl interactions among the adjacent receptor moieties. The parallel and stacked linear self-assemblies of free L2 and L3 ligands in absence of any solvent molecules in the crystal system become heavily governed by the weak πaryl···πaryl interactions as shown in figure 1c and 1e respectively. The free ortho-isomer L3 (figure 1e) is also additionally stabilized by strong intramolecular N−Hurea···Onitro interactions, just similar as in L3.DMSO structure (figure 1d). The construction of β-sheet-type architectures of each linear free receptor have also been established by solid-state FT-IR analysis. The existence of N−H···O hydrogen bonds among the urea –NH groups and urea carbonyl groups of adjacent free receptors’ moiety in solid state have been confirmed by the strong –NH stretching frequencies (~3350-3370 cm-1) and by the −C=O stretching frequencies (~1650-1670 cm-1) in each case (Figure S3, S6, S9 in the Supporting Information). 2.2.2. F-/OH- induced bicarbonate complexes [(n-TBA)2{(L1)(HCO3)2}] (1a), [(nTBA)2{(L2)(HCO3)2}(DMF)] (2a) and [(n-TBA)2{(L2)(HCO3)2}] (2b): The isolated single crystals suitable for XRD analysis of cyclic R22(8) type bicarbonate dimer entrapped neutral complexes were obtained from the basic DMF/DMSO solutions of p-isomer (L1) and m-isomer (L2). Structural elucidation reveals that fluoride and hydroxide induced (HCO3)2 entrapped complexes (1a and 2b respectively) crystallize in the triclinic space group P 1 (Z = 1) with identical molecular formulas, whereas the DMF solvated fluoride induced (HCO3)2 trapped complex 2a of m-isomer L2 crystallize in the monoclinic space group P 21/c (Z = 2). It is interesting to note that in all the three complexes the bicarbonate anions were not present in the individual solution mixtures of receptors prior to crystallization and we presume that in each case the source of bicarbonate is from the atmospheric CO2, where the in situ generated hydroxide anions from basic ligand/F- or ligand/OH- solution dissolves aerial CO2 to HCO3- at the air solvent interface. 2F¯ + H2O

OH- + HF2-

OH- + CO2

HCO3-

It has also been evident from the single crystal X-ray structures of complexes 1a, 2a and 2b that two molecules of bis-urea L1/L2 derivatives are responsible for one bicarbonate dimer binding i.e. two molecules of monovalent bicarbonate anions and note that one mmol of HCO3- anion is 8 ACS Paragon Plus Environment

Page 9 of 35 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 2. X-ray structures (partial) of anion complexes 1a, 2a, 2b depicting array of hydrogen bonding interactions on entrapment of (HCO3)2 dimer (a) within the self-assemblies of para-isomer L1 by Finduced aerial CO2 fixation in complex 1a, (b) within the DMF solvated self-assemblies of meta-isomer L2 by F- induced aerial CO2 fixation in complex 2a, (a) within the self-assemblies of meta-isomer L2 by OH- induced aerial CO2 fixation in complex 2b, (d) magnified view of cyclic (HCO3)2 trapping in 1a, (e) magnified view of cyclic (HCO3)2 trapping in 2a and (d) magnified view of cyclic (HCO3)2 trapping in 2b.

generated by the fixation of one mmol of CO2. In the bulk scale and based on the isolated yield of (HCO3)2 entrapped complexes of L1 and L2, it has been found that 6.7, 7.3 and 6.2 mmol of CO2 can be fixed respectively by 1 mmol of linear bis-urea derivatives. Structural elucidation reveals that the O−Hbicarbonate···Obicarbonate hydrogen-bonded anionic dimer (HCO3)2 is bound within the self-assemblies of either p-isomer or m-isomer with an array of nine, eleven and nine hydrogen

bonding

interactions

(N−Hurea···Obicarbonate,

C−Ho-aryl···Obicarbonate

and

C−HTBA···Obicarbonate) respectively in complexes 1a, 2a and 2b in the solid-state (Figure 2d, 2e, 2f). The asymmetric unit of each complex contains C2v-inversion-symmetric half unit of L1/L2 receptor, one monovalent bicarbonate anion with its corresponding n-TBA counter-cation and it is also evident that the adjacent urea-NH groups of a particular receptor are projected in antifashion in all complexes despite the presence of anionic guests (Figure 2a, 2b, 2c). Note that,



Page 10 of 35

one extra DMF solvent molecule is also crystallized with fluoride induced bicarbonate complex of L2 that contributes additional stability to complex 2a via several hydrogen-bonding interactions (Figure 2b). These kinds of (HCO3)2 anionic dimer entrapped non-cooperative selfassembly by m-phenylenediamine based receptors via F- induced CO2 fixation was recently reported by our group.45 However, aerial CO2 fixation as carbonate or bicarbonate trapped complexes by several preorganized receptors containing cooperative binding modes

was

previously reported by Gunnlaugsson et. al.,58 Gale et. al.59,60 Ghosh et. al.61 and from our group42,44,52,54 also. In contrast, herein the linear p-phenylenediamine based isomeric para- and meta-bisurea neutral receptors are still capable to capture dimeric association of bicarbonate created by donor-acceptor H-bonding interactions despite the absence of any receptor cooperativities or more coordinating sites. The presence of hydrogencarbonate and the existence of strong N−H···O hydrogen bonds in atmospheric CO2 fixed neutral complexes 1a, 2a and 2b have also been established by solid-state FT-IR analysis. In the cases of free receptors, the carbonyl (−C=O) stretching frequencies are found at ~1655-1665 cm−1, whereas in each hydrogen-carbonate trapped host-guest complex, they are observed at around ~1700-1710 cm−1, displaying the huge shifts of ~45 cm−1 for the –C=O stretching relative to free ligands due to the formation of strong N−H···O hydrogen bonds with the carbonate oxygen atoms, as is evident from the single crystal X-ray structures (Figure S11, S17, S19 in the Supporting Information). Note that, there is existence of stretching bands at around ~3450-3465 cm−1 in the FT-IR spectra of each complex that are assigned to the O–H stretching vibration of hydrogen-carbonate dimer anionic guests. Moreover, the intense and strong peaks at around ~3360 cm−1 as well as ~2960 cm−1 may be attributed to the -N−H stretching of the receptor urea groups and C−H stretching of the n-TBA groups in the complexes 1a, 2a and 2b. Additionally, the new peak at the fingerprint region of each complex is observed at around ~845 cm−1 that can be attributed to the asymmetric stretching frequency of the HCO3- anion. 2.2.3. Acetate complex [(n-TBA)2{(L1)(OCOCH3)2}] (1b) and hydrated-acetate complex [(nTBA)2{(L2)(OCOCH3)2(H2O)}] (2c): The hydrated/non-hydrated acetate complexes suitable for X-ray analysis were achieved from basic DMF/DMSO solutions of either meta-isomer or para-isomer with tetrabutylammonium acetate salt. Structural elucidation reveals that both the complexes 1b of L1 and 2c of L2


Page 11 of 35 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 3. X-ray structure (partial) of anion complexes 1b and 2c depicting array of hydrogen bonding interactions (a) on non-cooperative entrapment of bare acetate within the self-assemblies of para-isomer L1 in complex 1b, (b) on acyclic [(acetate)(water)]2 trapping within the self-assemblies of meta-isomer L2 in complex 2e, (c) magnified view of H-bonding interactions on acetate binding in 1c and (d) magnified view of hydrated-acetate cluster trapping in 2c.

crystallize in the triclinic space group P -1 (Z = 1) and each of their asymmetric units contain inversion-symmetric half L1/L2 ligand molecule, one monovalent acetate anion along with the corresponding n-TBA counter-cation, although complex 2c contains an extra half-occupied water molecule of crystallization. In complex 1c, the acetate anions are trapped through the noncooperative self-assembly of p-isomer L1 and each monovalent OCOCH3- anion is coordinated by a total of eight (two N−Hurea···Oacetate, two C−Ho-aryl···Oacetate and four C−HTBA···Oacetate) hydrogen-bonding interactions (Figure 3a, 3c). On the other hand, an uncommon type of Hbonded acyclic hydrogen-bonded acetate-water assembly is entrapped within the self-assemblies of symmetry-identical meta-isomers L2 in complex 2c with an array of total four N−Hurea···Oacetate, two C−Ho-aryl···Oacetate and six C−HTBA···Oacetate/water hydrogen bonding interactions (Figure 3b), where each symmetry-identical monovalent acetate anion and water 11 ACS Paragon Plus Environment


Page 12 of 35

molecule exhibit hexa-coordination and tetra-coordination respectively (Figure 3d). Note that, alike the bicarbonate complexes 1a, 2a and 2b, the adjacent urea –NH groups of a particular receptor moieties are projected in anti-fashion despite the presence of hydrated/non-hydrated anionic guests. The presence of acetate/hydrated-acetate and the existence of strong N−H···O hydrogen bonds in neutral acetate bound complexes 1b and 2c have also been proven by solidstate FT-IR analysis. Like the hydrogen-carbonate neutral complexes, the carbonyl (−C=O) stretching frequencies are found at ~1705 cm−1 for both acetate/hydrated-acetate trapped hostguest complexes, which describe the huge shifts of ~45 cm−1 for the –C=O stretching relative to free ligands due to the formation of strong N−H···O hydrogen bonds with the acetate oxygen atoms, as is evident from the single crystal X-ray structures (Figure S13, S21 in the Supporting Information). Furthermore, the intense and strong peaks at around ~2960 cm−1 may be attributed to the -C−H stretching of the n-TBA groups in the complexes 1b and 2c. Subsequently, the new peak at around ~860-880 cm−1 in the fingerprint region is also observed that can be ascribed for the asymmetric stretching frequency for the acetate in both complexes. 2.2.4.

Bisulphate

complex

[(n-TBA)2{(L1)(HSO4)2}]

(1c),

sulphate

complex

[(n-

TBA)4{(L2)3(SO4)2}] (2d) and biphosphate complex [(n-TBA)2{(L2)(H2PO4)2}] (2e): Good quality single crystals of larger tetrahedral monovalent or divalent oxyanion/s trapped neutral complexes were also obtained from the basic DMF/DMSO solutions of para-isomer L1 and meta-isomer L2 in the presence of either n-TBAHSO4 or n-TBAH2PO4 salts. The X-ray analysis reveals that the cyclic hydrogensulphate dimer entrapped complex 1c of L1, divalent single sulphate bound complex 2d of L2 and dihydrogenphosphate polymer trapped complex 2e of L2 crystallize in the same triclinic space group P -1 with Z = 1. The asymmetric unit of complex 1c and 2e consist of inversion-symmetric half L1/L2 receptor unit, one monovalent HSO4-/H2PO4- anion and their corresponding n-TBA counter-cation unit respectively. Structural elucidation reveals that the (HSO4-)2 anionic dimer formed by two O−Hbisulphate···Obisulphate donoracceptor interactions in complex 1c is bound within the self-assemblies of L1 with an array of total twelve hydrogen bonding interactions (N−Hurea···Obisulphate, C−Ho-aryl···Obisulphate and C−HTBA···Obisulphate), where each HSO4- anion exhibit octa-coordination (Figure 4a, 4d). Subsequently in complex 2e, a linear polymeric chain of (H2PO4-)n constructed by four O−Hbiphosphate···Obiphosphate donor-acceptor interactions around single monovalent H2PO4- anion is also trapped within the self-assemblies L2 by N−Hurea···Obiphosphate, C−Ho-aryl···Obiphosphate and 12 ACS Paragon Plus Environment

Page 13 of 35 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


C−HTBA···Obiphosphate interactions and each H2PO4- anion exhibit coordination number of ten (Figure 4c, 4f). On the other hand, complex 2d of m-isomer contain inversion-symmetric half L2 receptor unit, another symmetry-independent full L2 conformer, one divalent SO42- anion generated via H-bonding activated proton transfer from HSO4- anion and its corresponding two n-TBA counter-cations. Structural elucidation reveals that one divalent single sulphate anion in complex 2d is entrapped within the self-assemblies of conformational isomorphs of L2 with an array of total fifteen (N−Hurea···Osulphate, C−Ho-aryl···Osulphate and C−HTBA···Osulphate) hydrogen-

Figure 4. X-ray structures (partial) of anion complexes 1c, 2d, 2e depicting array of hydrogen bonding interactions (a) on entrapment of (HSO4)2 dimer within the self-assemblies of para-isomer L1 in complex 1c, (b) on divalent sulphate binding via H-bonding activated proton transfer within the self-assemblies of meta-isomer L2 in complex 2d, (a) on entrapment of (H2PO4)n polymer within the self-assemblies of meta-isomer L2 in complex 2e, (d) magnified view of cyclic (HSO4)2 trapping in 1c, (e) magnified view of SO42- binding in 2d and (d) magnified view of entrapment of linear polymeric aggregation of (H2PO4)n in 2e.

bonding interactions (Figure 4b, 4e). Note that in complex 2d, the adjacent urea –NH groups of one L2 conformer are present in cooperative syn-fashion, while they are in non-cooperative antifashion in other symmetry-independent conformer (Figure 4b). These kinds of existence of more than one molecular conformer in the same crystal is known by the term ‘conformational isomorphism’ in supramolecular chemistry caused may be due the interrupted crystallization and their occurrence clarifies the kinetic and thermodynamic crystal stability concepts, as exemplified by Desiraju et. al.62 It should also be noted that, six urea -NH groups are involved in close entrapment of divalent SO42- anion in complex 2d, whereas comparatively open self13 ACS Paragon Plus Environment


assemblies of only four urea –NH groups are enough to capture dimeric associations of monovalent HSO4- or H2PO4- anions in respective complexes 1c and 2e. The presence of hydrogensulphate or sulphate in respective complexes 1c and 2d as well as dihydrogenphosphate in complex 2e and their coordination via strong N−H···O hydrogen bonds have also been confirmed by solid-state FT-IR analysis (Figure S15, S23, S25 in the Supporting Information). In each complex, the carbonyl (−C=O) stretching frequencies are observed at around ~1705-1710 cm−1, showing a considerable shift of ~40-45 cm−1 relative to free receptors due to the formation of strong N−H···O hydrogen bonds with either of the tetrahedral oxyanions. Additional information regarding the presence of strong N−H···O hydrogen bonds between the ligands and HSO4-/SO42-/ H2PO4- in respective complexes 1c, 2d and 2e can be obtained by examining the – NH peak of the spectrum, which are observed at around ~3300 cm−1. Furthermore, the strong and intense peak at around ~2960 cm−1 in each complex is attributed to C−H stretching of the nTBA groups. Note that, there is also existence of stretching bands at around ~3435 cm−1 in the FT-IR spectra of complexes 1c and 2e that are assigned to the O–H stretching vibration of hydrogensulphate dimer and dihydrogenphosphate polymer anionic guest respectively corroborating the X-ray results. In addition, new peak are observed at 1100-1110 cm−1, which can be attributed to the symmetric stretching frequency of the sulphate or phosphate anions in respective complexes. 2.3. Effect of positional isomerism on anion binding: It has clearly been observed from the X-ray analysis that the para-isomer (L1) and meta-isomer (L2) readily forms neutral anion complexes, basically with the oxyanions and proved to be the decent receptors for construction of stable anionic host-guest self-assemblies. The isomeric variation of nitro-group functionalization in the terminal aryl groups of bis-urea receptors L1 and L2, didn’t affect much to the receptors’ conformational changes upon the binding of particular anionic guest, which may be ascribed for the less converging, less cooperative and more rigid nature of p-phenylenediamine based ligands. However, it is significant to note that, we were not been able to get any anion complexes from the ortho-isomer L3, despite the more rigid and planar architecture of p-phenylenediamine moiety compared to other isomeric aromatic diamines. Note that, efforts were made for achieving the single crystals of anion complexes of ortho-isomer L3 in different solution mixtures with various conditions, but crystallization of any anion complexes was not fruitful, instead in most of the cases we have ended up with the free 14 ACS Paragon Plus Environment

Page 14 of 35

Page 15 of 35 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


ligand structures of L3 obtained from different solvents. This unsuccessful crystallization of anion complexes of L3 probably is the consequences of the steric effect provided by the nitro group at the ortho-position, as observed from the intramolecular hydrogen-bonding interactions in the crystal structures of free ligand L3 and this hinders the facile inclusion and coordination of an anion. Actually the nitro-group is oriented toward the urea -NH receptor arms and the o-nitro aromatic substitution to the urea scaffold performs as a barrier through the connection of strong intramolecular hydrogen-bonding that resists the binding and entrapment of any anionic guests, in contrast to the p-isomer L1 or m-isomer L2. A correlation of N–H⋯A angle vs. H⋯A distance confirms that most of the N–H⋯A interaction between isomeric receptors with the anion in corresponding anion complexes are in the strong Hbonding region of d (H⋯A) ≤ 2.6 Å and d(D⋯A) ≤3.2 Å in solid state. The scattered plot of N– H⋯A angles vs. H⋯A distances (Figures S35, Supporting Information) of individual anion/hydrated anion complexes also validates that most of the interactions exhibit strong hydrogen-bonding character. Hydrogen bond data table and crystal parameters as well as refinement data of free receptors L1-L3 and all oxyanion complexes 1a-1c and 2a-2e are tabulated in table 3-4 and table S1, Supporting Information). 2.4. Hirshfeld surface analyses: The contribution of strong N–H⋯O bonds in free receptors or strong N–H⋯A bonds in the anion complexes along with several weak C–H⋯O, C–H⋯π interactions involved in the conformational changes of linear p-phenylenediamine based isomeric receptors in the above structural studies can also be visualized by the Hirshfeld surfaces (HSs), which is considered to be the useful tool to define the surface characteristics of molecules.63 Generally, HSs offer a unique way of visualizing intermolecular interactions by color-coding short or long contacts, where the color intensity designates the relative strength of the interactions. The two dimensional fingerprint plots (2D FPs) supplement these surfaces, quantitatively describe the nature and types of intermolecular connections experienced by the molecules in the crystal as ‘‘contact contribution’’.64 The percentage of contact contributions of the dnorm surface area of free ligands and anion bound dipodal receptor segments of each complex are given in Table 2. Figure 5a and 6a describe the HSs mapped with dnorm for the nitrophenyl functionalized isomeric free bisurea receptors L1-L3 obtained either from DMSO or DMF solvents and the oxyanion



Page 16 of 35

Fig. 5. Hirshfeld surface analysis displaying (a) the dnorm surfaces isomeric free receptors L1-L3 obtained from DMSO or DMF, (b) corresponding 2D FPs with the O⋯H interactions highlighted in color involved in N–H⋯O or C–H⋯O close contacts and (c) corresponding 2D FPs with the C⋯H interactions highlighted in color involved in C–H⋯O or C–H⋯π or C–H⋯X (Cl/Br) contacts. Table 2: Contact contributions from the dnorm surface area of dipodal segments in free receptors and in anion complexes: Contacts H⋯O H⋯S/P H⋯N H⋯C H⋯H

L1.DMSO 30.2 3.0 3.3 17.2 32.9

L2.DMSO 29.6 0.6 1.5 13.6 37.5

L3.DMSO 26.7 1.3 4.5 19.1 35.8

L2 29.0 --2.8 20.9 28.6

L3 35.2 --5.3 19.2 25.7

1a 35.7 --5.4 20.3 37.9

1b 32.2 --5.4 19.3 43.1

1c 37.0 0.0 5.4 18.2 37.5

2a 31.1 --4.5 19.1 43.2

2b 32.2 --5.5 21.1 39.3

2c 31.4 --5.3 19.0 41.9

2d 31.5 0.0 4.6 18.0 38.5

2e 36.4 0.0 3.7 15.4 40.5

bound dipodal receptor segments in all complexes respectively. The dnorm surfaces of free receptors highlight the strong inter-receptor N–H⋯O interactions among the urea N–H donors of particular dipodal ligand unit and carbonyl oxygen of adjacent ligands in solvent free receptor structures as well as the strong N–H⋯O interactions between urea N–H donors and O atom of DMSO solvated receptor structures, which are depicted as bright red spots on the surfaces (Figure 5a). Similarly, Figure 6a describes the strong N−H···A (anion) hydrogen bonds between urea N–H donors of receptors and O atom of oxyanions (carbonate/sulphate/acetate/phosphate)


Page 17 of 35 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 6. Hirshfeld surface analysis displaying (a) the dnorm surfaces of anion bound dipodal segments of complexes 1a-1c and 2a-2e, (b) corresponding 2D FPs with the O⋯H interactions highlighted in color involved in N–H⋯O or C–H⋯O close contacts and (c) corresponding 2D FPs with the C⋯H interactions highlighted in color involved in C–H⋯O or C–H⋯π or C–H⋯X (Cl/Br) contacts.

in the above-described complexes that are depicted as bright red spots on the surfaces. While the other interactions such as C–H⋯O, C–H⋯π are appeared as bright to faint red spots that exist between the adjacent ligand molecules (Figure 5a) or between the anion and o-aryl group of receptors or between the anion and n-TBA counter-cations (Figure 6a). The H⋯O close contacts (~26-36%) as observed from the 2D fingerprint plots of corresponding HSs in the free receptors (Figure 5b) as well as in anion complexes (Figure 6b) exhibit characteristic sharp ‘‘spikes’’ in the upper left and lower right of the plots, which also reveal the pseudo-symmetry in few cases on either side of the diagonal (de = di) such as in L2, L3 or L2.DMSO structures (Figure 5b). On the other hand, the corresponding 2D FPs for the H⋯C close contacts shows contact contributions of ~15-20% (table 2) exhibiting relatively soft characteristic ‘‘spikes’’ in the upper left and lower right of the plots for free receptors (Figure 5c) and single soft “spike” in 2D FPs for most of the anion complexes (Figure 6c). These results obtained from HSs and corresponding 2D FPs of free ligand segments and anion bound receptor complexes validate the solid state results obtained from single crystal X-ray analyses. 2.5. Solution-State Anion-Binding Studies: The 1H NMR analyses (DMSO-d6) of the free receptors L1-L3, the isolated anion complexes 1a1c, 2a-2e and in presence of equivalent amounts of different anions as observed from the solid state results further demonstrate the solution-state binding of inorganic anions. The qualitative as 17 ACS Paragon Plus Environment


Figure 7. (a) Representation of urea -NHa and -NHb protons in isomeric bisurea scaffolds L1/L2/L3, (b) expanded partial 1H NMR comparative stacked spectra of free ligands, (c) expanded partial 1H NMR comparative stacked spectra in the solution phase of L1 with oxyanions and (d) expanded partial 1H NMR comparative stacked spectra in the solution phase of L2 with oxyanions, as observed from the solid state displaying the maximum observable downfield shifts of urea proton upon anion complexation.

well as quantitative 1H NMR experiments using the quaternary ammonium (n-TBA/TEA) salts of OCOCH3-, SO42-, H2PO4- oxyanions in DMSO-d6 shows most significant changes of the urea NH protons, which are expected to be the primary site for anion recognition. Figure 7c, 7d represent the maximum amount of chemical shift changes observed in presence of different dimensions of oxyanions to the solutions of isomeric receptors. Subsequently, Figure 8a, 8b show the chemical shift changes observed upon quantitative gradual addition of OCOCH3(DMSO-d6) solutions as their n-TBA salts to the individual solutions of L1 and L2, whereas Figure 9a, 9b display the quantitative 1H-NMR titration of standard SO42- and H2PO4- salts to the individual solutions of L2, following the result of maximum chemical shift changes in solid state complexes. First of all, 1H NMR analysis of the free isomeric receptors reveals that ortho-isomer L3 exhibit the chemical shift values of δ -NHa = 9.581 ppm; δ - NHb = 9.784 ppm, that exist in far downfield region compared to the para-isomer L1 (δ -NHa = 8.846 ppm; δ - NHb = 9.400) ppm and meta-isomer L2 (δ -NHa = 8.749 ppm; δ - NHb = 9.173) (Figure 7b) and this may be the consequences of strong intramolecular N−H···O interactions in L3 between o-nitro group and adjacent urea -NH protons in solution state also as observed from solid state. 1H NMR analysis of 18 ACS Paragon Plus Environment

Page 18 of 35

Page 19 of 35 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


the cyclic bicarbonate dimer entrapped complexes of receptors L1 and L2 obtained from either For OH- induced aerial CO2 fixation showed average downfield shift of ∆δ = 1.20 ppm (∆δ -NHa = 1.16 ppm; ∆δ - NHb = 1.24 ppm) (Figure S10 Supporting Information), ∆δ = 2.74 ppm (∆δ -

Figure 8. Comparison between the expanded partial 1H NMR titration spectra of (a) L1 and (b) L2, with standard n-TBAOCOCH3 salt in DMSO-d6.

Figure 9. Comparison between the expanded partial 1H NMR spectra of L2 upon titration with (a) standard (n-TBA)2SO4 salt and (b) standard n-TBAH2PO4 salt in DMSO-d6.

NHa = 2.59 ppm; ∆δ - NHb = 2.89 ppm) (Figure S16 Supporting Information) and ∆δ = 0.73 ppm (∆δ -NHa = 0.71 ppm; ∆δ - NHb = 0.76 ppm) (Figure S18 Supporting Information) relative to the corresponding free receptors through severe broadening of urea -NH signals in complexes 1a, 2a and 2b respectively, which suggests the decent anion binding capabilities of the receptors in solution states. Subsequently, the 1H NMR data of the acetate and hydrated-acetate complexes 1b and 2c respectively showed huge average downfield shift of ∆δ = 3.31 ppm (∆δ -NHa = 3.19 ppm; ∆δ - NHb = 3.43 ppm) (Figure S12 Supporting Information) and ∆δ = 2.91 ppm (∆δ -NHa = 2.78 ppm; ∆δ - NHb = 3.03 ppm) for the -NH (Figure S20 Supporting Information). Whereas, 1H 19 ACS Paragon Plus Environment


NMR titration data of L1 and L2 separately with aliquots of 2.0 equiv. standard n-TBAOCOCH3 solution, the urea -NH protons of L1 shifted by ∆δ = 3.17 ppm (-NHa) and ∆δ = 3.42 ppm (-NHb) and the urea -NH protons of L2 shifted by ∆δ = 3.10 ppm (−NHa) and ∆δ = 3.38 ppm (-NHb) (Figure 8a, 8b), which are very closely resemble with the solid state results and also indicating more proficient participation of -NHa than -NHb in the host-guest assembly. It is important to mention here that, due to huge broadening followed by the splitting of both ureas –NH resonances upon acetate addition, the binding stoichiometries could not be determined in solution state. The significant broadening and splitting of urea -NH signals in 1H-NMR spectra have been appeared due to the consequences of rapid hydrogen bonding interactions between anion and receptor. Similarly, divalent sulfate and polymeric (H2PO4)n entrapped complexes 2d and 2e showed moderate average downfield shift of ∆δ = 1.27 ppm (∆δ -NHa = 1.07 ppm; ∆δ NHb = 1.47 ppm) (Figure S22, Supporting Information) and ∆δ = 2.14 ppm (∆δ -NHa = 2.02 ppm; ∆δ - NHb = 2.25 ppm) (Figure S24, Supporting Information) respectively for the -NH protons in their 1H NMR data. However, 1H NMR titration data of L2 with aliquots of standard (n-TBA)2SO4 solution experience urea -NH shift of ∆δ = 2.12 ppm (-NHa) and ∆δ = 2.61 ppm (NHb) (Figure 9a), while L2 with aliquots of standard (n-TBA)2H2PO4 solution show urea -NH shift of ∆δ = 1.15 ppm (-NHa) and ∆δ = 1.31 ppm (-NHb) (Figure 9b), also indicating more proficient -NHa participation than -NHb in anion binding supported from the solid-state evidence. The titration data of L2 with standard (n-TBA)2SO4 and (n-TBA)2H2PO4 gave the best fit for mixed equilibrium between 1:1 and 1:2 host-guest stoichiometry with apparent binding constant (log K) value of 3.31 and 2.34 respectively (Figures S28-S30 and S31-S33, Supporting Information). The cyclic (HSO4)2-dimer entrapped complex 1c showed average downfield shift of ∆δ = 0.14 ppm (∆δ -NHa = 0.13 ppm; ∆δ - NHb = 0.15 ppm) only for urea -NH protons (Figure S14 Supporting Information) and because of very negligible shift the titration experiments of L1with standard bisulphate salt could not performed. 3. Conclusions The effect of positional isomerism in a new class of nitrophenyl functionalized rigid as well as planar aromatic bis-urea receptors have been extensively established toward the solid-state binding of oxyanions of different dimensions, further validated by solution-state studies. In summary, structural elucidation unveiled the strongly basic fluoride or hydroxide ion induced atmospheric CO2 fixation in the form of air-stable crystals of cyclic bicarbonate dimer, entrapped 20 ACS Paragon Plus Environment

Page 20 of 35

Page 21 of 35 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


within the hydrogen-bonded self-assemblies of either para-nitro-functionalized receptor L1 or meta-nitro-functionalized receptor L2. Similar kind of planar monovalent acetate anions were also bound either in their bare or hydrated [(acetate)2(water)2] form within the non-cooperative self-assemblies of para-isomer L1 and meta-isomer L2 respectively. However, in the presence of quaternary ammonium salt of tetrahedral HSO4-, the para-isomer L1 captures cyclic (HSO4)2 dimer within the non-cooperative hydrogen-bonded array, but the meta-isomer L2 arrests divalent sulphate anion inside the mixed (cooperative and non-cooperative) self-assemblies via hydrogen-bonded activated proton transfer. Subsequently, receptor L2 has also proved to be a decent receptor for capturing (H2PO4)n linear anionic polymer by non-cooperative hydrogenbonding interactions in solid state. On the other hand, no structural evidence of anion binding with ortho-isomer L3 could be demonstrated, presumably because of the ortho-nitro group substitution which acts as a barricade through strong intramolecular N–H⋯O interactions that resists the facile inclusion of oxyanions within the dipodal scaffold, as observed and confirmed from free L3 receptor structures. The solution-state 1H- NMR studies and Hirshfeld surface analyses of anion complexes also corroborate the solid-state results. Thus, the set of nitrophenyl functionalized simple para-phenylenediamie based rigid positional isomeric bis-urea scaffolds provide a unique insight and excellent case of understanding the consequence of the oxyanion mediated development of hydrogen bonded supramolecular self-assemblies, that are reliable for data interpretation as well as justified for consistency in variation. 4. Experimental Section 3.1. Materials and Methods. All reagents and solvents were obtained from commercial sources and used as received without further purification. Para-phenylenediamine, isomeric nitrophenylisocyanates and quaternary ammonium salts salts were purchased from Sigma-Aldrich and used as received. Solvents for synthesis and crystallization experiments were purchased from Merck, India, and used as received. 1H NMR spectra were recorded on a Varian FT-600 MHz instrument, and chemical shifts were recorded in parts per million (ppm) on the scale using tetramethylsilane [Si(CH3)4] or a residual solvent peak as a reference. The electrospray ionization mass spectrometry (ESI-MS) spectra of free receptors L1-L3 were recorded in methanol. The FT-IR spectra of air-dried samples of free ligands and the anion complexes were recorded on a Perkin-Elmer-Spectrum One FT-IR spectrometer with KBr disks in the range 4000-450 cm−1. Binding constants were 21 ACS Paragon Plus Environment


obtained by 1H NMR (Varian 600 MHz) titrations of receptors with TEA/n-TBA salts of respective anions in DMSO-d6 at 298 K. The initial concentration of the corresponding receptor solution was 10 mM. Aliquots of anions were added from 50 mM stock solutions of anions. The residual solvent peak in DMSO-d6 (2.500 ppm) was used as an internal reference and each titration was performed with 10-12 measurements at room temperature. The association constant log K was calculated by fitting urea NHa/NHb signals using the WINEQNMR program.65 3.2. Syntheses and Characterization. 3.2.1. Receptor L1-L3. Each nitrophenyl functionalized isomeric receptors L1, L2 and L3 were obtained in quantitative yield by the reaction of para-phenylenediamine (0.324 g, 3.0 mmol) with 2.0 equiv of the 4-nitrophenylisocyanate (0.985 g, 6.0 mmol), 3-nitrophenylisocyanate (0.985 g, 6.0 mmol) and 2-nitrophenylisocyanate (0.985 g, 6.0 mmol) respectively in individual dry acetonitrile medium. The individual reaction mixtures in separate 250mL round-bottomed flask were stirred at room temperature and kept for overnight. The volume of the excess acetonitrile was reduced in vacuo and the obtained faint yellow solid products in each case were filtered off and washed with dry THF, dichloromethane and dry acetonitrile for to remove the unreacted reagents and then characterized by NMR and FT-IR analyses (Supporting Information). Furthermore, the pale yellow crystals of each isomeric ligand suitable for single crystal XRD analysis were isolated from either DMSO/DMF solvents. Yield = 80%, 75% and 75% for respective L1, L2 and L3. L1: 1H NMR (600 MHz, DMSO-d6) δ (ppm): 7.418 (s, 4H, Ar-H), 7.677-7.692 (d, 4H, ~9.0 Hz, Ar-H), 8.180-8.196 (d, 4H, ~9.6 Hz, Ar-H), 8.846 (s, 2H, NHa), 9.404 (s, 2H, NHb). IR spectra (KBr pellet): 3358 cm-1 vs(N–H), 3278 cm-1 vs(C-H), 1660 cm-1 vs(C=O), 1571 cm-1 vs(C=C), 1506 cm-1 vs(NO2-asym), 1332 cm-1 vs(NO2-sym),1223 cm-1 vs(C-N). ESI-MS, [M + 1]+ (m/z) Calculated for C20H16N6O6: 437.1165. Found: 437.1718. L2: 1H NMR (600 MHz, DMSO-d6) δ (ppm): 7.409 (s, 4H, Ar-H), 7.546-7.574 (t, 2H, ~8.4 Hz, Ar-H), 7.695-7.711 (d, 2H, ~9.6 Hz, Ar-H), 7.808-7.822 (d, 2H, ~8.4 Hz, Ar-H), 8.571 (s, 2H, Ar-H), 8.749 (s, 2H, NHa), 9.173 (s, 2H, NHb). IR spectra (KBr pellet): 3370 cm-1 vs(N–H), 3318 cm-1 vs(C-H), 1666 cm-1 vs(C=O), 1560 cm-1 vs(C=C), 1520 cm-1 vs(NO2-asym), 1345 cm-1 vs(NO2-sym), 1219 cm-1 vs(C-N). ESI-MS, [M + 1]+ (m/z) Calculated for C20H16N6O6: 437.1165. Found: 437.1233.


Page 22 of 35

Page 23 of 35 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


L3: 1H NMR (600 MHz, DMSO-d6) δ (ppm): 7.178-7.206 (t, 2H, ~8.4 Hz, Ar-H), 7.443 (s, 4H, Ar-H), 7.682-7.711 (t, 2H, ~8.4 Hz, Ar-H), 8.086-8.102 (d, 2H, ~9.6 Hz, Ar-H), 8.305-8.320 (d, 2H, ~9.0 Hz, Ar-H), 9.581 (s, 2H, NHa), 9.784 (s, 2H, NHb). IR spectra (KBr pellet): 3352 cm-1 vs(N–H), 3278 cm-1 vs(C-H), 1656 cm-1 vs(C=O), 1570 cm-1 vs(C=C), 1509 cm-1 vs(NO2-asym), 1338 cm-1 vs(NO2-sym), 1224 cm-1 vs(C-N). ESI-MS, [M + 1]+ (m/z) Calculated for C20H16N6O6: 437.1165. Found: 437.1240. 3.2.2.

Bicarbonate

complexes

[(n-TBA)2{(L1)(HCO3)2}]

(1a),

[(n-

TBA)2{(L2)(HCO3)2}(DMF)] (2a) and [(n-TBA)2{(L2)(HCO3)2}] (2b): The cyclic bicarbonate dimer entrapped complexes 1a and 2a of respective receptors L1 and L2 were attained as suitable crystals for X-ray diffraction analysis upon slow evaporation of 5 mL basic DMF solutions of individual L1/L2 (100 mg, 0.229 mmol) and excess of n-TBAF (10 eqv.), whereas the similar complex 2b of L2 was obtained from basic DMSO solutions of L2 (100 mg, 0.229 mmol) and excess of n-TBAOH (10 eqv.) The pale yellow crystals of each bicarbonate dimer entrapped complexes 1a, 2a and 2b were obtained from room temperature within 15-20 days and collected them by pressing between the filter papers before characterization by NMR, FT-IR analyses. Isolated yield: 65%, 60% and 70% based on respective complexes 1a, 2a and 2b. 1a: 1H NMR (600 MHz, DMSO-d6) δ (ppm): 0.911-0.935 (t, 12H, ~7.2 Hz, TBA-CH3), 1.2651.326 (m, 8H, TBA-CH2), 1.525-1.577 (m, 8H, TBA-CH2), 3.134-3.162 (t, 8H, ~ 8.4 Hz, N+TBA-CH2), 7.443 (s, 4H, Ar-H), 7.741-7.756 (d, 4H, ~9.0 Hz, Ar-H), 8.124-8.139 (d, 4H, ~9.0 Hz, Ar-H), 10.021 (bs, 2H, NHa), 10.636 (bs, 2H, NHb). IR spectra (KBr pellet): 3475 cm-1 vs(O–H), 3364 cm-1 vs(N–H), 2958 cm-1 vs(C-H), 1710 cm-1 vs(C=O), 1582 cm-1 vs(C=C), 1502 cm-1 vs(NO2-asym), 1338 cm-1 vs(NO2-sym), 1212 cm-1 vs(C-N), 848 cm-1 vs(HCO3-). 2a: 1H NMR (600 MHz, DMSO-d6) δ (ppm): 0.907-0.931 (t, 12H, ~7.2 Hz, TBA-CH3), 1.2611.323 (m, 8H, TBA-CH2), 1.521-1.574 (m, 8H, TBA-CH2), 3.132-3.160 (t, 8H, ~ 8.4 Hz, N+TBA-CH2), 7.426-7.65 (m, 6H, Ar-H), 7.684-7.697 (d, 2H, ~7.8 Hz, Ar-H), 7.862-7.876 (d, 2H, ~8.4 Hz, Ar-H), 8.653 (s, 2H, Ar-H), 11.354 (bs, 2H, NHa), 12.061 (bs, 2H, NHb). IR spectra (KBr pellet): 3448 cm-1 vs(O–H), 3352 cm-1 vs(N–H), 2964 cm-1 vs(C-H), 1706 cm-1 vs(C=O), 1565 cm-1 vs(C=C), 1509 cm-1 vs(NO2-asym), 1352 cm-1 vs(NO2-sym), 1224 cm-1 vs(C-N), 844 cm-1 vs(HCO3-).



2b: 1H NMR (600 MHz, DMSO-d6) δ (ppm): 0.914-0.939 (t, 12H, ~7.2 Hz, TBA-CH3), 1.2681.329 (m, 8H, TBA-CH2), 1.528-1.581 (m, 8H, TBA-CH2), 3.137-3.165 (t, 8H, ~ 8.4 Hz, N+TBA-CH2), 7.416 (s, 4H, Ar-H), 7.519-7.547 (t, 2H, ~8.4 Hz, Ar-H), 7.746-7.759 (d, 2H, ~7.8 Hz, Ar-H), 7.778-7.791 (d, 2H, ~7.8 Hz, Ar-H), 8.587 (s, 2H, Ar-H), 9.473 (bs, 2H, NHa), 9.929 (bs, 2H, NHb). IR spectra (KBr pellet): 3465 cm-1 vs(O–H), 3370 cm-1 vs(N–H), 2958 cm-1 vs(CH), 1559 cm-1 vs(C=C), 1704 cm-1 vs(C=O), 1508 cm-1 vs(NO2-asym), 1336 cm-1 vs(NO2-sym), 1217 cm-1 vs(C-N), 846 cm-1 vs(HCO3-). 3.2.3. Acetate complex [(n-TBA)2{(L1)(OCOCH3)2}] (1b) and hydrated-acetate complex [(nTBA)2{(L2)(OCOCH3)2(H2O)2}] (2c): The acetate complex 1b and hydrated-acetate complex 2c were prepared by charging excess of tetrabutylammonium acetate salts respectively (10 eqv.) into the 5 mL DMF/DMSO solution of L1 (100 mg, 0.229 mmol) and L2 (100 mg, 0.229 mmol) separately in a small glass vial. After the addition of acetate salts the resulting solutions were stirred for about 30 minutes and were left open to atmosphere for slow evaporation at room temperature. Colourless crystals of 1b and 2c suitable for single crystal X-ray analysis was obtained within 10-15 days. Yield: 65% of 1c based on L1 and 75% of 2c based on L2. 1b: 1H NMR (600 MHz, DMSO-d6) δ (ppm): 0.914-0.938 (t, 12H, ~7.2 Hz, TBA-CH3), 1.2671.328 (m, 8H, TBA-CH2), 1.526-1.579 (m, 8H, TBA-CH2), 1.773 (s, 3H, Acetate-CH3), 3.1353.163 (t, 8H, ~ 8.4 Hz, N+-TBA-CH2), 7.470 (s, 4H, Ar-H), 7.832-7.848 (d, 4H, ~9.6 Hz, Ar-H), 8.119-8.134 (d, 4H, ~9.0 Hz, Ar-H), 12.030 (s, 2H, NHa), 12.834 (s, 2H, NHb). IR spectra (KBr pellet): 3423 cm-1 vs(N–H), 2964 cm-1 vs(C-H), 1706 cm-1 vs(C=O), 1576 cm-1 vs(C=C), 1501 cm-1 vs(NO2-asym), 1305 cm-1 vs(NO2-sym), 1219 cm-1 vs(C-N), 853 cm-1 vs(-COO), 642 cm-1 vs(-COO deformation). 2c: 1H NMR (600 MHz, DMSO-d6) δ (ppm): 0.912-0.937 (t, 12H, ~7.2 Hz, TBA-CH3), 1.2651.327 (m, 8H, TBA-CH2), 1.525-1.578 (m, 8H, TBA-CH2), 1.777 (s, 3H, Acetate-CH3), 3.1343.162 (t, 8H, ~ 8.4 Hz, N+-TBA-CH2), 7.445 (s, 4H, Ar-H), 7.474-7.501 (t, 2H, ~8.4 Hz, Ar-H), 7.702-7.715 (d, 2H, ~7.8 Hz, Ar-H), 7.860-7.874 (d, 2H, ~8.4 Hz, Ar-H), 8.683 (s, 2H, Ar-H), 11.534 (s, 2H, NHa), 12.205 (s, 2H, NHb). IR spectra (KBr pellet): 3465 cm-1 vs(O–H), 3377 cm1

vs(N–H), 2966 cm-1 vs(C-H), 1702 cm-1 vs(C=O), 1535 cm-1 vs(C=C), 1508 cm-1 vs(NO2-

asym), 1320 cm-1 vs(NO2-sym), 1224 cm-1 vs(C-N), 885 cm-1 vs(-COO), 643 cm-1 vs(-COO deformation). 24 ACS Paragon Plus Environment

Page 24 of 35

Page 25 of 35 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


3.3.4.

Bisulphate

complex

[(n-TBA)2{(L1)(HSO4)2}]

(1c),

sulphate

complex

[(n-

TBA)4{(L2)3(SO4)2}] (2d) and biphosphate complex [(n-TBA)2{(L2)(H2PO4)2}] (2e): The cyclic bisulphate dimer entrapped complex 1c of L1 and divalent sulphate entrapped complex 2d of L2 were obtained as suitable crystals for X-ray diffraction analysis upon slow evaporation of 5 mL basic DMF/DMSO solution of L1 (100 mg, 0.229 mmol) and L2 (100 mg, 0.229 mmol) respectively from separate glass vial in presence of excess n-TBAHSO4 (10 eqv.). On the other hand, the polymeric (H2PO4)n trapped complex 2d of L2 was obtained from basic DMSO solutions of L2 (100 mg, 0.229 mmol) and excess of n-TBAH2PO4 (10 eqv.) The pale yellow crystals of complexes 1c, 2d and 2e thus attained within 15-20 days were isolated by filtration and dried at room temperature by pressing between the filter papers before characterization by NMR and FT-IR analyses. Isolated yield: 70%, 60% and 65% based on respective complexes 1c, 2d and 2e. 1c: 1H NMR (600 MHz, DMSO-d6) δ (ppm): 0.918-0.942 (t, 12H, ~7.2 Hz, TBA-CH3), 1.2711.332 (m, 8H, TBA-CH2), 1.532-1.585 (m, 8H, TBA-CH2), 3.142-3.170 (t, 8H, ~ 8.4 Hz, N+TBA-CH2), 7.419 (s, 4H, Ar-H), 7.692-7.707 (d, 4H, ~9.0 Hz, Ar-H), 8.175-8.191 (d, 4H, ~9.6 Hz, Ar-H), 8.979 (s, 2H, NHa), 9.551 (s, 2H, NHb). IR spectra (KBr pellet): 3435 cm-1 vs(O–H), 3331 cm-1 vs(N–H), 2960 cm-1 vs(C-H), 1712 cm-1 vs(C=O), 1562 cm-1 vs(C=C), 1502 cm-1 vs(NO2-asym), 1326 cm-1 vs(NO2-sym), 1205 cm-1 vs(C-N), 1108 cm-1 vs(-HSO4-). 2d: 1H NMR (600 MHz, DMSO-d6) δ (ppm): 0.895-0.920 (t, 24H, ~7.8 Hz, TBA-CH3), 1.2511.313 (m, 16H, TBA-CH2), 1.511-1.563 (m, 16H, TBA-CH2), 3.118-3.146 (t, 16H, ~ 8.4 Hz, N+TBA-CH2), 7.365 (s, 4H, Ar-H), 7.433-7.460 (t, 2H, ~8.4 Hz, Ar-H), 7.692-7.705 (d, 2H, ~7.8 Hz, Ar-H), 7.812-7.827 (d, 2H, ~9.0 Hz, Ar-H), 8.602 (s, 2H, Ar-H), 9.830 (s, 2H, NHa), 10.648 (s, 2H, NHb). IR spectra (KBr pellet): 3326 cm-1 vs(N–H), 2962 cm-1 vs(C-H), 1702 cm-1 vs(C=O), 1558 cm-1 vs(C=C), 1512 cm-1 vs(NO2-asym), 1306 cm-1 vs(NO2-sym), ), 1205 cm-1 vs(C-N), 1112 cm-1 vs(-SO42-). 2e: 1H NMR (600 MHz, DMSO-d6) δ (ppm): 0.916-0.940 (t, 12H, ~7.2 Hz, TBA-CH3), 1.2701.330 (m, 8H, TBA-CH2), 1.531-1.584 (m, 8H, TBA-CH2), 3.141-3.168 (t, 8H, ~ 8.4 Hz, N+TBA-CH2), 7.456-7.484 (t, 2H, ~8.4 Hz, Ar-H), 7.500 (s, 4H, Ar-H), 7.705-7.718 (d, 2H, ~7.8 Hz, Ar-H), 7.985-7.999 (d, 2H, ~8.4 Hz, Ar-H), 8.720 (s, 2H, Ar-H), 10.777 (s, 2H, NHa), 11.431 (s, 2H, NHb). IR spectra (KBr pellet): 3437 cm-1 vs(O–H), 3318 cm-1 vs(N–H), 2966 cm-1



Page 26 of 35

vs(C-H), 1705 cm-1 vs(C=O), 1582 cm-1 vs(C=C), 1516 cm-1 vs(NO2-asym), 1311 cm-1 vs(NO2sym), ), 1200 cm-1 vs(C-N), 1099 cm-1 vs(-H2PO4-). Crystallographic Refinement Details: The crystallographic data and details of data collection of isomeric free receptor structures L1-L3 Table 3: Crystal Parameters and Refinement Data of free receptors and anion complexes: Parameters

L1.DMSO

L2.DMSO

L3.DMSO

L2

L3

1a

1b

1c

Formula Fw Crystal system

C24H28N6O8S2 592.64 triclinic


C24H28N6O8S2 592.64 monoclinic

C20H16N6O6 436.39 monoclinic

C20H16N6O6 436.39 triclinic




Space group a/Å b/Å c/Å α/o β/o γ/o V/Å3 Z Dc/g cm-3 μ Mo Kα/mm-1 F000 T/K θ max. Total no. of reflections Independent reflections Observed reflections Parameters refined R1, I > 2σ(I)

P -1 7.027(7) 8.092(7) 13.279(12) 101.936(8) 94.021(8) 100.656(8) 721.3(12) 1 1.364 0.241 310.0 298(2) 24.996 4706

P -1 7.417(12) 9.607(14) 10.828(17) 106.215(13) 96.982(13) 103.563(13) 705.6(2) 1 1.395 0.246 310.0 298(2) 24.999 4395

P 21/c 8.885(7) 5.495(4) 28.494(2) 90.00 92.154(7) 90.00 1390.2(18) 2 1.416 0.250 620.0 298(2) 25.000 4692

P 21/n 6.770(3) 4.770(3) 29.712(16) 90.00 95.749(3) 90.00 954.7(9) 2 1.518 0.116 452.0 298(2) 28.590 14138

P -1 4.672(4) 5.936(7)) 17.365(13) 82.729(4) 86.665(6) 84.947(6) 475.25(8) 1 1.525 0.116 226.0 298(2) 25.000 6593

P -1 8.140(7) 10.766(6) 18.409(11) 88.114(5) 77.750(6) 69.833(7) 1478.3(19) 1 1.172 0.083 566.0 298(2) 24.998 9363

P -1 8.612(8) 10.217(9) 17.768(16) 94.155(7) 91.983(7) 106.768(8) 1490.5(2) 1 1.158 0.079 566.0 298(2) 24.999 10126

P -1 8.308(5) 10.844(8) 17.490(13) 93.273(6) 94.126(6) 98.275(6) 1551.7(19) 1 1.194 0.150 602.0 298(2) 24.999 10629

2547

2482

2457

2408

1649

5195

5233

5433

1667

1472

1762

2081

1379

2912

3318

3274

193

183

202

145

145

339

339

348

0.0687

0.0593

0.0662

0.0471

0.0589

0.0888

0.0692

0.0703

wR2, I > 2σ(I)

0.1417

0.1582

0.1872

0.1790

0.1476

0.1984

0.1687

0.1873

GOF (F2)

1.016

0.999

1.175

1.148

0.973

1.034

1.101

1.016

CCDC No.

1847547

1847548

1847549

1847550

1847551

1847552

1847553

1847554

and all the anion complexes 1a-1c and 2a-2e are given in Table 3-4. In each case, a crystal of suitable size was selected from the mother liquor and immersed in silicone oil, then mounted on the tip of a glass fibre and cemented using epoxy resin. The X-ray crystallographic intensity data were collected using Supernova, single source at offset, Eos diffractometer using Mo-Kα radiation (λ = 0.71073 Å) equipped with CCD area detector and corresponding data refinement and cell reduction were performed by CrysAlisPro.66 The data integration and reduction were carried out with SAINT and XPREP67 software and multi-scan empirical absorption corrections were applied to the data using the program SADABS.68 All the structures were solved by direct methods using SHELXTL-2014 and were refined on F2 by the full-matrix least-squares 26 ACS Paragon Plus Environment

Page 27 of 35 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


technique using the SHELXL-2014 program package.69 Graphics for structural illustrations are generated using MERCURY 2.370 for Windows. All non-hydrogen atoms were refined anisotropically and the hydrogen atoms attached to all the carbon atoms were geometrically fixed, the positional and temperature factors are refined isotropically. The hydrogen atoms are Table 4: Crystal Parameters and Refinement Data of anion complexes: Parameters

2a

2b

2c

2d

2e

Formula Fw Crystal system

C60H104N10O14 1189.53 monoclinic




C52H92N8O14P2 1115.28 triclinic

Space group a/Å b/Å c/Å α/o β/o γ/o V/Å3 Z Dc/g cm-3 μ Mo Kα/mm-1 F000 T/K θ max. Total no. of reflections Independent reflections Observed reflections Parameters refined R1, I > 2σ(I)

P 21/c 8.154(3) 11.276(4) 36.355(13) 90.00 94.733(2) 90.00 3331.0(2) 2 1.186 0.084 1292.0 298(2) 28.450 50536

P -1 7.921(16) 11.255(2) 16.684(3) 79.358(12) 85.246(13) 88.625(13) 1456.7(5) 1 1.189 0.084 566.0 298(2) 24.991 15038

P -1 9.0578(3) 9.7515(4) 18.6766(7) 91.447(2) 99.350(2) 108.564(2) 1537.81(10) 1 1.142 0.079 576.0 298(2) 25.000 11136

P -1 9.7001(8) 18.1688(13) 21.5764(17) 111.391(7) 95.955(7) 92.633(7) 3507.1(5) 1 1.170 0.111 1330.0 298(2) 24.998 24276

P -1 8.482(7) 11.632(9) 16.188(13) 85.317(6) 79.343(7) 87.979(7) 1564.0(2) 1 1.184 0.133 602.0 298(2) 24.995 10627

8338

5004

5353

12340

5488

6867

2737

3034

9131

3356

386

340

359

793

363

0.0806

0.1132

0.0525

0.0976

0.0672

wR2, I > 2σ(I)

0.1464

0.2158

0.1178

0.1847

0.1762

GOF (F2)

1.049

1.159

1.041

1.071

1.105

CCDC No.

1847555

1847556

1847557

1847558

1847559

located on a difference Fourier map and refined, wherever it is possible. In other cases, the hydrogen atoms are geometrically fixed. It is also important to mention here that few DELU, SIMU and DFIX restrains have been used during the refinement process to improve the hostguest architectures in few crystal structures such as in complex 1a, 2b and 2d. Moreover, the high residual density of 0.73 and 0.67 respectively for complexes 1a and 2a have been observed because of the unaccounted disorder of H17B atom and H19B atom in respective crystal structures. Structural illustrations have been drawn with ORTEP-3 for Windows.71 Crystallographic non-covalent interactions data are summarized in Table S1 (supporting information). 27 ACS Paragon Plus Environment


Page 28 of 35

4.4. Hirshfeld surface analysis: The Hirshfeld surfaces and 2D fingerprint plots (FPs) are built based on the electron distribution calculated as the sum of spherical atom electron densities and obtained from the results of single crystal X-ray diffraction studies. The HS surrounding a molecular fragment is well-defined by points where the contribution to the electron density from the molecule of interest is equal to the contribution from all the other molecules and two distances for each point on that isosurface are defined: de, the distance from the point to the nearest nucleus external to the surface, and di, the distance to the nearest nucleus internal to the surface. The normalized contact distance, dnorm is the ratio encompassing the distances of any surface point to the nearest interior (di) and exterior (de) atom and the van der Waals radii of the atoms, which is given by eqn (1) simplifies effective detection of the regions of particular importance to intermolecular interactions.72 dnorm = {(di - rivdw) / rivdw} + {(de – revdw) / revdw}

(1)

The value of dnorm is negative or positive or zero. The negative dnorm value indicates the sum of di and de is shorter than the sum of the relevant vdW radii, considered to be the closest contact and is visualized as red color in the HSs. The white colour denotes intermolecular distances close to vdW contacts with dnorm equal to zero, while contacts longer than the sum of vdW radii with positive dnorm values are coloured with blue. The combination plot of di vs de is the 2D fingerprint plot that recognizes the existence of various types of intermolecular interactions. The HSs are mapped with dnorm, the 2D FPs of ligands and all anion-receptor complexes are presented in Figure 5-6 and contact contributions from the dnorm surface area are summarized in table 2, which were generated using Crystal Explorer 3.1.73 Acknowledgments This work was supported by CSIR and SERB through grant 01/2727/13/EMR-II and SR/S1/OC62/2011, New Delhi, India. CIF IIT Guwahati and DST-FIST for providing instrument facilities. U.M. thanks IIT Guwahati for fellowship. Supplementary Material Figures, a table, and CIF files giving characterization data for the receptor L1-L3 and all the anion complexes 1a-1c and 2a-2e, FT-IR spectra and 1H NMR spectra, 1H NMR titration stack plots, job’s plot for solution state NMR, distance vs angle plots, hydrogen-bonding data table. References


Page 29 of 35 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1. Steed, J. W.; Atwood, J. L. Supramolecular Chemistry. John Wiley & Sons, Ltd.: New York, 2009. 2. Katayev, E. A.; Ustynyuk, Y. A.; Sessler, J. L. Receptors for tetrahedral oxyanions Coord. Chem. Rev. 2006, 250, 3004. 3. Edwards, P. R.; Hiscock, J. R.; Gale, P. A.; Light, M. E. Carbamate complexation by ureabased receptors: studies in solution and the solid state Org. Biomol. Chem. 2010, 8, 100. 4. Edwards, P. R.; Hiscock, J. R.; Gale, P. A. Stabilization of alkylcarbamate anions using neutral hydrogen bond donors Tetrahedron Lett. 2009, 50, 4922. 5. Steed, J. W. Coordination and organometallic compounds as anion receptors and sensors Chem. Soc. Rev. 2009, 38, 506. 6. Schottel, B. L.; Chifotides, H. T.; Dunbar, K. R. Anion-pi interactions Chem. Soc. Rev. 2008, 37, 68. 7. Sessler, J. L.; Cho, D.-G.; Lynch, V. Diindolylquinoxalines: Effective Indole-Based Receptors for Phosphate Anion J. Am. Chem. Soc. 2006, 128, 16518. 8. Wang, Z.; Luecke, H.; Yao, N.; Quiocho, F. A. A low energy short hydrogen bond in very high resolution structures of protein receptor-phosphate complexes Nat. Struct. Biol., 1997, 4, 519. 9. Pflugrath, J. W.; Quiocho, F. A. Sulphate sequestered in the sulphate-binding protein of Salmonella typhimurium is bound solely by hydrogen bonds Nature, 1985, 314, 257. 10. Manna, U.; Nayak, B.; Hoque, M. N.; Das, G. Influence of the cavity dimension on encapsulation of halides within the capsular assembly and side-cleft recognition of a sulfate– water cluster assisted by polyammonium tripodal receptors CrystEngComm, 2016, 18, 5036 11. Hoque, M. N.; Manna, U.; Das, G. Encapsulation of fluoride and hydrogen sulfate dimer by polyammonium-functionalised first- and second-generation tripodal: cavity-induced anion encapsulation Supramol. Chem., 2016, 28, 284. 12. Sessler, J. L.; Gross, D. E.; Cho, W.-S.; Lynch, V. M.; Schmidtchen, F. P.; Bates, G. W.; Light, M. E.; Gale, P. A. Calix[4]pyrrole as a Chloride Anion Receptor: Solvent and Countercation Effects J. Am. Chem. Soc., 2006, 128, 12281. 13. Gale, P. A.; Sessler, J. L.; Král, V.; Lynch, V. Calix[4]pyrroles: Old Yet New Anion-Binding Agents J. Am. Chem. Soc., 1996, 118, 5140.



14. Anzenbacher Jr., P.; Try, A. C.; Miyaji, H.; Jursı´kova´, K.; Lynch, V. M.; Marquez, M.; Sessler, J. L. Fluorinated Calix[4]pyrrole and Dipyrrolylquinoxaline: Neutral Anion Receptors with Augmented Affinities and Enhanced Selectivities J. Am. Chem. Soc., 2000, 122, 10268. 15. Gale, P. A.; Busschaert, N.; Haynes, C. J. E.; Karagiannidis, L. E; Kirby, I. L. Anion receptor chemistry: highlights from 2011 and 2012 Chem. Soc. Rev., 2014, 43, 205. 16. Wenzel, M.; Hiscock, J. R.; Gale, P. A. Anion receptor chemistry: highlights from 2010 Chem. Soc. Rev., 2012, 41, 480. 17. Gale, P. A. Anion receptor chemistry: highlights from 2008 and 2009 Chem. Soc. Rev., 2010, 39, 3746. 18. Caltagirone, C.; Gale, P. A. Anion receptor chemistry: highlights from 2007 Chem. Soc. Rev., 2009, 38, 520. 19. Gale, P. A.; García-Garrido, S. E.; Garric, J. Anion receptors based on organic frameworks: highlights from 2005 and 2006 Chem. Soc. Rev., 2008, 37, 151. 20. Gunnlaugsson, T.; Glynn, M.; Tocci, G. M.; Kruger, P. E.; Pfeffer, F. M. Anion recognition and sensing in organic and aqueous media using luminescent and colorimetric sensors Coord. Chem. Rev., 2006, 250, 3094. 21. Xu, Z.; Kim, S. K.; Yoon, J. Revisit to imidazolium receptors for the recognition of anions: highlighted research during 2006-2009 Chem. Soc. Rev. 2010, 39, 1457. 22. Moyer, B. A.; Bonnesen, P. V. In Physical factors in anion separation, Supramolecular chemistry of anions; Bianchi, A., Bowman- James, K., Garcia-Espana, E., Eds.; Wiley-VCH: New York, 1997. 23. Wang, X. B.; Yang, X.; Nicholas, J. B.; Wang, L. S. Bulk-like features in the photoemission spectra of hydrated doubly charged anion clusters Science 2001, 294, 1322. 24. McKee, M. L. Computational Study of the Mono- and Dianions of SO2, SO3, SO4, S2O3, S2O4, S2O6, and S2O8 J. Phys. Chem. 1996, 100, 3473. 25. Climate Change 2007: Synthesis Report, International Panel on Climate Change; Cambridge University Press: Cambridge, U.K., 2007. 26. Jenkinson, D. S.; Adams, D. E.; Wild, A. Model estimates of CO2 emissions from soil in response to global warming Nature 1991, 351, 304.


Page 30 of 35

Page 31 of 35 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


27. Barth, M. C.; Church, A. T. Regional and global distributions and lifetimes of sulfate aerosols from Mexico City and southeast China J. Geophys. Res., 1999, 104, 30231. 28. Heizer, W. D.; Sandler, R. S.; Seal, E.; Murrai, S. C.; Busby, M. G.; Schliebe, B. G.; Pusek, S. N. Intestinal effects of sulfate in drinking water on normal human subjects Dig. Dis. Sci., 1997, 42, 1055. 29. Milby, T. H.; Baselt, R. C. Hydrogen sulfide poisoning: Clarification of some controversial issues. Am. J. Ind. Med. 1999, 35, 192. 30. Dey, S. K.; Basu, A.; Chutia, R.; Das, G. Anion coordinated capsules and pseudocapsules of tripodal amide, urea and thiourea scaffolds RSC Adv., 2016, 6, 26568. 31. Dutta, R.; Ghosh, P. Recent developments in anion induced capsular self-assemblies Chem. Commun., 2014, 50, 10538 32. Arunachalam, M.; Ghosh, P. Anion induced capsular self-assemblies Chem. Commun., 2011, 47, 8477. 33. Brooks, S. J.; Gale, P. A.; Light, M. E. Carboxylate complexation by 1,1′-(1,2phenylene)bis(3-phenylurea) in solution and the solid state Chem. Commun., 2005, 4696 34. Brooks, S. J.; Gale, P. A.; Light, M. E. ortho-Phenylenediamine bis-urea–carboxylate: a new reliable supramolecular synthon CrystEngComm, 2005, 7, 586. 35. S Brooks, S. J.; Edwards, P. R.; Gale, P. A.; Light, M. E. Carboxylate complexation by a family of easy-to-make orthophenylenediamine based bis-ureas: studies in solution and the solid state New J. Chem., 2006, 30, 65. 36. Moore, S. J.; Haynes, C. J. E.; González, J.; Sutton, J. L.; Brooks, S. J.; Light, M. E.; Herniman, J.; Langley, G. J.; Soto-Cerrato, V.; Perez-Tomás, R.; Marques, I.; Costa, P. J.; Fèlix, V.; Gale, P. A. Chloride, carboxylate and carbonate transport by orthophenylenediamine-based bisureas Chem. Sci., 2013, 4, 103. 37. Li, R.; Zhao, Y.; Li, S.; Yang, P.; Huang, X.; Yang, X-J.; Wu, B. Tris Chelating Phosphate Complexes of Bis(thio)urea Ligands Inorg. Chem. 2013, 52, 5851. 38. Jose, D. A.; Kumar, D. K.; Ganguly, B.; Das, A. Efficient and Simple Colorimetric Fluoride Ion Sensor Based on Receptors Having Urea and Thiourea Binding Sites Org. Lett., 2004, 6, 3445.



39. Otón, F.; Tárraga, A.; Velasco, M. D.; Espinosa, A.; Molina, P. A new fluoride selective electrochemical and fluorescent chemosensor based on a ferrocene–naphthalene dyad Chem. Commun., 2004, 1658. 40. Xu, G.; Tarr, M. A. A novel fluoride sensor based on fluorescence enhancement Chem. Commun., 2004, 1050. 41. Manna, U.; Nayak, B.; Das, G. Dual Guest [(Chloride)3‑DMSO] Encapsulated Cation-Sealed Neutral Trimeric Capsular Assembly: Meta-Substituent Directed Halide and Oxyanion Binding Discrepancy of Isomeric Neutral Disubstituted Bis- Urea Receptors Cryst. Growth Des. 2016, 16, 7163. 42. Manna, U.; Kayal, S.; Nayak, B.; Das, G. Systematic size mediated trapping of anions of varied dimensionality within a dimeric capsular assembly of a flexible neutral bis-urea platform Dalton Trans., 2017, 46, 11956. 43. Manna, U.; Chutia, R.; Das G. Entrapment of Cyclic Fluoride–Water and Sulfate–Water– Sulfate Cluster within the Self-Assembled Structure of Linear meta-Phenylenediamine Based Bis-Urea Receptors: Positional Isomeric Effect Cryst. Growth Des. 2016, 16, 2893. 44. Manna, U.; Kayal, S.; Samanta, S.; Das, G Fixation of atmospheric CO2 as novel carbonate– (water)2–carbonate cluster and entrapment of double sulfate within a linear tetrameric barrel of a neutral bis-urea scaffold Dalton Trans., 2017, 46, 10374. 45. Manna, U.; Das, G Anion binding consistency by influence of aromatic meta-disubstitution of a simple urea receptor: regular entrapment of hydrated halide and oxyanion clusters CrystEngComm, 2017, 19, 5622. 46. Manna, U.; Halder, S.; Das, G. Ice-like Cyclic Water Hexamer Trapped within a Halide Encapsulated Hexameric Neutral Receptor Core: First Crystallographic Evidence of a Water Cluster Confined within a Receptor-Anion Capsular Assembly Cryst. Growth Des. 2018, 18, 1818. 47. Manna, U.; Das, G Progressive Cation Triggered Anion Binding by Electron-Rich Scaffold: Case Study of a Neutral Tripodal Naphthyl Thiourea Receptor Cryst. Growth Des. 2018, 18, 3138. 48. Chutia, R.; Dey, S. K.; Das, G. Positional Isomeric Effect in Nitrophenyl Functionalized Tripodal Urea Receptors toward Binding and Encapsulation of Anions Cryst. Growth Des., 2013, 13, 883. 32 ACS Paragon Plus Environment

Page 32 of 35

Page 33 of 35 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


49. Basu, A.; Das, G. Encapsulation of a discrete cyclic halide water tetramer [X2(H2O)2]2-, X = Cl-/Br- within a dimeric capsular assembly of a tripodal amide receptor Chem. Commun., 2013, 49, 3997. 50. Hoque, M. N.; Das, G. Cationic Tripodal Receptor Assisted Formation of Anion and Anion– Water Clusters: Structural Interpretation of Dihydrogen Phosphate Cluster and Sulfate–Water Tetramer [(SO4)2–(H2O)2]4– Cryst. Growth Des. 2014, 14, 2962. 51. Hoque, M. N.; Das, G. Hydrated anion glued capsular and non-capsular assembly of a tripodal host. Solid state recognition of bromide-water [Br5-(H2O)6]5- and iodide-water [I2(H2O)4]2- clusters in cationic tripodal receptor CrystEngComm 2014, 16, 4447. 52. Chutia, R.; Das, G. Hydrogen and halogen bonding in a concerted act of anion recognition: F− induced atmospheric CO2 uptake by an iodophenyl functionalized simple urea receptor Dalton Trans. 2014, 43, 15628. 53. Basu, A; Das, G. A C3-Symmetric Tripodal Urea Receptor for Anions and Ion Pairs: Formation of Dimeric Capsular Assemblies of the Receptor during Anion and Ion Pair Coordination J. Org. Chem., 2014, 2647. 54. Dey, S. K.; Chutia, R.; Das, G. Oxyanion-Encapsulated Caged Supramolecular Frameworks of a Tris(urea) Receptor: Evidence of Hydroxide- and Fluoride-Ion-Induced Fixation of Atmospheric CO2 as a Trapped CO32- Anion Inorg. Chem,. 2012, 51, 1727. 55. Dey, S. K.; Das, G. Selective inclusion of PO43− within persistent dimeric capsules of a tris(thiourea) receptor and evidence of cation/solvent sealed unimolecular capsules Dalton Trans. 2012, 41, 8960. 56. Dey, S. K.; Das, G. A selective fluoride encapsulated neutral tripodal receptor capsule: solvatochromism and solvatomorphism Chem. Commun. 2011, 47, 4983. 57. Rajbanshi, A.; Wan, S.; Custelcean, R. Dihydrogen Phosphate Clusters: Trapping H2PO4− Tetramers and Hexamers in Urea-Functionalized Molecular Crystals Cryst. Growth Des. 2013, 13, 2233. 58. Gunnlaugsson, T.; Kruger, P. E.; Jensen, P.; Pfeffer, F. M.; Hussey, G. M. Simple naphthalimide based anion sensors: Deprotonation induced colour changes and CO2 fixation Tetrahedron Lett., 2003, 44, 8909.



59. Brooks, S. J.; Garcia-Garrido, S. E.; Light, M. E.; Cole, P. A.; Gale, P. A. Conformational Control of Selectivity and Stability in Hybrid Amide/Urea Macrocycles Chem. – Eur. J., 2007, 13, 3320. 60. Brooks, S. J.; Gale, P. A.; Light, M. E. Anion-binding modes in a macrocyclic amidourea Chem. Commun., 2006, 4344. 61. Ravikumar, I.; Ghosh, P. Efficient fixation of atmospheric CO2 as carbonate in a capsule of a neutral receptor and its release under mild conditions Chem Commun., 2010, 46, 1082. 62. Desiraju, G. R. Crystal engineering: a holistic view Angew. Chem, Int. Ed. 2007, 46, 8342. 63. McKinnon, J. J.; Mitchell, A. S.; Spackman, M. A. Hirshfeld Surfaces: A New Tool for Visualising and Exploring Molecular Crystals Chem.–Eur. J., 1998, 4, 2136. 64. Clark, T. E.; Makha, M.; Sobolev, A. N.; Raston, C. L. Cryst. Growth Des., 2008, 8, 890. 65. Hynes, M. J. EQNMR: a computer program for the calculation of stability constants from nuclear magnetic resonance chemical shift data. J. Chem. Soc., Dalton Trans. 1993, 311. 66. CrysAlisPro, version 1171.33.34d; Oxford Diffraction Ltd. [release 27-02-2009 CrysAlis 171. NET]. 67. SMART, SAINT, and XPREP; Siemens Analytical X-ray Instruments Inc., Madison, WI, 1995. 68. Sheldrick, G. M. SADABS, Program for area detector adsorption correction, Institute for Inorganic Chemistry; University of Göttingen, Germany, 1996. 69. Sheldrick, G. M. Acta Crystallogr., Sect. C: Crystal structure refinement with SHELXL Struct. Chem., 2015, 71, 3. 70. Mercury 2.3 Supplied with Cambridge Structural Database; CCDC: Cambridge, U.K., 20011. 71. Farrugia, L. J. ORTEP-3 for windows - a version of ORTEP-III with a graphical user interface (GUI) J. Appl. Crystallogr., 1997, 30, 565. 72. Spackman, M. A.; McKinnon, J. J. Fingerprinting intermolecular interactions in molecular crystals CrystEngComm, 2002, 4, 378. 73. Wolff, S. K.; Grimwood, D. J.; McKinnon, J. J.; Turner, M. J.; Jayatilaka, D.; Spackman, M. A. CrystalExplorer 3.1 (2013), University of Western Australia, Crawley, Western Australia, 2005–2013, http://hirshfeldsurface.net/CrystalExplorer.


Page 34 of 35

Page 35 of 35 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


For Table of Contents Use Only

Self-assemblies of positional isomeric linear bis-urea ligands with oxyanions/hydrated oxyanions: Evidences of F- and OH- induced atmospheric CO2 fixation Utsab Manna, Asesh Das and Gopal Das*

Effect of positional isomerism on entrapment of monomeric, dimeric and polymeric association of oxyanions/hydrated-oxyanions is observed within the neutral self-assemblies of linear bis-urea receptors.


Self-assemblies of positional isomeric linear bis-urea ligands with

Recommend Documents