Terminal substituent induced differential anion coordination and self

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Terminal substituent induced differential anion coordination and self-assembly: Case study of Flexible Linear Bis-Urea Receptors Biswajit Nayak, Senjuti Halder, and Gopal Das Cryst. Growth Des., Just Accepted Manuscript • DOI: 10.1021/acs.cgd.8b01934 • Publication Date (Web): 27 Feb 2019 Downloaded from http://pubs.acs.org on March 1, 2019

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Crystal Growth & Design

Terminal substituent induced differential anion coordination and self-assembly: Case study of Flexible Linear Bis-Urea Receptors Biswajit Nayak, Senjuti Halder and Gopal Das * Department of Chemistry, Indian Institute of Technology Guwahati, Assam-781039, India E-mail: [email protected]

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Abstract For a comprehensive analysis of host-guest binding propensity in their neutral form, three linear flexible bis-urea receptors (L1–L3) with different terminal substituents has been synthesized. It has been established that with the existence of electronwithdrawing or π-acidic phenyl substituents, it acts as a possible system that can proficiently coordinate with anions of diverse dimensions constantly initiated by the size of the countercations. The 3,5-bis-(trifluoromethyl) phenyl derived isomer (L1) can readily form cooperative neutral self-assemblies irrespective of the size the monovalent halides (viz. chloride, bromide and iodide anions) and non-cooperative neutral self-assemblies with planar divalent carbonate anion. The meta-isomer L2 captures spherical halides i.e. chloride and bromide in an isostructural way forming 1:2 host-guest assembly, whereas in isomeric parareceptor L3 show cooperative binding with chloride anion having coordination number 3. However, due to the more flexibility and less hydrophobicity of receptor L2 and L3 as comparison to receptor L1, successful crystallization of any oxyanion complexes through meta and para-isomer was not successful.


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1. Introduction In recent years the importance of anion coordination by supramolecular non-covalent interactions with synthetically designed self-assembled neutral abiotic receptors has arose into an active research field1-7. This has directed to an expanding development of studies in the area of molecular recognition with variable binding motifs affixed on a suitable platform. Designing the artificial receptor is one of the utmost collective approaches, because the –NH functions of the receptor interact via H-bonds with anionic guests. In natural systems, several H-bond donor groups comprising pyrrole, thiourea/urea and amide, numerous neutral abiotic receptors have been widely used for effective and discriminating anion coordination.8–12 In addition to the bare anion recognition, recognition of hydrated anions is of great interest to researchers because in natural and biological environments, the majority of the anions befall in their hydrated form in such as marine water and several ecosystems13. Because of through impact on frequent biomedical, industrial, and environmental applications as well as significant role in living organisms, non-hydrated anion recognition has also been encouraged subsequently14. In the recent past, a number of research groups15–28 have been studied halides and oxyanions binding by acyclic urea/thiourea receptors derived from various amine to understand the role of the functional group with different hydrogen bonding ability in anion recognition,29 in addition to the receptor conformation.30,31 Amongst the halides, chloride ion plays a substantial role in biological processes, such as transportation of organic solutes through the cell membrane or signal transduction. It is a dominant anion in biological extra-cellular fluid additionally a major component of oceans 32. Because of small size, high hydration enthalpy, high electronegativity along with its roles in biological processes as well as in the drinking water distillation process, recognition of the smallest fluoride ion is of special importance33. In biomineralised materials surrounded by planar oxyanions, one of the major component is carbonate, in particular, working as a buffer in blood, and the exoskeletons of radiolarian, whereas in the form of acetyl coenzyme A acetate anion is exploited by the organisms 34-35. Due to the increased ingestion of fossil fuels by automobiles, industries etc. that is the foremost cause of a major rise in atmospheric CO2 concentration and that eventually demands the effectual activation and fixation of atmospheric CO2 into green chemicals36-38.Up to now, several structurally preorganized neutral or protonated anion receptors having tripodal cavity with various -NH functionalities have been approved39-43. In literature, in comparison to tripodal receptors the use of dipodal receptors towards anion recognition 3 ACS Paragon Plus Environment


is common as per the dipodal receptor scaffolds comprise of less number of coordination sites and also they exhibit less flexibility and more rigidity. Nevertheless, few dipodal anion receptors having urea/thiourea functionalization resulting from preorganized diamine over isomeric aromatic diamines were stated in literature by different groups44-51and also from our group52,53. In our continuing effort, herein we synthesize a set of three positional isomeric, one 3, 5-bis (trifluoromethyl) phenyl and two nitro-phenyl functionalized linearly flexible bis-urea receptors in the arena of positional and electronic isomeric effect of receptors. Receptor L1 can readily form cooperative 1:2 neutral self-assemblies with smaller halides to larger halides (i.e. chloride, bromide and iodide anions) and non-cooperative 4:2 neutral self-assemblies with planar divalent carbonate anion. Fascinatingly the meta-isomer L2 binds with spherical halides i.e. chloride and bromide in orthorhombic space group P b c n with Z = 4 forming 1:2 host-guest complex. Whereas its isomeric receptor L3 show cooperative capture of Cl- anion having coordination no 3 in presence of tetrabutylammonium chloride.

2. Results and discussion 2.1 Design Rationale for Anion Coordination To coordinate with the anions of a specific geometry and size, designing a specific receptor comprising of various terminal substituents, it should have preorganized orientation of the functional group capable of forming hydrogen-bond. In dry acetonitrile medium, by reacting the diamine with 3,5-bis(trifluoromethyl)phenyl isocyanate, m-nitro phenyl isocyanate and p-nitro

Scheme 1. Molecular Design and Schematic Diagram of Urea Receptors L1, L2, and L3. 4 ACS Paragon Plus Environment

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phenyl isocyanate in a 1:2 molar ratios, the 4,4'-methylenedianiline based three bisurea isomeric receptors L1, L2 and L3 were synthesized in good yield respectively. With two urea functions, ligands L1, L2 and L3 having highly electron withdrawing possess a well-organized dipodal cavity appropriate for anion coordination through their hydrogen bonding. The four – CF3 electron-withdrawing groups and two nitro groups containing highly acidic bis-urea receptors L1, L2 and L3 reliably orient both the urea arms towards the recognition of planar and tetrahedral oxyanions along with the halides. The ligands and its corresponding complexes of anion can deliver acuity into the coordination discrepancies of oxyanions and halides with the ligands which is analyzed from the single crystal X-ray studies. The outcomes allied with the formation of the neutral host–guest assembly by the receptors L1, L2 and L3, and that are then related to the coordination environment of oxyanions and halides in neutral anion complexes is framed in Table 1. Table 1: Significant remark on efficient anion coordination of isomeric receptors: Size of Anions

Anion salt added

Neutral receptor anion complexes and anion coordination number

Receptor-anion assemblies

Spherical Chloride (Cl-)

n-TBACl

Chloride entrapped Complex. C.N. of chloride = 3 and 2

Spherical Bromide (Br-)

n-TBABr

Bromide captured complex. C.N. of Bromide = 3

complex with L1 (1a), L2 (2a) and L3 (3a) complex with L1 (2a) and L2 (2b)

Spherical Iodide (I-)

n-TBAI

Iodide seized complex. C.N. of Iodide = 3

complex with L1 (2c)

Planar Carbonate (CO32-)

n-TEAHCO3

Planar carbonate coordinated complex C.N. of

complex with L1 (1d)

carbonate = 16

2.2 Structural characterization of the complexes: The single crystal X-ray structural revelation of tetrabutylammonium or tetraethylammonium countercations triggered anion coordinated complexes of 4, 4’-Methylenedianiline centered bisurea receptors L1, L2 and L3 has been illustrated in the subsequent figures. The significant observation on systematic anion coordination of receptors has also been framed in Table 1. From DMSO, DMF, or mixture of solvent DMF/DMSO, in presence of π-acidic aromatic terminals having electron withdrawing group, the dipodal scaffold is adept to bind anionic guests in the solid state. Even after numerous trials from different solvent medium, it is difficult to get crystals of the free receptors L1, L2 and L3. Here we are easily separate the single crystals of spherical halides (chloride, bromide and fluoride) complexes from their tetrabutylammonium salts. Additionally, the planar carbonate complex is as well isolated from the exceptional hostguest assemblage of a flexible dipodal scaffold. From the structural interpretation of chloride (complex 1a, 2a, 3a), bromide (complex 1b), iodide (complex 3a) and carbonate (complex 1d) complexes of ligands L1, L2, and L3 , it clearly shows that the interactions (urea)N−H···(anion)A are mostly involved in binding strengthened by some noncovalent intermolecular interactions. 5 ACS Paragon Plus Environment


It also supports as the basis for effective crystallization of complexes which are unexplored and tempts the structure of host-guest assembly. 2.3 Comparative Structural Analysis of the Complexes of Chloride [(n-TBA) {(L1) (Cl)}] (1a), [(nTBA) {(L2) (Cl}] (2a) and [(n-TBA) {(L3) (Cl)}] (3a): From DMF solution mixture, in presence of excess tetrabutylammonium chloride salts the 1:2 receptor-chloride complexes 1a, 1b and 1c were obtained of L1, L2 and L3 respectively. Complex 1a and complex 3a develops in monoclinic crystal system having space group C2/c with Z = 4 and space group P2/c with Z = 2 respectively, whereas complex 1b crystallizes in orthorhombic space group P b c n with Z = 4. From structural elucidation it exposes that the asymmetric structural unit of all complexes contains one ligand unit, one chloride (Cl-) anion and its corresponding tetrabutylammonium (TBA) counteraction.

Figure 1. Single crystal X ray structures portraying (a) complex 1a showing H-bonding

coordination environment of chloride coordinated ligands, (b) complex 2a displaying H-bonding interactions of chloride-receptor assemblies by receptor L2, (c) environment of hydrogen bonding coordination of two chloride coordinated receptors in complex 3a, (d, e, f) the packing diagram of complex 1a , 2a, and 3a respectively as seen down along the crystallographic C-axis (g) spacefill demonstration of TBA-cation sealed chloride-receptor complex in 1a, (h) spacefill depiction of chloride coordinated of complex 2a and (i) spacefill illustration of complex 3a. 6 ACS Paragon Plus Environment

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Complex 1a evidently displays that the flexible receptor L1 unit coordinate with the two chlorides in a cooperative manner via four urea N−H··· Cl interactions (Figure 1a) where the two urea groups are positioned anti to each other in presence of anion. Moreover, additionally the same two Cl− is CTBA−H···Cl hydrogen bonded with two tetrabutyl cations in face to face manner respectively. Altogether the two tri-coordinated chloride bound 1:2 neutral receptor-anion assembly become stabilized by two weak CTBA−H···Ourea interactions (Supporting). Moreover, unlike complex 1a, structure of complex 2a evidently reveals that the two urea groups are positioned opposite to each other and each urea group binds to one chloride ion via two urea N−H··· Cl interactions and each Cl− is hydrogen bonded with one tetrabutyl cations via one weak CTBA−H···Ourea interactions forming 1:2 host-guest assembly (Figure 1b). Compare to complex 1a, 1:2 host-guest assembly of complex 2a gain extra strength by four CTBA−H···benzene and six weak CTBA−H···Ourea interactions. The x-ray crystal structure of complex 3a evidently shows that the two adjacent urea groups are anti to each other and coordinate to two chloride ions via four urea N−H··· Cl anion interactions forming 1:2 host-guest assembly (Figure 1c) and get stabilized by weak forces like by two CTBA−H···benzene and two CTBA−H···Ourea interactions. As mentioned in table 1 here the coordination no off anion in complex 1a and 2a is 3 where complex 3a is having coordination no 2. 2.4 Comparative Structural Analysis of the Bromide Complexes [(n-TBA) {(L1) (Br)}] (1b) and Iodide Complex [(n-TBA) {(L1) (I)}] (1c): The spherical bromide and iodide entrapped complex 1b and 1c crystallizes in similar monoclinic crystal system having space group I2/c (Z = 4). The asymmetric structural unit of complex 1b and 1c comprises of single L1 receptor unit, single anion and its corresponding nTBA counter-cation. Structural elucidation reveals that the binding behavior of both the complex is very much different. In case of complex 1b, from the crystal structure it clearly shows that the flexible dipodal receptor L1 unit coordinates to four bromide ions by different interactions, where receptor unit binds to two bromide ions via four strong N−H···Br interactions and additionally bromide is coordinated to two tetrabutyl counter cation and another two identical receptor unit via four C−H··· Br interactions (Figure 2a). But here interestingly in solid state the receptor unit binds to another two symmetrically distinct bromide ion via aryl C−H···Br interactions which is supported by four strong N−H··· Br interactions from another two similar receptor units and two C−H··· Br interactions from two n-TBA cations which formed a very beautiful 1D polymeric type of network (Figure 2c). So here it is difficult to find out the stoichiometry of the complex. Even in the solution state, we are trying to figure out the solution sate binding of Br anion, where there is a very less downfield shift of NHa and NHb protons, but no any evidence of aryl CH-proton shift (Figure S31, Supporting information).



Figure 2. Single crystal X ray structures showing (a) H-bonding interaction of cation sealed Br coordinated receptors in complex 1b, (b) representation of space-fill of bromide sealed by four pair of TBA cation (c) supramolecular polymeric 1D network of bromide –receptor of complex 1b (d) packing diagram of bromide-receptor complex as seen down along the crystallographic b axis. In Complex 1c the larger spherical anion binds to the receptor unit via four strong urea N−H···I interactions and two tetrabutyl C−H···I interactions, where the two adjacent urea group binds to one I- via two N−H··· I and one C−H··· I interactions constructing 1:2 iodide-receptor complex (Figure 3a). Moreover the 1:2 monovalent iodide complex gains more stability by two weak CTBA−H···Ourea interactions.

Figure 3. Single crystal X-ray structures (partial) illustrating (a) hydrogen bonding interaction of iodide coordinated receptors in complex 1c, (b) Space-fill representation of iodide sealed by 8 ACS Paragon Plus Environment

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four TBA cation (c) packing diagram of iodide-receptor complex as seen down along the crystallographic a-axis. 2.5 Carbonate Complexes [(n-TEA) {(L1) (CO3)}] (1d): A suitable colorless crystal of TEAHCO3 salt with receptor L1 was obtained from DMF which is basic in nature. In triclinic crystal system (space group-P1) with Z = 2, the pseudocapsular planar carbonate seized complex crystallizes and the asymmetric structural unit of this complex comprise of two symmetry-independent neutral urea receptor L1 unit, one half-occupied divalent carbonate anion, its equivalent two monovalent n-TEA+ counteractions and two DMF solvent molecules. Interestingly the flexible dipodal receptor cavity containing urea platform L1 comes a little bit closer and the adjacent urea moieties are flipping outward away from the cavity in opposite direction. Receptor L1 in presence of excess HCO3- forms 4:2 host-guest complexations via different number of H-bond sharing of non-cooperative urea groups from two types of



Figure 4. Sinlgle crystal X-ray crystal structures showing (a) coordination atmosphere of divalent carbonate anion coordinated 4:2 host receptor pseudocapsular assembly in complex 1d, (b) the enlarged view of hydrogen bonded carbonate ion and urea −NH protons of L1, (c) packing diagram of host-guest complex 1d as seen along the crystallographic b axis and (d) DMF solvated space-fill representation of divalent carbonate ion with receptor L1. symmetrically equivalent receptor units. In complex 1d, crystal structural clarification reveals that the two symmetrically identical divalent carbonate anions accepts 20 strong N-H⋯Cl H-bonding interactions between which 18 H-bonds are donated by urea −NH groups of the symmetrically distinct receptors (where each O atom accepts three H-bond) and two are contributed by ortho-phenyl−CH of the receptor(Figure 4a). Out of the 20 N-H⋯O hydrogen bonds, 6 H-bonds are donated by two symmetrically identical receptors and rest of the 16 Hbonds are donated by one urea arm of 4 similar receptor units. Prior to crystallization, in the solution the divalent carbonate anions were not present, and it arises from H-bonding activated proton transfer reaction in complex 1d (HCO3− anion has deprotonated in CO32-). The divalent carbonate anion coordinated 4:2 host receptor pseudocapsular assembly gains additional strength by CTBA−H···benzene and seven weak CTBA−H···Ourea interactions. 2.6 Complex Of Chloride [(n-TBA) {(L2) (Cl)}] (2b) and Complex Of Bromide [(n-TBA) {(L2) (Br)}] (2c): In presence of tetrabutylammonium salt, both bromide and chloride anion coordination inside the flexible dipodal cavity of receptor L2 has been succeeded from DMSO solution mixture, to apprehend the extent of assembly development with large homologous sphere-shaped anions. From structural analysis, it exposes that the 1:2 receptor-anion complexes 2a and 2b crystallize from the identical orthorhombic crystal system having space group P b c n with Z = 4.

Figure 5. Single crystal X-ray structures portraying (a) hydrogen bonding interaction of bromide coordinated receptors in complex 2b, (b) Space-fill representation of iodide sealed by four TBA cation (c) complex 2b showing the wave like packing diagram of host-guest assembly as seen down along the crystallographic a-axis.


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More fascinatingly, the isostructural nature of complex 2a and 2b were validated by the single crystal study and it clearly indicates that in the asymmetric unit of both these complexes contains one ligand, one halide anion and one tetrabutylammonium cation. As already discussed about complex 2a in the above, similar to this in complex 2b the two urea groups are situated reverse to each other with respect to the substituent and each urea group coordinate to one bromide ion through two strong urea N−H··· Br interactions and additionally Br− is hydrogen bonded with one tetrabutylammonium cations via one weak CTBA−H···Ourea interactions forming 1:2 host-guest assembly (Figure 5a). Compare to complex 2a, 1:2 bromidereceptor assembly acquire additional stability by two CTBA−H···benzene and six weak CTBA−H···Ourea interactions. In the solid state, a link of angle vs. distance (N–H⋯A vs. H⋯A) favors that the maximum no of the N–H⋯A interactions among anion with the receptors in equivalent complexes of host-guest are in strong H-bonding area of d (H⋯A) ≤ 2.6 Å and d (D⋯A) ≤3.2 Å. Of all individual anion complexes, the scattered plot of N–H⋯A angles vs. H⋯A distances (Figures S33, Supporting Information) also confirms that maximum no of these interactions shows strong H-bonding character. H-bond data table and crystal parameters, as well as refinement data of all complexes of anion 1a-1d, 2a-2b and 3a are tabulated in table 2 and (Table S1, Supporting Information). 2.7 Study of Free Receptor by Density Functional Theory (DFT). For a structural explanation of free dipodal receptors a DFT study was executed, after several attempts to get crystal of the free receptor L1, L2 and L3 in different conditions from various solvents, but we are not able to nurture good quality crystals of bis-urea based

Figure 6. Molecular architecture of the receptors and optimized geometry of the free receptors L1, L2 and L3 using B3LYP/6-31+G(d,p) basis set. receptors. The DFT study reveals that in case of receptor L1 both the adjacent urea groups are in syn position showing complete cooperativity of urea −NH protons, whereas, in case of receptor L2 and L3, both the adjacent urea groups are in opposite 11 ACS Paragon Plus Environment


direction i.e. anti to each other showing non-cooperativity (Figure 6). Using the B3LYP method DFT optimizations were carried out with the 6-31+G (d,p) basis set. 2.8 Solution-State Anion-Binding Studies: To inspect the receptor-anion binding approach in the solution, here we have performed quantitative as well as qualitative proton (1H) NMR analysis of all host-guest complexes along with NMR-titration investigations in dimethyl sulfoxide-d6 at room temperature. It is nowadays reasonably evident that the performance of receptors in dilute solution is indeed quite diverse from their actions in the solid state. In the preliminary studies of L1, L2 and L3, where we found out that for urea −NH protons (−NHa and −NHb) most


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Figure 7. Expanded proton NMR spectra of (a) L1 upon titration with n-TBACl and (b) titration of L2 with n-TBACl in DMSO-d6. distinguishable changes have been observed, demonstrating that in solution the interaction between anion and the receptor is provided by the suitable sites of urea −NH functions. As demonstrated from the solid-state, with individual Cl- salts we have also executed proton NMR experiments in solution, in qualitative as well as in quantitative way, and compared to free receptors L1, L2 and L3 Figure S32 signifies the maximum recognizable change of urea −NH protons in host-guest complexes in solution. The 1H NMR spectra of free receptor L1 show urea –NH signals at 8.90 and 9.33 ppm, L2 shows urea –NH signals at 8.75 and 9.16 ppm and L3 shows urea –NH signals at 8.84 and 9.39 ppm. The 1H NMR spectra of chloride complexes 1a, 2a and 3a independently displays a huge downfield shift of urea hydrogen as compared to peaks of urea –NH of free ligands L1, L2 and L3 which indicates the hydrogen bonding of chloride with the receptors (Figure S32, Supporting information).On the other hand, complexes of the bromide (1b, 2b), and iodide (1c) displays slight downfield shift of urea –NH protons (Figure S32, Supporting information) demonstrating that in the solution state the interaction between these anions are dynamically adverse, and that is not a very rare case in the literature. Using aliquots of n-TBACl salt, we have executed proton (1H) NMR titration investigation of free receptor L1 consequently following the qualitative studies, and that shows immediate huge downfield shift of both urea −NH signals (Δδ −NHa = 0.38 ppm and −NHb = 0.68 ppm) following subsequent addition of 0.1 equiv Cl− ion (Figure 7a), which is exactly related to the proton NMR data of complex of chloride (Figure S32, Supporting Information). Correspondingly, in titration experiments the slow addition of tetrabutylammonium chloride salts to the solutions of receptor L2 directed to a downfield shift of urea –NH protons (Δδ −NHa = 0.42 ppm and −NHb = 0.56 ppm) comply with large broadening (Figure 7b) respectively, and that turn out to be very alike to the proton NMR data of chloride complex 2a. Subsequently in free urea ligand L3, the regular addition of Cl- salts to the receptor solutions of L3 in titration headed to an average downfield shift of urea – NH protons (Δδ −NHa = 0.53 ppm and −NHb = 0.61 ppm) trailed by large broadening (Figure 8) individually. Note that in chloride titrations, significantly larger shift of –NHb compared to −NHa signals suggests that in solution the chloride anions are more strongly bound to −NHb rather than −NHa protons of the urea receptor.



Figure 8. Extended proton NMR spectra of L3 upon titration with n-TBACl in DMSO-d6. 2.9 Self-aggregation microscopic studies of the Ligand and its chloride complexes: A logical solid state analysis of all the Cl complexes exhibited the presence of various noncovalent interactions such as H-bonding and C−H··· anion-coordination. Thus, we became fascinated in investigating the morphological behavior of the free receptor and Cl complexes in solution. To do so, an extensive FESEM imaging study was conducted with the freshly prepared DMF solution to inspect the topographical nature of the supramolecular polymeric assembly among the three ligands as well as the deviations in presence of Cl-. Interestingly, it was observed that the morphology of the different complexes was vastly different, even different than that of the free ligand. Excitingly, FESEM for L1, L2 and L3 portray three totally different kinds of morphology which in turn destroyed after treatment with Cl-. It was observed that the action of Cl- upon L2 and L3 were more prominent than L1 (Fig 9). The network type morphology for L2 and microplates for L3 became disappeared upon interaction with Cl- whereas for L1, the dense branched like structure got thinly distributed. For example, when L3 (in approximately 0.5 × 10−3 M DMF solution) was treated with Cl- (1:1), a morphologically micro plate-like (Fig. 9c) assembly of receptor L3 was destroyed (Fig. 9f). For clarification of image different scales bar are used in Fig 9.


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Figure 9. FESEM image of (a) network type assembly of receptor L1 and (b) L2 (c) micro plate-like assembly of receptor L3 and (d, e, f) FESEM image of receptors after addition of Clat room temperature. In order to confirm the existence of hydrogen bonded halides together with oxyanion via the urea −NH protons of the dipodal receptors L1, L2 and L3 in all anion complexes, FT-IR analysis in solid state was performed. In comparison to the free ligands (3116-3145 cm−1), in each instance the urea −NH stretching frequency of all the complexes display an normal shift of 50−90 cm−1 followed by consequent broadening of the peak, and it validate the presence of solid N−H···A H-bonds among anion and the receptors in analogous complexes. Furthermore, in each complex a distinguishable signal at around 2860−2950 cm−1 has also been found, which confirmed the presence of the stretching frequencies(C-H) of the tetrabutylammonium cation groups. 3. CONCLUSIONS Briefly, we have expansively established the consistent solid-state halide as well as oxyanion binding of substituted neutral dipodal receptors L1, L2, and L3, in presence πacidic, electronegative containing aryl substituted terminals. From single-crystal X-ray study, it confirms that the bis-urea receptors L1, L2, and L3 fully coordinated with the small spherical chloride within its dimeric cavity. The receptor L1 can readily form a cooperative neutral self-assemblies with smaller halides to larger halides i.e. chloride, bromide and iodide as well as binds with planar carbonate ion. The meta isomer, L2 forms 1:2 host-guest assembly with chloride and bromide in same space group, whereas 15 ACS Paragon Plus Environment


as its isomeric receptor L3 forms cooperative complex with chloride ion only. Anion binding studies in solution accompanied by 1H-NMR titration analysis and FESEM imaging study also supported the solid-state results, especially for spherical chloride. Successively, the flexible molecular structure of ligands L1, L2, and L3 consent the shape along with the preorganized cavity of the receptor to add directionality to the entire coordination and guide the recognition process. In solid state, evidence of this type of halides along with oxyanion binding with highly electron-withdrawing groups dipodal moiety specifically would be very cooperative to supramolecular scientists to comprehend the neutral receptor-anion assembly development. 4. Experimental Section 4.1. Materials and methods. All the reagents and solvents used were got from commercial sources and used as received. 4,4'-Diaminodiphenylmethane, 4-nitrophenyl isocyanate, 3-nitrophenylisocyante, 3,5bis(trifluoromethyl) phenyl isocyanate and from Sigma-Aldrich, all the all tetrabutylammonium and tetraethylammonium salts were bought. For crystallization experiments and synthesis, solvents were bought from Merck, India. On 400 MHz and 600 MHz NMR instrument, proton (1H) NMR spectra were recorded, and using tetramethylsilane [Si (CH3)4] or a residual solvent peak as a reference chemical shifts were recorded in ppm scale. FESEM imaging studies were performed by drop (2 µl) cast method on glass plates covered with Al-foil using Gemini 300 FESEM (Carl Zeiss). In methanol medium mass spectrum (ESI-MS) of L1, L2 and L3 was recorded. The IR spectra of dried samples of the receptors and its corresponding complexes of anion were recorded on a Perkin-Elmer FT-IR spectrometer by KBr disks in the range 4000–450 cm-1. Using a minimum volume of acetonitrile, the crystals of all anion complexes of L1, L2 and L3 were washed, followed by diethyl ether, and allowed to dry at room temperature. In Dimethyl sulfoxide-d6 at 298 K, binding stoichiometries and binding constants were achieved by proton NMR (600 MHz) titrations of receptors with tetrabutylammonium salts of corresponding anions. Preliminary concentrations were [anion]0 - 50 mM and [ligand]0 -10 mM. At room temperature, all titration was executed by 10–12 measurements and for an internal reference, the peak of solvent in Dimethyl Sulfoxide-d6 (2.50 ppm) was used. 4.1.2. Refinement parameter details of crystallographic data: The details of the refinement parameter of crystallographic data collection for all the anion complexes 1a, 1b, 1c, 1d, 2a, 2b and 3a of urea ligand L1, L2 and L3, are furnished in Table 2, and all of the above data have been dropped to the CCDC. In each case, a suitable size crystal isolated carefully was dipped in silicone oils followed by mounting on glass fiber tip. With Supernova, a single source at offset, the X ray crystallographic intensity data were collected ,Eos diffractometer using Mo−Kα radiation (λ = 0.71073 Å) equipped with a CCD area detector. 16 ACS Paragon Plus Environment

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With the help of SAINT54 and XPREP software, the data integration and reduction were undertaken, and multi-scan empirical absorption corrections were applied to the data via the program SADABS55. All the structures were solved through direct methods by employing SHELXTL-2014, and subjected to refinement on F2 by the full matrix least-squares technique using the SHELXL-2014 program package56 followed by MERCURY 2.357 for generation of the graphics for structural illustrations. All the non-hydrogen atoms were refined anisotropically while the hydrogen atoms attached to all the carbon atoms of respective crystal structures were geometrically fixed and the positional and temperature factors are refined isotropically. The hydrogen atoms are placed on a difference Fourier map and refined depending on their possibilities but in other cases the hydrogen atoms are geometrically fixed. 4.2.1 Receptor L1: The 4,4'-Diaminodiphenylmethane based flexible dipodal para-nitro phenyl functionalized bisurea receptor L1 (Scheme 1) was synthesized by following procedure. At room temperature to a 30 ml acetonitrile solution of 4,4'-Diaminodiphenylmethane (0.906 g, 6.0 mmol), 3,5bis(trifluoromethyl) phenyl isocyanate (0.292 g, 2.0 mmol) solutions was added dropwise under vigorous stirring for 24hr. A yellow precipitate was filtered off after overnight stirring and washed many times with THF and acetonitrile and then allowed to dry in vacuum. The yellow precipitate was dried in air and characterized by FT-IR and NMR. Yield = 82%, 1H NMR (DMSOd6, 600 MHz) δ (ppm): 3.84 (s, 1H, CH2), 7.14-7.16 (d, 4H, ~12 Hz, HAr), 7.38-7.40 (d, 4H, ~12 Hz, HAr), 7.62 (s, 2H, HAr), 8.12 (s, 4H, HAr), 8.90 (s, 2H, NHa), 9.33 (s, 2H, NHb).13C NMR (DMSO-d6, 150 MHz) δ (ppm): 114.7, 118.5, 119.6,123.0, 124.7, 129.6, 131.2, 136.2, 137.4, 142.5, 152.9. IR spectra: broad band at 3314 cm-1(N–H), 3116 cm-1(C-H), 2926 cm-1(C-H), 1556 cm-1(C=C),1660 cm-1(C=O). Calculated Mass: 708.1395, obtained ESI mass: m/z 726.1779 (L1+NH4+). 4.2.2 Receptor L2: By similar process alike L1, the receptor L2 was synthesized only by altering the initial material meta-nitrophenyl isocyante (1.098 g, 6.0 mmol) in place of 3,5-bis(trifluoromethyl) phenyl isocyanate. But here a whitish precipitate was obtained. Yield = 85%,1H NMR (DMSO-d6, 600 MHz) δ (ppm): 3.84 (s, 1H, CH2), 7.14-7.15 (d, 4H, ~6 Hz, HAr), 7.38-7.39 (d, 4H, ~6 Hz, HAr), 7.547.57 (t, 2H, ~6 Hz, HAr), 7.68-7.70 (d, 4H, ~12 Hz, HAr), 7.80-7.82 (d, 4H, ~12 Hz, HAr), 8.55 (s, 2H, HAr), 8.75 (s, 2H, NHa), 9.16 (s, 2H, NHb).13C NMR (DMSO-d6,150 MHz) δ (ppm): 112.4, 116.6, 119.2,124.7, 129.6, 130.6, 136.2, 137.7, 141.7, 148.7, 152.9. IR spectra: broad band at 3315 cm1(N–H), 3090 cm-1 (C-H), 2924 cm-1 (C-H), 1557 cm-1(C=C),1646 cm-1(C=O), 1430 cm-1(NO -asym), 2 -1 -1 1313 cm (NO2-sym), 1238 cm (C−N). Calculated Mass: 526.1601, obtained ESI mass: m/z 527.1704 (L2+H+), m/z 544.1958 (L2+NH4+). 4.2.3 Receptor L3: 17 ACS Paragon Plus Environment


Alike L1, receptor L3 was synthesized by changing the starting material p-nitro phenyl isocyante in place of m-nitro phenyl isocyante. Yield = 79%, 1H NMR (600 MHz,) δ (ppm): 3.84 (s, 1H, CH2), 7.15-7.16 (d, 4H, ~6 Hz, HAr), 7.38-7.39 (d, 4H, ~6 Hz, HAr), 7.67-7.68 (d, 4H, ~6 Hz, HAr), 8.178.19 (d, 4H, ~12 Hz, HAr), 8.84 (s, 2H, NHa), 9.39 (s, 2H, NHb).13C NMR (DMSO-d6,150 MHz) δ (ppm): 117.8, 119.3, 125.6,129.4, 136.4, 137.5, 141.3, 146.9, 152.4. IR spectra: broad band at 3341 cm-1(N–H), 3088 cm-1(C-H), 2923 cm-1(C-H), 1596 cm-1(C=C),1650 cm-1(C=O), 1411 cm-1 (NO2-asym), 1332 cm-1(NO2-sym), 1237 cm-1(C−N). Calculated Mass: 526.1601, obtained ESI mass: m/z 527.1705 (L3+H+). 4.3 Crystallization of receptor complexes: 4.3.1 Spherical chloride complex [(n-TBA {(L1) (Cl)}] (1a): In 5ml DMSO, by adding an excess (10 eqv.) of TBACl to the solution of L1 (100mg, 0.225 mmol), complex 1a was prepared. Under stirring, after addition of tetrabutylammonium chloride, the solution was filtered and at room temperature, it was allowed for slow evaporation. After 15-20 days block colorless crystals of complex 1a were acquired. Yield 67%.1H NMR (600 MHz, DMSOd6) δ (ppm): 0.92-0.95 (t, 12H, ~18 Hz, CH3-TBA), 1.28-1.34 (m, 8H, CH2-TBA), 1.54-1.59 (m, 8H, CH2 -TBA), 3.15-3.18 (t, 8H, ~ 18 Hz, N+- CH2-TBA), 3.84 (s, 1H, CH2), 7.14-7.16 (d, 4H, ~12 Hz, HAr), 7.38-7.40 (d, 4H, ~12 Hz, HAr), 7.62 (s, 2H, HAr), 8.12 (s, 4H, HAr), 9.07 (s, 2H, NHa), 9.63(s, 2H, NHb). IR spectra: 3187 cm-1(N–H), 3187 cm-1(C-H), 2963 cm-1 (C-H), 1671 cm-1(C=O), 733 cm1(C-Cl). 4.3.2 Bromide complex [(n-TBA {(L1) (Br)}] (1b): By adding an excess of TBABr (10 equiv) into the 5 mL DMF solution of L1 (100 mg, 0.142 mmol), the bromide coordinated of L1 as complex 1b was conquered. Under stirring, after an excess addition of tetrabutylammonium bromide, the clear solution was filtered and at room temperature, it was allowed for slow evaporation. By filtration the crystal of complex 1b was separated and it was allowed to dry at room temperature before characterization by FT-IR and NMR analyses. Yield: 65−65% established on L1. 1H NMR (600 MHz, DMSO-d6) δ (ppm): 0.920.95 (t, 12H, ~18 Hz, CH3-TBA), 1.28-1.34 (m, 8H, CH2-TBA), 1.54-1.59 (m, 8H, CH2-TBA), 3.153.18 (t, 8H, ~ 18 Hz, N+-CH2-TBA), 3.84 (s, 1H, CH2), 7.14-7.16 (d, 4H, ~12 Hz, HAr), 7.38-7.40 (d, 4H, ~12 Hz, HAr), 7.63 (s, 2H, HAr), 8.12 (s, 4H, HAr), 8.93 (s, 2H, NHa), 9.38 (s, 2H, NHb). IR spectra: 3233 cm-1(N–H), 3183 cm-1 (C-H), 2965 cm-1 (C-H), 1708 cm-1 (C=O), 681 cm-1(C-Br). 4.3.3 Larger iodide complex [(n-TBA {(L1) (I)}] (1c): In the presence of excess TBAI (10 equiv) suitable crystals of the monovalent iodide complex 1c was conquered by slow evaporation of a DMF solution mixture (5 mL) of L1 (100 mg, 0.142 mmol). By filtration, the crystals (colorless) of 1:2 receptor−anion complex 1c thus obtained 18 ACS Paragon Plus Environment

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were separated and before characterization by FT-IR and NMR analyses, it was dried at room temperature. Yield: 80% established on L1. 1H NMR (DMSO-d6, 600 MHz) δ (ppm): 1.28-1.34 (m, 8H, CH2-TBA), 1.54-1.59 (m, 8H, CH2-TBA), 3.15-3.18 (t, 8H, ~ 18 Hz, N+-CH2-TBA), 3.84 (s, 1H, CH2), 7.14-7.16 (d, 4H, ~12 Hz, HAr), 7.38-7.40 (d, 4H, ~12 Hz, HAr), 7.62 (s, 2H, HAr), 8.12 (s, 4H, HAr), 8.90 (s, 2H, NHa), 9.33 (s, 2H, NHb). IR spectra : 3264 cm-1(N–H), 3152 cm-1(C-H), 2968 cm1(C-H), 1709 cm-1(C=O), 682 cm-1(C-I). 4.3.4 Planar carbonate complex [(n-TBA {(L1) (CO3)}] (1d): By adding excess tetraethylammonium bicarbonate salts (∼10 equiv.) into 5 mL mixture of DMF/DMSO solutions of 100 mg of L1 in a small glass vial, the carbonate complex 1d was successfully conquered. After addition of carbonate salts, the resulting solution was stirred for half an hour and for slow evaporation, it was exposed open to the atmosphere. Within 15–20 days, the crystal (colorless) of divalent carbonate encapsulated complex of receptor L1 by Hbonding activated proton transfer reaction was obtained, separated by filtration and before characterization by FT-IR and NMR analyses, it was dried at room temperature. Yield: 70% established on L1. 1H NMR (DMSO-d6, 600 MHz) δ (ppm): 3.84 (s, 1H, CH2), 7.14-7.16 (d, 4H, ~12 Hz, HAr), 7.38-7.40 (d, 4H, ~12 Hz, HAr), 7.62 (s, 2H, HAr), 8.12 (s, 4H, HAr), 8.90 (s, 2H, NHa), 9.33 (s, 2H, NHb). 13C NMR (DMSO-d6, 150 MHz) δ (ppm): 7.5, 52.1, 117.4, 118.5, 119.7, 122.1, 123.7, 124.8, 129.2, 131.2, 141.0, 141.9, 154.4, and 164.2. IR spectra: 3259 cm-1(N–H), 3183 cm-1 (C-H), 2923 cm-1(C-H), 1703 cm-1(C=O). 4.3.5 Chloride complex [(n-TBA {(L2) (Cl)}] (2a): In 5ml DMSO by adding an excess (10 eqv.) of TBACl to the solution of L2 (100mg, 0.225 mmol), complex 2a was prepared. Under stirring, after an excess addition of tetrabutylammonium chloride, the clear solution was filtered and at room temperature, it was allowed for slow evaporation. Colorless plate crystals of complex 2a were obtained after 15-20 days. Yield: 72%.1H NMR (600 MHz, DMSO-d6) δ (ppm): 0.92-0.95 (t, 12H, ~18 Hz, CH3 -TBA), 1.28-1.34 (m, 8H, CH2-TBA), 1.54-1.59 (m, 8H, CH2-TBA), 3.15-3.18 (t, 8H, ~ 18 Hz, N+- CH2-TBA), 3.84 (s, 1H, CH2), 7.14-7.15 (d, 4H, ~6 Hz, HAr), 7.38-7.39 (d, 4H, ~6 Hz, HAr), 7.54-7.57 (t, 2H, ~6 Hz, HAr), 7.68-7.70 (d, 4H, ~12 Hz, HAr), 7.80-7.82 (d, 4H, ~12 Hz, HAr), 8.55 (s, 2H, HAr), 8.97 (s, 2H, NHa), 9.44 (s, 2H, NHb). IR spectra: 3212 cm-1(N–H), 3172 cm-1(C-H), 2963 cm-1(C-H), 1703 cm-1(C=O), 737 cm-1(C-Cl). 4.3.6 Bromide complex [(n-TBA {(L2) (Br)}] (2b): By slow evaporation of a 5 mL basic DMSO solution mixture of L2 (100 mg, 0.142 mmol), in the presence of TBABr (10 equiv) the monovalent bromide complex 2b was obtained from a glass vial as suitable crystals for single crystal X-ray analysis. By filtration, the crystals (colorless) of 1:2 receptor-anion complex 2b thus obtained were separated and dried at room temperature 19 ACS Paragon Plus Environment


before characterization by FT-IR and NMR analyses. Yield: 80% established on L2. NMR-1H (DMSO-d6, 600 MHz) δ (ppm): 0.92-0.95 (t, 12H, ~18 Hz, CH3-TBA), 1.28-1.34 (m, 8H, CH2-TBA), 1.54-1.59 (m, 8H, CH2-TBA), 3.15-3.18 (t, 8H, ~ 18 Hz, N+-CH2-TBA), 3.84 (s, 1H, CH2), 7.14-7.15 (d, 4H, ~6 Hz, HAr), 7.38-7.39 (d, 4H, ~6 Hz, HAr), 7.54-7.57 (t, 2H, ~6 Hz, HAr), 7.68-7.70 (d, 4H, ~12 Hz, HAr), 7.80-7.82 (d, 4H, ~12 Hz, HAr), 8.55 (s, 2H, HAr), 8.82 (s, 2H, NHa), 9.24 (s, 2H, NHb). IR spectra: 3214 cm-1(N–H), 3172 cm-1(C-H), 2963 cm-1 (C-H), 1702 cm-1(C=O), 737 cm-1 (C-Br). 4.3.7 Chloride complex [(n-TBA {(L3) (Cl)}] (3a): In a small glass vial by adding TBACl (10 equiv) into the DMF solution (5 mL) of L3 (100 mg, 0.142 mmol), the chloride coordinated of L3 as complex 3a was achieved. After the excess addition of tetrabutylammonium chloride, the solution mixture was stirred for about 30 min and for slow evaporation, it was kept back in an exposed atmosphere at normal room temperature. By filtration, the crystals of complex 3a was separated and dried before characterization by FT-IR and analyses. Yield: 65−70% established on L3. NMR -1H (DMSO-d6, 600 MHz) δ (ppm): 0.92-0.95 (t, 12H, ~18 Hz, CH3-TBA), 1.28-1.34 (m, 8H, CH2-TBA), 1.54-1.59 (m, 8H, CH2-TBA), 3.15-3.18 (t, 8H, ~ 18 Hz, N+- CH2-TBA), 3.84 (s, 1H, CH2), 7.15-7.16 (d, 4H, ~6 Hz, HAr), 7.38-7.39 (d, 4H, ~6 Hz, HAr), 7.67-7.68 (d, 4H, ~6 Hz, HAr), 8.17-8.19 (d, 4H, ~12 Hz, HAr), 9.05 (s, 2H, NHa), 9.64 (s, 2H, NHb). IR spectra: 3213 cm-1 (N–H), 3172 cm-1 (C-H), 2963 cm-1(C-H), 1702 cm-1(C=O), 663 cm1(C-Cl). Acknowledgments Through grant 01/2727/13/EMR-II and SR/S1/OC-62/2011, New Delhi, India, this work was supported by CSIR and SERB. CIF IIT Guwahati and DST FIST for providing the instrument facilities. For fellowship BN and SH thanks IIT Guwahati. Supplementary Material Characterization data of all ligand L1-L3 and its anion complexes 1a-1d, 2a-2b and 3a, figures, proton-NMR titration plots, plots of distance vs angle, job’s plot, H-bonding table and DFT data. References 1. Bowman-James, K. Alfred Werner Revisited: The Coordination Chemistry of Anions Acc. Chem. Res. 2005, 38, 671. 2. Gale, P. A.; Garcia-Garrido, S. E.; Garric, Anion receptors based on organic frameworks: highlights from 2005 and 2006. J. Chem. Soc. Rev. 2008, 37, 151. 3. Themed issue: Supramolecular chemistry of anionic species. Chem. Soc. Rev. 2010, 39, 3581. 4. Schottel, B. L.; Chifotides, H. T.; Dunbar, K. R. Anion-pi interactions Chem. Soc. Rev. 2008, 37, 68.


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24. Nayak, B.; Manna, U.; Das G.; Consistent binding aptitude of halides and oxyanions via cooperative vs. non-cooperative binding modes by neutral napthyl bis-urea receptors. ChemistrySelect 2018, 1, 1-8. 25. Busschaert, N.; Wenzel, M.; Light, M. E.; Iglesias-Hernandez, P.; Perez-Tomas, R.; Gale, P. A.; Structure–activity relationships in tripodal transmembrane anion transporters: The effect of fluorination. J. Am. Chem. Soc., 2011, 133, 14136. 26. Basu, A.; Das, G.; Encapsulation of divalent tetrahedral oxyanions of sulfur within the rigidified dimeric capsular assembly of a tripodal receptor: first crystallographic evidence of thiosulfate encapsulation within neutral receptor capsule. Dalton Trans. 2012, 41, 10792. 27. Dey, S. K.; Das, G.; Encapsulation of trivalent phosphate anion within a rigidified π-stacked dimeric capsular assembly of tripodal receptor. Dalton Trans. 2011, 40, 12048. 28. 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. 29. V. S. Bryantsev and B. P. Hay, Influence of Substituents on the strength of aryl C−H···Anion hydrogen bonds. Org. Lett. 2005, 7, 5031. 30. 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. 31. Lakshminarayanan, P. S.; Ravikumar, I.; Suresh, E.; Ghosh, P.; Encapsulation of halides within the cavity of a pentafluorophenyl-substituted tripodal amine receptor. Inorg. Chem. 2007, 46, 4769. 32. A systematic review of the efficacy and safety of fluoridation, National Health and Medical Research Council, Australian Government, 2007, available at: http://www.nhmrc.gov.au/. 33. Biochemistry of Halogens and Inorganic Halides, ed. K. L. Krik, Plenum Press, New York, 1991. 34. 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. 35. Milby, T. H.; Baselt, R. C.; Hydrogen sulfide poisoning: Clarification of some controversial issues. Am. J. Ind. Med. 1999, 35, 192. 36. Caldeira, K.; Jain A. K.; Hoffert, M. I.; Climate sensitivity uncertainty and the need for energy without CO2 emission. Science. 2003, 299, 2052. 37. Aresta, M.; Dibendetto, A.; Utilisation of CO2 as a chemical feedstock: opportunities and challenges. Dalton Trans. 2007, 2975. 38. Olah, G. A.; Goeppert, A.; Prakash, G. K. S.; Chemical recycling of carbon dioxide to methanol and dimethyl ether: from greenhouse gas to renewable, environmentally carbon neutral fuels and synthetic hydrocarbons. J. Org. Chem. 2009, 74, 487. 39. Dutta, R.; Ghosh, P.; Recent developments in anion induced capsular self-assemblies. Chem. Commun. 2014, 50, 10538 40. 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. 41. 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. 22 ACS Paragon Plus Environment

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42. Manna, U.; Das, G.; Halo-methylphenyl substituted neutral tripodal receptors for cation-assisted encapsulation of anionic guests of varied dimensionality. CrystEngComm, 2018, 20, 3741. 43. Manna, U.; Das, G.; CrystEngComm, Cyclic (H2O)6 confined hexameric host–guest assemblies and aerial CO2 fixation by electron-rich neutral urea/thiourea scaffolds. 2018, 20, 3741. 44. Brooks, S. J.; Gale, P. A.; Light, M. E.; Carboxylate complexation by 1,1′-(1,2-phenylene)bis(3phenylurea) in solution and the solid state. Chem. Commun. 2005, 4696. 45. Brooks, S. J.; Gale, P. A.; Light, M. E.; ortho-Phenylenediamine bis-urea–carboxylate: a new reliable supramolecular synthon. CrystEngComm, 2005, 7, 586. 46. Brooks, S. J.; Edwards, P. R.; Gale, P. A.; Light, M. E.; Carboxylate complexation by a family of easyto-make orthophenylenediamine based bis-ureas: studies in solution and the solid state New J. Chem, 2006, 30, 65. 47. 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 ortho-phenylenediamine-based bisureas. Chem. Sci. 2013, 4, 103. 48. 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. 49. R. Li,Y. Zhao, S. Li, P. Yang, X. Huang, X-J. Yang, and B. Wu Tris chelating phosphate complexes of bis(thio)urea ligands. Inorg. Chem. 2013, 52, 5851. 50. Xu, G.; Tarr, M. A.; A novel fluoride sensor based on fluorescence enhancement. Chem. Commun. 2004, 1050. 51. 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. 52. 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, 12, 7163. 53. 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. 54. M. Sheldrick, SAINT and XPREP, 5.1 ed., Siemens Industrial Automation Inc., Madison, WI, 1995. 55. Sheldrick G. M., SADABS, empirical absorption Correction Program, University of Göttingen, Göttingen, Germany, 1996. 56. Sheldrick G. M., Acta Crystallogr., Sect. C: Crystal structure refinement with SHELXL Struct. Chem., 2015, 71, 3. 57. Mercury 2.3 Supplied with Cambridge Structural Database CCDC: Cambridge, U.K., 20011.


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

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Table 2: Crystal Parameters and Refinement Data of anion complexes: Formula

C63 H92 Cl2 F12 N6 O2

C63 H92 Br2 F12 N6 O2

C63 H92 F12 I2 N6 O2

C85 H93 F24 N12 O9

C59 H94 Cl2 N8 O6

C59 H94 Br2 N8 O6

C59 H94 Cl2 N8 O6

CCDC

1871250

1871249

1871251

1871252

1871254

1871253

1871255

Fw

1264.33

1353.23

1447.23

1882.71

1082.32

1171.22

1082.32

Crystal system

monoclinic

monoclinic

monoclinic

triclinic

orthorhombic

orthorhombic

monoclinic

Space group

C 2/c

I 2/c

I 2/c

P1

Pbcn

Pbcn

P 2/c

a/Å

43.914(3)

19.7327(10)

20.3365(9)

12.2455(10)

37.9221(17)

38.047(2)

19.3291(18)

b/Å

8.7711(5)

8.9156(9)

9.0636(4)

17.2779(13)

9.7702(4)

9.7801(12)

9.7601(14)

c/Å

19.3487(13)

40.391(3)

39.9667(19)

23.5317(17)

17.1521(8)

17.2351(16)

16.9098(15)

α/

o

90.00

90.00

90.00

99.612(5)

90

90

90

o

β/

111.830(4)

95.951(5)

97.865(4)

98.177(4)

90

90

93.717(9)

γ/o

90.00

90.00

90.00

105.591(4)

90

90

90

V/Å3

6918.2(8)

7067.6(9)

7297.4(6)

4635.6(6)

6355.0(5)

6413.3(10)

3183.4(6)

4

4

4

2

4

4

2

1.214

1.221

1.317

1.349

1.213

1.129

Z Dc/g cm

-3

1.131

μ Mo Kα/mm

0.186

0.328

0.934

0.121

0.154

1.315

0.154

T/K

298(2)

298(2)

298(2)

298(2)

298(2)

298(2)

298(2)

θ max.

20.0610

20.9020

20.6790

18.90

18.56

24.2690

20.0910

Total no. of

28126

19300

22096

65643

53409

21465

13860

8461

20997

7321

7393

7255

4014

6419

2544

3469

2301

-1

reflections Independent

8165

8172

reflections Observed reflections

6326

2834

Parameters refined

389

397

388

1191

344

344

344

R1, I > 2σ(I)

0.1012

0.0891

0.0643

0.0926

0.0951

0.0637

0.0985

wR2 (all data)

0.2489

0.2636

0.2365

0.2165

0.2636

0.2786

0.2570

GOF (F2)

1.143

1.043

1.163

1.118

0.864

1.024

0.971


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For Table of Contents Use Only Terminal substituent induced differential anion coordination and self-assembly: Case study of Flexible Linear Bis-Urea Receptors Biswajit Nayak, Senjuti Halder and Gopal Das *

Efficient binding abilities of flexible neutral linear bis-urea receptors towards anions and its aggregation studies is solid as well as in solution.


Terminal substituent induced differential anion coordination and self

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