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Dual guest [(Chloride)3-DMSO] encapsulated cation-sealed neutral trimeric capsular assembly: meta-substituent directed halide and oxyanion binding discrepancy of isomeric neutral di-substituted bis-urea receptors Utsab Manna, Biswajit Nayak, and Gopal Das Cryst. Growth Des., Just Accepted Manuscript • DOI: 10.1021/acs.cgd.6b01370 • Publication Date (Web): 16 Nov 2016 Downloaded from http://pubs.acs.org on November 17, 2016

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Crystal Growth & Design

Dual guest [(Chloride)3-DMSO] encapsulated cation-sealed neutral trimeric capsular assembly: meta-substituent directed halide and oxyanion binding discrepancy of isomeric neutral di-substituted bis-urea receptors Utsab Manna, Biswajit Nayak 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].

ACS Paragon Plus Environment


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ABSTRACT: A logically synthesized ortho-phenylenediamine based chloro-methyl di-substituted neutral organic bis-urea receptor L1 with the aid of three symmetry-independent units encapsulate an unusual triangular [(Chloride)3-DMSO] guest assembly (complex 1a) via formation of DMSO+host+salt co-crystals within its trimeric paddle-wheel shaped cavity sealed by three n-TBA cations and exhibits diverse anion binding properties with oxyanions along with the chloride complex of its isomeric bromo-methyl di-substituted bis-urea receptor L2. Receptor L2 and L1 both forms similar kind of noncapsular 2:2 host-guest assembly in presence of excess chloride (complex 2a) and acetate (complex 1b) respectively by non-cooperative H-bonding interactions of urea groups which are attributed to the effect of meta-functionalization with respect to adjacent N-H part of urea moiety, whereas another planar oxyanion carbonate is doubly encapsulated within the tetrameric capsular cavity of L1 in solid state (complex 1c). Moreover, receptor L2 conforms similar kind of cation sealed 2:1 host-guest pseudo-capsular complex in presence of larger coordinating anions such as tetrahedral sulfate (complex 2b) and octahedral hexafluorosilicate (complex 2c). 1H-NMR titration experiments are also performed using nTBA/TEA salts of anions to investigate the solution state anion binding behavior of isomeric L1 and L2 and corroborate the results obtained in the solid-state studies.

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1. Introduction Encouraged by the critical roles of anions in living organisms and in a range of environmental, biological and medical purposes, impact of anions are frequently mediated by proteins in the form of molecular receptors.1-5 In natural system, proteins can selectively and efficiently bind anions with different dimensions by explicit non-covalent interactions,6-9 and this observations in nature have motivated supramolecular researchers to design and develop numerous abiotic artificial receptors containing multiple hydrogen bond donor groups, such as amide10-13, urea/thiourea14 pyrrole/indole15-16 and imidazolium17-18 functionalities that can interact through hydrogen bonds with the anionic guests. Thus, synthetic design of suitable receptors capable of strong and discriminating recognition behavior towards different dimension of anions such as spherical (halides), planar (acetate, nitrate or carbonate), tetrahedral (sulfate or phosphate), octahedral (hexafluorosilicate) etc. is an area of immense and ever increasing interest to the supramolecular community.19-21 Due to the strong and tunable hydrogen bonding abilities and their relatively easy syntheses, besides flexible tripodal scaffolds, receptors synthesized from rigid ortho or meta phenylenediamine containing urea/thiourea recognition sites are of particular interest, which in turn enhance their use in both simple and complex systems for studying anion recognition chemistry.22-36 Among the halides, excess of fluoride in drinking water causes dental and skeletal fluorosis, moreover beyond its toxic level in human body fluoride can cause osteosarcoma, chloride ion is essential for its significant role in biological processes like signal transduction or transport of organic solutes through the cell membrane.37-39 On the other hand, among oxyanions, sulfate is bound in proteins in a neutral environment inside the hydrophobic cavity in Salmonella typhimurium bacteria and furthermore the harmful effect of sulfate has also been considered as a major hurdle to cleanup efforts in the remediation of nuclear waste, carbonate works as a buffer in the blood as well as the major anions in bio-mineralized materials such as the exoskeletons of radiolarian and acetate is utilized by organisms in the form of acetyl coenzyme A etc.40-41 Consequently, the systematic complexation of these biologically and environmentally needful anions by suitable ortho-phenylenediamine based neutral organic synthetic hosts are one of the primary and challenging target in anion coordination chemistry in recent years. Although, some orthophenylenediamine based mono-substituted bis-urea receptors and their oxyanion binding studies reported in recent years such as Light et. al. reported carboxylate complexation by a family of ortho-phenylenediamine based bis-ureas42, Wu et. al. in 2013 proposed tris chelating phosphate complexes of ortho-phenylene based bis(thio)urea Ligands43 and Gale et. al. in 2015 exposed highly fluorinated ortho-phenylene based receptors functioning as highly effective transmembrane anion antiporters44, but the systematic investigation of both electron withdrawing (Chloro/bromo) and donating (methyl) functionalized di-substituted isomeric bis-urea scaffolds and their diverse halide and oxyanion binding behavior depending upon the substituents are uncommon

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Scheme 1. Synthetic scheme of halo-methyl di-substituted receptors L1 and L2.

and still inspiring research area to the supramolecular communities. In our continuing effort to design the host for encapsulation of hydrated and/or solvated anion cluster,45-54 herein we structurally demonstrate an unprecedented n-TBA cation sealed (chloride)3-DMSO dual guest encapsulation (1a) via development of solvent+host+salt cocrystals inside the paddle-wheel shaped trimeric host cavity followed by trimerization of chloride-ligand adduct of chloro-methyl di-substituted receptor L1, whereas its isomeric bromo-methyl receptor L2 forms 2:2 non-cooperative chloride complex (2b). In addition, discriminating behavior of L1 and L2 toward larger anions resulted in the formation of non-cooperative 2:2 L1-acetate (1b), fully encapsulated 4:2 L1-CO32- (1c) and pseudo-encapsulated cation-sealed 2:1 L2-SO42- (2b), L2-SiF62- (2c) complex in solid state.

2. Results and Discussion 2.1. Design aspects of anion binding receptors The ortho-phenylenediamine based two isomeric bis-urea receptors L1 and L2 were synthesized in high yield by the reaction of ortho-phenylenediamine with two equivalents of respective 3-chloro-4-methylphenyl isocyanate and 4-bromo-3-methylphenyl isocyanate in acetonitrile medium (scheme 1). A suitable receptor to bind with anions, should have to be a particular supramolecular architecture and both L1 and L2 possess two urea moieties with 3,4-halo-methyl/methyl-halo di-functionality at two terminal aromatic pods which can receive guests of varied dimensionality either in cooperative syn-fashion or in non-cooperative antimode of urea groups, so thus having various interacting possibilities depending upon the guests as well as positional aromatic functionalization of hosts. The purposeful inclusion of urea groups in highly organized dipodal scaffold becomes beneficial to determine the binding discrepancies of anionic guests via non-covalent interactions. Crystallisation followed by single crystal X-ray analysis of host-guest complexes has traditionally been the main focus in anion-recognition chemistry to understand the structural discernment of the complexes.

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Crystal Growth & Design 2.2. Relative X-ray structural analysis of anion complexes

Single crystal XRD analysis study of receptor-anion neutral complexes and discriminating binding behavior of receptors towards halides and oxyanions of varied dimensionality depending upon the meta-substituents of di-functionalized isomeric receptors and the size of anions are tabulated and presented in table 1 and figure 1, 2, 3, 4, 5 and 6 respectively. Table 1 Key observation of size dependent diverse anion binding behaviors of receptors Anions with size Spherical Chloride (Cl-)

Neutral receptor-anion Complexes

Observation

1)DMSO+L1+TBACl co-crystals and paddle-wheel shaped triangular host-guest assemblage

Anion recognition is affected by the position of meta-substituents with respect to adjacent N-H part of urea groups (syn/anti) of a particular receptor

2)Non-cooperative dimeric 2:2 host-guest assembly of L2-Cl Planar Acetate (OCOCH3-)

Non-cooperative dimeric 2:2 host-guest assembly of L1-OAc

Planar Carbonate (CO32-)

Double carbonate encapsulation of L1 in 4:2 hostguest fashion

Tetrahedral Sulphate (SO42-)

n-TBA Cation sealed 2:1 host-guest encapsulation of L2-SO4

Octahedral cate (SiF62-)

n-TBA Cation sealed 2:1 host-guest encapsulation of L2-SiF6

Hexafluorosilli-

Anion recognition is probably affected by the size of the anion which overcomes the meta-substituent effect seen in case of spherical and planar anion

2.2.1. (Chloride)3-DMSO encapsulated complex (n-TBA)3[(L1)3(Cl)3(DMSO)] (1a): Structural elucidation of complex 1a [(L1.TBACl)3.DMSO], which crystallizes in triclinic P-1 space group from DMSO solution, revealed the trimeric paddle-wheel shaped capsular assembly of L1 with encapsulated (chloride)3-DMSO triangular guest assemblage within its complementary cavity (Figure 1a) properly sealed by three n-TBA cations (Figure. 1c). Notably, it is evident from xray analysis of complex 1a that the three L1 receptors are not C3-symmetric due to three symmetrically distinct conformations (cis/trans) of meta-chloro groups with respect to the adjacent urea moieties of each receptor. The two (Cl7 and Cl9) among three chlorides are displaying six (four N–H⋯Cl receptor-anion, one DMSO-C–H⋯Cl solvent-anion and one n-TBA-C–H⋯Cl cation-anion) coordination and Cl8 shows only four strong N–H⋯Cl receptor-anion interactions. Moreover three C–H⋯O (two n-TBA-DMSO and a receptor-DMSO) and several intermolecular H-bonding C–H⋯Cl, halogen bonding Cl⋯Cl, anion-pi (Cl⋯ᴨ) interactions are also helped to offer an appropriate binding pocket to engulf an interesting (chloride)3-DMSO assembly (Figure 1b, Table 2). In this trischelate (Cl)3-DMSO triangular assembly (Figure 1e) the average distance among three chlorides in the vertices are 6.823 Å and the average distance among three n-TBA N atoms are 9.784 Å (Figure 1d), whereas the average distance from central DMSO sulphur to three chlorides and three n-TBA nitrogens are 4.22 Å and 5.69 Å respectively (Figure 1f). All the L1 receptor N-H-bonding interactions stabilizing the solvated-anion dual guest assembly are in the strong H-bonding range d(H⋯Cl) ≤ 2.6 Å and d(D⋯Cl) ≤ 3.3 Å (Table 2)

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Figure 1. (a) space-fill view of encapsulated (Chloride)3-DMSO inside three units of L1, (b) H-bonding contacts of guests with cation and receptors, (c) n-TBA cation sealed paddle-wheel shaped anion-solvent-receptor trimeric capsular assembly, (d) distances among three guest chlorides and three N atoms of n-TBA cations, (e) magnified view of triangular shaped (Chloride)3DMSO guest assemblage and (f) distances from central S atom of guest DMSO to guest chlorides and three N atoms of n-TBA cations.

Table 2 Selective bond parameters of the interactions of [Cl3(DMSO)] cluster with L1 in complex 1a

D-H⋯A d(D⋯H)/Å a N1–H1N⋯Cl7 0.86 a N2–H2N⋯Cl7 0.86 N3–H3N⋯Cl7a 0.86 a N4–H4N⋯Cl7 0.86 a N5–H5N⋯Cl8 0.86 a N6–H6N⋯Cl8 0.86 a N7–H7N⋯Cl8 0.86 a N8–H8N⋯Cl8 0.86 a N9–H9N⋯Cl9 0.86 N10–H10N⋯Cl9a 0.86 a N11–H11N⋯Cl9 0.86 a N12–H12N⋯Cl9 0.86 b C107–H10B⋯O3 0.97 a b Symmetry Codes: x, y, z; 1-x, 1-y, 1-z

d(H⋯A)/Å 2.42 2.28 2.55 2.49 2.43 2.52 2.45 2.48 2.47 2.44 2.46 2.45 2.56

d(D⋯A)/Å 3.299(6) 3.271(6) 3.304(6) 3.297(6) 3.251(7) 3.299(6) 3.262(6) 3.305(6) 3.296(7) 3.277(6) 3.292(7) 3.285(7) 3.525(8)

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2σ(I)

P-1 18.100(3) 19.280(3) 19.376(3) 79.210(10) 77.267(9) 83.013(10) 6455.7(18) 2 1.152 0.266 2396.0 298(2) 17.08 73277

P 21/c 11.462(6) 19.797(12) 18.614(9) 90.00 93.946(5) 90.00 4214.0(4) 4 1.172 0.197 1596.0 298(2) 22.88 19817

C 2/c 24.818(13) 18.488(13) 28.168(17) 90.00 106.979(5) 90.00 12361.7(14) 8 1.297 0.252 5120.0 298(2) 16.88 85636

P 21/c 11.886(11) 20.089(3) 17.645(3) 90.00 93.257(11) 90.00 4206.6(10) 4 1.279 2.027 1688.0 298(2) 21.35 21299

P 21/c 20.091(8) 17.917(8) 24.194(10) 90.00 108.794(2) 90.00 8245.3(6) 4 1.326 2.034 3432.0 298(2) 21.43 122796

P -1 14.393(15) 18.219(19) 18.926(19) 116.87(10) 97.800(8) 101.029(9) 4203.1(9) 2 1.337 1.993 1756.0 298(2) 17.76 40119

28151

10643

14494

9709

18504

19195

12607

6910

8599

6760

8218

4345

1356 0.0979

477 0.0958

751 0.0879

440 0.0755

904 0.0634

926 0.1110

wR2, I > 2σ(I)

0.2132

0.2013

0.2065

0.1660

0.1506

0.2221

GOF (F )

1.193

1.090

1.178

0.883

0.879

0.999

CCDC No.

1484815

1484816

1484817

1484818

1484819

1484820

2

3. Conclusion In conclusion, the rationally synthesized ortho-phenylenediamine based easy-to-make 3-chloro-4-methyl di-substituted organic bis-urea receptor L1 demonstrated full encapsulation of an unusual triangular (chloride)3-DMSO anion-solvent dual guest assembly via DMSO+host+salt cocrystals within its trimeric complementary capsular cavity perfectly sealed by three n-TBA cations in solid state. While its isomeric 4-bromo-3-methyl di-substituted bis-urea receptor L2 formed non-capsular 2:2 host-guest assemblies with chloride ion via non-cooperative H-bonding interactions of the urea moieties. Moreover, L1 formed non-capsular cation sealed 2:2 assembly and fully encapsulated 4:2 assembly with acetate and double carbonate anions respectively. In continuation with the diverse binding properties, isomeric L2 formed cation sealed 2:1 pseudo-capsular host-guest assembly with bigger tetrahedral sulfate and octahedral hexafluorosilicate anions. Especially, L1 has proved to be a decent and proficient organic receptor for engulfing the large (Cl)3-DMSO guest assemblage by efficient co-operative effect of six urea moieties and three n-TBA cations


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while its alike isomeric receptor L2 were unable do the same. The results of diverse halide and oxyanion binding of the two receptor systems are reliable to interpret the data and consistent to justify the variation. The relative 3D orientations of the metasubstituents with respect to adjacent urea N-H moieties of particular receptor possibly played a vital role for the stabilization of unusual conformation to arrest the relatively large guest. The report of encapsulation of anion-solvent dual guest assemblage within trimeric capsular assembly of a neutral acyclic receptor entirely sealed by the three counter-cations is unique and our approach would be useful to develop new categories of host-guest assemblies.

4. Experimental Section 4.1. Materials and Methods 1

H and 13C NMR spectra of L1, L2, 1a, 1b, 1c, 2a, 2b, 2c were recorded on FT-400 and FT-600 MHz spectrometer in DMSO−d6 at 298

K. IR spectra were recorded with KBr disks in the range 4000–500 cm–1. The starting materials o-phenylenediamine, 3-chloro-4methylphenyl isocyanate and 4-bromo-3-methylphenyl isocyanate and all the tetrabutylammonium (n-TBA) and tetraethylammonium (TEA) salts and solvents were obtained from commercial sources and used as received. Chemical shifts for 1H and 13C NMR were reported in parts per million (ppm), calibrated to the residual solvent peak set. Binding stoichiometries of host to guest were determined from 1H NMR (Varian 600 MHz) titrations of L1 and L2 with tetraethylammonium (TEA) or n-tetrabutylammonium (n-TBA) salts of respective anions in DMSO-d6 at 298 K. The initial concentration of the corresponding receptor solution was 5 mM. Aliquots of anions were added from 50 mM stock solutions of anions (up to 1:10 host/guest stoichiometry). The residual solvent peak in DMSO-d6 (2.500 ppm) was used as an internal reference, and each titration was performed with 18−20 measurements at room temperature.

4.2. Syntheses and Characterization 4.2.1. Synthesis of receptor L1 A solution of o-phenylenediamine (0.324 g, 3.0 mmol) in 120 mL of acetonitrile was added dropwise to a solution of 3-Chloro-4methylphenyl isocyanate (958 μL, 7.0 mmol) in acetonitrile (120 mL). After vigorous stirring for 24 h, the white precipitate was filtered off and washed several times with acetonitrile, THF and then dried in vacuum to yield L1 (Yield = 82%). M.P: 192-194˚C, 1H NMR (600 MHz, DMSO-d6) δ (ppm): 2.748 (s, 6H, Ar-CH3), 7.339-7.355 (m, 2H, Ar-H), 7.426-7.439 (d, 2H, ~7.8 Hz, Ar-H), 7.4717.485 (d, 2H, ~8.4 Hz, Ar-H), 7.815-7.831 (m, 2H, Ar-H), 7.975 (s, 2H, Ar-H), 8.327 (s, 2H, NHa), 9.426 (s, 2H, NHb). 13CNMR (150 MHz, DMSO-d6) δ (ppm): 18.82 (×2C, Ar-CH3), 112.90 (×2C, Ar-C), 116.87 (×2C, Ar-C), 118.12 (×2C, Ar-C), 124.21 (×2C, Ar-C), 128.17 (×2C, Ar-C), 131.17 (×2C, Ar-C), 131.22 (×2C, Ar-C), 133.13 (×2C, Ar), 139.03 (×2C, Ar-C), 153.12 (×2C, -C=O). IR spectra (KBr pellet): 3328 cm-1 vs(N–H), 3145 cm-1 vs (C-H), 2864 cm‾1 vs(C-H), 1670 cm-1 vs(C=O), 665 cm-1 vs(C-Cl). ESI-MS: m/z 444.1072 [L1+H].



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4.2.2.

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Synthesis of receptor L2

For L2, similar like L1, 120 mL acetonitrile solution of o-phenylenediamine (0.324 g, 3.0 mmol) was added dropwise to a solution of 4-Bromo-3-methylphenyl isocyanate (984 μL, 7.0 mmol) in acetonitrile (120 mL). After vigorous stirring for 24 h, the precipitate was filtered off and washed several times with acetonitrile, THF and then dried in vacuum to yield L2 as off-white solid (Yield = 88%). M.P: 204-206˚C. 1H NMR (400 MHz, DMSO-d6) δ (ppm): 2.699 (s, 6H, Ar-CH3), 7.279-7.303 (m, 2H, Ar-H), 7.446-7.468 (d, 2H, ~8.8 Hz, Ar-H), 7.635-7.657 (d, 2H, ~8.8 Hz, Ar-H), 7.665 (s, 2H, Ar-H), 7.762-7.786 (m, 2H, Ar-H), 8.280 (s, 2H, NHa), 9.342 (s, 2H, NHb).

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CNMR (100 MHz, DMSO-d6) δ (ppm): 22.72 (×2C, Ar-CH3), 115.84 (×2C, Ar-C), 117.69 (×2C, Ar-C), 120.49 (×2C, Ar-C),

124.23 (×2C, Ar-C), 127.27 (×2C, Ar-C), 131.24 (×2C, Ar-C), 132.25 (×2C, Ar-C), 137.43 (×2C, Ar), 139.45 (×2C, Ar-C), 153.13 (×2C, C=O). IR spectra (KBr pellet): 3326 cm-1 vs(N–H), 3138 cm-1 vs (C-H), 2862 cm‾1 vs(C-H), 1665 cm-1 vs(C=O), 580 cm-1 vs(C-Br). ESIMS: m/z 533.0139 [L2+H].

4.2.3. Chloride complex (n-TBA)3[(L1)3(Cl)3(DMSO)] (1a): Complex 1a was prepared by charging excess (10 eqv.) of tetrabutylammonium chloride to the solution of L1 (100mg, 0.225 mmol) in 5ml DMSO. After addition of tetrabutylammonium chloride under stirring, the clear solution was warmed to ~ 80ºC, then solution was filtered and allowed for slow evaporation at room temperature. After 20 days colorless block crystals of 1 were obtained (Yield 66%). M.P: 247-249˚C. 1H NMR (600 MHz, DMSO-d6) δ (ppm): 1.160-1.185 (t, 12H, ~7.2 Hz, TBA-CH3), 1.515-1.576 (m, 8H, TBA-CH2), 1.777-1.829 (m, 8H, TBA-CH2), 2.787 (s, 6H, Ar-CH3), 3.385-3.413 (t, 8H, ~ 9.0 Hz, N+-TBA-CH2), 7.298-7.326 (m, 2H, ArH), 7.441-7.457 (d, 2H, ~9.6 Hz, Ar-H), 7.471-7.484 (d, 2H, ~7.8 Hz, Ar-H), 7.874-7.901 (m, 2H, Ar-H), 7.947 (s, 2H, Ar-H), 8.655 (s, 2H, NHa), 9.812 (s, 2H, NHb). 13CNMR (150 MHz, DMSO-d6) δ (ppm): 14.14 (×4C, TBA-CH3), 19.46 (×4C, TBA-CH2), 19.86 (×4C, TBACH2), 23.71 (×2C, Ar-CH3), 58.17 (×4C, TBA-N+CH2), 117.35 (×2C, Ar-C), 118.56 (×2C, Ar-C), 124.09 (×2C, Ar-C), 124.40 (×2C, Ar-C), 128.64 (×2C, Ar-C), 131.47 (×2C, Ar-C), 131.81 (×2C, Ar-C), 133.74 (×2C, Ar), 139.83 (×2C, Ar-C), 153.71 (×2C, -C=O). IR spectra (KBr pellet): 3386 cm-1 vs(N–H), 3148 cm-1 vs (C-H), 2868 cm‾1 vs(C-H), 1674 cm-1 vs(C=O), 668 cm-1 vs(C-Cl).

4.2.4.

Acetate complex [(n-TBA){L1(CH3COO)}] (1b):

Complex 1b was obtained by adding an excess of tetrabutylammonium acetate (10 eqv.) into a 5 mL DMSO solution of L1 (100mg, 0.225 mmol). After the addition of acetate, the solution was stirred for about 30 min and allowed to slowly evaporate for crystallization, which after 20 days of exposure to unmodified atmosphere yielded colurless crystals suitable for single crystal XRD analysis. Yield 80%, M.P: 224-226˚C. 1H NMR (600 MHz, DMSO-d6) δ (ppm): 1.158-1.183 (t, 12H, ~7.8 Hz, TBA-CH3), 1.511-1.572 (m, 8H, TBA-CH2), 1.768-1.820 (m, 8H, TBA-CH2), 2.103 (s, 3H, Acetate-CH3), 2.752 (s, 6H, Ar-CH3), 3.371-3.399 (t, 8H, ~ 8.4 Hz, N+-TBACH2), 7.221-7.248 (m, 2H, Ar-H), 7.451-7.465 (d, 2H, ~8.4 Hz, Ar-H), 7.503-7.518 (d, 2H, ~9.0 Hz, Ar-H), 8.002-8.028 (m, 2H, Ar-H), 8.001 (s, 2H, Ar-H), 9.796 (s, 2H, NHa), 10.832 (s, 2H, NHb). 13CNMR (150 MHz, DMSO-d6) δ (ppm): 14.12 (×4C, TBA-CH3), 19.45 (×4C, TBA-CH2), 19.85 (×4C, TBA-CH2), 23.70 (×2C, Ar-CH3), 25.96 (×1C, Acetate-C), 58.16 (×4C, TBA-N+CH2), 117.34 (×2C, Ar-C), 118.50 (×2C, Ar-C), 123.03 (×2C, Ar-C), 123.31 (×2C, Ar-C), 128.12 (×2C, Ar-C), 130.86 (×2C, Ar-C), 131.70 (×2C, Ar-C), 133.67 (×2C,


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Ar), 140.50 (×2C, Ar-C), 153.93 (×2C, -C=O), 176.71 (×1C, Acetate-C=O). IR spectra (KBr pellet): 3388 cm-1 vs(N–H), 3146 cm-1 vs (C-

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H), 2866 cm‾1 vs(C-H), 1671 cm-1 vs(C=O), 664 cm-1 vs(C-Cl).

4.2.5. Carbonate complex [2(TEA){(L1)2(CO3)}] (1c): Complex 1c was initially obtained by charging an excess of teraethylammonium bicarbonate (10 eqv.) into a 5 mL DMSO solution of L1 (100mg, 0.225 mmol). After the addition of carbonate, the solution was stirred for about 30 min at room temperature and allowed to slowly evaporate crystallization from the test-tube. Slow evaporation of the filtrate at room temperature yielded yellowish white crystals of 1c within 30 days. Isolated yield of 1c: 75% based on L1, after 30 days of exposure at room temperature. M.P: 258-260˚C. 1H NMR (600 MHz, DMSO-d6) δ (ppm): 1.396-1.421 (t, 24H, ~7.2 Hz, TBA-CH3), 2.799 (s, 6H, Ar-CH3), 3.431-3.467 (t, 16H, ~ 7.2 Hz, N+-TBA-CH2), 7.305-7.333 (m, 2H, Ar-H), 7.444-7.458 (d, 2H, ~8.4 Hz, Ar-H), 7.476-7.489 (d, 2H, ~7.8 Hz, Ar-H), 7.903-7.931 (m, 2H, Ar-H), 7.983 (s, 2H, Ar-H), 8.832 (s, 2H, NHa), 9.822 (s, 2H, NHb). 13CNMR (150 MHz, DMSO-d6) δ (ppm): 7.71 (×8C, TEA-CH3), 19.45 (×2C, Ar-CH3), 52.05 (×8C, TEA-N+CH2), 117.50 (×2C, Ar-C), 118.73 (×2C, Ar-C), 124.18 (×2C, Ar-C), 124.33 (×2C, Ar-C), 128.59 (×2C, Ar-C), 131.50 (×2C, Ar-C), 131.74 (×2C, Ar-C), 133.72 (×2C, Ar), 139.93 (×2C, Ar-C), 153.79 (×2C, -C=O), 173.78 (×1C, Carbonate-C=O). IR spectra (KBr pellet): 3381 cm-1 vs(N–H), 3152 cm-1 vs (C-H), 2864 cm‾1 vs(C-H), 1668 cm-1 vs(C=O), 662 cm-1 vs(C-Cl).

4.2.6. Chloride complex [(n-TBA){(L2)(Cl)}] (2a): Chloride complex of L2 was obtained as suitable crystals for X-ray diffraction analysis upon slow evaporation of a 5 mL DMSO solution of L2 (100 mg, 0.187 mmol) in presence of excess n-TBACl (10 eqv.). The colorless crystals thus obtained 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% based on L2. M.P: 212-214˚C. 1H NMR (400 MHz, DMSO-d6) δ (ppm): 1.115-1.151 (t, 12H, ~7.2 Hz, TBA-CH3), 1.460-1.551 (m, 8H, TBA-CH2), 1.722-1.801 (m, 8H, TBA-CH2), 2.701 (s, 6H, Ar-CH3), 3.338-3.378 (t, 8H, ~ 8.0 Hz, N+-TBA-CH2), 7.254-7.291 (m, 2H, Ar-H), 7.456-7.472 (d, 2H, ~6.4 Hz, Ar-H), 7.634-7.656 (d, 2H, ~8.8 Hz, Ar-H), 7.668 (s, 2H, Ar-H), 7.786-7.824 (m, 2H, Ar-H) , 8.390 (s, 2H, NHa), 9.466 (s, 2H, NHb). 13CNMR (100 MHz, DMSO-d6) δ (ppm): 14.15 (×4C, TBA-CH3), 19.86 (×4C, TBA-CH2), 23.31 (×4C, TBA-CH2), 23.71 (×2C, Ar-CH3), 58.17 (×4C, TBA-N+CH2), 116.29 (×2C, Ar-C), 118.21 (×2C, Ar-C), 121.00 (×2C, Ar-C), 124.32 (×2C, Ar-C), 124.54 (×2C, Ar-C), 131.41 (×2C, Ar-C), 132.83 (×2C, Ar-C), 137.99 (×2C, Ar), 140.15 (×2C, Ar-C), 153.69 (×2C, -C=O). IR spectra (KBr pellet): 3379 cm-1 vs(N–H), 3142 cm-1 vs (C-H), 2864 cm‾1 vs(C-H), 1668 cm-1 vs(C=O), 586 cm-1 vs(C-Br).

4.2.7.

Sulphate complex [2(n-TBA){(L2)2(SO4)}] (2b):

Complex 2b was prepared by charging an excess of tetrabutylammonium sulphate (10 eqv.) into a 5 mL DMSO solution of L2 (100 mg, 0.187 mmol). After the addition of sulphate salt the resulting solution was stirred for about 30 min and was left open to atmosphere in a test-tube for slow evaporation at room temperature. Colourless crystals of 2b suitable for single crystal X-ray analysis was obtained within 20 days. Yield: 65-70% based on L2. M.P: 253-255˚C. 1H NMR (400 MHz, DMSO-d6) δ (ppm): 1.291-1.328 (t, 24H, ~7.6 Hz, TBA-CH3), 1.636-1.727 (m, 16H, TBA-CH2), 1.895-1.989 (m, 16H, TBA-CH2), 2.899 (s, 6H, Ar-CH3), 3.509-3.551 (t,



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8H, ~ 8.4 Hz, N+-TBA-CH2), 7.389-7.428 (m, 2H, Ar-H), 7.596-7.618 (d, 2H, ~8.8 Hz, Ar-H), 7.715-7.737 (d, 2H, ~8.8 Hz, Ar-H), 7.836 (s, 2H, Ar-H), 8.241-8.282 (m, 2H, Ar-H) , 9.764 (s, 2H, NHa), 10.441 (s, 2H, NHb). 13CNMR (100 MHz, DMSO-d6) δ (ppm): 14.12 (×8C, TBA-CH3), 19.84 (×8C, TBA-CH2), 23.05 (×8C, TBA-CH2), 23.69 (×2C, Ar-CH3), 58.15 (×8C, TBA-N+CH2), 115.85 (×2C, Ar-C), 118.25 (×2C, Ar-C), 121.06 (×2C, Ar-C), 123.35 (×2C, Ar-C), 123.48(×2C, Ar-C), 130.59 (×2C, Ar-C), 132.36 (×2C, Ar-C), 137.53 (×2C, Ar), 140.72 (×2C, Ar-C), 153.49 (×2C, -C=O). IR spectra (KBr pellet): 3385 cm-1 vs(N–H), 3143 cm-1 vs (C-H), 2863 cm‾1 vs(C-H), 1664 cm-1 vs(C=O), 588 cm-1 vs(C-Br).

4.2.8. Hexafluorosilicate complex [2(n-TBA){(L2)2(SiF6)}] (2c) Hexafluorosilicate complex of L2 was obtained as suitable crystals for X-ray diffraction analysis upon slow evaporation of a 5 mL DMSO solution of L2 (100 mg, 0.187 mmol) from glass vial in presence of excess n-TBAF (10 eqv.). The colorless crystals of SiF62- on reaction of fluoride with glass-silica thus obtained 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% based on L2.M.P: 265-267˚C. 1H NMR (400 MHz, DMSO-d6) δ (ppm): 1.123-1.160 (t, 24H, ~7.2 Hz, TBA-CH3), 1.467-1.556 (m, 16H, TBA-CH2), 1.729-1.819 (m, 16H, TBA-CH2), 2.714 (s, 6H, Ar-CH3), 3.345-3.387 (t, 16H, ~ 8.8 Hz, N+-TBA-CH2), 7.255-7.298 (m, 2H, Ar-H), 7.478-7.500 (d, 2H, ~8.8 Hz, Ar-H), 7.626-7.648 (d, 2H, ~8.8 Hz, Ar-H), 7.690 (s, 2H, Ar-H), 7.828-8.870 (m, 2H, Ar-H) , 8.469 (s, 2H, NHa), 9.426 (s, 2H, NHb). 13CNMR (100 MHz, DMSO-d6) δ (ppm): 13.96 (×8C, TBA-CH3), 19.68 (×8C, TBA-CH2), 23.12 (×8C, TBA-CH2), 23.49 (×2C, Ar-CH3), 58.12 (×8C, TBA-N+CH2), 116.05 (×2C, Ar-C), 118.07 (×2C, Ar-C), 120.85 (×2C, Ar-C), 124.15 (×2C, Ar-C), 124.21(×2C, Ar-C), 131.28 (×2C, Ar-C), 132.53 (×2C, Ar-C), 137.67 (×2C, Ar), 140.02 (×2C, Ar-C), 153.42 (×2C, -C=O). IR spectra (KBr pellet): 3387 cm-1 vs(N–H), 3146 cm-1 vs (C-H), 2868 cm‾1 vs(C-H), 1670 cm-1 vs(C=O), 586 cm-1 vs(C-Br).

4.3. Crystallographic Refinement Details: The crystallographic data and details of data collection for complexes 1a, 1b, 1c, 2a, 2b and 2c are given in Table 2. 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. Intensity data for the crystals were collected Mo-Kα radiation (λ = 0.71073Å) at 298(2) K, with increasing ω (width of 0.3° per frame) at a scan speed of 6 s/ frame on a Bruker SMART APEX diffractometer equipped with CCD area detector. The data integration and reduction were processed with SAINT55 software. An empirical absorption correction was applied to the collected reflections with SADABS.56 The structures were solved by direct methods using SHELXTL-2014 and were refined on F2 by the full-matrix least-squares technique using the SHELXL-2014 program package.57 Graphics are generated using MERCURY 2.3.58 The hydrogen atoms attached to all the carbon atoms were geometrically fixed and the positional as well as temperature factors are refined isotropically. Structural illustrations have been drawn with ORTEP-3 for Windows.59 In all cases, nonhydrogen atoms are treated anisotropically. Wherever possible, the hydrogen atoms are located on a difference Fourier map and refined. In other cases, the hydrogen atoms are geometrically fixed. Crystallographic refinement data details are summarized in Table 2.


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Acknowledgments This work was supported by CSIR and SERB through grant 01/2727/13/EMR-II and SR/S1/OC-62/2011, 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 and L2 and its complexes 1a, 1, 1c, 2a, 2b, 2c, IR 13

1

1

spectra, PXRD pattern, C NMR and H NMR spectra, H NMR titration stack plots, , job’s plot for solution state NMR, distance vs angle plots, hydrogen-bonding data, optimized structure, calculated energy and coordinates of optimized geometry of receptors.

References 1.

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47. Manna, U.; Nayak, B.; Hoque M. N.; Das, G. Influence of the cavity dimension on encapsulation of halides within the capsular as-

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sembly and side-cleft recognition of a sulfate–water cluster assisted by polyammonium tripodal receptors CrystEngComm, 2016, 18, 5036-5044. 48. 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, 3997-3999. 49. Basu, A.; Das, G. A C3v-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, 79, 2647-2656. 50. Chutia, R.; Dey, S. K.; Das, G. Self-Assembly of a Tris(Urea) Receptor as Tetrahedral Cage for the Encapsulation of a Discrete Tetrameric Mixed Phosphate Cluster (H2PO4–•HPO42–)2 Cryst. Growth Des. 2015, 15, 4993-5001. 51. 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, 1727-1738. 52. Basu, A ; 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 Dalton Trans. 2012, 41, 10792-10802. 53. Dey, S. K.; Das, G. A selective fluoride encapsulated neutral tripodal receptor capsule: solvatochromism and solvatomorphism Chem. Commun. 2011, 47, 4983-4985. 54. Hoque, M. N; Basu, A.; Das, G. Pyridine–Urea-Based Anion Receptor: Formation of Cyclic Sulfate–Water Hexamer and Dihydrogen Phosphate–Water Trimer in Hydrophobic Environment Cryst. Growth Des. 2014, 14, 6-10. 55. Sheldrick, G. M. SAINT and XPREP, 5.1 ed.; Siemens Industrial Automation Inc.: Madison, WI, 1995. 56. Sheldrick, G. M. SADABS, empirical absorption Correction Program; University of Göttingen: Göttingen, Germany, 1997. 57. Sheldrick, G. M. Acta Crystallogr., Sect. C: Crystal structure refinement with SHELXL Struct. Chem., 2015, 71, 3–8. 58. Mercury 2.3 Supplied with Cambridge Structural Database; CCDC: Cambridge, U.K., 20011-20012. 59. Farrugia, L. J. ORTEP-3 for Windows - a version of ORTEP-III with a Graphical User Interface (GUI) J. Appl. Crystallogr., 1997, 30, 565.

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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 Utsab Manna, Biswajit Nayak and Gopal Das* Anion binding discrepancies depending upon aromatic meta-functionalization with respect to adjacent receptor urea moiety and anion size are observed by two isomeric neutral halo-methyl di-substituted bisurea receptors.


Encapsulated Cation-Sealed Neutral Trimeric ... - ACS Publications

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