Coordination Polymers Capable of Gelation and Selective SO

Jul 6, 2012 - L1)2(H2O)2}Br·H2O]∝ CP4 derived from N, Ń-(3-pyridyl) m- phenyleneurea (L1) capable of gelling aqueous solvents (DMF/ water); in situ ...
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CuII Coordination Polymers Capable of Gelation and Selective SO4−2 Separation Published as part of the Crystal Growth & Design virtual special issue in Honor of Prof. G. R. Desiraju Mithun Paul, N. N. Adarsh,† and Parthasarathi Dastidar* Department of Organic Chemistry, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Kolkata 700032,West Bengal, India S Supporting Information *

ABSTRACT: A crystal engineering rationale has been exploited to generate a series of CuII coordination polymers namely [{Cu(μL1)(SO4)(H2O)3}·H2O]∝ CP1, [{Cu(μ-L1)2(H2O)2}F·2H2O]∝ CP2 [{Cu(μ-L1) 2 (H 2 O) 2 }Cl·H 2 O] ∝ CP3 and [{Cu(μL1)2(H2O)2}Br·H2O]∝ CP4 derived from N, Ń -(3-pyridyl) mphenyleneurea (L1) capable of gelling aqueous solvents (DMF/ water); in situ crystallization of CP1 has been exploited to separate SO42‑ anion selectively from a complex mixture of oxo anions (SO42−, NO3−, ClO4−, CF3SO3−). While the gels are characterized by optical-, scanning electron microscopy and rheology, structure− property (gelation, as well as anion separation) correlation has been attempted by using single crystal- and powder-X-ray diffraction data.

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INTRODUCTION Supramolecular gels1 (SGs) are visco-elastic materials obtained from small molecules (typically 2σ(I)] data/restraints/ params GOF on F2 final R indices [I > 2σ(I)]

879279 C18H18N6O4 382.38 0.24 × 0.18 × 0.08 monoclinic P2(1)/c 13.55(2) 10.455(17) 14.00(2) 90.00 91.81(4) 90.00 1982(6) 4 800 0.094 100(2) 0.0746 −11/11, −8/8, −11/11 1.50/17.00 5562/1156/936

876331 C18H16CuN6O10S 580.03 0.26 × 0.15 × 0.08 monoclinic P2(1) 6.5115(13) 19.407(3) 9.7353(17) 90.00 97.43 90.00 1219.9(4) 2 598 1.045 100(2) 0.0581 −6/6, −19/20, −9/10 2.10/22.00 4931/2756/2508

876332 C36H44CuN12O10F2 906.37 0.28 × 0.18 × 0.06 monoclinic C2/c 23.341(2) 10.2257(9) 19.3694(18) 90.00 118.396(2) 90.00 4066.8(6) 4 1884 0.618 100(2) 0.0340 −27/15, −11/12, −22/22 1.98/25.00 9867/3561/3125

876333 C36H33CuN12O8Cl2 896.18 0.24 × 0.16 × 0.10 monoclinic C2/c 22.6201(14) 9.1958(6) 21.2862(14) 90.00 118.1490(10) 90.00 3904.0(4) 4 1840 0.765 100(2) 0.0426 −27/27, −11/11, −26/26 2.04/26.02 19416/3824/2959

876334 C36H33CuN12O8Br2 985.10 0.23 × 0.12 × 0.09 monoclinic C2/c 22.625(5) 9.293(2) 21.596(7) 90.00 118.573(3) 90.00 3987.8(18) 4 1984 2.619 100(2) 0.0583 −19/20, −8/7, −19/14 2.05/19.32 4013/1651/1128

1156/0/261

2756/1/325

3561/2/293

3824/0/268

1651/0/268

1.048 R1 = 0.0673 wR2 = 0.1805 R1 = 0.0842 wR2 = 0.1961

1.022 R1 = 0.0642 wR2 = 0.1551 R1 = 0.0698 wR2 = 0.1595

1.172 R1 = 0.0651 wR2 = 0.1477 R1 = 0.0748 wR2 = 0.1528

1.156 R1 = 0.0478 wR2 = 0.1515 R1 = 0.0647 wR2 = 0.1657

0.757 R1 = 0.0610 wR2 = 0.1689 R1 = 0.0936 wR2 = 0.2051

R indices (all data)

Figure 1. (a) Molecular structure of free ligand L1 displaying anti−syn−anti conformation in its single crystal structure; (b) herringbone packing of L1 displaying lattice occluded water molecules (red balls).

177.5(18)°]. The ligand adapts syn−syn−syn conformation with significant nonplanarity as revealed from the dihedral angles between the central aromatic rings and the urea moieties are found to be 20.55° and 48.82° and between urea moieties and the terminal pyridyl rings is 6.68°. Because of extended coordination of the ligand with the adjacent metal centers and its syn−syn−syn conformation, a 1D looped-chain coordination polymer is formed. The chains are packed in parallel fashion sustained by various hydrogen bonding involving urea moiety, metal bound water, lattice occluded water and the F− anion [N···O = 2.857(5)-3.268(5) Å, ∠N−H···O = 147.7− 170.9° ; O···O = 2.804(5)-2.818(5) Å, ∠O−H···O = 145.5− 169.1°, and O···F = 2.631(5)−2.657(4) Å, ∠O−H···F = 168.3−179.4°] (Figure 3). The CPs, namely, [{Cu(μL1) 2 (H 2 O) 2 }Cl·H 2 O] ∝ CP3 and [{Cu(μ-L1) 2 (H 2 O) 2 }-

further sustained by urea-sulfate hydrogen bonding [N···O = 2.885(12)−3.113(12) Å, ∠N−H···O = 116.1−166.1° and O···O = 2.737(10)−3.033(14) Å] resulting in an overall 3D hydrogen bonded network (Figure 2) Crystal Structure of [{Cu(μ-L1)2(H2O)2}F·2H2O]∝ CP2. Light green crystals of CP2 belongs to the centrosymmetric monoclinic space group C2/c . The asymmetric unit is comprised of a half occupied CuII metal center located on a 2-fold axis, one fully occupied ligand molecule L1 coordinated to the metal center via pyridyl N, two half occupied metal bound water molecules located on a 2-fold axis, one fully occupied F− counteranion and two lattice occluded water molecules located on general positions. The metal center displayed near-ideal octahedral geometry [∠N1−Cu1−O28 = 90.3(9)°, ∠O27−Cu1−N1 = 89.7(9)°, ∠N25−Cu1−N25 = 4137

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Figure 2. (a) Molecular structure of L1 in the single crystal structure of CP1 displaying syn−syn−syn conformation; (b) parallel packing of 1D coordination polymer in CP1 displaying lattice occluded water molecules (megenta balls) involved in various H-bonding interactions.

Figure 3. (a) Molecular structure of L1 in the single crystal structure of CP2 displaying syn−syn−syn conformation; (b) 1D looped chain coordination polymer displaying occluded fluoride (green ball) water (red ball) clusters; (c) Parallel packing of the looped chain sustained by various H-bonding interactions.

chains are packed in parallel fashion through various H-bonds involving urea moiety, metal bound water, lattice occluded water and the Br− anion [N···O = 2.810(13)-2.959(13) Å, ∠N−H···O = 143.9−164.6°; O···O = 2.800(2)−3.010(3) Å, ∠O−H···O = 119.1° O···Br = 3.337(9) Å, ∠O−H···Br = 137.7°, N···Br = 3.285(10)−3.362(9) Å, ∠N−H···Br = 152.6− 158.7°) (Supporting Information). It may be noted that the TGA data of L1 and all the CPs also correspond well with the structures revealed by single crystal X-ray diffraction (see Experimental Section and Supporting Information). Thus the SXRD analyses clearly reveal that all these CPs are lattice occluded molecular solids which could be potential candidates for metallogelation (vide supra). After several trials, we are able to produce opaque gels from the reaction mixtures suited for the synthesis of CP1 and CP3 in a slightly different solvent (DMF/water) system as compared to that used in the original CP synthesis (DMF/water/EtOH). When the ligand

Br·H2O]∝ CP4, display identical space group and near identical cell parameter with that of CP2 meaning that the CPs CP2, CP3, and CP4 are isomorphous. Thus, the overall crystal structures of CP3 and CP4 are similar to that of CP2. Here in the cases of CP3 and CP4, the ligand L1 adapted syn−syn−syn conformation with significant nonplanarity as revealed from the dihedral angles between the central aromatic ring and the urea moieties (for CP3 40.8 and 37.9°; for CP4 36.7 and 40.7°) and between urea moieties and the terminal pyridyl rings (for CP3 22.0 and 7.9°; for CP4 19.3 and 8.3°). In both the cases, a disordered water molecule is occluded in the crystal lattice. Like CP2 each 1D looped chain in CP3 recognizes each other by various H-bonds involving urea moieties, metal bound water, lattice occluded water and the Cl− anion [N···O = 2.834(10)−2.988(4) Å, ∠N−H···O = 147.6− 166.5°; O···O = 2.714(18)−3.163(6) Å, ∠O−H···O = 119.1°, O···Cl = 3.253(3) Å, ∠O−H···Cl = 147.4°]. In CP4, 1D looped 4138

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Figure 4. Panels a and b are the SEM micrographs of the gels G1 and G2 at 4.0 wt %; panels c and d are the optical micrographs of the gels G1 (2.4 wt %) and G2 (1.8 wt %), respectively.

solution (DMF) is mixed with an aqueous solution of CuSO4 followed by sonication (15 min), a light green opaque gel (G1) is formed within minutes. On the other hand, when the reaction is performed with CuCl2 instead of CuSO4 keeping the other components unchanged, a deep green opaque gel (G2) is formed only after heating the reaction mixture for about 15 min at 120 °C (Scheme 1). It may noted be that sonication does not produce G2 whereas heating does not produce G1. The minimum gelator concentration considering all the reaction mixtures are 4.7 and 3.0 wt % for G1 and G2, respectively. Thermoreversibility tests reveal that G2 is thermoreversible whereas G1 is thermoirreversible. Interestingly, only G2 is capable of showing thixotropic property. To evaluate the morphological features of the gel-network both optical- and scanning electron microscopy (OM and SEM, respectively) are performed. OM of G1 reveals the presence of colloidal particle whereas that of G2 displays thin network of fibres. In SEM, highly entangled network of fibers is seen in both the cases (Figure 4). Rheology. For further characterization of the gels, rheological experiments are performed using dynamic rheology. The experiments reveal they behave like a typical gel in response to an applied force. Here in both the cases (G1 and G2) the elastic modulus G′ remain invariant with the frequency and considerably higher than the loss modulus G″ over a certain range of frequencies, which is indicative of their viscoelastic nature (Figure 5) To get an insight into the gel-network structure, we perform detailed structure−property correlation studies using SXRD

Figure 5. Rheological response of the gels G1 and G2.

and powder X-ray diffraction (PXRD) as discussed (vide supra). Figure 6 depicts PXRD plots of CP1 and G1 under various conditions. It is clear that the PXRD patterns of the simulated, the bulk and the xerogel are near superimposable meaning that the as synthesized bulk CP1 has excellent crystalline phase purity and the gel-network in the xerogel of G1 has the same crystal structure of CP1. However, the appearance of one small peak below 10° 2-theta in the PXRD pattern of the xerogel of G1 could be due to the formation of a small amount of a new crystalline phase during xerogel formation. It is interesting to note that if G1 is kept at room temperature for about two weeks, most of the gel material is transformed into deep green polycrystalline material. The PXRD plot of this polycrystalline material is found to be superimposable with that of the simulated PXRD of CP1 meaning that the gel-network in G1 is transformed into well4139

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Figure 6. PXRD comparison plots of (a) G1 and (b) G2 under various condition.

Figure 7. FT-IR, PXRD, and elemental analysis at various conditions displaying selective separation of sulfate anion as CP1.

defined crystals of CP1. In the case of CP3 and G2, the PXRD patterns of the simulated, the bulk and the polycrystalline materials directly from G2 are found to be near superimposable meaning that the gel-network in G2 is transformed into welldefined crystals of CP3. However, the PXRD pattern of the xerogel of G2 turns out to be amorphous in nature (Figure 6); this could be due to the loss of lattice occluded solvent from the gel network in G2. It may be noted that if a sample of G2 obtained by vortexing-settling down cycle (thixotropy testing of G2, vide supra) is allowed to settle down, polycrystalline material as obtained from G2 made under normal condition is not observed. This could be due to the fact that the nuclei for CP3 are understandably disturbed due to vortexing. Recognition and separation of anions from a complex mixture of anions are important in the context of environmental issues. However, because of the different extent of

hydration, it is a challenging task to separate anion from a complex mixture of anions27 having lower hydration energy as compared to the target anion. For example, in the Hofmeister series28 that enlists various anions as per their hydration energy, SO42− anion is much deeper in the series having one of the highest hydration energy. Thus, it is generally not easy to separate SO42− from a complex mixture of anions placed much earlier than SO42− in the Hofmeister series. It has recently been proposed that in situ crystallization of CPs can be exploited to separate anion from a complex mixture of anions. For this purpose, ligands having hydrogen bonding backbone has been exploited with the anticipation that the ligand backbone would take part in specific hydrogen bonding interactions29 with the target anion thereby facilitating the crystallization of CP having the anion of choice. Since in the present study, the ligand L1 is equipped with bis-urea backbone and considering the ability of 4140

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is synthesized by following a reported procedure.25 The elemental analysis is carried out using a Perkin-Elmer 2400 Series-II CHN analyzer. FT-IR spectra are recorded using Perkin-Elmer Spectrum GX, and TGA analyses are performed on a SDT Q Series 600 Universal VA.2E TA Instruments. Powder X-ray patterns are recorded on a Bruker AXS D8 Advance Powder (Cu Kα1 radiation, λ = 1.5406 Å) Diffractometer. The mass spectrum is recorded on QTOF Micro YA263. NMR spectras (1H and 13C) are recorded using 300 MHz Bruker Avance DPX300 spectrometer. Characterization Data L1. Yield: 900 mg, 56.25%. m.p: 265−267 °C after recrystallization from H2O/MeOH (1: 2 v/v). Anal. Data Calcd for C18H16N6O2: C, 62.06; H, 4.63; N, 24.12. Found: C, 61.86, H, 4.61, N, 23.74. 1H NMR (300 MHz, DMSO-d6): δ = 7.09−7.12 (2H, d, J = 9 Hz, Ar−H), 7.23−7.18 (1H, t, J = 9, 9 Hz, Ar−H), 7.34− 7.30 (2H, dd, J = 6, 9 Hz, Py−H), 7.70 (1H, s, Ar−H), 7.96−7.93 (2H, d, J = 9 Hz, Py−H), 8.20−8.19 (2H, d, J = 3 Hz, Py−H), 8.62 (2H, s, Py−H), 8.78 (2H, s, urea N−H), 8.87 (2H, s, urea N−H). HRMS(ESI) Calcd for C18H16N6O2 349.14 (M + 1). Found: [M + Na]+ 349.12. F T-IR (KBr, cm−1): 3346 (s, N−H stretch), 3242 (s, O−H stretch), 3059, 3022 (s, aromatic C−H stretch), 2908, 2827 (s, aliphatic C−H stretch), 1710, 1647 (s, urea CO stretch), 1641 (s, urea N−H bend), 1608, 1595, 1535, 1485, 1425, 1421, 1408, 1327, 1294, 1209, 1186, 1122, 1103, 854, 786, 767, 734, 700, 626, 551. Synthesis and Characterization of CPs. [{Cu(μ-L1)(SO4)(H2O)3}.H2O]∝ CP1 is synthesized by adding carefully a DMF− ethanol solution of L1 (30 mg, 0.086 mmol) to an aqueous solution of CuSO4·5H2O (10.76 mg, 0.043 mmol) and the solution is left for slow evaporation at room temperature. DMF/Water/Ethanol are taken in a 1:2:2 ratio of total volume 20 mL. After two week X-ray quality plate shaped green crystals are obtained. The crystals are washed in distilled water and finally with methanol and characterized by elemental analysis, X-ray powder diffraction (XRPD) and FT-IR. Yield: 67.4% (17 mg, 0.029 mmol). Elemental analysis calcd for C18H24CuN6O10S (%): C 37.27, H 4.17, N 14.49. Found: C 38.09, H 3.75, N 15.04. FTI.R (KBr pellet): 3286(s, urea N−H stretch), 3084(aromatic C−H stretch), 1693 (s, urea CO stretch), 1606 (s, N−H bend), 1572s, 1483s, 1431s, 1296s, 1219, 1111s (vs, SO42− νasymm S−O), 1064 (w, SO42νsymm, S−O), 607w cm−1. TGA of a crystalline sample of CP1 shows a weight loss of 12.52%, which corresponds to the loss of one solvated and three coordinated water molecules (calcd weight loss = 12.4%, temperature range 44− 105 °C). These results match well with the respective single crystal structure. [{Cu(μ-L1)2(H2O)2}F·2H2O]∝ CP2 is synthesized by adding carefully a DMF−ethanol solution of L1 (30 mg, 0.086 mmol) to an aqueous solution of CuF2.xH2O (4.37 mg, 0.043 mmol) and the solution is left for slow evaporation at room temperature. DMF/ water/ethanol are taken in a 1:2:2 ratio of total volume 20 mL. After one week X-ray quality block shaped green crystals are obtained. The crystals are washed in distilled water and finally with methanol and characterized by elemental analysis, X-ray powder diffraction (XRPD), and FT-IR. Yield: 53.5% (21 mg, 0.023 mmol). Elemental analysis calcd for C36H44CuF2N12O10 (%): C, 47.71; H, 4.89; N, 18.54. Found: C 47.90, H 4.71, N 18.53. FT-IR (KBr pellet): 3381(w, urea N−H stretch), 3088(aromatic C−H stretch), 1716 (s, urea CO stretch), 1614 (s, N−H bend), 1589s, 1537s, 1481s, 1425s, 1325, 1296s, 1274s, 1207s, 808 m, 698 m cm−1. TGA of a crystalline sample of CP2 shows a weight loss of 10.63%, which corresponds to the loss of two solvated and two coordinated water molecules (calcd weight loss = 8.28%, temperature range 75− 175 °C). These results match well with the respective single crystal structure. [{Cu(μ-L1)2(H2O)2}Cl·H2O]∝ CP3 is synthesized by adding carefully a DMF−ethanol solution of L1 (30 mg, 0.086 mmol) to an aqueous solution of CuCl2·2H2O (7.34 mg, 0.043 mmol) and the solution is left for slow evaporation at room temperature. DMF/ Water/Ethanol are taken in a 1:2:2 ratio of total volume 20 mL. After one week X-ray quality plate shaped green crystals are obtained. The crystals are washed in distilled water and finally with methanol and characterized by elemental analysis, X-ray powder diffraction (XRPD),

SO42‑ to coordinate to the metal center as in the case of CP1, we perform competitive in situ crystallizaiton experiments with the aim of separating an important anion such as SO42− from a complex mixture of anions (NO3−, ClO4−, and CF3SO3−) having much lower hydration energies.30 Thus, the ligand L1 is reacted with metal salts under various conditions: (a) noncompetitive condition, in this case, the procedure to synthesize CP1 has been followed; (b) competitive condition I, in this case, the ligand L1 is reacted with a mixture of CuII salts having different counteranions (SO42−, NO3−, ClO4−, and CF3SO3−) keeping the metal: ligand ratio 1:2 (for each metal salt) and other parameters unchanged as in the case of the synthesis of CP1; (c) competitive condition II, in this case, the molar ratio L1:CuSO4:Cu(NO3)2:Cu(ClO4)2/Cu(OTf)2 is 2:1:2:2:2 keeping rest of the parameters unchanged as in the case of the synthesis of CP1. The resultant crystalline materials in all these experiments are subjected to FT-IR, PXRD, elemental analysis and EDX. FT-IR spectra (Figure 7) clearly indicate that the isolated crystalline materials obtained from the above-mentioned in situ crystallization experiments are chemically same having SO42‑ as counteranion as revealed from the presence of 1111 cm−1, (SO42− νasymm S−O) and 1064 cm−1, (SO42− νsymm, S−O) band for SO42−. PXRD data (Figure 7) further confirm that in all these conditions, exclusively CP1 is produced. Both elemental analysis and EDX data support the separation of SO42− in the form of CP1 from a complex mixture of anions (Supporting Information).

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CONCLUSIONS Thus, we have demonstrated the merit of crystal engineering approach in generating a series of CuII coordination polymers capable of displaying multiple properties such as metallogelation and anion (sulfate) separation. Out of the four CPs synthesized, only two of them (CP1 and CP3) produce gel under suitable conditions although all of them should in principle display gelation ability as per our crystal engineering rationale. It may be mentioned that not all the molecules or systems having the potential to act as a gelator show gelation ability. This means that we still need to understand the finer details of the gelation mechanism in the molecular lavel. After the formation of the gel-network (SAFINs), it is important that the target solvent molecules must have compatible surface property to be immobilized within the network. Otherwise, all the gelator molecules/systems would have gelled all the solvents tested. But this seldom happens. So, we believe that although the coordination polymers CP2 and CP4 do have the potential to display metallogelation property, the gel-networks in these cases might not have the compatible surface property to act as gelators with the aqueous solvent system that is used in the experiments. PXRD, SXRD based structure−property correlation also establish the gel-network structures of the xerogels of G1 and G2 supporting the crystal engineering rationale based on which the present work began. The hydrogen bonding backbone and ability of SO42− to coordinate the metal center has also been exploited to separate SO42− in an anti Hofmeister fashion. We believe that the multiple properties displayed by the series of CuII CPs would be beneficial to the crystal engineering community in particular and the material science community in general.

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EXPERIMENTAL SECTION

Materials and Methods. All chemicals are commercially available (Aldrich) and used without further purification except ligand L1 which 4141

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and FT-IR. Yield: 57% (22 mg, 0.024 mmol). Elemental analysis calcd for C36H40CuCl2N12O8 (%): C, 47.87; H, 4.46; N, 18.61. Found: C 48.13, H 3.97, N 18.18. FT-IR (KBr pellet): 3254w (urea N−H stretch), 3064(aromatic C−H stretch), 1691 (m, urea CO stretch), 1610 (s, N−H bend), 1591s, 1537s, 1483s, 1425s, 1276s, 1211, 806 m, 700s cm−1. TGA of a crystalline sample of CP3 shows a weight loss of 8.04%, which corresponds to the loss of one solvated and two coordinated water molecules (calcd weight loss = 8.14%, temperature range 65− 205 °C). These results match well with the respective single crystal structure. [{Cu(μ-L1)2(H2O)2}Br·H2O]∝ CP4 is synthesized by adding carefully a DMF - ethanol solution of L1 (30 mg, 0.086 mmol) to an aqueous solution of CuBr2 (9.62 mg, 0.043 mmol), and the solution is left for slow evaporation at room temperature. DMF/Water/Ethanol are taken in a 1:2:2 ratio of total volume 20 mL. After one week X-ray quality plate shaped green crystals are obtained. The crystals are washed in distilled water and finally with methanol and characterized by elemental analysis, X-ray powder diffraction (XRPD), and FT-IR. Yield: 65.1% (24 mg, 0.028 mmol). Elemental analysis calcd for C36H40CuBr2N12O8 (%): C, 43.58; H, 4.06; N, 16.94. Found: C 44.29, H 3.77, N 16.91. FT-IR (KBr pellet): 3250(w, urea N−H stretch), 3072(w, aromatic C−H stretch), 1695 (s, urea CO stretch), 1591 (s, N−H bend), 1539s, 1427s, 1431s, 1278s, 1211s, 802 m, 775 m, 700 m cm−1. TGA of a crystalline sample of CP4 shows a weight loss of 6.64%, which corresponds to the loss of one solvated water molecules and two coordinated water molecules (calc. weight loss = 5.54%, temperature range 48−198 °C). These results match well with the respective single crystal structure. X-ray Crystallography. Single crystal X-ray data are collected using MoKα (λ = 0.7107 Å) radiation on a BRUKER APEX II diffractometer equipped with CCD area detector. Data collection, data reduction, structure solution/refinement are carried out using the software package of APEX II. All the structures (L1 and CP1-CP4) are solved by the direct methods and refine in a routine manner. In all the cases, nonhydrogen atoms are treated anisotropically. Whenever possible, the hydrogen atoms are located on a difference Fourier map and refined. In other cases, the hydrogen atoms are geometrically fixed. CCDC No. 876331−876334 and 879279 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/conts/retrieving.html (or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB21EZ, UK; fax: (+44) 1223−336−033; or [email protected]. uk).

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X-ray diffraction was performed at the DST-funded National Single Crystal Diffractometer Facility at the Department of Inorganic Chemistry, IACS.

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ASSOCIATED CONTENT

* Supporting Information S

Molecular plots and hydrogen bonding parameters for L1 and CP1−CP4, crystal structure illustrations for CP3−CP4, TGA, anion separation experiments and EDX. This material is available free of charge via the Internet at http://pubs.acs.org.

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REFERENCES

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]; parthod123@rediffmail.com. Present Address †

Institute of Condensed Matter and Nanosciences,Université Catholique de Louvain, Place L. Pasteur 1,1348 Louvain-laNeuve, Belgium.

Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We thank Department of Science & Technology (DST), New Delhi, India for financial support. M.P and N.N.A thank CSIR and IACS for research fellowships, respectively. Single crystal 4142

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