Coordination Polymers Built with a Linear Bis-Imidazole and Different

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Coordination Polymers Built With a Linear bis-Imidazole and Different Dicarboxylates: Unusual Entanglement and Emission Properties Ruchi Singh, and Parimal K. Bharadwaj Cryst. Growth Des., Just Accepted Manuscript • DOI: 10.1021/cg400756z • Publication Date (Web): 17 Jun 2013 Downloaded from http://pubs.acs.org on June 22, 2013

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Crystal Growth & Design

Revised manuscript No: cg-2013-00756z Coordination Polymers Built With a Linear bis-Imidazole and Different Dicarboxylates: Unusual Entanglement and Emission Properties Ruchi Singh and Parimal K. Bharadwaj* *

Department of Chemistry, Indian Institute of Technology Kanpur, 208016, India Email: [email protected]

Abstract The linear linker bis(4-imidazol-1-yl-phenyl)-diazene (L) has been used to construct eight new coordination polymers with Zn(II), Cd(II) and Co(II) metal ions and different carboxylate donor ligands viz., 1,1′-ferrocenedicarboxylic acid (H2Fc), 2′,5′-dimethylterphenyl-4,4″-dicarboxylic acid (H2MDA), diphenic acid (H2DPA), biphenyl-4,4′-dicarboxylic acid (H2BIPH), 4,4′-oxybis (benzoic acid) (H2BIOXY), L-(−)-malic acid (H3MA) and 2,2′-dibromo-6,6′-dinitrobiphenyl-4,4′-dicarboxylic acid (H2DBDPA). Compounds formed solvothermally are, {[Cd(L)(Fc)(H2O)]·(H2O)2}n (1), {[Cd(L)(MDA)]·DMF·CH3OH}n {[Cd2(L)2(BIPH)2(H2O)2]·H2O}n

(2),

{[Zn(L)(MDA)]·3H2O}n (5),

(3),

{[Cd(L)(DPA)]}n

{[Cd2(L)2(BIOXY)2]·H2O·CH3OH}n

(4), (6),

{[Zn3(L)5(LMA)2]·2.5H2O}n (7) and {[Co(L)(DBDPA)]·H2O}n (8). All the complexes have been characterized by single crystal X-ray diffraction, IR spectroscopy, thermogravimetry, elemental analysis and powder X-ray diffraction (PXRD). Interestingly, all complexes topologically exhibit 4connected net except complex 7 which is (4,6). Moreover, the degree of interpenetration varies in 1-8. Complexes 1, 4 and 6 exhibit commonly occurring sql topology with no interpenetration, while complexes 2 and 3 are 8-fold interpenetrated dia net. Contrary to this, complexes 5 and 8 show rare cdl and dmp nets with three and five mutual interpenetrative nets, respectively. However, 7 forms a novel pkb6 topological net with two-fold interpenetration. Upon excitation at 322 nm, complexes 1-8 exhibit solid-state luminescence at room temperature.

ACS Paragon Plus Environment


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Introduction Synthesis of coordination poymers through self assembly1 can be influenced by several factors such as coordination preferences of the metal-ions, topology of the ligands, counter ions as well as the solvent system. With the phenomenal growth in the synthesis of coordination polymers in recent years, a rich variety of new structures are now available in the literature. Many of these are particularly intriguing as several independent motifs are found to be entangled in various ways. Interpenetration, a sub-class of entanglement observed in several coordination polymers, has been widely investigated over the past decade. In coordination networks with large void spaces resulting from structural constraints imposed by the ligands, the voids are filled either with solvent molecules as guests or through interpenetration of individual networks. Interpenetration of two or more independent motifs result in integrally intact, thermally stable frameworks with enhanced internal surface area for potentially useful applications2 besides being aesthetically pleasing. However, control over interpenetration still remains a challenge since the resultant structure is affected by numerous factors.3 Considering various organic linkers, carboxylate donor ligands4 have proven to be of great importance as constructors owing to their strong coordination ability in diverse modes to satisfy the geometric requirement of metal centers leading to frameworks of higher dimensions and interesting topologies. We had earlier observed that the linear ligand bis(4-imidazol-1-yl-phenyl)-diazene (L) coordinates with Cd(II), Zn(II) and Co(II) metal ions to form 2D-grid like structures.5 Thus, it was anticipated that employment of a semi-rigid linear ligand incorporating imidazole donors at either end combined with aromatic dicarboxylates (Scheme 1) would be a feasible method for the construction of coordination polymers with varied degrees of interpenetration and intriguing topologies. In addition to structural variations, coordination polymers offer a unique platform for the rational design and synthesis of solid-state luminescent materials with a wide range of environments


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for lumophores in crystalline form.6 Luminescent compounds are potential candidates in several contemporary areas of chemistry, biology and materials research.7,8 Coordination polymers built with closed shell transition metal ions such as Zn(II)/Cd(II) are potential candidates in luminescence studies as they do not quench emission intensity like paramagnetic metal ions.9

Space for Scheme 1

In this article, we have explored the role of dicarboxylate ligands collected in Scheme 1 along with the linker, bis(4-imidazol-1-yl-phenyl)-diazene (L) to obtain eight new coordination polymers.

Experimental Section Materials. Reagent grade 4-fluoronitrobenzene, imidazole, 4-chloro-3-nitro-benzoic acid, 1,4dibromo-2,5-dimethylbenzene, 4-methoxycarbonylphenylboronic acid, tetrakis(triphenylphosphine) palladium, 1,1'-ferrocene dicarboxylic acid (H2Fc), diphenic acid (H2DPA), biphenyl-4,4'-dicarboxylic acid (H2BIPH), 4,4'-oxybis(benzoic acid) (H2BIOXY), L-(−)-malic acid (H3LMA), Cd(NO3)2·4H2O, Zn(NO3)2·6H2O, Co(NO3)2·6H2O metal salts were obtained from Aldrich and used as received. Nbromosuccinimide, K2CO3, copper powder (electrolytic grade), zinc dust and all solvents were procured from S.D. Fine Chemicals, India. All solvents were purified following standard methods prior to use. Physical Measurements. Physical measurements and elemental analyses were made on the synthesized coordination polymers as described earlier.10 Solid-state photoexcitation and emission spectra were recorded using double UV-Vis-NIR spectrophotometer (Varian Model Cary 5000) and Jobin Yvon Horiba Fluorolog-3 spectrofluorimeter at room temperature. Powder X-ray diffraction



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(CuKα radiation, scan rate 3o/min, 293 K) patterns were collected on a Bruker D8 Advance Series 2 powder X-ray diffractometer. Single-Crystal X-ray Studies. Single crystal X-ray data on 1-8 were collected at 100 K on a Bruker SMART APEX CCD diffractometer using graphite monochromated MoKα radiation (λ=0.71073 Å). For each compound, the data corrections, data integration and reduction were carried out as described earlier.10 The structure was solved by the direct methods using SHELXTL-9711 and refined on F2 by full-matrix least-squares using the SHELXL-97 program12 package. All non-hydrogen atoms were refined anisotropically except O3w in 5 and N17, C3, C7, C43, C66 and C94 in 7 which were refined isotropically. The hydrogen atoms attached to carbon atoms were positioned geometrically and treated as riding atoms using SHELXL default parameters. The hydrogen atoms of one coordinated water molecule in 5 were located, while hydrogen atoms of the other coordinated and lattice water and methanol molecules could not be located in the difference Fourier maps. The hydrogen atoms of coordinated and lattice water molecules in 1 and 6 could not be located in the difference Fourier maps. For compounds 2, 3 and 7 squeeze refinement has been performed using PLATON13 that shows one N,N-dimethylformamide and one methanol molecule in 2, three water molecules in 3 and 2.5 water molecules in 7 per formula weight respectively. The contributions of all the solvent atoms have been incorporated in both the empirical formulae and formula weights. Several DFIX and DANG commands were used to fix the bond distances and bond angles in complexes 5, 6, 7 and 8. The crystal and refinement data are collected in Table 1 while selective bond distances and angles are given in Table S1. Space for Table 1

Synthesis of the ligands


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The ligands L and 2′,5′-dimethylterphenyl-4,4″-dicarboxylic acid (H2MDA) were synthesized using earlier reported procedures.5,14

Synthesis of the ligand H2DBDPA Ligand H2DBDPA was synthesized from 2,2′-dinitrobiphenyl-4,4′-dicarboxylic acid which was prepared as described earlier.15 2,2′-dinitrobiphenyl-4,4′-dicarboxylic acid (1.0 g, 3.01 mmol) was taken in conc. H2SO4 (20 mL) and heated to 80 °C with constant stirring. To this N-bromosuccinimide (1.18 g, 6.63 mmol) was added in three portions within 15 min. After 12 hours the reaction mixture was poured into crushed ice (100 g) to give a white precipitate. It was filtered, washed with water and then dried to obtain 2,2′-dibromo-6,6′-dinitrobiphenyl-4,4′-dicarboxylic acid (H2DBDPA). Yield ~60%. 1H-NMR (CDCl3, 500 MHz, δ): 8.68(s, 2H; HAr), 8.61(s, 2H; HAr);

13

C-NMR (CDCl3, 125

MHz, δ): 164.54, 148.55, 138.63, 136.33, 134.95, 125.28, 125.09; ESI-MS: m/z [M−1] 488.83 (100 %); calculated 489.84; IR (KBr, cm-1): 3090(m), 2873(w), 1707(s), 1607(m), 1535(s), 1453(m), 1401(m), 1343(s), 1270(s), 1158(m), 1109(w), 914(m), 758(m), 734(s).

Synthesis of Complexes {[Cd(L)(Fc)(H2O)]·2H2O}n (1). A mixture containing ligand L (0.04 g, 0.13 mmol), 1,1´-ferrocene dicarboxylic acid (H2Fc) (0.04 g, 0.13 mmol) and Cd(NO3)2·4H2O (0.79 g, 0.25 mmol) in 3 mL DMF, 1 mL MeOH and 1 mL H2O were sealed in a Teflon lined autoclave and heated under autogenous pressure to 100 °C for two days and then allowed to cool to room temperature at the rate of 1°C per minute. Needle-shaped brown colored crystals of 1 were collected in ~40% yield. The crystals were washed with water followed by acetone and then air-dried. Anal. calcd. for C30H28N6O7CdFe: C, 47.86; H, 3.75; N, 11.16%. Found: C, 47.76; H, 3.87; N, 11.07%. IR (KBr, cm-1): 3442(m), 3106(m),



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2925(w), 1602(m), 1564(m), 1517(s), 1480(s), 1383(s), 1354(s), 1302(s), 1267(m), 1122(w), 1060(m), 962(m), 843(s), 802(s). {[Cd(L)(MDA)]·DMF·MeOH}n (2). The same synthetic method as above was used except that H2Fc was replaced by H2MDA (0.04 g, 0.13 mmol). Block shaped orange colored crystals of 2 were collected in ~37% yield. The crystals were washed with water followed by acetone and then air-dried. Anal. calcd. for C44H41N7O6Cd: C, 60.31; H, 4.72; N, 11.19%. Found: C, 60.44; H, 4.67; N, 11.08%. IR (KBr, cm-1): 3636(m), 3436(s), 2922(m), 1654(s), 1603(m), 1513(s), 1395(s), 1304(s), 1246(m), 1120(m), 1100(w), 1060(s), 1015(m), 961(s), 852(s). {[Zn(L)(MDA)]·3H2O}n (3). A mixture containing ligand L (0.04 g, 0.13 mmol), H2MDA (0.04 g, 0.13 mmol) and Zn(NO3)2·6H2O (0.76 g, 0.25 mmol) in 3 mL DMF, 1 mL MeOH and 1 mL H2O were sealed in a Teflon lined autoclave and heated under autogenous pressure to 100 °C for two days and then allowed to cool to room temperature at the rate of 1 °C per minute. Block shaped red colored crystals of 3 were collected in ~38% yield. The crystals were washed with water followed by acetone and then air-dried. Anal. calcd. for C40H36N6O7Zn : C, 61.74; H, 4.66; N, 10.80%. Found: C, 61.86; H, 4.69; N, 10.77%. IR (KBr, cm-1): 3427(m), 3113(m), 3079(m), 2873(m), 1615(s), 1514(s), 1300(s), 1255(s), 1061(s), 854(s), 810(m), 752(s). [Cd(L)(DPA)]n (4). The synthesis of 4 was similar to that of 1 except that H2DPA (0.03 g, 0.13 mmol) was used instead of H2Fc. Prism shaped orange colored crystals of 4 were obtained in ~ 45% yield. Anal. calcd. for C32H22N6O4Cd: C, 57.63; H, 3.32; N, 12.60%. Found: C, 57.75; H, 3.38; N, 12.48%. IR (KBr, cm-1): 3436(br, w), 3123(m), 1600(m), 1573(s), 1547(s), 1510(s), 1441(m), 1391(s), 1303(s), 1243(s), 1160(m), 1121(m), 1058(s), 961(s), 932(m), 851(s), 823(m),771(m), 754(m). {[Cd2(L)2(BIPH)2(H2O)2]·H2O}n (5). The same synthetic method as that used for 1 was adopted except that H2Fc was replaced by H2BIPH (0.03 g, 0.13 mmol). Prism shaped orange colored crystals


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of 5 were collected in ~37% yield. The crystals were washed with water followed by acetone and then air-dried. Anal. calcd. for C64H50N12O11Cd2: C, 55.38; H, 3.63; N, 12.11%. Found: C, 55.43; H, 3.68; N, 12.08%. IR (KBr, cm-1): 3377(s), 3121(s), 2980(w), 1681(s), 1604(s), 1580(s), 1511(s), 1426(m), 1382(s), 1299(s), 1175(w), 1125(m), 1060(m), 960(m), 930(m), 846(s), 771(s), 757(s). {[Cd2(L)2(BIOXY)2]·H2O·CH3OH}n (6). Complex 6 was synthesized in a similar manner as that used for 1 except that the co-ligand in this case was H2BIOXY (0.03 g, 0.13 mmol). Rod shaped orange colored crystals of 6 were obtained in ~45% yield. The crystals were washed with water followed by acetone and then air-dried. Anal. calcd. for C65H50N12O12Cd2: C, 55.14; H, 3.56; N, 11.87%. Found: C, 55.23; H, 3.67; N, 11.81%. IR (KBr, cm-1): 3436(s), 3144(m), 1590(s), 1517(s), 1392(s), 1329(m), 1306(s), 1222(s), 1160(s), 1126(m), 1060(s), 1012(m), 961(s), 933(m), 876(s), 845(s), 782(s), 771(s). {[Zn3(L)5(LMA)2]·2.5H2O}n (7). A mixture containing ligand L (0.04 g, 0.13 mmol), H3LMA (0.02 g, 0.13 mmol) and Zn(NO3)2·6H2O (0.76 g, 0.25 mmol) in 3 mL DMF, 1 mL MeOH and 1 mL H2O were sealed in a Teflon lined autoclave and heated under autogenous pressure to 100 °C for two days and then allowed to cool to room temperature at the rate of 1°C per minute. Clear solution was obtained which on slow evaporation at room temperature gave prism shaped orange crystals of 7 in ~ 26% yield. Anal. calcd. for C98H81N30O12.5Zn3: C, 56.72; H, 3.93; N, 20.25%. Found: C, 56.89; H, 3.99; N, 20.12%. IR (KBr, cm-1): 3390(m), 3111(m), 1601(s), 1520(s), 1433(m), 1384(m), 1306(s), 1263(m), 1127(s), 1063(s), 1032(w), 963(s), 850(s), 731(m). {[Co(L)(DBDPA)]·H2O}n (8). A mixture containing ligand L (0.04 g, 0.13 mmol), H2DBDPA (0.06g, 0.13 mmol) and Co(NO3)2·6H2O (0.74 g, 0.25 mmol) in 3 mL DMF, 1 mL MeOH and 1 mL H2O were sealed in a Teflon lined autoclave and heated under autogenous pressure to 100 °C for two days and then allowed to cool to room temperature at the rate of 1 °C per minute. Red colored prism shaped crystals of 8 were obtained in ~45% yield. Anal. calcd. for C32H21N8O9Br2Co: C, 43.66; H, 2.40; N, 12.73%. Found: C, 43.54; H, 2.49 ; N, 12.79%. IR (KBr, cm-1): 3437(br, m), 3123(m), 2923(w), ACS Paragon Plus Environment


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1601(s), 1528(s), 1446(s), 1385(s), 1343(s), 1305(s), 1250(m), 1155(m), 1063(s), 943(m), 917(m), 851(s), 789(m), 731(s).

Results and Discussion All the coordination polymers, once isolated are stable in air and insoluble in common organic solvents and water. The IR spectra of 1-8 show strong absorption bands between 1400-1600 cm-1 that are diagnostic of coordinated carboxylate groups.16 The broad peak in the region, 3377-3442 cm-1 in case of complexes 1, 3, 5, 6, 7 and 8 indicates the presence of both coordinated and non-coordinated water molecules.17 In case of complex 2, peaks at ~3636 cm-1 and ~1654 cm-1 suggest the presence of lattice methanol and DMF molecules respectively.

Structural description Complex 1 crystallizes in the monoclinic space group P21/c and its asymmetric unit contains one Cd(II) ion, two halves of L and one Fc2- ligands besides one coordinated and two lattice water molecules. Each Cd(II) ion is equatorially bonded to two carboxylates from two different Fc2- ligands both in monodentate (Cd–O=2.278(5)Å) and chelating (Cd–O=2.328(5)Å) modes. The fourth equatorial site is occupied by a water molecule (Cd–O = 2.249(5)Å). The two axial sites on the metal are occupied by two imidazole N from two L ligands (Cd–N=2.280(5)–2.281(5)Å). This gives a distorted CdN2O4 octahedral geometry around the metal ion (Fig. 1a).18 The Cd–O and Cd–N bond lengths are within the range reported for octahedral Cd(II) based coordination polymers.19a

Space for Figure 1


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An infinite 2D layer structure (Fig. 2) is formed with interpenetration of two layers (Fig. 3 (a)). These are further stacked in ---ABAB--- fashion through strong H-bonding interactions to form an overall 3D architecture. Topological analysis20 shows that it is a uninodal 4-connected sql net with point symbol {44.62}(Fig. 3(b)).

Space for Figures 2 and 3

Single crystal X-ray structural study reveals that complexes 2 and 3 crystallize in monoclinic crystal system. Their structures were successfully solved and converged in the space group P21/c and P2/c respectively. The asymmetric unit of both the complexes are quite similar: one Cd(II), one L and one MDA2- ligands besides one DMF and one MeOH molecules in the lattice in 2 while in 3, three lattice H2O molecules are present in addition to one Zn(II) and the ligands. In each case, the metal ion has distorted octahedral MN2O4 coordination with ligation from two imidazole N atoms of two different L ligands (M−N = 2.063(3)−2.283(4)Å) and two chelated carboxylate O atoms of two MDA2- ligands (M−O=2.050(3)−2.419(3)Å) (Fig. 1b). Both M−O and M−N bond distances are within normal statistical errors.19a,b


In 2 and 3, each metal center is connected by L ligand units to form a 1D chain structure, which is pillared by MDA2- ligands to generate a 3D diamondoid network as depicted in Fig. 4. This binding mode generates a large void which is filled by mutual interpenetration of seven more independent frameworks, resulting in an overall eight-fold interpenetrated 3D structure (Fig. 5). Imidazole and phenyl rings of the L ligand are twisted to different extents in 2 and 3. The diamondoid cages are



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delineated by four cyclohexane-like windows in chair conformation showing different metal···metal distances as summarized in Table 2. The interpenetrating diamondoid cages in 2 are also slightly tilted as compared to 3 as shown in Figs. 6(b) and 7(b). Toplogically20, both the complexes form a uninodal 4-connected dia net (Figs. 6 and 7) with point symbol {66}. A number of diamondoid-like networks with extensive interpenetration ranging between 2 to 12 have been reported.21 A handful of 8-fold interpenetrated diamondoid coordination polymers of Cd(II) and Zn(II) are also reported.22

Space for Figures 6 and 7 Space for Table 2 Compound 4 crystallizes in the monoclinic space group P21/c with the asymmetric unit consisting of one Cd(II), one coordinated DPA2- and one coordinated L ligand. The Cd(II) ion is in a distorted MN2O4 octahedral geometry18 with ligation from four O atoms from two different DPA2- ions (Cd–O = 2.208(4)–2.571(4) Å) and two imidazole N atoms from two L ligands (Cd–N = 2.262(4)–2.275(4) Å) (Fig. 1c). All Cd– O and Cd–N bond lengths are within normal statistical errors.19a The L ligands with Cd(II) ions form a 1D chain with the Cd···Cd distance of 19.55 Å. The DPA2- ligands bind the metal ions in chelating mode connecting the chains to generate a 2D layer with rhombic grid (Fig. 8). These 2D layers stack in an ---ABAB--- fashion through strong CH···π and π···π interactions giving rise to an overall 3D supramolecular framework.


Topological analysis20 reveals a uninodal sql 4-connected net with the point symbol {44.62} (Fig. 9). Complex 5 also crystallizes in the monoclinic space group P21/c with the asymmetric unit consisting of two Cd(II) ions and two L and BIPH2- ligands besides two coordinated and one lattice


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water molecules. As shown in Fig. 1(d), both the Cd(II) ions are located in a six-coordinate environment and shows a distorted octahedral geometry18 with coordination from two imidazole N (Cd−N = 2.291(2)−2.335(2) Å), three carboxylate O (Cd−O = 2.211(2)−2.500(2) Å) and one water O atoms (Cd−Ow = 2.298(2)−2.309(2) Å). All Cd−O and Cd−N bond distances fall within the range observed for Cd(II) based coordination polymers.19a The structure can be described as a 2D rhombicgrid of dimension 15.58 × 20.06 Å2 generated by combination of four dicarboxylate ligands and four metal centers, which is extended to a 3D coordination polymer through the linear imidazole donor ligand. The overall 3D structure is stabilized by C−H···π (2.820(3) Å) and π···π interactions (3.337(3) Å) which is further reinforced by intricate H-bonding interactions involving lattice as well as metal coordinated water molecules. Due to mutual interpenetration of identical 3D frameworks, a three-fold interpenetrating architecture is observed (Fig. 10). Space for Figures 10 and 11

If each Cd(II) ion acts as a four connected square planar node, topologically on the basis of this simplification 5 has a uninodal four connected rare cdl toplogy.20, 23 The point symbol for this topology is {42.6.83}( Fig. 11). Complex 6 crystallizes in the triclinic space group P-1. The asymmetric unit consists of two Cd(II) ions, two L and two BIOXY2- ligands besides one H2O and one MeOH molecules. Each Cd(II) ion forms distorted octahedral geometry18 with coordination from four carboxylate O (Cd−O = 2.232(5)−2.526(5) Å), two imidazole N atoms (Cd−N=2.232(6)−2.269(5) Å)(Fig.1e). All bond distances involving the metal ions are within normal statistical errors.19a Here, each Cd(II) ion serves as a 4-connected node and is linked by L and BIOXY2- ligands to form a rectangular corrugated grid of dimension, 14.36 × 19.61 Å2. Space for Figures 12-14 ACS Paragon Plus Environment


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Lattice water and methanol molecules occupy the void spaces in the grid. The resulting 2D grid layers are further stacked in ---ABAB--- fashion through weak non-covalent interactions involving C−H···π (2.834(3) Å) and π···π interactions24 (3.249(5) Å) between adjacent layers which is further reinforced through strong H-bonding with lattice solvent molecules to form an overall 3D supramolecular framework (Figs. 12 and 13). Topological analysis20 of 5 reveals a uninodal sql 4-connected net with the point symbol {44.62}(Fig.14). Complex 7 crystallizes in the triclinic chiral space group P1 with the asymmetric unit consisting of three Zn(II), five L and two LMA3- ligands besides two and a half H2O molecules. Zn1 has a distorted octahedral MN4O2 coordination environment from N atom of imidazole moieties of four L ligands (Zn−N=2.078(9)−2.190(10)Å) and carboxylate O of two LMA3- ligands (Zn−O= 2.068(8)−2.079(7)Å) in monodentate fashion. On contrary to this, Zn2 and Zn3 exhibit distorted octahedral MN3O3 coordination geometry by ligation from three independent imidazole N atom of L ligand units (Zn−N = 2.093(11)−2.126(10)Å) and three O atoms of LMA3- ligands (Zn−O = 2.084(8) −2.196(8)Å) in chelating mode (Fig 1f). All Zn−O and Zn−N bond distances are comparable to those observed in other Zn(II) complexes.19b Both L and LMA3- ligands mutually coordinate with metal ions in such a way to form a doubly 2D distorted rhombic grid structure with distances between two metal ions as 19.61, 22.86 and 26.43 Å. These rhombic grids further propagate via. L ligand along crystallographic b-axis leading to a three dimensional double-layered supramolecular architecture (Fig. 15). Space for Figures 15 and 16


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Topologically20, Zn1 ion is considered as six-connected node, while Zn2 and Zn3 metal ions are fourconnected nodes. On the basis of this simplification, 7 has a 3D two-fold interpenetrated novel (4,6)connected pkb6 net (Fig. 16). The point symbol for this network is {4.64.8}2{42.612.8}. Complex 8 crystallizes in the orthorhombic space group Pnna with the asymmetric unit consisting of one Co(II) ion, one L ligand, one DBDPA2- ligand and one lattice water molecule. The metal ion exhibits a distorted octahedral environment supplied by N atoms of imidazole moieties of two L ligands (Co−N = 2.052(5)Å) and two oxygen atoms of two DBDPA2- ligand (Co−O = 2.057(5)−2.329(5)Å) (Fig.1g). The lengths of Co−N and Co−O are within the range reported for Co(II) based coordination polymers.19c Each completely deprotonated DBDPA2- anion connects two Co(II) centers with µ2-η1:η1:η1:η1 chelating mode and each L ligand connects two Co(II) centers in such a way that the imidazole rings are nearly coplanar. Each Co(II) ion is connected by alternating L and DBDPA2- ligands to form 1D zigzag chains. However, these chains form a 6-membered macrocycle consisting of two L and four DBDPA2- ligands in chair like cyclohexane conformation. These macrocycles are further extended via. L and coligand DBDPA2- to generate an overall 3D framework. Moreover, the mutual interpenetration of five independent equivalent frameworks gives rise to an overall 5-fold interpenetrated final framework. The void space in 8 is occupied by water molecules as shown in Fig. 17. Space for Figures 17 and 18 Topological analysis20 reveals that each Co(II) ion acts as a four connected node which are connected through L and DBDPA2- ligands to give rise to a rare 3D dmp net25 with point symbol {65.8}(Fig.18). TGA analyses Thermal stabilities of all complexes were examined.26 Complex 1 shows weight loss of ~7.2% in the temperature range, 70-180 ºC that corresponds to loss of both lattice and coordinated water molecules.



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The de-solvated framework is found to be stable up to ~285 ºC. Complex 2 exhibits a weight loss of ~12.0% within the temperature range 70-350 ºC which is attributed to the release of lattice methanol and DMF molecules from the framework. Decomposition of the complex is accomplished only above 380 oC. Complex 3 undergoes a weight loss of ~6.95% in the temperature range 70-135 oC and is thermally stable upto 400 ºC. No weight loss was found for complex 4 before decomposition of the framework occurs at 360 ºC. Complex 5 shows a weight loss of ~3.89% corresponding to loss of both coordinated and lattice water molecules around 80-160 ºC and the framework is stable upto 390 ºC. Complex 6 shows a weight loss of ~3.53% in the temperature range 60-130 ºC which is attributed to the loss of one methanol and one water molecule from the framework. The desolvated framework is stable upto ~360 ºC. Complexes 7 and 8 exhibits a weight loss of ~2.17% in temperature range 70130ºC and ~2.05% in 60-135ºC assigned to the release of two and a half and one water molecule respectively. The decomposition of the frameworks occurred at around ~290 ºC and ~380 ºC respectively. (Supplementary information, S13-S20). PXRD analysis Powder X-ray diffraction (PXRD) patterns of complexes 1–8 were in excellent agreement with the simulated patterns. The observed differences in intensity could be due to preferred orientation of the powder samples (Supplementary information, S21-S28). Luminescence Studies. Luminescence behavior of complexes of d10 metal ions with nitrogen and carboxylate donor ligands has been a subject of immense current research.27 Metal-organic frameworks have been reported to exhibit high thermal stability and the ability to tune emission intensity of the free-organic ligands after coordination with metals. The photoluminescent spectra of complexes 1–8 and metal-free L ligand have been investigated in the solid state at room temperature. The emission spectra of these complexes are depicted in Fig. 19. The maxima of emission peaks of complexes 1–8 are observed at 426, 397, 405, 423, 408, 412, 406, and 365 nm with λex= 322nm. Metal-free L ligand ACS Paragon Plus Environment

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fluoresced in the solid state with emission peak at 420 nm. The profile of the emission band of 1-8 is quite similar to that of the free-organic ligands, but the emission maxima of all the complexes show slight shift in wavelength. This inequality in emission behavior could be due to differences in metal ions, carboxylate coligands, azo containing imidazole L ligand, and also encapsulated lattice molecules. However, the role of structural complexity and framework robustness cannot be ignored. Considering above factors, it is equally difficult to assign its emissions, as it is neither metal-to-ligand charge transfer (MLCT) nor ligand-to-metal charge transfer (LMCT) in nature as d10 configurations are not easily susceptible to oxidize/reduce.28 The possibility of cluster-centered transitions can also be ruled out because of the Metal···Metal separation is more than ~3.6 Å. Therefore, the blue/red shift in 1-8 could be attributed to a change in energy levels (HOMO-LUMO) of carboxylate-based anionic and neutral L ligands. The profile of emission bands suggests the possibility of intraligand (π–π*) transitions.29

Space for Figure 19

Compared with the ligand, these complexes exhibit enhancement in luminescence intensity except in 8. Usually, upon complexation with metal, enhancement in the intensity and also quantum efficiencies have been observed as the metal cluster effectively increases the rigidity of the ligand and reduces the loss of energy by radiation-less decay.30 Inimically, quenching of emission intensity is observed in 8 due to presence of paramagnetic metal center.9 Conclusions In conclusion, we have described construction of eight new coordination polymers of Zn(II), Cd(II), and Co(II) ions using a linear L ligand and various carboxylate-based coligands under solvothermal conditions. In all the polymers the channel surfaces are decorated with azo functional groups provided



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with basic nitrogen sites. Interestingly, all complexes are structurally and topologically quite different which arises due to varied geometry and flexibility of carboxylate coligands used. Complexes 1, 4 and 6 show very familiar sql topology, while complexes 2 and 3 are simplified in dia net. Contrary to this, complexes 5 and 8 show rare cdl and dmp net. However, the complex 7 forms a coordination polymer with a novel (4,6)-connected, 2 nodal net with novel pkb6 topology. The successful syntheses of 1-8 further enriches crystal engineering methods that can provide new perspectives for design and fabrication of different kinds of interpenetrated networks. Solid-state emission characteristics of the coordination polymers also present new vistas for materials design. Presently we are looking at different modes of interpenetrated networks for useful applications.

Acknowledgment We gratefully acknowledge the financial support received from the Department of Science and Technology, New Delhi, India (to P.K.B.) We thank Musheer Ahmad for his help on topological analysis. Supporting Information X-ray crystallographic data in CIF format, table for selected bonds and distances for 1-8, and complete data for IR, UV, TGA analysis, ESI-MS, and NMR. This material is available free of charge via the Internet at http://pubs.acs.org/. References 1. (a) Roesky, H. W.; Andruh, M. Coord. Chem. Rev. 2003, 236, 91. (b) Holliday, B. J.; Mirkin, C. A. Angew. Chem., Int. Ed. 2001, 40, 2022. (c) Noro, S-i.; Kitaura, R.; Kondo, M.; Kitagawa, S.; Ishii, T.; Matsuzaka, H.; Yamashita M. J. Am. Chem. Soc. 2002, 124, 2568. (d) Samai, S.; Biradha, K. Cryst. Growth Des. 2011, 11, 5723. (e) Carlucci, L.; Ciani, G.; Macchi,


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P.; Proserpio, D. M.; Rizaato, S. Chem. Eur. J. 1999, 5, 237. (f) Biradha, K.; Sarkar, M.; Rajput, L. Chem. Commun. 2006, 4169. (h) Dobrzańska, L.; Kleinhans D. J.; Barbour, L. J. New J. Chem. 2008, 32, 813. (i) Janiak, C. Dalton Trans. 2003, 2781. 2. (a) Yaghi, O. M. Nat. Mater. 2007, 6, 92. (b) Liu, B.; Yang, Q.; Xue, C.; Zhong, C.; Chen, B.; Smit B. J. Phys. Chem. C, 2008, 112, 9854. (c) Ma, S.; Sun, D.; Ambrogio, M.; Fillinger, J. A.; Parkin, S.; Zhou, H.-C. J. Am. Chem. Soc. 2007, 129, 1858. (d) Kitagawa, S.; Matsuda, R. Coord. Chem. Rev. 2007, 251, 2490. (e) Ma, L.; Lin, W. Angew. Chem., Int. Ed. 2009, 48, 3637. 3. (a) Zhang, J. J.; Wojtas, L.; Larsen, R. W.; Eddaoudi, M.; Zaworotko, M. J. J. Am. Chem. Soc., 2009, 131, 17040. (b) Chamayou, A.-C.; Janiak, C. Inorg. Chim. Acta 2010, 363, 2193. (c) Wu, H.-P.; Janiak, C.; Uehlin, L.; Klüfers, P.; Mayer, P. Chem. Commun.1998, 2637. 4. (a) Aakeröy, C. B.; Champness, N. R.; Janiak, C. CrystEngComm 2010, 12, 22. (b) Habib, H. A.; Sanchiz, J.; Janiak, C. Dalton Trans. 2008, 1734. 5. (a) Sharma, M. K.; Bharadwaj, P. K. Inorg. Chem. 2011, 50, 1889. (b) Singh, R.; Ahmad, M.; Bharadwaj, P. K. Cryst. Growth Des. 2012, 12, 5025. 6. (a) Cui, Y.; Yue, Y.; Qian, G.; Chen, B. Chem. Rev. 2012,1126. (b) Allendorf, M. D.; Bauer, C. A.; Bhakta, R. K.; Houk, R. J. T. Chem. Soc. Rev. 2009, 38, 1330. (c) Rocha, J.; Carlos, L. D.; Almeida Paz, F. A.; Ananias, D. Chem. Soc. Rev. 2011, 40, 926. 7. (a) Lan, Y.-Q.; Jiang, H.-L.; Li, S.-L.; Xu, Q. Inorg. Chem. 2012, 51, 7484. (b) Yu, Q.; Zhang, X.; Bian, H.; Liang, H.; Zhao, B.; Yan, S.; Liao, D. Cryst. Growth Des., 2008, 8, 1140. (c) Samai, S.; Biradha, K. Cryst. Growth Des. 2011, 11, 5723. (d) Carlucci, L.; Ciani, G.; Macchi, P.; Proserpio, D. M.; Rizaato, S. Chem. Eur. J. 1999, 5, 237. (e) Biradha, K.; Sarkar, M.; Rajput, L. Chem. Commun. 2006, 4169. (f) Dobrzańska, L.; Kleinhans, D. J.; Barbour, L. J. New J. Chem. 2008, 32, 813.



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8. (a) McGarrah, J. E.; Kim, Y. J.; Hissler, M.; Eisenberg, R. Inorg.Chem. 2001, 40, 4510. (b) Wu, Q.; Esteghamatian, M.; Hu, N. X.; Popovic, Z.; Enright, G.; Tao, Y.; D’Iorio, M.; Wang, S. Chem. Mater. 2000, 12, 79. (c) Taylor, K. M. L.; Rieter, W. J.; Lin, W. J. Am. Chem. Soc. 2008, 130, 14358. (d) Taylor, K. M. L.; Jin, A.; Lin, W. Angew. Chem., Int. Ed. 2008 47, 7722. (e) Luo, F.; Batten, S. R. Dalton Trans. 2010, 39, 4485. 9.

(a) Zeng, F.; Ni, J.; Wang, Q.; Ding, Y.; Ng, S. W.; Zhu, W.; Xie, Y. Cryst. Growth Des. 2010, 10, 1611. (b) Bauer, C. A.; Timofeeva, T. V.; Settersten, T. B.; Patterson, B. D.; Liu, V. H.; Simmons, B. A.; Allendorf, M. D. J. Am. Chem. Soc. 2007, 129, 7136. (c) McManus, G. J.; Perry, M.; Wagner, B. D.; Zaworotko, M. J. J. Am. Chem. Soc. 2007, 129, 9094. (d) Tzeng, B. C.; Chiu, T. H.; Chen, B. S.; Lee, G. H. Chem. Eur. J. 2008, 14, 5237. (f) Suen, M. C.; Wang, J. C. J. Coord. Chem. 2007, 60, 257.

10. Ahmad, M.; Das, R.; Lama, P.; Poddar, P.; Bharadwaj, P. K. Cryst. Growth Des. 2012, 12, 4624. 11. Sheldrick, G. M. SHELXTL Reference Manual, version 5.1;Bruker AXS: Madison, WI, 1997. 12. Sheldrick, G. M. SHELXL-97: Program for Crystal Structure Refinement; University of Gottingen: Gottingen, Germany, 1997. 13. Spek, A. L. PLATON; The University of Utrecht: Utrecht, The Netherlands, 1999. 14. Jiang, H. -L.; Feng, D.; Liu, T. -F.; Li, J. -R.; Zhou, H.-C. J. Am. Chem. Soc. 2012, 134, 14690. 15. Das, R. K.; Aijaz, A.; Sharma, M. K.; Lama P.; Bharadwaj, P. K. Chem. Eur. J. 2012, 18, 6866.


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16. (a) Lisnard, L.; Mialane, P.; Dolbecq, A.; Marrot, J.; Clemente-Juan, J. M.; Coronado, E.; Keita, B.; de Oliveira, P.; Nadjo, L.; Secheresse, F. Chem. Eur. J. 2007, 13, 3525. (b) Li, X. J.; Wang, X. -Y.; Gao, S.; Cao, R. Inorg. Chem. 2006, 45, 1508. 17. (a) Dobrzynska, D.; Jerzykiewicz, L. B.; Jezierska, J.; Duczmal, M. Cryst. Growth Des. 2005, 5, 1945. 18. (a) Banerjee, S.; Lassahn, P.-G.; Janiak, C.; Ghosh, A. Polyhedron 2005, 24, 593. (b) Banerjee, S.; Ghosh, A.; Wu, B.; Lassahn, P.-G.; Janiak, C. Polyhedron 2005, 24, 593. 19. (a) Wu, C.-D.; Ayyappan, P.; Evans, O. R.; Lin, W. Cryst. Growth Des. 2007, 7, 1690. (b) Bourne, S. A.; Lu, J.; Moulton, B.; Zaworotko, M. J. Chem. Commun. 2001, 861. (c) Ghosh, S. K.; Bharadwaj, P. K. Inorg. Chem. 2005, 44, 5553. 20. (a) The network topology was evaluated by the program“TOPOS-4.0”, see http:// www.topos. ssu.samara.ru; Blatov, V. A. IUCr Comp Comm Newsl. 2006, 7, 4. (b) Blatov, V. A.; Shevchenko, A. P.; Serezhkin, V. N. J. Appl. Crystallogr. 2000, 33, 1193. (c) Blatov, V. A.; O’Keeffe, M.; Proserpio, D. M. CrystEngComm 2010, 12, 44. 21. (a) Carlucci, L.; Ciani, G.; Macchi, P.; Proserpio, D. M.; Rizzato, S. Chem. Eur. J. 1999, 5, 237.(b) Roy, S.; Mahata, G.; Biradha, K. Cryst. Growth Des. 2009, 9, 5006. (c) Hirsch, K. A.; Wilson, S. R.; Moore, J. S. Inorg. Chem. 1997, 36, 2960. 22. (a) Lin, W.; Ma, L.; Evans, O. R. Chem. Commun. 2000, 2263. (b) Cheng, J.-J.; Chang, Y.-T.; Wu, C.-J.; Hsu, Y.-F.; Lin, C.-H.; Proserpio, D. M.; Chen, J.-D. CrystEngComm 2012, 14, 537. 23. Wang, N.; Ma, J.-G.; Shi, W.; Cheng, P. CrystEngComm 2012, 14, 5198. 24. Janiak, C. J. Chem. Soc., Dalton Trans. 2000, 3885. 25. Blatov, V. A.; Carlucci, L.; Ciani, G.; Proserpio, D. M. CrystEngComm 2004, 6, 378. 26. See Supporting Information.



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27. (a) McGarrah, J. E.; Kim, Y. J.; Hissler, M.; Eisenberg, R. Inorg.Chem. 2001, 40, 4510. (b) Lee, E. Y.; Jang, S. Y.; Suh, M. P. J. Am. Chem. Soc. 2005, 127, 6374. (c) Habib, H. A.; Hoffmann, A.; Ho ppe, H. A.; Steinfeld, G.; Janiak, C. Inorg. Chem. 2009, 48, 2166. (d) Habib, H. A.; Hoffmann, A.; Höppe, H. A.; Janiak, C. Dalton Trans. 2009, 1742. 28. (a) Barbieri, A.; Accorsi, G.; Armaroli, N. Chem. Commun. 2008, 2185. (b) Campagna, S.; Puntoriero, F.; Nastasi, F.; Bergamini G.; Balzani, V. Top. Curr. Chem. 2007, 280, 117. 29. (a) Du, M.; Jiang, X. J.; Zhao, X. J. Inorg. Chem. 2007, 46, 3984. (b) Zaworotko, M. J. Nature 2008, 451, 410. (c) Plessis, M. D.; Barbour, L. J. Dalton Trans. 2012, 41, 3895. (d) Shustova, N. B.; Cozzolino, A.F.; Dincă, M. J. Am. Chem. Soc. 2012, 134, 19596. (e) Zhang, L.; Qin, Y. -Y.; Li, Z. -J.; Lin, Q. -P.; Cheng, J. -K.; Zhang J.; Yao Y. -G. Inorg. Chem. 2008, 47, 8286. 30. (a) Zheng, S. L.; Yang, J. H.; Yu, X. L.; Chen, X. M.; Wong, W. T. Inorg. Chem. 2004, 43, 830. (b) Valeur, B. Molecular Fluorescence: Principles and Applications; Wiley-VCH: Weinheim, Germany, 2002. (c) Ahmad, M., Bharadwaj, P. K. Polyhedron 2013, 52, 1145.


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Table 1.Crystal and structure refinement data for 1-8 Compound

1

2

3

Empirical formula Formula wt.

C30H28N6O7CdFe

C44H41N7O6Cd

C40H36N6O7Zn

752.84

876.23

778.12

666.96

Crystal system

Monoclinic

Monoclinic

Monoclinic

Monoclinic

Space group

P21/c

P21/c

P2/c

P21/c

a, Å

15.045(5)

16.023(5)

15.526(4)

8.055(5)

b, Å

20.017(3)

24.182(6)

12.813(3)

17.819(5)

c, Å

9.736(5)

10.566(5)

10.324(2)

18.976(5)

α (°)

90.000

90.000

90.00

90.000

β (°)

94.604(5)

104.666(5)

104.633(4)

100.336(5)

γ (°)

90.000

90.000

90.00

90.000

U, Å

2922.6(19)

3961(2)

1987.2(8)

2679(2)

Z

4

4

2

4

1.697

1.293

1.210

1.653

µ, mm-1

1.283

0.597

0.663

0.867

F(000)

1496

1568

748

1344

Refl. collected

15752

21346

10640

14384

3568

5196

2665

3626

1.024

0.995

1.068

1.043

3

ρcalc g/cm

3

Independent refl. GOOF


4 C32H22N6O4Cd


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Final R indices

R1= 0.0562

R1= 0.0556

R1= 0.0857

R1= 0.0450

[I>2σ(I)]

wR2 = 0.1275

wR2 = 0.1415

wR2 = 0.2363

wR2 = 0.1021

R indices

R1= 0.0961

R1= 0.0760

R1= 0.1051

R1= 0.0733

(all data)

wR2 = 0.1612

wR2 = 0.1550

wR2 = 0.2475

wR2 = 0.1373

Compound

5

6

7

8

Empirical formula Formula wt.

C64H50N12O11Cd2

C65H50N12O12Cd2

C98H81N30O12.5Zn3

C32H21N8O9Br2Co

1387.96

1415.97

2075.04

880.32

Crystal system

Monoclinic

Triclinic

Triclinic

Orthorhombic

Space group

P21/c

P-1

P1

Pnna

a, Å

29.729(4)

11.857(5)

11.443(5)

8.733(2)

b, Å

16.864(5)

12.448(3)

12.965(3)

22.980(5)

c, Å

10.889(3)

22.213(5)

17.669(5)

16.283(4)

α (°)

90.000

101.996(5)

99.748(5)

90.00

β (°)

92.976(5)

99.977(5)

101.328(5)

90.00

γ (°)

90.000

107.559(5)

103.586(5)

90.00

U, Å

5452(3)

2958.0(18)

2433.7(16)

3267.8(13)

Z

4

2

1

4

1.686

1.583

1.385

1.789

µ, mm-1

0.860

0.795

0.808

3.041

F(000)

2792

1420

1044

1752

Refl. collected

38842

16133

13103

16284

Independent refl.

8132

8069

7881

2098

GOOF

1.031

1.068

1.015

1.048

3

ρcalc g/cm

3


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Final R indices

R1= 0.0329

R1= 0.0699

R1= 0.0848

R1= 0.0954

[I>2σ(I)]

wR2 = 0.0702

wR2 = 0.1874

wR2 = 0.2247

wR2 = 0.2521

R indices

R1= 0.0479

R1= 0.0929

R1= 0.1040

R1= 0.1239

(all data)

wR2 = 0.0764

wR2 = 0.2340

wR2 = 0.2480

wR2 = 0.2782

Table 2. Representation of Dihedral angles and M···M distances in 2 and 3 Complex

2

3

Dihedral Angle (°)

31.88

47.87

26.96

29.54

(C9−C4−N2−C3)

(C9−C4−N2−C3)

19.56 X 19.29

19.92 X 19.67 X 20.17

Torsional Angle (°) M···M distance (Å)

32.71 X 48.62 Diagonal M···M distances (Å)

36.23 X 45.03 37.19 X 49.24


33.66 X 45.80 36.43 X 47.88


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

N

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N N

N N

N

L COOH O Fe HOOC

COOH

H2BIOXY HOOC

H2Fc

COOH

HOOC

COOH

H2MDA NO2 Br COOH

HOOC

COOH

H2BIPH Br O2N

H2DBDPA COOH ∗

HOOC

COOH

HOOC OH

H3LMA H2DPA

Scheme 1


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Figure 1

Figure 2 ACS Paragon Plus Environment


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

Figure 3

Figure 4


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Figure 5

Figure 6



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

Figure 7

Figure 8


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Figure 9

Figure 10



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

Figure 11

Figure 12

Figure 13 ACS Paragon Plus Environment

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Figure 14

Figure 15



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

Figure 16

Figure 17


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Figure 18

Figure 19



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Coordination Polymers Built With a Linear bis-Imidazole and Different Dicarboxylates: Unusual Entanglement and Emission Properties Ruchi Singh and Parimal K. Bharadwaj* *

Department of Chemistry, Indian Institute of Technology Kanpur, 208016, India Email: [email protected] Captions for the Scheme and Figures

Scheme 1

Carboxylate based various coligands

Figure 1

Metal coordination modes in 1-8 Perspective view of 2D grid showing embedded water molecules in space-

Figure 2 fill model in 1. Perspective view of (a) 2D structure stacked in ---ABAB--- fashion, and (b) Figure 3 topological view of uninodal sql net in 1 Figure 4

Perspective view of 3D diamondoid network in 2 (left) & 3 (right).

Figure 5

Diagrammatic depiction of 3D view along b-axis 2 (left) & 3 (right). Perspective view of (a) Topological view of uninodal 4-connected dia net,

Figure 6 and (b) section of 8-fold interpenetrated adamantoid net in 2. Perspective view of (a) Topological view of uninodal 4-connected dia net, Figure 7 and (b) section of 8-fold interpenetrated adamantoid net in 3. Figure 8

Representation of 2D rhombic grid in 4.

Figure 9

Topological view of uninodal sql net in 4. Perspective view of 3D architecture showing embedded water molecules in

Figure 10 space-fill model in 5. Figure 11

Topological view of rare 3D cdl net in 5.


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Figure 12

Perspective view of framework showing weak interactions in 6.

Figure 13

2D grid layers stacked in ---ABAB--- fashion in 6.

Figure 14

Topological view of uninodal sql net in 6.

Figure 15

3D view along b-axis with double-layered rhombic grid in 7.

Figure 16

Topological view of (4,6)-connected novel pkb6 net in 7.

Figure 17

Perspective view of (a) 3D architecture showing embedded water molecules in space-fill model, and (b) 6-membered macrocycle in chair like cyclohexane conformation in 8.

Figure 18

Topological view of rare 3D dmp net in 8.

Figure 19

Solid state emission spectra of 1-8.



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Coordination Polymers Built With a Linear bis-Imidazole and Different Dicarboxylates: Unusual Entanglement and Emission Properties Ruchi Singh and Parimal K. Bharadwaj* *

Department of Chemistry, Indian Institute of Technology Kanpur, 208016, India Email: [email protected]

Eight new Zn(II), Cd(II) and Co(II) based coordination polymers exhibiting diverse topologies with varying degree of interpenetration have been synthesized. Solid-state photoluminescence studies has been carried out for all the complexes. For the Table of Contents


Coordination Polymers Built with a Linear Bis-Imidazole and Different

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