3-yl)vinyl)-1H

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Diversity in the Coordination Polymers of 2-(2-(pyridin-4/3yl)vinyl)-1H-benzimidazole and Dicarboxylates/Disulfonates: Photochemical Reactivity and Luminescence Studies Abhijit Garai, Somnath Sasmal, and Kumar Biradha Cryst. Growth Des., Just Accepted Manuscript • DOI: 10.1021/acs.cgd.6b00578 • Publication Date (Web): 20 Jun 2016 Downloaded from http://pubs.acs.org on June 28, 2016

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Crystal Growth & Design

Diversity in the Coordination Polymers of 2-(2-(pyridin-4/3yl)vinyl)-1H-benzimidazole and Dicarboxylates/Disulfonates: Photochemical Reactivity and Luminescence Studies Abhijit Garai, Somnath Sasmal and Kumar Biradha* Department of Chemistry, Indian Institute of Technology, Kharagpur 721302, India ABSTRACT: Solvothermal reactions of Cd(II) or Zn(II) with two unsymmetrical olefinic ligands containing benzimidazole and 3pyridyl/4-pyridyl moieties and ancillary anionic linkers such as dicarboxylates or disulfonates resulted in the coordination polymers containing diversified geometries. The crystal structure analyses of about eight of such CPs reveal that the coordination networks found here include one dimensional (1D) chains of metal and dicarboxylates/disulfonates with ligands as pendents, twodimensional corrugated layers containing rectangular grids and three-dimensional (3D) coordination network. In two of the complexes, Cd2O2 acts as secondary building unit (SBU) to form 2D-layer of metal and dicarboxylates. The interdigitation of the pendent ligands of 1D-chains resulted in the required alignment of double bonds of L1 or L2 for photochemical [2+2] reaction, in two of the CPs. These CPs upon irradiation were found to undergo solid state [2+2] cycloaddition reactions with 100% conversion. All the complexes including irradiated ones found to exhibit intense emission in solid state luminescence studies.

The quest for new materials based on coordination polymers (CPs) is of ever increasing given their multifunctional properties.1-8 Various new ligands and their combinations are being exploited for the design and synthesis of novel CPs. The use of symmetrical bis-pyridyl ligands containing various spacers in combination with several dicarboxylates and transition metals is one of the well exploited strategies that resulted in plethora of CP-based functional materials.9-16 Recently, several bisimidazole ligands in combination with dicarboxylates were also shown to result in novel CPs upon reaction with transition metals.17-23 However, the CPs of ligands containing the combination of benzimidazole and pyridyl moieties have not been explored to that extent. Some of the functional properties of CPs include gas storage,24-25 magnetism,26-27 non-linear optical activity,28-29 photochemical reactivity,30-31 luminescence,32-33 catalysis34-35 and sensors.36-37 Further, the CPs containing ligands with olefins are of great importance in order to synthesize photoreactive coordination polymers.38-47 Bis-(4-pyridyl)-ethylene is well utilized ligand for building up photoreactive CPs.48-53 Recently, it was shown by us and others that the photoreactive coordination polymers of bis-olefin containing ligands have an ability to produce CPs of organic polymers via post synthetic irradiation.54-59 In this manuscript, we aim to explore the CPs of unsymmetrical olefin containing pyridyl and benzimidazole moieties in combination with ancillary ligands such as dicarboxylates and their photochemical reactivities. The ligands L1 & L2 (Scheme 1) are of our choice for such studies due to following special features: 1) they have a potential to produce CPs which can undergo solid state photochemical [2+2] reactions; 2) they are effective bilinkers to lead to the formation of 1D, 2D and 3D coordination polymers with void spaces; 3) they contain two groups that have different coordination abilities; 4) the presence of benzimidazole moiety and conjugated-π system are anticipated to form CP-based luminescent materials.

N

N

N N

N

N

H

L1

H

L2

Scheme 1: Structural drawings for L1 and L2. The ligand L1 was shown by us earlier to form photoreactive gels and coordination polymer upon reaction with Ag(I).60 It is interesting to note here that the gel and crystalline CPs resulted in different stereoselective dimers upon irradiation which indicated that the packing of the 1D CPs in gel differs from that of the crystal structure. This is a unique example in which the [2+2] reaction served as a tool to establish the differences between crystalline and gel state molecular aggregations. In addition, to date, only one coordination polymer of the ligand L1 was reported that contains Co(II) and terephthalate linker.61 We note here that no coordination polymer of the ligand L2 has been reported to date. In this work, Zn(II) and Cd(II) coordination polymers of the ligands L1 and L2 with incorporation of dicarboxylate and disulfonate linkers as ancillary ligands have been explored. The systematic variation of the geometries of the coordination networks as the L changes from 3-pyridyl to 4-pyridyl and lengths of the dicarboxylates increases, was studied in detail by analyzing the crystal structures of their coordination polymers. From crystal structure analyses, it was found that two out of eight complexes studied here fulfill the reactivity criteria for solid state [2+2] photochemical reactions.62 As the ligands contain conjugated-π system, the ligands and CPs exhibited intense luminescence emissions.

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Results and discussion The ligands L1 and L2 were synthesized from the condensation reactions of o-phenylenediamine with 4-pyridylacrylic acid and 3-pyridylacrylic acid respectively in presence of polyphosphoric acid.63 The crystallization reactions were conducted by reacting L1 or L2 with Cd(NO3)2 or Zn(NO3)2 in the presence of sodium salts of succinic acid (SA), glutaric acid (GA), adipic acid (AA), terephthalic acid (TA) and 1,5napthalenedisulfonic acid (NDSA). Suitable single crystals of coordination polymers 1-8 for single crystal X-ray diffraction were obtained by employing solvothermal conditions in MeOH-H2O solvent system. The crystal structures of these coordination polymers were analysed in terms of network geometries and hydrogen bonds. The photochemical reactivities and luminescence properties were studied based on their structural aspects. The pertinent crystallographic details and hydrogen bonding geometries for complexes 1-8 were given in Table 1 and Table 2 respectively. {[Zn(L1)(SA)]·H2O}n, 1 {[Zn(L2)(SA)]·2(H2O)}n, 2 {[Cd(L2)(SA)]·2(H2O)}n, 3 {[Cd(L2)(GA)]·(H2O)}n, 4 {[Zn(L1)2(AA)]·4(H2O)}n, 5 {[Zn(L2)(TA)(H2O)]·(H2O)}n, 6 {[Cd(L1)2(NDSA)(H2O)2]·2H2O}n, 7 {[Cd(L2)2(NDSA)(H2O)2]}n, 8

(a)

(c)

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Corrugated 2D-layers containing rectangular grids. Both complexes 1 and 2 contain Zn(II) as well as same dicarboxylate such as succinate but the difference is 1 contains L1 (4pyridyl) while 2 contains L2 (3-pyridyl). Accordingly the crystal structures of 1 and 2 found to have some similarities and dissimilarities. Both complexes crystallized in P21/c space group with considerable differences in cell parameters. The asymmetric units possess one unit each of Zn(II), ligand (L1 for 1 and L2 for 2), succinate and uncoordinated water molecules (one for 1 and two for 2). For both the complexes, the coordination environment of Zn(II) is distorted tetrahedral and the four corners are occupied by two N-atoms (one of them is pyridyl and another one is imidazole nitrogen) from two ligand molecules and two O-atoms from two succinates. In these two complexes, SA remains in gauche conformation with CC-C-C torsion angles are 72.70° and 66.72° for the complexes 1 and 2 respectively. The overall network in 1 and 2 can be described as highly corrugated 2D-layers with (4,4) geometry (Figure 1a, b). The rectangular grids exhibit dimensions of 9.64×6.14 Å2 and 10.09×6.93 Å2 in 1 and 2 respectively. The longer and shorter dimensions are the separation of Zn(II) ions by L and SA respectively. The 2D-networks interact with each other via hydrogen bonding between water molecules and carboxylates (Figures 1c, d).

(b)

(d)

Figure 1. Illustrations for the crystal structures of 1 and 2: Corrugated 2D-layers containing rectangular grids (a) in 1 and (b) in 2, the metal centers joined by lines for the sake of clarity. Notice the difference between the layers. Hydrogen-bonding between the layers (c) in 1 and (d) in 2.


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Conformational changes in L2 resulted in alteration of 3D to 2D-network. The complexes 3 and 4 crystallize in Pbca space group and asymmetric units of these two com-

plexes contain one unit each of Cd(II), ligand L2, dicarboxylate (SA for 3 and GA for 4) and uncoordinated water molecules (two for 3 and one for 4).

(a)

(b)

(d) (c)

(f)

(e)

(g)

Figure 2. Illustrations for the crystal structures of 3 and 4: Coordination sphere of Cd(II) (a) in 3 and (b) in 4; 2D-layers of metal and dicarboxylates via Cd2O2 SBU (c) in 3 and (d) in 4, notice tetramer of water in the layers of 3; (e) 3D-coordination network in 3 formed via pillaring of layers by L2; (f) Binding of the L2 to the Cd(II) centers of the 2D-layer above and below the plane in 4; (g) Interdigitation of 2D-layers via hydrogen bonding in 4.



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In both the complexes, the Cd(II) centers exhibit distorted pentagonal bipyramidal geometry, with five oxygen atoms from three succinates (for 3) or glutarates (for 4) situated in the equatorial plane and two nitrogen atoms (one pyridyl and one imidazole) from two ligands (L2) in the axial positions (Figure 2a, b). In the complex 3, among the three succinates coordinated to one metal center, two are chelated to metal with bite angles of 52.78° and 55.27° and similarly, in the complex 4, the bite angles are 52.04° and 54.97°. In case of complex 3, SA remains in anti-conformation with C-C-C-C torsion angle

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of 170.21°. The Cd(II) and dianions form 2D-layers in both the structures which are composed of Cd2O2 SBUs (Figure 2c, d). In the layer, each dianion is connected to three Cd(II) centers: two through chelation and one through µ2-O bridge. These two layers differ significantly, in 3 they contain bigger cavities which are occupied by water tetramer, whereas in 4 they have smaller cavities as they are squeezed due to longer alkyl chains. Further, the major difference between these two structures is that 3 exhibits a 3D-network while 4 exhibits a 2Dnetwork. This is due to the difference in the geometry of L2

(b)

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3.723 Å

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4.639 Å

5.023 Å

(g)

Figure 3. Illustrations for the crystal structures of 5 and 6: 1D-chains of metal and dicarboxylates (a) in 5 and (b) in 6 with L1 and L2 as pendents; Interdigitation of 1D-chains (c) in 5 and (d) in 6; (e) the packing via hydrogen bonding with water molecules in 5; (f) π-π stacking and double bond distances of L2 in 6; (g) hydrogen bonded 2D-network along ab plane in 6.


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and its binding to the layers. In 3, L2 exhibits a trans geometry with respect to the coordination of N-atoms of 3-pyridyl and benzimdazole moiety, while they are cis in 4. In 3, L2 with trans geometry acts as pillar to link the 2D-layers to 3Dnetworks with a separation distance of 8.887 Å (Figure 2e). Whereas in 4, L2 with cis geometry binds to the same 2D-layer (Figure 2f). Further in complex 3, the water molecules form tetramer via O-H···O hydrogen bonding (O···O: 2.791 Å and 2.878 Å) (Figure 2c). Among the four water molecules in the cluster, two hydrogen bonded further to benzimidazole via N-

(a)

H···O (2.785 Å) and the other two form O-H···O (O···O: 2.772 Å) hydrogen bonds with SA. In case of complex 4, the 2D layers are interdigitated and interact via hydrogen bonding (N-H···O: 2.804 Å and O-H···O: 2.833 Å) between water molecules and imidazole or carboxylates of GA (Figure 2g). 1D-networks by AA and TA with L1 and L2 as pendents. The longer dicarboxylates such as adipate and terephthalate resulted in one-dimensional Zn(II) CPs with L1 and L2 respectively.

(b)

(d) (c)

(f)

(e)

(g)

3.513 Å

Figure 4. Illustrations for the crystal structures of 7 and 8: 1D-chains of NDSA and Cd(II) with ligands as pendents (a) in 7 and (b) in 8; Hydrogen bonding interactions between 1D-chains to form 3D network (c) in 7 and (d) in 8; The linking of 1D-chains to form 2D-layer via hydrogen bonding and π-π interactions (e) in 7 and (f) in 8; (g) π-π stacking and double bonds alignment between L2 molecules in 8.



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The complex 5 crystallizes in C2/c space group and complex 6 crystallizes in P-1 space group. The asymmetric unit of 5 is comprised of half unit each of Zn(II) and AA, one unit of water and two units of uncoordinated water molecules. Whereas that of 6 is constituted by one unit each of Zn(II) and L2, two half units of TA, and one unit each of coordinated and uncoordinated water molecules. In both complexes, the Zn(II) ion adopts distorted tetrahedral geometry: in 5 the four coordination sites are occupied by two imidazole nitrogens and two Oatoms of carboxylates of AA; in 6 they are occupied by two Oatoms of TA, one ligand imidazole N-atom and one water molecule. In both cases, the coordination of Zn(II) with dicarboxylates resulted in the formation of 1D-chains which are linear in 5 and zigzag in 6 (Figure 3a, b). In these chains, the Zn(II) ions are separated by 8.291 Å in 5 and 11.128 Å and 11.027 Å in 6. In both cases, as the pyridyl groups do not coordinate to the metals, the ligands bind to the chains as pendents through benzimidazole coordination with repeat distances of 8.291 Å and 16.872 Å in 5 and 6 respectively. The 1D chains are interdigitated as the pendent ligands interact with each other via π-π stacking interactions between benzimidazole and pyridine moieties (Figure 3c & 3d). Accordingly in 5, the double bonds found to be in required alignment for photochemical reaction with a distance of 3.723 Å. In 6, the distance between the olefins found to be larger with unfavorable arrangement for [2+2] solid state reaction (Figure 3f). The uncoordinated pyridyl units involve in O-H···N hydrogen bonding with water molecules in both cases. The hydrogen bonding between water, benzimidazole, pyridine and carboxylate moieties join the chains into a three-dimensional network (Figure 3d, e). 1D-networks by NDSA with L1 or L2 as pendents. The complexes 7 and 8 crystallize in C2/c and P-1 space groups respectively. The asymmetric units are constituted by half unit each of Cd(II) and NDSA, and one unit each of ligand and coordinated water, in addition 7 contains one uncoordinated water molecule. In both complexes, the Cd(II) ion

adopts distorted octahedral geometry. The equatorial positions of Cd(II) in 7 are occupied by two pyridyl nitrogen atoms of L1 and two oxygen atoms from two coordinated water molecules whereas two axial positions are occupied by two Oatoms of NDSA units. In 8, the Cd(II) is coordinated by two imidazole N-atoms of L2 and two O-atoms of NDSA in the equatorial plane and the axial sites are occupied by two water molecules. In both complexes, NDSA acts as linker and forms one-dimensional chain while the ligands act as pendents (Figure 4a, b). However, they differ in their way of coordination: in 7, the two L1 units bind via 4-pyridyl coordination such that N-Cd-N angle is 85.65°; while in 8, the two L2 units bind via benzimidazole coordination such that N-Cd-N angle is 180°. In 1D-chains, the NDSA separates metal ions by 11.880 Å and 11.673 Å in 7 and 8 respectively. In both, the hydrogen bonding between water molecules, sulfonate and benzimidazole moieties govern the 3D-packing of the chains (Figure 4c-4e). Further in 8, the 1D-chains interdigitate as the pendent ligands (L2) interact with each other via π···π interactions with a centroid of Py to centroid of C6 of benzimidazole distance of 3.638 Å (Figure 4f). Such arrangement resulted in the parallel alignment of double bonds with a distance of 3.513 Å which satisfies photochemical reactivity criteria (Figure 4g). Solid-state [2+2] photochemical reaction. Crystal structure analyses of 1-8 indicate that the complexes 5 and 8 have a required alignment of olefinic double bonds of L1 in 5 and L2 in 8 with the olefin-to-olefin distances of 3.723 Å and 3.513 Å respectively. Therefore, these two complexes were investigated further for their photochemical reactivity. The finely grounded samples were irradiated in sunlight for 36 hours. The 1 H-NMR spectra of the irradiated material as well as nonirradiated complexes of 5 and 6 were recorded in D6-DMSO solvent. For 5, it is observed that two new double-triplets in the region 4.82-5.01 ppm are formed and the peak for imidazole-proton (connected with nitrogen atom) is shifted completely from 12.76 ppm to 12.20 ppm (Figure 5).

N

H H N

N H H

N H

N H

(b)

After Irradiation

N

N

H N

N

(a)

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Before Irradiation

Figure 5. 1H-NMR spectra for 5: (a) before irradiation and (b) after irradiation.


In the case of 8, two new double-triplets in the region 4.785.10 ppm are formed for the irradiated sample and here also, the peak for imidazole-proton is shifted from 12.73 ppm to 12.21 ppm (Figure S20). In these two complexes, olefinic proton peaks of the ligands (7.52 and 7.63 ppm for L1 in complex 5, and 7.21 and 7.53 ppm for L2 in complex 8) are disappeared after irradiation. These observations clearly indicate that photochemical [2+2] cycloaddition reaction occured with 100% conversion in both the complexes. From the crystal structures of 5 and 8 and 1H-NMR spectra of irradiated samples it can be stated that both resulted in the formation of head-to-tail dimers. Further, the head-to-tail geometry of L1 was confirmed by comparing 1H-NMR spectra with that of the earlier reported one for L1 by us in Ag(I) CPs.60

somewhat weaker and hence fluorescence quenching was not observed in 7. 1.0 (1) (2) (3) (4) (5) (6) (7) (8)

0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1

Luminescence study. The exploration of luminescence properties of CPs is of importance given the various applications such as in chemical sensors,64-65 electroluminescent display,66 and so on. Generally, d10 metal complexes are promising materials to exhibit photoluminescence properties.67 The solid state luminescence of the complexes 1-8 (Figure 6) as well as the free ligands L1 and L2 (Figure S19) have been investigated at room temperature. It is observed that the free ligands L1 and L2 exhibit emission band around 480 nm and 492 nm respectively with excitation at 375 nm. The metalcomplexes 1-8 show emission bands in the range of 457-485 nm (λmax values: 485 nm (1), 469 nm (2), 459 nm (3), 458 nm (4), 457 nm (5), 458 nm (6), 468 nm (7), 481 nm (8)) upon excitation at 375 nm. The observed emissions of the complexes are probably contributed by intraligand π*-π transition since similar emissions are also observed for the ligands. The differences observed in emission behavior could be attributed to their differences in network geometries, crystal packing, metal-ligand binding, nature of the organic dicarboxylates and sulfonates and other intermolecular interactions. 7 exhibits one extra emission band at around 536 nm and probably, it originates from 1,5-napthalenedisulfonate. However, in the case of 8, this additional band is absent as a result of fluorescence quenching by π-π stacking (3.885 Å) between 1,5napthalenedisulfonate and C6-ring of benzimidazole of L2, whereas for 7, such type of π-π stacking (4.404 Å) is

(a)

0.0 -0.1 400

500

550

600

650

700

Wavelength(nm)

Figure 6. Luminescence spectra for the coordination polymers 18.

Emission properties for irradiated complexes of 5 and 8. In order to investigate the effect of photochemical cycloaddition reactions on luminescence properties, the solid state fluorescence study of the irradiated complexes of 5 and 8 was carried out with excitation wavelength of 375 nm. In case of 5, the irradiated sample found to exhibit emission maxima at 473 nm while that of 5 is at 457 nm indicating the red shift (Figure 7a). In case of 8, the irradiated sample found to exhibit emission maxima at 446 nm while that of 8 is at 481 nm indicating the blue shift (Figure 7b). However, in both the cases, the fluorescence intensity is decreased after irradiation. The anomaly found in shifting the emission maxima after irradiation for the complexes 5 and 8 can be attributed to the differences in the dianions, ligands and crystal structures.

(b)

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450

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5(non-irradiated) 5(irradiated)

8(non-irradiated) 8(irradiated)

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Normalized Intensity

0.8


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Figure 7. Luminescence spectra for non-irradiated and irradiated complexes of (a) 5 and (b) 8.


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Conclusions The ligands L1 and L2 in combination with dicarboxylates and disulfonates were shown to form coordination polymers containing Cd(II) and Zn(II) metal ions. The dicarboxylate ions such as SA (1 & 2), AA (5) and TA (6) were found to form 1D-chains through Zn(II) and carboxylate coordination. In 1 and 2, these chains are interconnected through L1 and L2 to form a corrugated 2D-layer. The degree of corrugation was found to be higher in 2 compared to that of layers in 1 due to the differences in pyridyl substitution. In 5 and 6, the Zn(II) and carboxylate chains are coordinated by only benzimidazole moieties of L1 and L2 but not by pyridine moieties which is in accordance with higher basicity of benzimidazole N-atom than that of pyridyl N-atoms. In complexes 3 and 4, the coordination of dicarboxylates such as SA (3) and GA (4) with Cd(II) lead to the formation of 2D-layers which have similar connectivity. Both the layers are propagated by Cd2O2 SBU but the cavities in the 2D-layer of 3 are found to big enough to encapsulate water tetramers. These 2D-layers are inter connected by L2 to form 3D-network in 3, while such layers are intraconnected by L2 in 4. Such differences in connectivity occurred due to the differences in geometry of L2: in 3 the coordination sites are trans to each other while in 4 they are cis to each other. The complexes 7 and 8 contain 1D-chains of Cd(II) and NDSA with ligand L1 and L2 as pendents respectively. However, the connection of pendents in these two chains found to be different: in 7 the 4-pyrdyl unit is coordinated leaving the benzimidazole moiety uncoordinated, while in 8 the benzimidazole moiety is coordinated leaving the 3pyridyl moiety uncoordinated. The interdigiation of pendents (L1 & L2) of 1D-chains in complexes 5 and 8 resulted in the required geometry of olefins for solid state [2+2] reaction which found to form cyclobutane products with 100% yield upon irradiation. All the complexes exhibited ligand-based luminescence albeit with minor differences in their emission profiles due to presence of various organic linkers and packing arrangements. Experimental Section General methods. Fourier transform-IR (FT-IR) spectra were recorded with a Perkin-Elmer Instrument Spectrum Rx Serial No. 73713 and NMR spectra were recorded on a Bruker DRX200 spectrometer. Elemental analysis has been carried out by Perkin-Elmer Series II 2400. Powder XRD patterns were recorded with a Bruker D8-advance diffractometer. The diffuse reflectance spectra (DRS) were recorded with a Cary model 5000 UV−vis-NIR spectrophotometer and the solid state luminescence was recorded with a Spex Fluorolog-3 (model FL3-22) spectrofluorimeter. Synthesis of 1. Complex 1 was prepared by solvothermal reaction with the ligand L1 (0.011 g), Zn(NO3)2 (0.0150 g) and Na-succinate (0.0081 g) using 10 mL MeOH-H2O (1:3) solvent-mixture in a sealed glass tube at 95°C. After 2 days, yellow colored crystals were obtained with 43% yield. Elemental anal. Calcd for C18 H17 N3 O5 Zn (%): C, 51.39; H, 4.08; N, 9.99. Obsd (%): C, 51.22; H, 4.17; N, 9.81. IR Data (KBr, cm1 ): 3545.18(w), 3438.86(m), 2910.66(w), 2775.38(w), 2364.28(w), 1616.29(s), 1571.56(s), 1447.77(m), 1420.02(s), 1394.12(m), 1322.65(w), 1291.31(m), 1229.09(w), 1030.54(w), 960.48(m), 885.07(w), 817.92(w), 742.46(m), 638.17(w), 525.64(w).

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Synthesis of 2. Complex 2 was prepared by solvothermal reaction with the ligand L2 (0.011 g), Zn(NO3)2 (0.0150 g) and Na-succinate (0.0081 g) using 10 mL MeOH-H2O (1:3) solvent-mixture in a sealed glass tube at 95°C. After 3 days, light yellow colored crystals were obtained with 57% yield. Elemental anal. Calcd for C18H19N3O6Zn (%): C, 49.27; H, 4.37; N, 9.58. Obsd (%): C, 49.45; H, 4.31; N, 9.43. IR Data (KBr, cm-1): 3506.17(m), 3358.92(mb), 1592.18(s), 1446.87(m), 1420.18(s), 1389.75(m), 1320.79(w), 1281.93(m), 1180.05(w), 1127.29(w), 1043.69(w), 975.43(m), 877.62(w), 808.19(w), 747.84(m), 690.44(w). Synthesis of 3. Complex 3 was prepared by solvothermal reaction with the ligand L2 (0.011 g), Cd(NO3)2 (0.0154 g) and Na-succinate (0.0081 g) using 10 mL MeOH-H2O (1:3) solvent-mixture in a sealed glass tube at 90°C. After 3 days, light yellow colored crystals were obtained with 38% yield. Elemental anal. Calcd for C18H19CdN3O6 (%): C, 44.50; H, 3.95; N, 8.65. Obsd (%): C, 44.72; H, 3.88; N, 8.71. IR Data (KBr, cm-1): 3473.25(mb), 3385.60(mb), 3195.03(mb), 3061.00(m), 2916.89(w), 1620.02(w), 1560.46(s), 1540.78(s), 1484.99(w), 1441.35(s), 1416.45(s), 1319.65(m), 1279.37(w), 1261.55(w), 1231.13(m), 1179.77(w), 1156.12(w), 1033.98(w), 1000.45(w), 977.12(m), 934.16(w), 877.89(w), 805.96(m), 764.95(w), 749.88(m), 714.33(w), 678.89(m), 441.36(w). Synthesis of 4. Complex 4 was prepared by solvothermal reaction with the ligand L2 (0.011 g), Cd(NO3)2 (0.0154 g) and Na-glutarate (0.0088 g) using 10 mL MeOH-H2O (1:3) solvent-mixture in a sealed glass tube at 90°C. After 3 days, light yellow colored crystals were obtained with 46% yield. Elemental anal. Calcd for C19H19CdN3O5 (%): C, 47.37; H, 3.98; N, 8.72. Obsd (%): C, 47.24; H, 4.08; N, 8.89. IR Data (KBr, cm-1): 3477.36(m), 3368.06(mb), 3101.79(mb), 2936.24(m), 1663.15(w), 1646.34(w), 1623.94(w), 1543.24(s), 1474.41(w), 1422.90(s), 1352.07(w), 1319.94(m), 1277.93(m), 1227.99(w), 1191.52(w), 1152.23(w), 1131.46(w), 1050.27(w), 1027.87(w), 994.48(w), 973.25(m), 897.03(w), 880.10(w), 856.47(w), 803.99(w), 766.11(w), 752.41(m), 714.13(w), 693.75(w), 664.71(w), 641.38(w), 544.23(w), 521.18(w), 442.10(w), 409.62(w). Synthesis of 5. Complex 5 was prepared by solvothermal reaction with the ligand L1 (0.011 g), Zn(NO3)2 (0.0150 g) and Na-adipate (0.0095 g) using 10 mL MeOH-H2O (1:3) solventmixture in a sealed glass tube at 95°C. After 3 days, light yellow colored crystals were obtained with 62% yield. Elemental anal. Calcd for C34H38N6O8Zn (%): C, 56.40; H, 5.30; N, 11.61. Obsd (%): C, 56.21; H, 5.48; N, 11.73. IR Data (KBr, cm-1): 3638.05(w), 3392.68(mb), 3062.42(w), 2946.50(w), 2864.19(w), 2753.08(w), 2646.09(w), 1598.30(s), 1443.67(m), 1417.86(m), 1398.20(m), 1320.46(w), 1283.18(w), 1268.80(w), 1229.67(w), 1152.01(w), 1039.67(w), 1001.70(w), 973.13(m), 884.02(w), 806.34(m), 766.30(w), 751.84(m), 607.44(w), 519.00(w), 442.31(w), 411.48(w). Synthesis of 6. Complex 6 was prepared by solvothermal reaction with the ligand L2 (0.011 g), Zn(NO3)2 (0.0150 g) and Na-terephthalate (0.0106 g) using 10 mL MeOH-H2O (1:3) solvent-mixture in a sealed glass tube at 90°C. After 3 days, light yellow colored crystals were obtained with 58% yield. Elemental anal. Calcd for C22H19N3O6Zn (%): C, 54.28; H, 3.94; N, 8.63. Obsd (%): C, 54.43; H, 3.85; N, 8.52. IR Data (KBr, cm-1): 3499.42(w), 3343.65(w), 3283.95(w),


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2901.23(wb), 2777.77(w), 2365.86(w), 1618.15(s), 1579.11(s), 1452.06(m), 1393.75(s), 1342.38(s), 1046.98(w), 982.15(w), 884.72(w), 830.54(m), 811.98(m), 742.43(m), 593.06(w), 515.01(w). Synthesis of 7. Complex 7 was prepared by solvothermal reaction with the ligand L1 (0.011 g), Cd(NO3)2 (0.0154 g) and Na-1,5-napthalenedisulfonate (0.0165 g) using 10 mL MeOHH2O (1:3) solvent-mixture in a sealed glass tube at 95°C. After 3 days, yellow colored crystals were obtained with 64% yield. Elemental anal. Calcd for C38H36CdN6O10S2 (%): C, 49.97; H, 3.98; N, 9.20. Obsd (%): C, 49.86; H, 4.03; N, 9.35. IR Data (KBr, cm-1): 3552.56(m), 3460.98(m), 3274.81(mb), 3213.99(mb), 1610.83(s), 1559.70(w), 1430.09(m), 1317.07(w), 1282.66(w), 1238.90(m), 1221.55(s), 1175.25(s), 1032.68(s), 967.54(w), 954.07(w), 871.93(w), 795.42(m), 766.62(m), 754.69(m), 693.53(w), 612.26(m), 564.30(w), 522.66(m), 461.61(w), 442.28(w). Synthesis of 8. Complex 8 was prepared by solvothermal reaction with the ligand L2 (0.011 g), Cd(NO3)2 (0.0154 g) and Na-1,5-napthalenedisulfonate (0.0165 g) using 10 mL MeOHH2O (1:3) solvent-mixture in a sealed glass tube at 95°C. After 3 days, light yellow colored crystals were obtained with 53% yield. Elemental anal. Calcd for C38H32CdN6O8S2 (%): C, 52.03; H, 3.68; N, 9.58. Obsd (%): C, 52.27; H, 3.59; N, 9.46. IR Data (KBr, cm-1): 3349.79(mb), 3168.12(s), 3115.22(s), 1648.10(w), 1592.99(w), 1528.05(w), 1498.14(w), 1486.98(w), 1443.57(s), 1413.13(m), 1318.39(w), 1278.24(w), 1238.30(m), 1219.76(s), 1196.78(s), 1173.05(s), 1121.27(w), 1032.62(s), 971.90(m), 930.49(w), 855.01(w), 843.13(w), 793.06(m), 767.87(m), 741.95(s), 710.28(w), 692.64(w), 663.91(w), 604.27(s), 565.80(w), 530.73(w), 466.14(w), 437.49(w). Crystal Structure Determination. All the single crystal data were collected on a Bruker-APEX-II CCD X-ray diffractometer that uses graphite monochromated Mo Kα radiation (λ = 0.71073 Å) at room temperature (293 K) or low temperature (100 K) by the hemisphere method. The structures were solved by direct methods and refined by least-squares methods on F2 using SHELX-2014.68 Non-hydrogen atoms were refined anisotropically, and hydrogen atoms were fixed at calculated positions and refined using a riding model. The H atoms attached to the O atom or N atoms are located and refined using a riding model.

ASSOCIATED CONTENT Supporting Information. IR spectra, XRPD patterns, DRS, Luminescence spectra, 1H-NMR spectra and TGA of complexes

AUTHOR INFORMATION Corresponding Author *E-mail: [email protected]. Fax: +91-3222282252. Tel.: +91-3222-283346.

Notes The authors declare no competing financial interest.

ACKNOWLEDGMENT We acknowledge DST (SERB), New Delhi, India for financial support and DST-FIST for the single crystal X-ray diffractometer, and A.G. thanks IIT Kharagpur for a research fellowship.

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Table 1. Crystallographic Parameters for Coordination polymers 1−8

Formula

1

2

3

4

5

6

7

8

C18H17N3O5Zn

C18H19N3O6Zn

C18H19CdN3O6

C19H19CdN3O5

C34H38N6O8Zn

C22H19N3O6Zn

C38H36CdN6O10S2

C38H32CdN6O8S2

Mol.Wt.

420.71

438.73

485.76

481.77

724.07

486.77

913.25

877.21

T (K)

293(2)

100(2)

293(2)

293(2)

293(2)

98(2)

293(2)

293(2)

System

monoclinic

monoclinic

orthorhombic

orthorhombic

monoclinic

triclinic

monoclinic

triclinic

Space group

P21/c

P21/c

Pbca

Pbca

C2/c

P-1

C2/c

P-1

a (Å)

8.4439(2)

9.2377(3)

12.9537(1)

12.5170(5)

8.2911(2)

6.9151(3)

18.5433(7)

7.8888(9)

b (Å)

17.377(3)

15.1273(5)

16.1547(2)

16.0706(6)

22.218(5)

11.9748(4)

11.6993(5)

9.8140(1)

c (Å)

12.238(2)

13.7847(5)

17.7750(2)

18.2133(8)

19.183(4)

12.9289(5)

19.2248(8)

11.6734(1)

α (°)

90.00

90.00

90.00

90.00

90.00

92.6770(1)

90.00

80.440(3)

β (°)

99.007(6)

108.610(1)

90.00

90.00

99.289(6)

104.3320(1)

103.1920(1)

88.983(3)

90.00

90.00

90.00

90.00

90.00

98.6860(1)

90.00

83.324(3)

V (A )

1773.5(6)

1825.57(11)

3719.7(6)

3663.7(3)

3487.4(1)

1021.43(7)

4060.6(3)

885.17(2)

Z

4

4

8

8

4

2

4

1

1.576

1.596

1.735

1.747

1.379

1.583

1.494

1.646

R1 [I > 2σ(I)]

0.0479

0.0312

0.0263

0.0391

0.0659

0.0400

0.0558

0.0310

2

0.1492

0.1156

0.1201

0.1288

0.2167

0.0842

0.1762

0.0851

γ (°) 3

3

D(g/cm ) wR2 (on F , all data)



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

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Table 2. Geometrical Parameters of Hydrogen Bonds in the coordination polymers 1−8

Compounds

Type

H···A (Å)

D···A (Å)

D-H···A (deg)

1

O–H···O N–H···O C–H···O C–H···O

1.85 1.95 2.56 2.55

2.853(6) 2.763(5) 3.149(5) 3.424(6)

164 163 122 157

2

O–H···O O–H···O O–H···O O–H···O N–H···O

1.90 1.81 2.02 1.98 1.88

2.730(3) 2.708(3) 2.839(3) 2.836(3) 2.703(3)

177 164 164 166 155

3

N–H···O C–H···O C–H···O C–H···O

2.00 2.53 2.48 2.30

2.781(4) 3.288(4) 3.350(4) 3.199(4)

150 139 155 162

4

N–H···O C–H···O

1.96 2.59

2.804(5) 3.278(6)

160 130

5

N–H···O

1.88

2.699(4)

160

6

N–H···O C–H···O C–H···O C–H···O C–H···O

1.84 2.45 2.46 2.58 2.57

2.714(3) 3.395(3) 3.227(4) 3.467(4) 3.441(3)

175 176 138 155 152

7

N–H···O

2.01

2.831(6)

160

8

N–H···O

1.92

2.769(3)

171


Page 13 of 13

For Table of Contents Use Only

Diversity in the Coordination Polymers of 2-(2-(pyridin-4/3yl)vinyl)-1H-benzimidazole and Dicarboxylates/Disulfonates: Photochemical Reactivity and Luminescence Studies Abhijit Garai, Somnath Sasmal and Kumar Biradha*

1.0 (1) (2) (3) (4) (5) (6) (7) (8)

0.9 0.8


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


0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 -0.1 400

450

500

550

600

650

700

Wavelength(nm)

Photochemical Reactivity

Metal

Ligand

Luminescence Linker

Structural Variation

The benzimidazole and pyridine containing olefin ligands were shown to perform three type of roles: act as pendents to metaldicaboxylate chains, link the metal-dicabxylate chains to 2D-layers and link the metal-dicarboxylate 2D-layers to 3D-networks. The 1D-chains containing asymmetric olefin ligands as pendents were shown to be photoactive through the interdigitation of pendents of adjacent 1D-chains and produce corresponding cyclo butane products upon irradiation.


3-yl)vinyl)-1H

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