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Five new azo-functionalized coordination polymers, namely {[Cd(3,3′-azbpy)(suc)]·(MeOH)}n (1), [Cd(3,3′-azbpy)(msuc)]n (2), {[Cd(3,3′-azbpy)(2,2′-dmglut)(H2O)]·2(H2O)}n (3), {[Cd(3,3′-azbpy)(glut)]·2.5(H2O)}n (4) and {[Co2(3,3′-azbpy)2(tp)(H2O)3]·H2O} (5), have been synthesized from 1,2-di(pyridine-3yl)diazene (3,3′-azbpy) using four different aliphatic and one aromatic dicarboxylic acid salt [succinate (suc2−), methyl succinate (msuc2−), 2,2′-dimethyl glutarate (2,2′-dmglut), glutarate (glut2−) and terephthalate (tp2−)] and two different transition metal salts by the slow diffusion technique at room temperature. The structures of the synthesized compounds 1–5 were characterized by single crystal X-ray diffraction analysis and by elemental analysis, infrared spectroscopy (IR), powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA) and UV–Vis spectroscopy. Compounds 1 and 2 show a honeycomb 3D structure, whereas, compound 3 exhibits a two-dimensional (2D) 2-fold interpenetrating network. Compound 4 shows a wavy 2D sheet structure and compound 5 exhibits a zero dimensional structure which forms a 2D sheet by means of hydrogen bonding, which by further π⋯π interactions forms an overall supramolecular 3D structure. Sorption studies with CO2 and N2 were also done for all the frameworks and a surface characteristic adsorption has been observed.

Anion exchange materials are important for their application in toxic anion control process. Coordination Polymers (CPs) with weakly coordinated anions and lattice anions may be practically useful in anion exchange process. To explore this anion exchange properties by Coordination Polymers (CPs) we have synthesized two water insoluble cationic CPs {[Mn(bix)3(H2O)2].bix.(NO3)2}n (1), {[Cd(bix)2(NO3)2].(H2O)2}n (2) by using N,N-donors linkers bix {bix = 1,4-bis(imidazol-1-ylmethyl)- benzene}. Structure of complex 1 is 1D and contains lattice NO3– anion and the complex 2 is 2D and contains weakly coordinated NO3–anion. Both these complexes along with another previously published structurally similar CP {[Cd(bix)2(NO3)2]}n (3), response in anion exchange studies with foreign anions. All the anion exchange processes have been monitored by FT-IR spectroscopy and PXRD measurements.

A family of dicyanamide bridged compounds namely {[Co(dca)4(2-abim)2]}n (1), {[Ni(dca)4(2-abim)2]}n (2), {[Cd(dca)4(2-abim)2]}n (3), {[Zn(N(CN)2)2(4-bpdb)]}n (4) and {[Cd(N(CN)2)2(4-bpdb)]}n (5); [where dca = dicyanamide, 2-abim = 2-aminobenzimidazole and 4-bpdb = 1,4-bis-(4-pyridyl)-2,3-diaza-1,3-butadiene] have been synthesized by stirring at room temperature. These compounds have been characterized by single crystal diffraction analysis, infrared spectroscopy (IR) and powder X-ray diffraction (PXRD). Complexes 1–3 are isostructural and exhibit two-dimensional (2D) metal-dca sheet with pendant 2-abim ligand. Compound 4 forms [Zn(N(CN)2)]n chains with a pendent dca and a bridging dca linker, which are further connected by bridging 4-bpdb ligands extending into a 2D layer structure. In case of compound 5 each Cd(II) centers connect with four bridging dca linkers to form [Cd(N(CN)2)]n double chains, which are further connected by bridging 4-bpdb ligands extending into a 2D layer structure. Here [Cd2(N(CN)2)] and 4-bpdb spacer are interpenetrated to each other and resemble polyrotaxane-type structures. Photoluminescent properties of compounds 3–5 were also studied and they exhibit nice ligands based photoluminescence properties at room temperature.

Post synthetic modification of coordination polymers have been extensively studied through years, to obtain several marvelous functional materials. Apart from the usual metal or ligand exchange, irreversible structural transformation strategy may also be a useful approach to perform post synthetic modification in coordination polymers for creating functional materials. Considering this approach, three coordination polymer of Zn(II) and Co(II) namely, {[Zn(beb)(dmglut)]}n (1), {Co2(beb)2(hipt)2(H2O)1.5(MeOH)}]n (2) and {[Zn2(beb)2(fum)2]}n (3) (Whereas beb = 1-(2-(1H-benzoimidazol-1-yl)ethyl)-1H-benzoimidazole, dmglut = 3,3′-dimethylglutarate, hipt = 5-hydroxyisophthalate and fum = fumarate) have been synthesized from flexible beb ligand and three different dicarboxylates. Compound 1 and 2 are with a two dimensional structure which are adjoined by weak forces to form a supramolecular three dimensional architecture. Compound 3 has a three dimensional structure with unidirectional channels. Compound 2 and 3 have undergone irreversible structural transformation. These transformations are thoroughly monitored by PXRD analysis, UV–vis spectroscopy, and IR spectroscopy. Solid state emission spectral analyses for two Zn(II) CPs and gas sorption analyses for all the compounds has been also performed.

Assembly of 5-nitroisophthalate (nip2−) with first row transition metal salts [Mn(II), Fe(II), Co(II), Zn(II)] in combination with the various neutral auxiliary N,N′-donor linkers, e.g., 2,5-bis-(4-pyridyl)-3,4-diaza-2,4-hexadiene (4-bpdh), 1,3-bis(4-pyridyl)propane (bpp) and 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene (4-bpdb), yielded eight new coordination polymers (CPs), namely {[Mn(4-bpdh)(nip)(H2O)2]·H2O}n (1), {[Fe(4-bpdh)(nip)(H2O)2]·H2O}n (2), {[Co(4-bpdh)(nip)(H2O)2]·H2O}n (3), {[Mn2(bpp)2(nip)2(H2O)2]·H2O}n (4), {[Fe(bpp)(nip)(H2O)]·H2O}n (5), [Zn(bpp)(nip)(H2O)]n (6), {[Fe(4-bpdh)1.5(nip)]·(4-bpdh)0.5}n (7) and {[Fe(4-bpdb)(nip)]·(4-bpdb)0.5(H2O)}n (8) using the slow diffusion technique at room temperature. The complexes 1–8 were characterized by single crystal X-ray diffraction analysis and were further characterized by elemental analysis, infrared spectroscopy (IR) and powder X-ray diffraction (PXRD). Complexes 1–3 are isostructural and exhibit a one-dimensional (1D) metal-carboxylate chain with pendant 4-bpdh ligands, which is further extended into a three-dimensional supramolecular structure by means of H-bonding and π–π interactions. Complexes 4–6 are also isomorphous, but distinctly different from the first three complexes. They exhibit a similar 2-fold interpenetrated three-dimensional (3D) net with 66 dia net topology. Compound 7 displays a two-dimensional (2D) grid-like structure, having 4-bpdh ligands in the crystal void, and this is further extended by means of intermolecular π–π interactions into a 3D supramolecular structure, whereas compound 8 possesses a different 2D grid structure containing free 4-bpdb ligands in the void spaces. The thermal stabilities and UV–Vis spectra of all the complexes and the luminescent properties of complex 6 were also studied.

Using the same bridging ligand, diphenyl phosphate (dpp), and different co-ligands, 1,10-phenanthroline (phen)/2,2′-bipyridine (bpy), two structurally similar Cu(II) complexes, [Cu(μ-dpp)(phen)(NO3)]2 (1) and [Cu(μ-dpp)(bpy)(NO3)]2 (2), were synthesized. These complexes were characterized by single crystal X-ray diffraction as well as other physico-chemical methods. Both complexes are dinuclear in nature, but complex 1 is extended into a 3D supramolecular architecture by π–π interactions, whereas complex 2 forms a 2D supramolecular layered structure by π–π and C–H…π interactions. We further explored the DNA binding ability of these complexes by an agarose gel electrophoresis study. Although the coordination structures of these two complexes are very similar, complex 1 was found to be more effective at DNA binding. Complex 1 showed a greater cytotoxic effect on the human hepatocellular carcinoma cell line HepG2 compared to complex 2. Moreover, complex 1 induced more S-phase arrest and apoptosis in HepG2 cells than complex 2, as determined by fluorescence activated cell sorters (FACs). Thus our results indicated that changing the co-ligands in copper complexes may rendered an overall change in the supramolecular structure as well as significant variations in the biological activities.

Two new compounds of Mn(II) with the same bridging ligand, trans 4,4′-azobispyridine (azbpy), and different co-ligands, 1,10-phenanthroline (phen) and 2,2′-bipyridine (bpy), have been synthesized and characterized by X-ray crystallography and other physicochemical methods. Although the compounds were prepared under similar reaction conditions, as well as using the same reactant ratios, their compositions and solid state structures are entirely different in the two cases. Compound 1, with [Mn(azbpy)(phen)Cl2]n and [Mn(phen)2Cl2] moieties, constructs a supramolecular 3D self assembly through π–π interactions, whereas in 2 the [Mn(azbpy)(bpy)Cl2]n moiety and the lattice azbpy forms the supramolecular 3D arrangement by both π–π and C–H⋯π interactions. A thermogravimetric study of the complexes and the solid state fluorescence spectra of the ligand and complexes corroborate their structures.

Two new copper(II) complexes {[Cu(H 2 biim)(H 2 O)(suc)](H 2 O)} n ( 1 ) and {[Cu(H 2 biim) 2 (H 2 O)][Cu(H 2 biim) 2 (glut)](glutH)(NO 3 ) · 2.5H 2 O} n ( 2 ) (H 2 biim, 2,2′-biimidazole; suc, succinate dianion; glut, glutarate dianion) have been synthesized and characterized by single crystal X-ray diffraction study and thermal analysis. Complex 1 comprises of 1D zigzag coordination polymers, elongated along the crystallographic b -axis, connected through H-bonding and face-to-face π–π interactions to form a robust 3D network. Whereas complex 2 is built up of bischelated [Cu(II)(H 2 biim) 2 ] 2+ units, glutarate and nitrate anions and water molecules, held together through an extensive H-bonded system. The resulting 3D supramolecular architecture defines channels which are filled by lattice water molecules and disordered nitrate anions.