Structural Investigation and Solid State Emission Studies of Co(II), Zn(II) and Cd(II) Coordination Polymers Built with a Bifurcated Ligand

Abstract

The bifurcated ligand 5-di(1H-benzo[d]imidazol-1-yl) benzonitrile (DBIBN) under solvothermal condition, undergoes basic as well as acid hydrolysis to the corresponding carboxylic acid (DBIBA). Four new coordination polymers; {[Cd(DBIBA)(CH3COO)]} n (1), {[Zn(DBIBA)(CH3COO)]⋅H2O} n (2), {[Zn(DBIBA)(OC2H5)]⋅H2O} n (3) and {[Co(DBIBA)(CH3COO)]⋅H2O} n (4) have been synthesized under solvothermal conditions. Compound 1 has a 3D structure with uninodal 4-connected crb/BCT topology with point symbol of {4.65}. In contrast, compounds 2–4 are 2D layered structures having uninodal 3-connected hcb net with a vertex symbol of {63}. The 2D layers are further assembled to an overall 3D supramolecular architecture with strong π–π interactions between layers. Further reinforcement of the 3D assembly occurs due to an array of H-bonding interactions with lattice water molecules present within the layers. All the compounds have been characterized by single X-ray crystallography, IR spectroscopy, TGA, PXRD measurements and elemental analysis. Although the metal-free DBIBN ligand exhibits fluorescence, it is quenched in the coordination polymers.