Crystallographic, theoretical and conductivity studies of two new complexes [Ni(II) and Cu(II)] based on mixed ligands approach

Two new complexes [Ni(C7H3NO5) (C15H11N3)]. 4(H2O) (1) and [Cu(C7H3NO5) (C15H11N3)]. 4(H2O) (2) have been synthesized using mixed chelating ligands [4-hydroxypyridine-2,6-dicarboxylic acid (chelidamic acid) (C7H5NO5) and 2,2 ':6 ',2 ''-terpyridine (C15H11N3)] in aqueous medium. The two complexes were characterized by UV-visible, IR spectroscopy as well as by single-crystal X-ray diffraction analysis. The geometries of both the complexes are distorted octahedral with N4O2 chromophore. The non-covalent interactions found in the solid state architectures of complexes 1 and 2 have been described focusing on pi center dot center dot center dot pi stacking and hydrogen bonding interactions. These non-covalent interactions played an imperative role in building of multi-dimensional supramolecular architectures. These interactions have been explored theoretically by density functional theory (DFT) focusing on the antiparallel pi-pi stacking in self-assembled dimers and the hydrogen bonding networks mediated by the lattice water molecules. MEP surface calculations combined with QTAIM and NCI plot analysis were used to rationalize and characterize the non covalent interactions involved in the assemblies. The low optical band gaps of the two complexes exhibit semiconducting property leading to potentially fabricate Schottky Barrier Diode.