Crystallographic elucidation of an isophthalic-derived amido Schiff base Cu(II) coordination polymer: a...

Herein, we synthesized an isophthalic-derived two-arm-containing amido Schiff base ligand (H₂L), bis(2-hydroxybenzylidene)isophthalohydrazide, and its copper complex (complex 1), characterized by elemental analysis, IR spectra, mass spectroscopy and single crystal X-ray diffraction techniques. The single-crystal X-ray structural analysis revealed that complex 1 crystallizes in a triclinic system with space group P1̄. The asymmetric unit of complex 1 consists of one ligand having two arms containing amide, imine and phenol tridentate donor sites, on either side of the isophthalic central benzene ring, and bonded with Cu1 and Cu2 atoms. Two pyridine molecules coordinate with two (Cu1, Cu2) atoms to form a four-coordinate basal plane. The axial positions are occupied by the phenoxide bridge oxygen atom of the similar type of another complex and vice versa to form a 1D coordination polymer. The 1D polymer is self-assembled through strong intermolecular hydrogen bonding to give a 2D sheet structure. These 2D sheets are further accumulated to fabricate 3D supramolecular aggregates via weak CH⋯π interactions. The optical band gap of complex 1 in the solid state has been determined experimentally and compared with the theoretical value obtained from DFT calculations, confirming the semiconducting properties of complex 1. The electrical conductivity of complex 1 was recorded under dark and visible light conditions, and the measured I-V characteristics of the complex under these conditions exhibited a highly non-linear rectifying behavior signifying a Schottky diode nature. This Cu(II) polymer-based device shows some paramount behaviour under the irradiance of light, which is obvious in light-sensing Schottky devices. The rectification ratio of the complex 1-based device was found to be 20.45 and 41.64 under light and photo irradiation conditions, respectively. Such types of coordination polymer are advantageous for the fabrication of optoelectronic devices.