Structural aspects, spectroscopic and third order nonlinear optical properties of mixed ligand complexes from NNO tridentate Schiff base: Crystal structure of a rare proton bridged Ni(II) complex

Abstract

Three novel mixed ligand complexes of cadmium(II), zinc(II) and nickel(II), derived from the parent Schiff base 4-chloro-2-((2-(dimethylamino)ethylimino)methyl)phenol, were synthesized and characterized by means of single crystal XRD, elemental analysis, IR, electronic and NMR spectral studies. In all the three complexes either reactant amine or aldehyde coordinates to the metal centers along with Schiff base and nickel(II) complex is having a rare proton bridged structure. While complex 1 crystallizes in orthorhombic Pbca space group, both complexes 2 and 3 crystallize in triclinic P1‾ space group. Different types of intermolecular interactions present in the crystal systems paved way to form 1D and 2D supramolecular assemblies and the visual analysis of those intermolecular interactions was achieved through Hirshfeld surface analysis. All the three complexes exhibited a negative solvatochromic behavior. Photoluminescent studies were carried out and quenching of fluorescence was observed in all complexes which is supported by the quantum yield values. Third order NLO properties were investigated by Z-scan technique with 75 fs laser pulse at 800 nm. NLO responses of the complexes were controlled by nonlinear refractive processes which make them suitable candidates for optical switching applications.