Mononuclear photoluminescent salicylaldimato copper(II) complex: synthesis, characterization, mesomorphic investigation and DFT study

A new photoluminescent disc-like copper (II) metallomesogen of the type [CuL2] {H2L = 2,4-bis((E)-((4-(hexadecyloxy)phenyl)imino)methyl)phenol} have been synthesized. The compounds were characterized by elemental analyses, Fourier transform infrared spectroscopy (FTIR), 1H, 13C nuclear magnetic resonance (NMR), ultraviolet – visible spectroscopy (UV – Vis), thermogravimetric analysis (TGA) and high-resolution mass spectrometry. Mesomorphic behavior of the compounds was probed with the help of polarizing optical microscopy (POM) and differential scanning calorimetry (DSC). The organization of the molecules in the mesophase was investigated by X-ray diffraction techniques. The ligand is non-mesogenic but the copper complex exhibited thermally stable columnar mesophases at about 86°C. The copper complex is a blue-light emitter both in solution and in the solid state. The Density Functional Theory (DFT) study was carried out using 6–31 G (d, p) basis set with unrestricted B3LYP level to obtain a stable, optimized structure, which revealed a distorted square-planar geometry for the copper complexes.