Mesogenic L-histidine Based Schiff Base and its Zn(II) Complex: Synthesis, Photophysical Properties, AIE and TD-DFT Study.

A new photoluminescent Schiff base ligand derived from L-histidine and its zinc(II) complex have been synthesized and characterized by various analytical techniques. The mesomorphic properties of the compounds were examined, revealing that only the ligand exhibits liquid crystalline property of the nematic phase. The photophysical properties of both the ligand and its zinc(II) complex were studied in solvents of varying polarity using UV-Vis and emission spectroscopic techniques. Both compounds displayed blue light fluorescence in solution at room temperature, with the Zn(II) complex exhibiting higher emission intensity. The aggregation induced emission (AIE) of Zn(II) complex was investigated through optical spectroscopy in non-coordinating and coordinating solvents. The optical band gap of the compounds determined from the absorption spectra was found to be within the range typical for semi-conducting materials. The Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT) calculations were carried out to obtain the optimized geometry, as well as to assess the photophysical properties of the compounds theoretically.