New Fluorescent Nickel(II) Complexes as a Catalyst for Biodiesel Formation: Synthesis, Structure, Spectral Properties, and DFT Calculations

Abstract

Two fluorescent heterocyclic ligands were obtained by reduction of imidazo[4,5-e][2,1]benzoxazole derivatives with Fe/HCl. New fluorescent nickel(II) complexes were synthesized by coordination of Ni(II) cation with the heterocyclic ligands. The structure of the complexes was established by spectral and analytical data, Job plot, and DFT calculations. Photophysical properties of Ni(II) complexes were characterized by UV-Vis and fluorescence spectroscopy. The optimized geometry, spectral properties, and energy difference between the HOMO and LUMO frontier orbitals of the ligands and Ni(II) complexes were obtained by DFT calculations at the B3LYP/6-311++G(d,p) level. The calculated spectral properties are in good agreement with the experimental values. The complexes were also tested as homogeneous catalysts for the transesterification of corn oil with methanol. The structure of the obtained product was confirmed by 1H NMR analysis. The catalytic results showed that the new Ni(II) complexes can be considered as potential candidates for the development of new catalytic systems for biodiesel production.