Syntheses and Characterization of a Series of Nickel Bis(dithiolene) Near-IR Dyes

Four nickel bis(dithiolene) complexes with different substituent groups were synthesized and characterized.The physical and chemical properties of the complexes were systematically studied.The UV-Vis-NIR spectra demonstrate strong and broad absorptions in the NIR region(700～1 100 nm).The substituent effect and solvent effect of the complexes were investigated.The electron donating substituent results in the red-shifted absorption band,while the electron withdrawing substituent results in the hypsochromic-shifted absorption band.The red-shifted absorption band expanded with the increase of the polarity of the solvent.The electrochemical properties were investigated by both cyclic voltammetry/differential pulse voltammetry(CV/DPV).Furthermore,the HOMO and LUMO energy levels of the dyes were obtained by density functional theory(DFT) calculations.TG studies reveal good thermal stability of the complexes.