Synthesis, characterization, and optical properties of new metal complexes with the multi-sulfur 1,2-dithiolene ligand

Metal complexes containing a new multi-sulfur atom containing 1,2-dithiolene ligand, [4′,5′:5,6] [1,4] dithiino[2,3-b] quinoxaline-1′,3′-dithiolate, have been synthesized and characterized by electrochemical measurements, IR, UV–NIR and ESR spectroscopies. X-ray structure analysis reveals that the anions of the Ni-complex derived from the new ligand form a zig-zag chain along the b axis, and the anions of Au complex of the ligand stack along the a axis while the cations occupy the holes. The Ni-complex exhibits remarkable absorption at 1082 nm (ɛ = 15 000 dm3 mol−1 cm−1) and good solubility that render this complex as a promising near-IR dye for Q-switching neodymium lasers. The third-order non-linear optical properties of the complexes are measured by the Z-scan technique with a 6.5 ns pulsed laser at 532 nm. The Au complexes exhibit non-linear optical absorptive abilities, while the non-linear absorption of the nickel complex is negligible. All of the complexes show effective self-defocusing performance. The third-order non-linear optical susceptibilities for the Au complexes have been determined to be of the order of 10−13 esu.

Graphical abstractMetal complexes containing the multi-sulfur dithiolene ligand, [n-Bu4N]n[Ni(L)2] (n = 1, 1; n = 0, 2), [R4N][Au(L)2] (R = n-Bu, 3; R = Et, 4) (L = [4′,5′:5,6] [1,4] dithiino[2,3-b] quinoxaline-1′,3′-dithiolate), have been synthesized and characterized. Complex 1 exhibits a remarkable absorption at 1082 nm (ɛ = 15 000 dm3 mol−1 cm−1) and good solubility that makes it a promising near-IR dye for Q-switching neodymium lasers. Gold complexes 3 and 4 exhibit third-order non-linear optical absorptive abilities. All complexes show effective self-defocusing performance.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► A new multi-sulfur containing 1,2-dithiolene type ligand and four metal complexes are synthesized. ► The nickel complex 1 exhibits remarkable absorption at 1082 nm and is a promising near-IR dye. ► The third-order non-linear optical properties of complexes 1, 3 and 4 are studied.