Syntheses, characterization and third-order nonlinear optical properties of a class of thiazolylazo-based metal complexes

► A new class of metal complexes based on a thiazolylazo dye has been synthesized. ► The structures of ZnII and NiII have been elucidated by X-ray crystallography. ► Solution UV-Vis titration revealed the spontaneous formation of mononuclear species. ► Third-order NLO studies confirmed that metal complexes had improved NLO behaviors.