flavin (Fl-(H)TSC: 2-[2-(3,4-dihydro-7,8-dimethyl-2,4-dioxobenzo[g]pteridin-10(2H)-yl)ethylidene]-hydrazinecarbothioamide) and its Pt(II) complex [Pt(Fl-TSC)2], and characterized it using X-raydiffraction, UV–visible absorption and luminescence spectroscopy. X-ray structural analysis for [Pt(Fl-TSC)2] revealed that the structure of the isoalloxazine part was almost the same as that in lumiflavin (7,8,