We synthesized a thiosemicarbazone-functionalized 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-ray diffraction, 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 ...