Tuning excited state of bipyridyl platinum(II) complexes with bio-active flavonolate ligand: Structures, photoreactivity, and DFT calculations

Platinum(II) complexes with coordinated bio-active molecules that can undergo photo-induced oxygenation are finding applications in photoactivated chemotherapy (PCT). A series of bipyridyl(bpy) Pt(II) complexes with ligand flavonolate (fla(-)) [Pt(II)BpyFla(R)][BF4] [BF4] (R = p- OMe (1), p-Me (2), p-H (3)) were prepared and characterized. Their photochemical and photophysical properties were investigated. Complexes 1-3 exhibit emission at similar to 530 nm, as compared to the analogous [Pd(II)BpyFla(R)][BF4] with no emission upon irradiation. In addition, Pt(II) complexes undergo oxygenation reaction with oxygen with near visible light, indicating photocleavage of ligand flavonolate. Carbon monoxide(CO) release was observed by deoxymyoglobin from oxygenation of Pt(II) flavonolate complexes. Density functional theory calculations predict a mixed, Pt/fla- to bpy, metal/ligand-to-ligand charge transfer (ML-LCT) state in complexes 1-3.