Emission solvatochromic behavior of a pentacoordinated Zn(II) complex: A viable tool for studying the metallodrug-protein interaction

A metal complex with antitumoral activity, Zn(Curcumin)(bypiridine)Cl, was characterized from a photophysical point of view, showing a green emission and a positive solvatochromism. These characteristics can be conveniently used to study its interaction with Human Serum Albumin (HSA), a protein carrier of many non-aqueous biologically-active compounds in the blood stream. The intrinsic fluorescence of HSA was quenched by Fluorescence Resonance Energy Transfer toward the Zn(II) complex, and the Stern-Volmer equation was applied to determine the bimolecular quenching rate constant of the interaction.