Fluorescent Copper(II) Complexes of Asymmetric Bis(Thiosemicarbazone)s: Electrochemistry, Cellular Uptake and Antiproliferative Activity

Abstract

Two new Cu(II) complexes, of the type CuL1 and CuL2, of asymmetric bis(thiosemicarbazone) ligands were synthesized wherebutan-2-ylidene) hydrazine carbothioamide and L2 = (E)-N-methyl-2-(3-oxobutan-2-ylidene) hydrazine carbothioamide and characterized by elemental analysis, HRMS, IR, EPR and cyclic voltammetry. The complexes undergo reversible one-electron reduction at E 1/2 = ∼ À 0.52 V vs Ag/AgCl. Interaction of CuL1 and CuL2 with human serum albumin monitored by fluorescence spectroscopy revealed static quenching with binding constants of the order of 10 5 M À 1 . Their cellular uptake and cytotoxicity were studied on MCF-7 and NIH-3T3 cells. The results indicate that CuL1 is more cytotoxic owing to its cellular permeability.