Synthesis, radiolabelling and confocal fluorescence microscopy of styrene-derivatised bis(thiosemicarbazonato)zinc and -copper complexes

The synthesis of zinc(II) and copper(II) complexes of an unsymmetrical bis(thiosemicarbazonato) ligand containing a reactive styrene group are reported. The compounds have been characterised by a range of techniques including reverse-phase HPLC, cyclic voltammetry, NMR, UV/Vis, electron paramagnetic resonance and fluorescence emission spectroscopy. Time-dependent density functional theory calculations have been used to assign the electronic absorption spectrum of [Zn(II)ATSM] and probe the nature of the fluorescent excited state. Electrochemistry experiments show that the copper(II) complex undergoes quasi-reversible one-electron reduction at biologically accessible potentials and is within the range proposed for the complex to be hypoxia-selective. The copper-64 radiolabelled complex has been prepared in aqueous solution and characterised by reverse-phase radio-HPLC. Cellular uptake in HeLa cells has been observed using confocal fluorescence microscopy. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008).