Water-soluble Re6-clusters with aromatic phosphine ligands – from synthesis to potential biomedical applications

The development of water-soluble hexanuclear cluster complexes of low toxicity is a promising task due to their potential biomedical applications such as bioimaging and photodynamic therapy. Herein, we present the syntheses of two new water-soluble hexarhenium cluster complexes with terminal amphiphilic phosphine ligands, and delineate their photoluminescence and X-ray excited optical luminescence (XEOL) properties. These cluster complexes, namely [{Re6Q8}(PPh2CH2CH2COO)6]4− (Q = S (1); Se, (2)), have the least cytotoxicity among all the tested hexanuclear metal-clusters, are capable of penetrating into cells and exhibit moderate photodynamic toxicity toward Hep-2 cells.