A comparative study of hydrophilic phosphine hexanuclear rhenium cluster complexes’ toxicity

The octahedral rhenium cluster compound Na(2)H(8)[{Re(6)Se(8)}(P(C(2)H(4)CONH(2))(C(2)H(4)COO)(2))(6)] has recently emerged as a very promising X-ray contrast agent for biomedical applications. However, the synthesis of this compound is rather challenging due to the difficulty in controlling the hydrolysis of the initial P(C(2)H(4)CN)(3) ligand during the reaction process. Therefore, in this report we compare the in vitro and in vivo toxicity of Na(2)H(8)[{Re(6)Se(8)}(P(C(2)H(4)CONH(2))(C(2)H(4)COO)(2))(6)] with those of related compounds featuring the fully hydrolysed form of the phosphine ligand, namely Na(2)H(14)[{Re(6)Q(8)}(P(C(2)H(4)COO)(3))(6)] (Q = S or Se). Our results demonstrate that the cytotoxicity and acute in vivo toxicity of the complex Na(2)H(8)[{Re(6)Se(8)}(P(C(2)H(4)CONH(2))(C(2)H(4)COO)(2))(6)] solutions were considerably lower than those of compounds with the fully hydrolysed ligand P(C(2)H(4)COOH)(3). Such behavior can be explained by the higher osmolality of Na(2)H(14)[{Re(6)Q(8)}(P(C(2)H(4)COO)(3))(6)] versus Na(2)H(8)[{Re(6)Se(8)}(P(C(2)H(4)CONH(2))(C(2)H(4)COO)(2))(6)].