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

Abstract

The octahedral rhenium cluster compound Na₂H₈[{Re₆Se₈}(P(C₂H₄CONH₂)(C₂H₄COO)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(C₂H₄CN)₃ ligand during the reaction process. Therefore, in this report we compare the in vitro and in vivo toxicity of Na₂H₈[{Re₆Se₈}(P(C₂H₄CONH₂)(C₂H₄COO)₂)₆] with those of related compounds featuring the fully hydrolysed form of the phosphine ligand, namely Na₂H₁₄[{Re₆Q₈}(P(C₂H₄COO)₃)₆] (Q = S or Se). Our results demonstrate that the cytotoxicity and acute in vivo toxicity of the complex Na₂H₈[{Re₆Se₈}(P(C₂H₄CONH₂)(C₂H₄COO)₂)₆] solutions were considerably lower than those of compounds with the fully hydrolysed ligand P(C₂H₄COOH)₃. Such behavior can be explained by the higher osmolality of Na₂H₁₄[{Re₆Q₈}(P(C₂H₄COO)₃)₆] versus Na₂H₈[{Re₆Se₈}(P(C₂H₄CONH₂)(C₂H₄COO)₂)₆].