Rhenium and Technetium Complexes with Pentadentate Thiocarbamoylbenzamidines: Steps toward Bioconjugation

Article abstract of DOI:10.1021/acs.inorgchem.5b00769

Thiocarbamoylbenzimidoyl chlorides, PhC(Cl)=N-(C=S)-NR¹R², react with 2-(iminodiacetic acid)benzylamine under formation of the potentially pentadentate ligands H₃L (R¹, R² = Et) and H₃L-COOEt (R¹ = Me, R² = C₆H₄-4-COOEt) in high yields. Hydrolysis of H₃L-COOEt in NaOH/MeOH gives quantitatively another benzamidine ligand H₃L-COOH. The novel ligands readily react with (NBu₄)[MOCl₄] (M = Re, Tc) under formation of stable complexes with the general composition [MO(L)], in which they are triply deprotonated and fully occupy the remaining five coordination positions of the {MO}³⁺ cores. In a "proof-of-principle" reaction for possible bioconjugations, the complex [ReO(L-COOH)] has been labeled with triglycine ethyl ester in high yields.