A 'preformed chelate approach' model for coupling amine-modified rhenium and technetium '3+1' mixed ligand complexes to carboxylate residues Crystal structure of ReO[CH_3SCH_2CH_2N(CH_2CH_2S)_2][p-SC_6H_4NH_4] and ReO[CH_3SCH_2CH_2N(CH_2CH_2S)_2][p-S

摘要

Selected '3 + 1' mixed ligand oxorhenium and oxotechnetium complexes containing the SNS/S donor atom set have been modified by introduction of a bifunctional amine anchor on the p-position of the thiophenolato monodentate ligand. A representative series of complexes containing several tridentate ligands was prepared both at macromolar (Re complexes) and nanomolar (~(99m)Tc complexes) amounts. Coupling of these complexes to activated carboxylate groups was performed according to the 'preformed chelate approach' using benzoyl chloride as a model molecule. Coupling yields were high both at nanomolar and millimolar metal concentration, as revealed by high-performance liquid chromatographic analysis of ~(99m)Tc and Re species adopting parallel radiometric and photometric detection modes. All Re compounds have been characterized by classical analytical methods. In addition, the structures of representative parent ReO[CH_3SCH_2CH_2N(CH_2CH_2S)_2][p-SC_6H_4NH_2] and daughter ReO[CH_3SCH_2CH_2N(CH_2CH_2S)_2][p-SC_6H_4NHCOC_6H_5] complexes were solved by X-ray crystallography. Both compounds adopt a distorted trigonal bipyramidal geometry around rhenium, wherein the oxo group and the sulfur atoms of the SNS ligand occupy the equatorial plane and the nitrogen atom and the sulfur of the monothiol are located at the apical positions trans to each other.