A ‘preformed chelate approach’ model for coupling amine-modified rhenium and technetium ‘3+1’ mixed ligand complexes to carboxylate residues
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 (Tc-99m 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 Tc-99m 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[CH3SCH2CH2N(CH2CH2S)(2)][p-SC6H4NH2] and daughter ReO[CH3SCH2CH2N(CH2CH2S)(2)][p-SC6H4NHCOC6H5] 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. (C) 1999 Elsevier Science ltd. All rights reserved.
Synthesis and characterization of five-coordinate rhenium(V) and technetium(V) mixed ligand bifunctional complexes carrying the SNS/S or the SNN/S donor atom set. Crystal structure of ReO{[(C2H5)2NCH2CH2N(CH2CH2S)2](p-H2N–PhS)} and ReO{[(CH2)4NCH2CH2NCH2CH2S](p-H2N–PhS)}
摘要:
Two parallel series of bifunctional mixed ligand oxorhenium and oxotechnetium complexes containing the SNS/S or the SNN/S donor atom set are synthesized and characterized in this study. The amine bifunctional anchor is positioned on the common monothiolate p-H2N-Ph-SH coligand, which by reacting in equimolar amounts with a tridentate aminethiolate ligand LH2 [LH2:CH3CH2N(CH2CH2SH)(2), (CH3CH2)(2)NCH2-CH2N(CH2CH2SH)(2), (CH2)(4)NCH2CH2NHCH2CH2SH and (CH3CH2)(2)NCH2CH2NH-CH2CH2SH] and the corresponding oxometal precursor, leads to the generation of these series. Two representative members ReO{[(C2H5)(2)NCH2CH2N(CH2CH2S)(2)](p-H2N-PhS)} and ReO{[(CH2)(4)NCH2CH2NCH2CH2S](p-H2N-PhS)} are further characterized by crystallographic analysis. The SNS/S analogs adopt a distorted trigonal bipyramidal geometry, while the SNN/S ones prefer a distorted square pyramidal geometry around the metal. Extrapolation of structure at tracer level is investigated by chromatographic methods and is established only for the SNS/S, but not for the SNN/S compounds. Thus, by this initial evaluation, the applicability of the bifunctional SNS/S (but not the SNN/S) system for tagging biomolecules with Tc-99m is demonstrated. (C) 1999 Elsevier Science S.A. All rights reserved.