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)(2)NCH2CH2N(CH2CH2S)(2)](p-H2N-PhS)} and ReO{[(CH2)(4)NCH2CH2NCH2CH2S](p-H2N-PhS)}

Two parallel series of bifunctional mixed ligand oxorhenium and oxotechneti um complexes containing the SNS/S or the SNN/S donor atom set are synthesiz ed and characterized in this study. The amine bifunctional anchor is positi oned on the common monothiolate p-H2N-Ph-SH coligand, which by reacting in equimolar amounts with a tridentate aminethiolate ligand LH2 [LH2:CH3CH2N(C H2CH2SH)(2), (CH3CH2)(2)NCH2-CH2N(CH2CH2SH)(2), (CH2)(4)NCH2CH2NHCH2CH2SH a nd (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 SN S/S analogs adopt a distorted trigonal bipyramidal geometry, while the SNN/ S ones prefer a distorted square pyramidal geometry around the metal. Extra polation of structure at tracer level is investigated by chromatographic me thods and is established only for the SNS/S, but not for the SNN/S compound s. 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 de monstrated. (C) 1999 Elsevier Science S.A. All rights reserved.