Synthesis and Characterization of [MIII(PS)2(L)] Mixed-Ligand Compounds (M = Re, 99Tc; PS = Phosphinothiolate; L = Dithiocarbamate) as Potential Models for the Development of New Agents for SPECT Imaging and Radiotherapy

Abstract

The synthesis and characterization of a new series of neutral, six-coordinated mixed-ligand compounds [M(III)(PS)2(L)] (M = Re; (99)Tc), where PS is bis(arylalkyl)- or trialkylphosphinothiolate and L is dithiocarbamate, are reported. Stable [M(III)(PS)2(L)] complexes were easily synthesized, in good yield, starting from precursors where the metal was in different oxidation states (III, V, and VII), involving ligand-exchange and/or redox-substitution reactions. The compounds were characterized by elemental analysis, positive-ion electrospray ionization mass spectrometry, multinuclear NMR spectroscopy, cyclic voltammetry, and X-ray diffraction analysis. All complexes are constituted by the presence of the [M(III)(PS)2](+) moiety, where two phosphinothiolate ligands are tightly bound to the metal and the remaining two positions are saturated by a dithiocarbamate chelate, also carrying bulky bioactive molecules [e.g., (2-methoxyphenyl)piperazine]. X-ray analyses were performed on crystalline specimens of four different Re/(99)Tc compounds sharing a distorted trigonal-prismatic geometry, with a P2S4 coordination donor set. The possibility of easily preparing these [M(III)(PS)2(L)] complexes, starting from the corresponding permetalate anions, in mild reaction conditions and in high yield, lays the first stone to the preparation of a new series of M(III)-based (M = (99m)Tc/(188)Re) compounds potentially useful in theragnostic applications.