Synthesis and characterization of the 'Sulfur-rich' bis(perthiobenzoato)(dithiobenzoato)technetium(III) heterocomplex

The diamagnetic ‘sulfur-rich’ technetium(III) complex [99gTc(S2CPh)(S3CPh) 2] 1 has been characterized both in solid and solution states at ground level, and found to be identical by HPLC concordance experiments with the corresponding Tc-99m agent prepared at ‘carrier free’ level. The latter displays significant biological properties being able to label in vitro leukocytes in whole blood with high yields. The established mixed coordination sphere of 1, which is isostructural to the third-row rhenium complex [Re(S2CPh)(S3CPh)2] 2, comprises a dithiobenzoate and two perthiobenzoate fragments in a distorted trigonal prismatic arrangement. Redox behaviors indicate that the technetium complex is easier to reduce and more difficult to oxidize than the rhenium analog. The knowledge of the molecular structure of these new ‘sulfur rich’ species makes now possible to improve their biological activity by subtly tuning the substituents on the dithiobenzoate fragments.