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.