Potential of the "[M(CO)3]+" (M = Re, Tc) Moiety for the Labeling of Biomolecules

The synthesis of [MX3(CO)3]2- (M = 188Re, Re, 99Tc) directly from the corresponding permetallates is described. Intermediates and byproducts have been isolated and characterized. Preliminary direct labeling studies at r.t. revealed a slow but irreversible incorporation of "[188Re(CO)3]+" into intact antibodies. The best yield was 40% after 20 h with 0.8 mg/ml of intact antibody. To elucidate possible coordination sites in proteins, the synthesis and formation of model complexes has been investigated by means of 1H NMR spectroscopy and X-ray structure analysis. A high tendency for imidazole (im) coordination has been found and is examplified in the model complexes [ReBr(histamine)(CO)3] and [Re2(μ-OH)2(im)2(CO)6], which structures will be presented. Additionally, complexation with the macrocyclic thioether ligand [20-aneS6] was studied in order to establish a post-labeling protocol with this type of chelator. The structure of [(20-aneS6-OH){Tc(CO)3}2]2+ will be presented.