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

Abstract

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.