Dicarbonyl-nitrosyl-complexes of rhenium (Re) and technetium (Tc), a potentially new class of compounds for the direct radiolabeling of biomolecules

Re- and Tc-complexes of the oxidation state (+I) offer a useful synthetic pool for the labeling of biomolecules due to their co-ordination properties and stability, which are superior to compounds of the oxidation state (+V). Based on the results for Tc-tricarbonyl complexes it was the topic of this work to develop an access to similar but higher charged compounds, which could be performed by replacing a neutral [CO]-group by a [NO](+)-group. The resulting Re(I)- and Tc(I)-dicarbonyl-nitrosyl complexes, such as [N(CH(2)Ch(3))(4)][ReX3(CO)(2)(NO)], show a tendency for co-ordination at carboxylic and amine groups of biomolecules (X = Br, Cl). This was shown with picolinic acid (H-pic), a suitable model for amino acids, forming the neutral complex [ReX(pic)(CO)(2)(NO)]. In. a similar fashion conjugation of [Re-188(CO)(2)(NO)](2+) - or [Tc-99m(CO)(2)(NO)](2+) -compounds to proteins or antibodies is feasible. This approach opens a way to a potentially new class of radiopharmaceuticals.