Synthesis,radiochromatography and biodistribution of99mTc-dimethylphosphinoethane (DMPE) complexes

The title complexes were prepared from no-carrier-added^99mTc–TcO ₄ ^– and the air-sensitive reducing ligand DMPE under argon in ethanol-water. At acidic pH Tc(III)Cl₂ dmpe₂]⁺ was formed, while alkaline pH led to the formation of Tc(I)dmpe₃]⁺. About 150°C and at least 10^–3M DMPE was needed to achieve over 95% yield in less than 1 hour, otherwise the Tc(V)O₂dmpe₂]⁺ intermediate was present. Electrophoresis demonstrated the unit positive charge and reversed-phase ion-pair HPLC provided separation and identification of^99mTc-products by direct comparison with known⁹⁹Tc-complexes. In rats the^99mTc-complexes were excreted by kidneys and liver and reached high heart/blood but only low heart/lung and heart/liver ratios. In dogs satisfactory myocardial scintigrams were obtained in spite of high liver activity.