SYNTHESIS, CHARACTERIZATION AND BIODISTRIBUTION OF TRIS(BETA-DIKETONATO)TECHNETIUM(III) COMPLEXES

New tris(beta-diketonato) complexes of trivalent Tc-99/Tc-99m with the ligands hexane-2,4-dione, heptane-2,4-dione, heptane-3,5-dione, and octane-3,5-dione were synthesized by reduction of pertechnetate with dithionite in the presence of excess beta-diketone. The complexes were purified by HPLC, identified by elemental analysis and FAB mass spectrometry, and characterized by vis./u.v./i.r, spectrophotometry. The hexane-2,4-dionato complex crystallizes in the monoclinic space group P2(1)/c, isostructurally with pentane-2,4-dionatotechnetium(III). Biodistribution measurements in mice showed the neutral and lipophilic Tc-99m-diketonato complexes to penetrate the blood-brain barrier. However, increasing lipophilicity decreased the brain uptake except for the heptane-2,4-dionato complex, which displayed the highest uptake of 0.82% injected dose/g.