Synthesis, structural characterization and radiochemistry of di- and tricarbonyl Re(I) and 99mTc(I) complexes with 8-hydroxyquinoline or 8-mercaptoquinoline and triphenylphosphine

Abstract

In this work, we focused on the development of mixed ligand technetium and rhenium complexes of the general formula fac-[99mTc/Re(CO)3(PPh3)(ox/tq)] and cis, trans-[99mTc/Re(CO)2(PPh3)2(ox/tq)] where 8-hydroxyquinoline (oxH) and 8-mercaptoquinoline (tqH) act as [NO] and [NS] bidentate ligands. The synthesis of rhenium complexes fac-[Re(CO)3(PPh3)(ox/tq)] Re3/Re4 was conducted by reacting oxH or tqH and triphenylphosphine with fac-(NEt4)2[Re(CO)3Br3] (1) or by reacting triphenylphosphine with the dimer complexes fac-[Re(CO)3(ox/tq)]2Re1/Re2. The synthesis of the rhenium complexes cis, trans-[Re(CO)2(PPh3)2(ox/tq)] Re5/Re6 was conducted either by reacting 1 with oxH/tqH in equimolar amounts and triphenylphosphine in excess or by reacting oxH/tqH with the precursor mer, trans-[Re(CO)3(PPh3)2Cl]. All the complexes were characterized by IR, NMR and X-ray crystallography. The analogous 99mTc complexes were prepared by reacting oxH/tqH and PPh3 with the precursor fac-[99mTc(CO)3(OH2)3]+ (2). When the reaction mixture was left at rt for 2h the monophosphino complexes fac-[99mTc(CO)3(PPh3)(ox/tq)] 99mTc3/99mTc4 were formed, while by applying heating at 75°C for 30min the dicarbonyl complexes cis, trans-[99mTc(CO)2(PPh3)2(ox/tq)] 99mTc5/99mTc6 were formed quantitatively. The 99mTc complexes were identified by HPLC chromatographic comparison with the analogous rhenium complexes and their stability was studied.