Study on the formation of mixed ligand oxorhenium and oxotechnetium complexes (SNS/S combination)

When a mixture of the tridentate aminedithiol ligand EtN(CH2CH2SH)2, L1H2, and a monodentate thiol p-CIC6H4SH, L2H, is added to a suitable RevO or 99mTcvO precursor, the following complexes are theoretically possible: (i) neutral mixed ligand complexes MOL1L2 (syn, 1 and 1' for rhenium and technetium respectively, and anti, 2 and 2') (ii) binuclear complex of the tridentate ligand, (MO)2(L1)3, 3 and 3', (iii) anionic complex of the monothiol [MO(L2)4], 4 and 4'. All of the above types of complexes have been synthesized by exchange reaction using ReOCl3(PPh3)2 as precursor and selectively monitoring reaction stoichiometry. The crystal structures of 1, 3, and 4 are determined by X-ray crystallography. All the above types of complexes have been prepared at technetium-99m level by exchange reaction using Tc-99m glucoheptonate as precursor and the appropriate ligand(s), as shown by high performance liquid chromatographic (HPLC) analysis. The major reaction product is the syn isomer while none of other complexes forms during the reaction, when a L1H2/L2H 1/1 molar ratio is retained. This fact satisfies a very important prerequisite for the further evaluation of the above mixed ligand system, SNS/S, in biological systems at tracer level, Tc-99m. (author)