Oxorhenium and oxotechnetium [SNS/S] mixed ligand complexes having a pendant diisopropylaminoethyl- group. Synthesis, characterization and biodistribution studies.

A novel SNS tridentate ligand, the N,N-bis(2-mercaptoethyl)-N',N'-diisoprop ylethylenediamine was synthesized and the corresponding oxorhenium and oxot echnetium "mixed ligand" complexes using 3 monodentate aromatic thiols as c oligands were prepared and characterized. Rhenium complexes were obtained as crystals with high yield by substitution of ligand and coligand on the trichlorobis(triphenylphosphine)- rhenium(V) oxide, using a molar ratio ligand:coligand:precursor of 1. Characterizatio n was performed by HPLC analysis, W-vis and IR spectra, elemental analysis and X-ray diffraction. Results were consistent with the ReOLC structure. Th e complexes adopted a distorted trigonal bipiramidal geometry and were neut ral due to ionization of all sulphur atoms upon complexation. Consequently Tc-99m complexes were also prepared and evaluated in mice as p otential brain imaging agents. Labelling was performed by substitution usin g Tc-99m-glucoheptonate as precursor. The labelling yield was over 85% and the radiochemical purity of the complexes over 90%. Biodistribution in mice demonstrated high uptake and retention in brain. However comparison with previously reported "mixed ligand" complexes showed that the incorporation of the diisopropylaminoethyl group in the SNS/S bac kbone is not enhancing the biological characteristics of this type of compl exes.