A class of asymmetrical nitrido 99mTc heterocomplexes as heart imaging agents with improved biological properties

Asymmetrical heterocomplexes containing a terminal technetium-nitrogen
multiple bond coordinated to one diphosphine ligand (PNP) and one
dithiocarbamate ligand (DBODC), were obtained through a sinple two-step
procedure under controlled conditions. The resulting complexes [99mTc(N)
(PNP)(DBODC)]+ are monocationic, and possess a distorted square-pyramidal
geometry where the Tc=N multiple bond occupies an apical position and the
diphosphine and dithiocarbamate ligands span the residual four
coordination positions on the basal plane through the two phosphorous
atoms and the two sulfur atoms, respectively. Biodistribution data in
rats demonstrated that these complexes were rapidly extracted by the
myocardium, and retained in this region for a prolonged time. After a few
minutes post-injection, lung uptake becomes negligible, and liver washout
was extremely rapid and quantitative.