CATIONIC )(DIARS)(2)(SR)(2)](-PHENYLENEBIS(DIMETHYLARSINE), SR(-) EQUALS THIOLATE)() COMPLEXES AS POTENTIAL MYOCARDIAL PERFUSION IMAGING AGENTS (DIARS EQUALS O)

Reduction-substitution reactions on [(TcO4)-Tc-99m](-) with both o-phe nylenebis(dimethylarsine) (DIARS) and various thiols produce a series of monocationic [Tc-99m(DIARS)(2)(SR)(2)](+) complexes. Addition of [( TcO4)-Tc-99g](-) to the above reaction mixtures allows the characteriz ation of the ''carrier-added'' complexes by means of reverse-phase hig h-performance liquid chromatography with radiometric and optical detec tion systems. The identity of the [Tc-99g(DIARS)(2)(SR)(2)](+) complex es is confirmed by fast atom bombardment mass spectroscopy; equivalenc e of the [Tc-99g(DIARS)(2)(SR)(2)](+) and [Tc-99m(DIARS)(2)(SR)(2)](+) species is demonstrated by identical HPLC retention times. All the [T c-99m(DIARS)(2)(SR)(2)](+) complexes tested accumulate in the myocardi um of Sprague-Dawley rats with an average uptake of 1.5-2.0% of inject ed dose/g at 30 min. Thus, as designed, these nonreducible Tc(III) com plexes do not exhibit the rapid myocardial washout observed for reduci ble Tc(III) complexes. These [Tc-99m(DIARS)(2)(SR)(2)](+) complexes al so exhibit an initially high liver uptake, but the presence of ether g roups within the thiolate ligands causes this liver uptake to decrease over time without affecting the heart uptake, thereby improving the h eart/liver ratio.