Technetium Phosphine Complexes Myocardial Imaging

The positive charge on the complex is probably critical for myocardial cell uptake. Indeed, this was the rationale of Deutsch and coworkers who noted that cationic species such as ammonium salts and alkali metal ions accumulate in normal heart muscle 

7 ra/ -[Tc(dmpe)2Cl2] is highly water soluble and can be administered by injection in saline. However, the ligand itself is highly unstable in air. How kinetically and thermodynamically stable is the Tc complex It is thought to be relatively stable towards substitution in vivo since the complex can apparently be recovered intact from tissue (heart, liver and bile) soon after injection.  

The complex itself is an intermediate obtained during the reduction of Tc(IV) or Tc(VII) with excess diphqsphine  

The Re complex trans-[Re(dmpe)2Cl2] is more difficult to reduce (by 190 mV) than the Tc analogue. This may account for the lower liver and higher heart uptake of the Re complex compared to the Tc complex despite their similar structures. It would be interesting to compare the kinetics of their ligand substitution reactions. 

It seems unlikely that the physiological consequences resulting from the administration of Tc phosphine complexes will be significant. The amounts used are minute (nmol). 

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