The relative quantum efficiencies for loss of cis-Rh(phen)(2)Cl-2(+) (
when phen = 1,10-phenanthroline) in the presence of dA (deoxyadenosine
), dG (deoxyguanosine), and uric acid have been measured in phosphate
buffer. The relative reactivity was uric acid > dG > dA with the quant
um efficiency in the presence of uric acid (under argon) approximately
unity and that in the presence of dA essentially equal to that for ci
s-Rh(phenCl2+ alone. The product distribution was found to be oxygen d
ependent. cis-Rh(phenCl2+ aquation products were primarily formed in t
he presence of oxygen while adduct formation was the primary chemistry
in the absence of oxygen. Reductive quenching mechanisms are invoked
to account for the increased reactivity in the presence of dG (one ele
ctron) and uric acid (two electron). Such a mechanism provides a ratio
nale for the previously observed site of covalent binding of the metal
to dG.