J. Grodkowski et al., RADIOLYTIC REDUCTION OF RHODIUM PORPHYRINS - CHAIN-REACTION IN ALKALINE 2-PROPANOL, Journal of physical chemistry, 99(16), 1995, pp. 6019-6023
Rhodium(III) tetramesitylporphyrin (Rh(III)TMP) undergoes radiolytic r
eduction in deoxygenated alkaline alcohol solutions to produce a trans
ient Rh(II)TMP and then a stable Rh(I)TMP. When the solvent was 2-PrOH
and the KOH concentration was >0.02 mol L(-1), the radiolytic yield o
f reduction was considerably higher than the total yield of reducing r
adicals, indicating a chain reaction. The chain propagation process is
suggested to be a reaction of the intermediate Rh(II)TMP with the sol
vent and the base to yield Rh(I)TMP and an additional reducing radical
, (CH3)(2)CO-. No chain reaction was observed with [KOH] < 0.01 mol L(
-1) or when the solvent was MeOH. With pyridine as an axial ligand, re
duction occurs on the porphyrin ring to yield Rh(III)TMP.-, which then
yields the stable Rh(I)TMP. Further radiolytic reduction of Rh(I)TMP
in 2-PrOH takes place at the porphyrin ring to yield the chlorin and m
ore highly reduced products.