[EPR study of the mechanism of photooxidation of chlorophyll a by nitro compounds].

An ESR signal with g-value of 2,0026 and peak-to-peak with 8,5 Oe was observed in ethanole solutions of chlorophill a and nitroderivatives of naphtalene under red light illumination. The ESR signal consisted of chlorophyll cation radical resonance, superimposed on an nitronaphtalene anion radical. Less than the ratio greater than between the quantities of these radicals and the character of decay kinetics are influenced by the medium acidity. An analysis of kinetic curves is performed, and the effect of the medium acidity on the mechanism of one-electron transfer reaction between chlorophyll and nitronaphtalene molecules is explained.