CHARGE RECOMBINATION REACTIONS IN PHOTOEXCITED C-60-AMINE COMPLEXES STUDIED BY PICOSECOND PUMP-PROBE SPECTROSCOPY

Photoexcitation of complexes between fullerene C60 and organic amines in benzene solutions is known to result in charge separation (CS) and subsequent charge recombination (CR) reactions, which lead to varying yields of fullerene triplet formation. Picosecond flash photolysis stu dies are carried out on C60-diphenylamine (DPA), C60-triethylamine (TE A), C60-diazabicyclooctane (DABCO), and C60-triphenylamine (TPA) syste ms to find out mechanistic details of the triplet formation on CR by i nducing heavy atom and polarity effects by using suitable solvents. It is found that in the case of C60-DPA, C60-TEA, and C60-DABCO systems proton transfer from the amine cation to the C60 anion in the ion pair state dominates, leading to poor triplet yields, which improve in hea vy atom containing solvents. In TPA, proton transfer is not possible a nd hence fullerene triplet yields are high. Increase of solvent polari ty for this system results in decreased C60 triplet yields with a cons equent increase in the ion dissociation yield. A suitable reaction sch eme is proposed to explain the results obtained.