Ca. Steren et H. Vanwilligen, ELECTRON-TRANSFER QUENCHING OF C-60 TRIPLETS - AN FT-EPR STUDY OF C-60-TCNE IN BENZONITRILE, Proceedings of the Indian Academy of Sciences. Chemical sciences, 106(7), 1994, pp. 1671-1679
A Fourier transform EPR study was made of photoinduced processes in a
benzonitrile solution of C-60 and tetracyanoethylene (TCNE). It was fo
und that TCNE reduces the tripIet lifetime of C-60 as had been found e
arlier in a flash photolysis study. However, the experimental data sho
w that this is not due to encounters between TCNE and C-3(60), but rat
her stems from the presence of a trace amount of the anion radical TCN
E(-). Encounters between doublet radicals and triplets can result in r
eductive quenching of the tripIet, thereby causing a reversible reduct
ion in, TCNE(-) concentration. Alternatively, the encounters can be no
n-reactive and generate spin polarization in the paramagnetic molecule
s. In the FT-EPR spectrum of TCNE(-) the spin polarization causes tran
sient intensity enhancements for some of the hyperfine lines and inten
sity reductions for the others. The measurements show no evidence of o
xidative quenching of C-3(60).