Photoinduced Electron Transfer from Polygermane to C60 Studied by Laser Flash Photolysis

Abstract

Electron transfer from poly(phenylmethylgermylene) (PMePhGe) to photoexcited C{sub 60} in benzene-acetonitrile solution has been investigated by 532 nm laser flash photolysis in the near-IR region. The transient absorption band of the C{sub 60} triplet state ({sup 3}C{sub 60}{sup *}) appeared immediately after nanosecond laser exposure. The rate constant of the electron transfer from PMePhGe to {sup 3}C{sub 60}{sup *} was determined to be 2.33 x 10{sup 8} M{sup -1} s{sup -1}, which was similar to that for poly(methylphenylsilylene). Electron transfer from the singlet state of C{sub 60} ({sup 1}C{sub 60}{sup *}) was investigated by fluorescence quenching experiments and the quenching rate constant was determined to be 4.00 x 10{sup 10} M{sup -1} s{sup -1}. The rate constant of intersystem crossing from {sup 1}C{sub 60}{sup *} to {sup 3}C{sub 60}{sup *} was determined to be 1.10 x 10{sup 9} s{sup -1} by picosecond time-resolved absorption spectroscopy using a streak camera. Electron transfer from {sup 1}C{sub 60}{sup *} to PMePhGe and intersystem crossing from {sup 1}C{sub 60}{sup *} to {sup 3}C{sub 60}{sup *} are competitive, and the intersystem crossing is dominant in a dilute solution system. When a 355 nm laser was used as the excitation light, photochemical intermediates were produced frommore » the direct photolysis of PMePhGe in addition to the electron transfer. 36 refs., 9 figs.« less