Delocalization of free electron density through phenylene-ethynylene: structural changes studied by time-resolved infrared spectroscopy.
We have studied the photochemistry of 1,4-bis(2-[4-tert-butylperoxycarbonylphenyl]ethynyl)benzene (1) and tert-butyl 4-(2-{4-[2-(4-phenyloxycarbonylphenyl)-1-ethynyl]phenyl}-1-ethynyl)peroxybenzoate (2). Excitation of 1 and 2 by a 355-nm laser pulse leads to the rapid formation of aroyloxyl radicals. An unpaired electron conjugated with the phenylene-ethynylene core is substantially delocalized over the pi-system of the chromophore. The -CC- vibrational frequencies of these radicals are red-shifted relative to 1 and 2 as measured by time-resolved IR spectroscopy. This shift is attributed to the change in the triple bond character due to delocalization of the free electron.
Polyansky
Dmitry E
DE
Center for Photochemical Sciences, Bowling Green State University, Bowling Green, Ohio 43403, USA.
Danilov
Evgeny O
EO
Voskresensky
Sergey V
SV
Rodgers
Michael A J
MA
Neckers
Douglas C
DC