title: Delocalization of free electron density through phenylene-ethynylene: structural changes studied by time-resolved infrared spectroscopy.
abstract: 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.
authors.affiliation: Center for Photochemical Sciences, Bowling Green State University, Bowling Green, Ohio 43403, USA.
authors.forename: Dmitry E
authors.initials: DE
authors.lastname: Polyansky
authors.forename: Evgeny O
authors.initials: EO
authors.lastname: Danilov
authors.forename: Sergey V
authors.initials: SV
authors.lastname: Voskresensky
authors.forename: Michael A J
authors.initials: MA
authors.lastname: Rodgers
authors.forename: Douglas C
authors.initials: DC
authors.lastname: Neckers