Femtosecond photolysis of CH2Br2 in acetonitrile: Capturing the bromomethyl radical and bromine-atom charge transfer complex through deep-to-near UV probing

Dibromomethane (CH2Br2) in acetonitrile is a suitable precursor to characterize the absorption signatures the CH2Br radical and solvent Br- charge-transfer complexes. Following irradiation of CH2Br2 at nm, the iso-H2C-Br-Br isomer product rapidly converts back to the parent species, and transient spectra reveal the bands of solvent-separated radical species, the CH2Br radical peaking at nm, as well as the CH3CN center dot Br complex at 272 nm. The absorption of CH2Br exhibits minor solvatoshifts upon going from acetonitrile to cyclohexane, and the molecular decadic extinction coefficient of CH3CN center dot Br is estimated to be 1470 M-1 cm(-1). (C) 2011 Elsevier B.V. All rights reserved.