Effect of matrix polarity on the charge-transfer band of the benzyl radical-halide ion complex

Abstract

Broad, unstructured spectra of fluorescence and fluorescence excitation were observed at ca. 520 and 420 nm for a transient complex of the benzyl (Bz•) radical-iodide ion generated by the dissociative electron attachment to benzyl iodide in a 2-methyltetrahydrofuran matrix at 77 K. Compared with the transition energy of similar spectra for several halide ions (X") in the nonpolar 3-methylhexane matrix, the transition energy of the spectra in question could be interpreted by the solvation energy of Bz-X™ and Bz™---X together with the ionization energy of X™ and the electron affinity of Bz• and confirmed the previously suggested assignment that the spectra are due to the charge-transfer band of the complex. The effect of the solvation energy was confirmed also for the Bz-Cl™ complex in 3-methylhexane and 3-methylpentane matrices, whose dielectric constants are slightly different from each other.