Free radicals in an adamantane matrix. IX. Optical excitation and emission spectra of benzyl radical and its monofluorinated derivatives

Abstract

The electronic emission and excitation spectra of benzyl radical and its monofluorinated derivatives have been obtained in an adamantane matrix. The spectra obtained for benzyl radical were similar to those found in other condensed phases; in addition, adamantane offers advantages in ease of sample preparation and handling, of radical identification by EPR, and of variable-temperature spectral studies. The electronic spectrum of the α-fluorobenzyl radical and the complete spectra of the o -, m -, and p -fluorobenzyl radicals in a condensed phase are reported for the first time. The 0–0 bands for the first three electronic transitions (4500, 3100, and 2600 Å) in adamantane are, respectively, (in cm−1) for benzyl 21 682, 31 566, 38 095; 0-fluorobenzyl 21 650, 31 546, 37 807; m -fluorobenzyl 21 505, 31 211, 37 594; p -fluorobenzyl 20 938, 32 051, 37 244; α-fluorobenzyl 21 478, 31 153, 35 714. The values for all of the fluorobenzyls are red shifted relative to benzyl except for the 3100 Å transition of p -fluorobenzyl. We have observed and analyzed vibrational fine structure in the 4500 and 3100 Å systems of all of the radicals.