Dynamic Spectral Shifts of Molecular Anions in Organic Glasses

Article abstract of DOI:10.1021/j100210a032

Time-dependent spectra of the radical anions of pyromellitic dianhydride and p-dinitrobenzene have been observed after formation by pulse radiolysis in frozen 2-methyltetrahydrofuran and triacetin glasses.At temperatures near the glass transition, the spectra shift toward the blue over the entire observed time range (100 ns - 100 s), while at temperatures well below the glass transition, the spectral shifts can be stopped or greatly slowed.The magnitudes of the shifts are not large (typically ca. 10 nm), but because they are larger than the vibrational line widths, dramatic kinetics may be observed: the absorbance grows or decays by more than a factor of five at some wavelengths.The observations are consistent with a solvent molecule reorientation mechanism for spectral shifts of molecular ions in low-temperature organic glasses.