Boron photochemistry : XI. A study of the unusual luminescence and spectral properties of anilinodimesitylboranes

Anilinodimesitylboranes fluoresce showing the largest Stokes shifts yet reported, which correspond to energy losses of 35.3–61.8 kcal/mole. The dependence of wavelengths of fluorescence on the polarity of the solvent indicates that the first excited singlet state is highly dipolar in nature. A scheme involving an excited-state dipolar

species is used to explain the large loss of energy corresponding to the Stokes shifts for the anilinodimesitylboranes. Delayed emission found at 77 K corresponding to fluorescence is attributed to electron ejection—recombination-type luminescence. No emission was found at longer wavelengths corresponding to triplet emission. It is proposed that the photochemical rearrangements of anilinodimesitylboranes in the presence of iodine occur by interception of an excited singlet or excited charge-transfer state.