ChemInform Abstract: Triplet Energy of 2,2‐Dimethylisoindene from Electron‐Energy‐Loss Spectroscopy and Photoinduced Triplet Energy Transfer.

Abstract

The excited electronic states of 2,2-dimethylisoindene (1) have been studied by electron-energy-loss spectroscopy. Its vertical gas-phase triplet (13B2), and singlet (I'B2) excitation energies are 1.61 and 3.19 eV, respectively. The excited states are thus lowered by 0.49 eV and 1.21 eV, respectively, when compared to the corresponding states of (all-E)-octatetraene, which serves as a reference compound. These shifts are partially reproduced by ZINDO calculations. The spectra give no evidence for a 2'A, state below the 1 'B, state, but this lack of observation does not exclude its existence. The lowest triplet state T,(1) was further characterized by flash photolysis. T, (1)