Triplet-state energies and substituent effects of excited aroyl compounds in the gas phase

Triplet-state energy values obtained from the gas phase are still scarce. I n this study, the triplet-state energies of 58 aroyl compounds, introduced as gas chromatographic peaks at atmospheric pressure and typically 473 K, h ave been determined from the 0-0 bands of their n-->pi* type phosphorescenc e spectra in excited nitrogen. Correlations of those gas-phase triplet-stat e energies with Hammett constants could be observed for substituted acetoph enones, benzaldehydes and benzophenones. (C) 2000 Elsevier Science B.V. All rights reserved.