Study of acyl group migration by femtosecond transient absorption spectroscopy and computational chemistry.

摘要: The primary photophysical and photochemical processes in the photochemistry of 1-acetoxy-2-methoxyanthraquinone (1a) were studied using femtosecond transient absorption spectroscopy. Excitation 1a at 270 nm results population a set highly excited singlet states. Internal conversion to lowest npi* state, followed by an intramolecular vibrational energy redistribution (IVR) process, proceeds with time constant 150 +/- 90 fs. 1npi* state undergoes very fast intersystem crossing (ISC, 11 1 ps) form triplet pipi* which contains excess energy. cooling occurs somewhat faster (4 than ISC. migration acetoxy group, on potential surface 220 30 ps. spectra states 1a, as well product, 9-acetoxy-2-methoxy-1,10-anthraquinone (2a), detected. assignments supported time-dependent DFT calculations UV-vis proposed intermediates. All stationary points for acyl group ground surfaces localized, influence substitution rate constants thermal was analyzed.