3-benzodioxole in its S-1(pi,pi*) excited state. The effect of the electronic excitation on the anomeric effect Spectroscopic determination of the vibrational potential energy surface and conformation of 1

The electronic absorption spectra and the laser-induced fluorescence spectra of supersonic-jet-cooled 1,3-benzodioxole molecules have been investigated to map out the vibronic energy levels in the S1(,+*) electronic excited state. These were used to determine a two-dimensional potential energy surface in terms of the ring-puckering and ring-flapping vibrational coordinates, and the molecule was found to be puckered with a dihedral angle of 22. The barrier to planarity in the excited state is 264 cm-1 (3.16 kJ/mol) as compared to 164 cm-1 (1.96 kJ/mol) in the ground state. This increase is attributed to reduced suppression of the anomeric effect by the benzene ring resulting from decreased bonding character in the S1(,:*) state. As expected, the motion along the flipping coordinate is governed by a more shallow potential energy well. Ab initio calculations carried out for both the ground and excited states support the experimental conclusions.

Spectroscopic determination of the vibrational potential energy surface and conformation of 1,3-benzodioxole in its S-1(pi,pi*) excited state. The effect of the electronic excitation on the anomeric effect Academic Article