Assignment of the 290-nm electronic band system of indazole [1,2-benzodiazole] as [formula omitted] by rotational band contour analysis

Abstract

The 0 0 0 band of the S 1- S 0 electronic absorption system of indazole at 290 nm has been analyzed, and the results of the computer simulation of its rotational contour have shown that this band is and A B hybrid with an intensity ratio A B = 1.22 . The S 1- S 0 electronic system is assigned as A ̃ 1 A′(ππ ∗)- X ̃ 1A′ . The same result has already been reached for benzimidazole (E. Cané et al., J. Mol. Spectrosc. 150, 222–228 (1991)), and other ring-condensed aza-aromatic compounds although the relative amount of the type B and A components is different in each band. The transition moment is in the molecular plane nearly equidistant from the a- and b-inertial axes ( θ = ±42°).