Electronic Structure and Spectra of s-Tetrazine

Abstract (1) π-Electronic structure and the nature of the electronic transitions in the s-tetrazine molecule has been elucidated using the semiempirical LCAO SCF MO method. (2) There is satisfactory agreement between the calculated and the observed values of the excitation energy for the transition to the lowest excited state. (3) Tsubomura’s qualitive argument concerning the influence of configuration interaction on the lowest energy transition of nitrogen heterocycles has been confirmed by the quantitative calculation. (4) The cause of the intensification of 1Lb band compared with the parent hydrocarbon has been analysed by the same method employed previously, and it has been confirmed that, also in the case of s-tetrazine the perturbation on MO by hetero-replacement has only a small influence on the oscillator strength. (5) The spectral simirarity of nitrogen heterocycles with the parent hydrocarbon has been ascribed to the fact that their MO’s correspond closely each other, and it has been pointed out that the configuration interaction plays a very important role in the determination of spectra, which is also a cause for the spectral similarity.