Study of electronic structure of certain phenazasilines by quantum chemistry and UV spectroscopy methods

A spectroscopic and quantum-chemical investigation of heterocyclic derivatives of 9,10-dihydroanthracene, viz., phenazasilines EtN(C₆H₄)₂SiMe₂ (I), MeN(C₆H₄)₂SiMe₂ (II), and EtN(C₆H₄)₂SiHME (III), was carried out. The experimental absorption spectra were theoretically interpreted by calculating the electronic structure of the molecules by the CNDO/S3 method, whose system of semiempirical parameters was supplemented by the silicon parameters. The nonplanar structure of the phenazasiline heterocyclic ring and the presence of two butterfly type conformations in the molecule of III was taken into account. The calculated bond lengths and oscillator forces of the electronic transitions agree well with the UV spectroscopy data and the photoelectronic spectrum of the molecule of II. The polarization spectra of phenazasilines I–III were predicted.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 21, No. 2, pp. 229–232, March–April, 1985.