Dichroism and Configuration Analysis of 2-Ethylthio-1,3-Diazaazulene

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Abstract
Electronic absorption spectrum of 2-ethylthio-1,3-diazaazulene (ESDA) is investigated by means of dichroism analysis using the stretched PVA film. Seven π-π* bands and an allowed n-π* band are assigned. The experimental assignment of π-π* bands is in good agreement with the theoretical result using the PPP calculation. The effect of substituent groups on 1,3-diazaazulene (DA) is discussed by making use of a correlation diagram of SCF MO’s of ESDA, 2-ethoxy-1,3-diazaazulene (EODA), DA, and the substituent groups. Configuration analysis of wave functions for ESDA and EODA is carried out, and the substituent effects of the ethylthio and ethoxyl groups are compared. The result shows that the ethylthio group perturbs the electronic structure of DA more strongly than the ethoxyl group.