Experimental and theoretical investigation of the electronic absorption spectra of 2-H(methyl, methylthio, phenyl)-3,4-dihydro-4-quinazolinylidenecyanoacetic ester

The effect of substituents (Me, SMe, Ph) in position 2 has been studied on the nature of the absorption bands of 2-H-3,4-dihydro-4-quinazolinylidenecyanoacetic esters and a very high sensitivity on the substituent has been detected for the short wave maxima. On the basis of data calculated by the ZINDO/S method the featureless long-wave absorption band was assigned to an electronic transition from HOMO to LUMO caused by charge transfer from fragments of the benzene ring and the N=C—N bond to the >C=C—C=O fragment. Dedicated to Professor L. I. Belen’kii on his 75th birthday. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 227–232, February, 2006.