Collect. Czech. Chem. Commun. 1979, 44, 884-894

Electronic absorption spectra and π-electron structure of 2-propenylidene-1,2-dihydropyridine and its derivatives

Josef Kuthana, Dušan Ilavskýb and Jiří Krechla

a Department of Organic Chemistry, Prague Institute of Chemical Technology, 166 28 Prague 6
b Department of Organic Chemistry, Slovak Institute of Technology, 880 37 Bratislava


The results of the PPP calculations of the singlet-singlet transitions of 1-methyl-3'-cyano-3'-alkoxycarbonyl-2-propenylidene-1,2-dihydropyridines II and 1-methyl-4-amino-3,3'-dicyano-3',5-di(methoxycarbonyl)-2-propenylidene-1,2-dihydropyridine (III) are in a satisfactory agreement with the experimental absorption curves in the visible and near ultraviolet region. Based on this finding, the absorption of the parent heterocyclic system of 2-propenylidene-1,2-dihydropyridine (I) is predicted. Some aspects of the π-electron structure of the substances I-III in the S0, S1 S2 and states are discussed.