Collect. Czech. Chem. Commun. 1994, 59, 262-272

Photocolouration of 2,4,4,6-Tetraaryl-1,4-dihydropyridines: A Semiempirical Quantum Chemical Study

Stanislav Böhma, Michal Hoceka, Stanislav Nešpůrekb and Josef Kuthana

a Department of Organic Chemistry, Prague Institute of Chemical Technology, 166 28 Prague 6, Czech Republic
b Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, 162 06 Prague 6, Czech Republic


Molecular geometries of 1,4-dihydropyridines Ia, Ib and their possible photoisomers IIa - Va and IIb - Vb were optimized by the PM3 method. The electronic absorption spectra were calculated by the CNDO/S-CI procedure and compared with the experimental spectroscopic data. A probable mechanism of the photocolouration of Ia, Ib, caused by sunlight or UV illumination, is proposed, and structures IIIa, IIIb are assigned to violet or green coloured species.