Naslov
Photoelectron Spectra, Electronic Structures, and Conformational Properties of Substituted 2-Styrylpyrroles

Autori
Rademacher, Paul ; Basarić, Nikola ; Kowski, Klaus ; Šindler-Kulyk, Marija

Izvornik
European Journal of Organic Chemistry (1434-193X) (2002), 3; 551-556

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
Conformational analysis; Density functional calculations; Electronic Structure; Photoelectron spectroscopy

Sažetak
The UV photoelectron spectra of three pairs of cis/trans-isomers of 2-(2-methylstyryl)pyrroles (1-6) have been recorded and analysed, making use of density functional theory (DFT) calculations at the B3LYP level. Compounds 1 and 2 have no further substituents in the pyrrole ring. In the other compounds the pyrrole ring is substituted by a methyl group in the 1-(3,4) or 5-position (5,6). Twisted conformations were calculated for 1-6 in which the toluene ring is generally much more distorted from the plane of the central C=C double bond than the pyrrole ring. In the cis-isomers (2, 4, 6) the torsion angle of the toluene groups amounts to about 50 o, while in the trans-isomers (1, 3, 5) the torsional angle is only about half as large. The energy difference delta IP values of the ionization bands associated with the molecular orbitals (MOs) pi7 and pi3 is related to torsion. Calculated delta IP values are generally 5-10 % larger than the experimental values, indicating that torsional vibrations contribute to the apparent distortion of the molecules. The results clearly indicate that PE spectroscopy - in combination with high-level quantum chemical calculations - is a verasatile method to distinguish E/Z isomers of heterocyclic stilbene-like molecules.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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