Naslov
Vibrational Coupling in trans-Azobenzene and Its Isotopomers

Autori
Meić, Zlatko ; Baranović, Goran ; Smrečki, Vilko ; Novak, Predrag ; Keresztury, Gabor ; Holly, Sandor

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
Book of Abstracts / Mink, J ; Jalsovsky, G ; Keresztury, G. - Budimpešta : Hungarian Academy of Sciences (MTA), 1996

Skup
XXIII. European Congress on Molecular Spectroscopy

Mjesto i datum
Balatonfüred, Mađarska, 25.08.1996. - 30.08.1996

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Međunarodna recenzija

Sažetak
In order to clarify the nature of coupling of vibrational coordinates of the azo group with its surrounding, the molecule of trans-azobenzene (tAB) was chosen. It is interesting to compare this coupling with those of isoelectronic compounds containing two phenyl groups connected to a bridging group, such as cis-stilbene (cSB), trans-stilbene (tSB) and trans-N-benzylideneaniline (tBA), already treated by our group. trans-Azobenzene molecule belongs to the C_2h point group with four symmetry species: a_g (Raman active, in-plane), a_u (infrared active, in-plane), b_g (Raman active, out-of-plane) and b_u (infrared active, out-of-plane). In the FT Raman spectrum of powdered tAB a very strong Raman band (a_g) was found at 1440 cm(-1), having no a counterpart in the infrared spectrum. Since it is shifted to 1428 cm(-1) in (N-15)-tAB, it was assigned to the N=N stretching mode. This is a very low value in comparison with 1630 cm(-1) (C=C str.), 1639 cm(-1) (C=C str.) and 1626 cm(-1) (C=N str.) in neat cSB, tSB and tBA, respectively. However, in (D_10)-tAB the strongest Raman band appears at 1466 cm(-1) without any stronger band around. The normal coordinate calculations of tAB, using the AM1 procedure, indicate a substantial contribution to the N=N stretching from the phenyl group mode 19b. In the case of (D_10)-tAB the N=N mode is decoupled, because the light phenyl groups are substituted by the heavy ones, which increases the N=N stretching frequency. Another indication of the strong coupling of azo and phenyl modes in tAB is the appearance of numerous bands in the infrared spectrum of 4-D-tAB (C_S point group) in comparison with tAB itself (C_2h). Such an activation of infrared absorptions was not observed in analogous cSB, tSB and tBA isotopomers.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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