Study of stereospecificity of 1H, 13C, 15N and 77Se shielding constants in the configurational isomers of the selenophene-2-carbaldehyde azine by NMR spectroscopy and MP2-GIAO calculations

✍ Scribed by Andrei V. Afonin; Dmitry V. Pavlov; Alexander I. Albanov; Ekaterina P. Levanova; Galina G. Levkovskaya

• Publisher: John Wiley and Sons
• Year: 2011
• Tongue: English
• Weight: 210 KB
• Volume: 49
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.2824

✦ Synopsis

In the ^1^H and ^13^C NMR spectra of selenophene‐2‐carbaldehyde azine, the ^1^H‐5, ^13^C‐3 and ^13^C‐5 signals of the selenophene ring are shifted to higher frequencies, whereas those of the ^1^H‐1, ^13^C‐1, ^13^C‐2 and ^13^C‐4 are shifted to lower frequencies on going from the EE to ZZ isomer or from the E moiety to the Z moiety of EZ isomer. The ^15^N chemical shift is significantly larger in the EE isomer relative to the ZZ isomer and in the E moiety relative to the Z moiety of EZ isomer. A very pronounced difference (60–65 mg/g) between the ^77^Se resonance positions is revealed in the studied azine isomers, the ^77^Se peak being shifted to higher frequencies in the ZZ isomer and in the Z moiety of EZ isomer. The trends in the changes of the measured chemical shifts are reasonably reproduced by the GIAO calculations at the MP2 level of the ^1^H, ^13^ C, ^15^ N and ^77^Se shielding constants in the energy‐favorable conformation with the syn orientation of both selenophene rings relative to the C = N groups. The NBO analysis suggests that such an arrangement of the selenophene rings may take place because of a higher energy of some intramolecular interactions. Copyright © 2011 John Wiley & Sons, Ltd.