Résumé:
Styrene is the smallest system containing an unsaturated vinyl group bound to an aromatic ring, thus it can be considered as a model for understanding the interactions acting in these systems. In the last decades, a lot of efforts was devoted to determinate very accurately the molecular conformation and physical properties of styrene molecules. In fact, the planarity of these molecular systems and the magnitude of the internal barrier to rotation of the vinyl moiety has been a permanent subject of controversy. It is a crucial problem because the shape of the torsional potential function reflects simultaneously the interaction of the π electron systems and the steric hindrance between the hydrogens of the vinyl group and those of the phenyl ring. With the intention to more understand this problem, structural and dynamic molecular of 4-bromo-β-dicyano-styrene have been studied her.
The crystal structure of 4-bromo-β-dicyano-styrene was determined by X-rays diffraction on a single crystal. The molecule is planar and crystallizes in the P-1 space group. In the solid state, anti-ferroelectric molecules are linked into dimmers through dipolar and π-π interactions. The translated dimmers and linked via C–H…N interactions. In parallel, the molecular structure and vibrational spectrum of 4-bromo- β-dicyano-styrene we have been also investigated by DFT calculations combined with Infrared/Raman spectroscopies. The molecular geometry have been optimized at B3LYP level with the 6.311G** base. The predicted conformation is also planar.
Vibrational assignements of the fundamental modes have been corroborated by comparing predicted and experimental spectra.
