Effects of styrene unit on molecular conformation and spectral properties of CN[sbnd]PhCH[dbnd]NPhCH[dbnd]CHPh[sbnd]CN

Abstract

Compound CN-PhCH=NPhCH=CHPh-CN with both stilbene and benzylidene aniline units was synthesized, and studied from the viewpoint of molecular conformation and spectroscopic property by a combined use of experimental and computational methods. The maximum UV absorption wavelength (λmax) of the compound in ethanol, acetonitrile, chloroform and cyclohexane solvents were measured, and the 13C NMR chemical shift value δC(CN) in chloroform-d was determined. The crystal structure of the compound was determined by X-ray diffraction. The frontier molecular orbital was calculated by density functional theory method. The results show that the UV absorption spectrum of the titled compound is similar to those of Schiff bases, while there is a larger red shift of λmax comparing to that of CN-PhCH=NPh-CN. Moreover, the molecular configuration of the titled compound relative to CN is anti-form, having a more obvious twisted structure. The spectral and structural behaviors are further supported by the results of frontier molecular orbital analyses, NBO, electrostatic potentials and TD-DFT calculations. The study provides deeper insights into the molecular conformation of Schiff bases.