Effect of substituents and conjugated chain length on the UV spectra of ,-di-substituted phenyl polyenes

A series of ,-di-substituted phenyl polyenes, p-X-Ph(CH=CH)nPh-p-Y (n=1, 2, or 3) were synthesized, and their ultraviolet (UV) absorption maximum wavelength were determined. The correlation between molecular structure and the maximum wavelength energy (wavenumber/cm-1) was carried out. The results show that the maximum wavelength energy of the title compounds is mainly affected by both substituent excited-state parameters and maximum wavelength energy of the parent molecule. However, the two influence factors are not independent, and the action of substituent is governed by the parent molecular absorption energy. In the case of the compounds containing NO2 or NH2 groups, the influence of interaction of polarity parameters on the maximum wavelength energy must also be considered. In addition, the exploration was also made for the quantifying correlation of UV absorption maximum wavelength energy with the conjugated polarizability potential CPP replacing the parent molecular absorption energy. And the results indicate that the equation with CPP parameters is more accurate and convenient. Copyright (c) 2013 John Wiley & Sons, Ltd.