Studies on the effect of opposite terminal groups in phenylpolyenic conjugative systems

Abstract

Seven homologous series p-A=B-C5H4(CH=CH)nX=Y (A=B: NO2, X=Y: CHO, COMe, CN, NO2; A=B: CN, X=Y: CHO, CN; A=B: H, X=Y: NO2) were synthesized, the effect of opposite terminal groups in phenylpolyenic conjugative systems has been studied by means of UV, XPS, 13C NMR and quantum chemical calculation. The results show that: 1. There exists the effect of opposite terminal groups exists in phenylpolyenic and other aromatic conjugative systems-2. When A=B and X=Y are the same, the group (-X=Y) connected at polyenic chain is a terminal group, while the other is an opposite terminal group. When the two groups are different, the one with weaker conjugative power plays the role of the opposite terminal group. 3. The effect of opposite terminal groups increases successively in the order of CN, COMe, CHO, NO2 and can be quantitatively described with substitute equivalent ΔNs. The λmax of compound containing an opposite terminal group can be calculated by the homologous equation 10−4 \documentclass{article}\pagestyle{empty}\begin{document}$ \tilde v = a + b/(1/2)^2 N'^{- S} a $\end{document}, most of the calculated values are in agreement with experiment results.