科研之友
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摘要
Long-range electronic substituent effects were targeted using the substituent dependence of dC(C-N), and specific cross-interactions were explored extendedly. A wide set of N-(4-Xbenzylidene)-4-(4-Ystyryl) anilines, p-XC6H4CH-NC6H4CH-CHC6H4p-Y (X?=?NMe2, OMe, Me, H, Cl, F, CN, or NO2; Y?=?NMe2, OMe, Me, H, Cl, or CN) were prepared for this study, and their 13C NMR chemical shifts dC(C-N) of C-N bonds were measured. The results show that both the inductive and resonance effects of the substituents Y on the dC(C-N) of p-XC6H4CH-NC6H4CH-CHC6H4p-Y are less than those of the substituents Y in p-XC6H4CH-NC6H4p-Y. Moreover, the sensitivity of the electronic character of the C-N function to electron donation/electron withdrawal by the substituent X or Y attenuates as the length of the conjugated chain is elongated. It was confirmed that the substituent cross-interaction is an important factor influencing dC(C-N), not only when both X and Y are varied but also when either X or Y is fixed. The long-range transmission of the specific cross-interaction effects on dC(C-N) decreases with increasing conjugated distance between X and Y. The results of this study suggest that there is a long-range transmission of the substituent effects in p-XC6H4CH-NC6H4CH-CHC6H4p-Y.
