Fifty-three samples of multi-substituted benzylideneanilines XArCH=NArYs (abbreviated XBAYs) were synthesized and their NMR spectra were determined. An extensional study of substituent effects on the 1 H NMR chemical shifts (δ H (CH=N)) and 13 C NMR chemical shifts (δ C (CH=N)) of the CH=N bridging group from di-substituted to multi-substituted XBAYs was made based on a total of 182 samples of XBAYs, together with the NMR data of other 129 samples of di-substituted XBAYs quoted from literatures. The results show that the substituent specific cross-interaction effect parameter (∆ (∑ σ) 2) plays an important role in quantifying the δ C (CH=N) values of XBAYs, but it is negligible for quantifying the δ H (CH=N) values; the other substituent parameters also present different influences on the δ C (CH=N) and δ H (CH=N). On the whole, the contributions of X and Y to the δ C (CH=N) of XBAYs are balanced, but the δ H (CH=N) values of XBAYs mainly rely on the contributions of X.
Effects of meta-substituent of 3,4 ′ /4,3 ′ /3,3 ′-substituted benzylideneanilines (XBAYs) on the electrochemical reduction potentials (E (Red)) were investigated, in which 49 samples of target compounds were synthesized, and their reduction potentials were measured by cyclic voltammetry. The substituent effects on the E (Red) of target compounds were analyzed and an optimality equation with four parameters (Hammett constant σ of X, Hammett constant σ of Y, excited-state substituent constant σ ex CC of X, and the substituent specific cross-interaction effect ∆σ ex CC 2 between X and Y) was obtained. The results show that the factors affecting the E (Red) of 3,4 ′ /4,3 ′ /3,3 ′-substituted XBAYs are different from those of 4,4 ′-substituted XBAYs. For 3,4 ′ /4,3 ′ /3,3 ′-substituted XBAYs, σ(X) and σ(Y) must be employed, and the contribution of ∆σ ex CC 2 is important and not negligible. Compared with 4,4 ′-substituted XBAYs, X group contributes less to 3,4 ′ /4,3 ′ /3,3 ′-substituted XBAYs, while Y group contributes more to them. Additionally, it was observed that either para-substituted XBAYs or meta-substituted XBAYs, the substituent effects of X are larger than those of Y on the E (Red) of substituted XBAYs.
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