The compounds N-(benzylidene)-anilines XArCH=NArY (XBAY), N-(phenyl-ethylene)-anilines XArC(CH₃)=NArY (XPEAY) and N-phenyl-α-phenylnitrones XArCH=N(O)ArY (XPNY) have bridging group CH=N, C(CH₃)=N and CH=N(O) respectively, in which the C(CH₃)=N has a side-group methyl CH₃ at carbon end and the CH=N(O) has a side-group O atom at nitrogen end. In this work, a series of XPEAY and XPNY were synthesized, and their longest wavelength maximum λ_max (nm) of ultraviolet absorption spectra were measured. Then the change regularity of the ν_max (cm^-1, ν_max=1/λ_max) of XPEAY and XPNY were investigated, and they were compared with that of XBAY (reported by ref.26). The results indicate: (1) There are no good linear relationships between the ν_max of XBAYs and XPEAYs or XPNYs. (2) In case of a same set of X-Y group couples, the distribution of λ_max of XPEAYs is larger than that of XPNYs. (3) The side-group CH₃ makes the effect of σ(X) larger than that of σ(Y) on the ν_max of XPEAYs, whereas the O atom makes the effect of σ(Y) larger than that of σ(X) on the ν_max of XPNYs. (4) The cross-interaction between X and Y has important effect on the all ν_max. However, the cross-interaction between CH₃ and X/Y has not important effect on the ν_max of XPEAY, and the cross-interaction between O and X/Y has not important effect on the ν_max of XPNY. Copyright © 2016 John Wiley & Sons, Ltd.

For studying the substituent effects on the ν_max of substituted benzylideneanilines (XBAYs) systematically, 12 samples of 3,3′-disubstituted XBAYs and 52 samples of multi-substituted XBAYs were synthesized, and the substituent effects on their ν_max were investigated in this paper. A modified regression equation quantifying the ν_max of 4,4′/4,3′/3,4′/3,3′-disubstituted and multi-substituted XBAYs (shown as Eq. (3)) was obtained. The results showed that the substituent effects on the ν_max of 3,3′-substituted and multi-substituted XBAYs became more complicated. In Eq. (3), the contributions of the meta-parameters to the ν_max of XBAYs were different from those of the corresponding para-parameters. For the substituent cross-interaction effects, there is no difference whatever the substituents are at meta-position or para-position. Compared with Eq. (1), Eq. (3) obtained in this paper has a wider application and more accuracy in quantifying the ν_max of substituted XBAYs. Copyright © 2016 John Wiley & Sons, Ltd.

The reduction potentials (E_Red) of 30 N-(phenyl-ethylene)-anilines (XArC(Me)=NArY) were determined, and the effect of substituents on E_Red was investigated. During the reduction process, a molecule obtains an electron to form a radical anion; the electron distribution is somewhat similar to that of the excited state. Therefore, the substituent effect cannot be described thoroughly only with Hammett parameter, which is a classic descriptor for electronic effect of substituent in ground state. Excited-state substituent constant was employed as a structural descriptor characterizing the stability of radical anion. The performances of quantitative structure-reduction potential relationship model can be largely improved by introducing excited-state substituent constant to the model, which has been confirmed by the investigations of reduction potentials of disubstituted N-benzylidenebenzenamines, aryl-substituted acetophenone azines, and 1-substituted naphthalenes. It is indicated that the excited-state substituent effect is very important to the correlation of reduction potentials of Schiff bases. Copyright © 2015 John Wiley & Sons, Ltd.

The two conceptual systems of organic homologous compounds and homo-rank compounds give insight into the influence of structures on the properties of mono-substituted alkanes X_i–(CH₂)_j–H from the transverse (change of repeating unit number j of CH₂) and longitudinal (change of functional group X_i) perspectives, respectively. This paper aims to combine the organic homo-rank compounds approach together with the homologous compounds approach to explore the property change rules of mono-substituted alkanes involving various substituents. Firstly, based on the concept of organic homologous compounds, the properties of mono-substituted straight-chain alkane homologues were linearly correlated to the two-thirds power of the number of carbon atoms (N^2/3) in alkyl, and regression equations such as Q = A + BN^2/3 were obtained. The regression coefficients A and B vary with different substituents X_i, so coefficients A and B were employed to characterize the structural information of substituent X_i. The structural features of alkyls (–(CH₂)_j–H, that is, –C_jH_2j+1) were described by the polarizability effect index (PEI_(R)) and vertex degree–distance index (VDI). Then based on four parameters A, B, PEI_(R), and VDI, quantitative structure–property relationship models were built for the boiling points (Bp) and refractive indexes (n_D) of each mono-substituted alkane homo-rank series, where j = 3–10 and the substituents X_i involve F, Cl, Br, I, NO₂, CN, NH₂, COOH, CHO, OH, SH, and NC. Good results indicate that the combination of an organic homo-rank compounds method and a homologous compounds method has exhibited obvious advantages over traditional methods in the quantitative structure–property relationship study of mono-substituted alkanes concerning various substituents. Copyright © 2015 John Wiley & Sons, Ltd.

Comparison of ¹³C NMR of C = N bond chemical shifts δ_C(C = N) in substituted N-(phenyl-ethylene)-anilines XArC(Me) = NArY (XPEAYs) with that in substituted N-(benzylidene)-anilines XArCH = NArY (XBAYs) was carried out. The δ_C(C = N) of 61 samples of XPEAYs were measured, and the substituent effect on their δ_C(C = N) were investigated. The results show the factors affecting the δ_C(C = N) of XPEAYs are quite different from that of XBAYs. A penta-parameter correlation equation was obtained for the 61 compounds, which has correlation coefficient 0.9922 and standard error 0.12 ppm. The result indicates that, in XPEAYs, the inductive effects of substituents X and Y are major factors affecting the δ_C(C = N), while the conjugative effect of them have very little effect on the δ_C(C = N) and can be ignored. The substituent-specific cross-interaction effects between X and Y and between Me of C = N bond and substituent Y are important factors affecting the δ_C(C = N). Also, the excited-state substituent parameter of substitute Y has certain contribution to the δ_C(C = N). Copyright © 2015 John Wiley & Sons, Ltd.

Based on the topological characteristics of distance matrices and adjacency matrices of molecular graphs, a new concept of organic homo-rank compounds was proposed. Based on this concept, compounds can be classified into new groups other than the traditional homologues. Furthermore, novel structure–property relationship approach named as homo-rank compounds method can be developed. The feasibility of homo-rank compounds method was explored by estimating the enthalpy of formation of organic compounds. The group contribution index (GCI_X) and group polarizability potential index (GPI_X) of substituents X were defined and determined for mono-substituted alkanes RX (X includes 20 substituents). The research results show that the enthalpies of formation of organic homo-rank compounds and their isomers can be correlated very well with the parameters GCI_X and GPI_X. Combining the method of homologues with that of homo-rank compounds, a general and simple quantitative correlation equation (8) was established to estimate the enthalpy of formation for RX, and the calculation precision is within the chemical accuracy ‘1 kcal/mol’. For 242 samples of RX, the average absolute deviation between the experimental and the calculated values is 2.42 kJ/mol. In addition, the enthalpies of formation of more than 2800 samples of RX were estimated. The approaches of organic homo-rank compounds and organic homologues are independent of but complementary to each other. The combination of these two methods can help us to understand the organic molecular structure–property relationships more deeply, and to investigate these relationships more conveniently and accurately. Copyright © 2015 John Wiley & Sons, Ltd.

Fifty-two samples of substituted benzylideneanilines XPhCHNPhYs (XBAYs) were synthesized, and their NMR spectra were determined in this paper. Together with the NMR data of other 77 samples of XBAYs quoted from literatures, the ¹H NMR chemical shifts (δ_H(CHN)) and ¹³C NMR chemical shifts (δ_C(CHN)) of the CHN bridging group were investigated for total of 129 samples of XBAYs. The result shows that the δ_H(CHN) and δ_C(CHN) have no distinctive linear relationship, which is contrary to the theoretical thought that declared the δ_H(CHN) values would increase as the δ_C(CHN) values increase. With the in-depth analysis, we found that the effects of σ_F and σ_R of X/Y group on the δ_H(CHN) and the δ_C(CHN) are opposite; the effects of the substituent specific cross-interaction effect between X and Y (Δσ²) on the δ_H(CHN) and the δ_C(CHN) are different; the contributions of parameters in the regression equations of the δ_H(CHN) and the δ_C(CHN) [Eqns (4) and 7), respectively] also have an obvious difference. Copyright © 2015 John Wiley & Sons, Ltd.

Thirty-one samples of 3,4′/4,3′-disubstituted benzylideneanilines (XBAY) with specified UV–Vis absorption maximum wavelength (λ_max) were designed and synthesized by applying the equation (Eqn (1)) which was abstracted from the UV–Vis absorption maximum wavelength energy (ν_max = 1/λ_max) of 4,4′-disubstituted benzylideneanilines. Then, the UV–Vis data (λ_max) of the designed compounds were measured in anhydrous ethanol. The predicted UV–Vis data of designed compounds are in agreement with the experimental ones, in which the mean absolute error is 2.9 nm. The results show that Eqn (1) is applicative for the prediction of UV–Vis absorption λ_max values of both 4,4′-disubstituted benzylideneanilines and 3,4′/4,3′-disubstituted benzylideneanilines. For a same pair of groups (X and Y), one can at least get four disubstituted benzylideneaniline compounds which have different λ_max values. It perhaps provides a convenient method to design an optical material for benzylideneaniline compounds. Copyright © 2014 John Wiley & Sons, Ltd.

The ¹³C NMR chemical shifts of six kinds of substituted benzylidene anilines, with different backbone conjugation length, have been used as a probe to investigate the long-range transmission of substituent effects. In this context, it was found that for substituents Y at the aniline unit, the transmission of the inductive and conjugative effects depend on the chemical bond numbers n_(Y) between Y and the imine carbon, and the parameters n_(Y)⁻²σ_F(Y) and n_(Y)⁻²σ_R(Y) are suitable to scale the corrected inductive and conjugative effects, respectively. However, for substituents X, the chemical bond numbers n_(X) between X and the imine carbon influences only the transmission of inductive effects of X, and the n_(X)⁻²σ_F(X) item is appropriate to evaluate the modified inductive effects of X. Similarly, Δσ_(cor)² was proposed to describe the transmitted effect of the cross-interaction effect. With the parameters n_(X)⁻²σ_F(X), σ_R(X), n_(Y)⁻²σ_F(Y), n_(Y)⁻²σ_R(Y), Δσ_(cor)², and δ_C(parent), the δ_C(C = N) values of 181 samples can be well correlated. The correlation coefficient is 0.9957, and the standard derivation is only 0.23 ppm. Moreover, the multi-parameter correlation equation is predicted well the δ_C(C = N) of other 25 samples of designed conjugated benzylidene anilines. Copyright © 2012 John Wiley & Sons, Ltd.

A series of α,ω-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 © 2013 John Wiley & Sons, Ltd.

The weakest bound potential method was proposed to estimate the ionization potential (IP) of polyhalogenated methanes, that is, the model IP = aχ_ve + bPEI_fi + c was developed, in which χ_ve is molecular electronegativity calculated by valence electrons equilibration method, and polarizability effect index (PEI)_fi is the influence of polarizability effect. The result indicates that the model is reasonable and effective to predict the IP for polyhalogenated methanes. Besides, the quantum chemistry method, the MOPAC AM1 method, and the density functional theory (B3LYP) method were employed to calculate the IP values of the same polyhalogenated methanes, and those results were less than that of the weakest bound potential method. Furthermore, the experimental values of 67 polyhalogenated hydrocarbons were correlated with the parameters χ_ve and PEI_fi. The regression results show a good correlation (R = 0.988), and the average absolute error between the experimental values and the calculated values is only 0.10 eV. Copyright © 2011 John Wiley & Sons, Ltd.