The Establishment Of A New Substituent Constant σ_cc⁺ And Its Application In QSPR

Quantitative structure-property relationship（QSPR）of compounds has become an important branch of chemometrics,by establishing the QSPR model not only to predict or estimate the nature of the unknown samples,but also to analyse the characteristics of structure parameters,which have the largest impact on properties of compounds.Researchers may understand the effect of the micro-structure of materials on their macro-properties at the molecular level,which have certain guidance effect on molecular design.QSPR research has an important theoretic and application value in the field of chemistry,life science and environmental science.In most cases,QSPR study involves the pick-up and selection of the structural parameters,the development of QSPR models,the detailed explanations,validations and applications of these models.How to efficiently extract the structural descriptors,i.e,the structural parameters,is the key to the QSPR study.In the present work,the studies have carried out as the following:（1）Using mono-substituted benzene as model molecule,the average vertical ionization potential（IP）data were measured by PE method,and the new substituent parameter σ_cc⁺ was proposed and constructed（2）The parameter σ_cc⁺ was correlated with other substituent parameters such as σ_mb,σ⁺,σ_p,σ_c^·,σ_α^·,σ_JJ^·,σ_cc^{ex (}and the correlation results showed that the parameter σ_cc⁺ was essentially different from other parameters and expressed different electronic effects of substituents.Unified single-parameter model equation IP=a+bσ_cc⁺ was obtained by correlating parameter σ_cc⁺ with ionization potentials of mono-substituted benzene,mono-substituted naphthalene,γ-substituted anthracene and p-substituted pyridine.The equation had good correlation,high stability and strong predictive ability.The quantitative relationship between ionization potentials and parameters was explained directly.（3）The IP of XPhY-p,XPhY-m and XPhY-o disubstituted benzene were correlated with Σσ_cc⁺ and σ_cc⁺（XY）parameters respectively,and the two-parameter model equation IP=a+bΣσ⁺_cc+cσ⁺_cc（XY） was obtained.The equation had few parameters,good stability and strong prediction ability.It directly clarified the quantitative relationship between IP and double parameters Σσ_cc⁺ and σ_cc⁺ （XY）.The factors affecting XPhY disubstituted benzene IP were analyzed and discussed,which provided a new method for theoretical calculation of the ionization energy of XPhY disubstituted benzene.（4）The parameter σ_cc⁺ was correlated with ionization potential of the carbonyl oxygen lone pair（no I.P.）and enthalpies of complexation（ΔH°）of the carbonyl group with born trifluoride for p-substituted aromatic carbonyl compounds,benzaldehyde,acetophenone and N,N-dimethylbenzamide on three kinds of derivatives,and satisfactory results were achieved.The σ_cc⁺ and σ_cc^{ex p}arameters had been associated with the p-XArC（Me）=CHArY-parameters had been associated with the p-XArC（Me）=CHArY-p compound wave number ν_max(cm^-1)in the UV spectrum,and already satisfactory related results had been obtained.