间位基团激发态取代基常数的扩展及应用

Extension and Application of Excited-State Constants of meta-Substituents

合成了七个系列含间位取代基X的二苯乙烯m-XArCH=CHArY-p(简称m-XSBY-p),其中X为NO_2、I、CHCH_2、Ph、Et、NMe_2和CCH。在无水乙醇中测定它们的紫外(UV)吸收光谱,得到紫外吸收最大波长λ_(max)(nm)。对λ_(max)的波数ν_(max)(cm^(-1))进行定量相关,采用曲线拟合方法,得到上述7个间位基团的激发态取代基常数σ_(CC(m))^(ex)。将对位基团和间位基团的σ_(CC)^(ex)与Hammett常数σ进行对比,表明σx_(CC)^(ex)与σ分别表达取代基不同的电子效应。另外,合成了含上述间位基团的二芳基希夫碱(10个)和二苯乙烯(14个),用所得σ_(CC(m))^(ex)预测它们的λ_(max),并用实验测定它们的λ_(max),结果表明预测值与实验值相吻合,验证了所得σ_(CC(m))^(ex)常数的可靠性。收集了225个化合物(涉及二取代苯及二苯乙烯)的ν_(max),建立了一个统一的定量方程来表达这些化合物ν_(max)的变化规律。

Seven series of 3,4＇-disubstituted stilbenes were synthesized, with meta-substituents X （m-XSBY- p） including： NO2, I, CHCH2, Ph, Et, NMe2, and CCH （m-XSBY-p）. The longest wavelength maximum λmax （nm） in ultraviolet absorption spectra of the compounds were measured. A quantitative correlation analysis was performed in terms of energy, the vmax （cm-1） for 3,4＇-disubstituted stilbenes. The excited-state substituent constants σcc（m） of the seven meta-substituents were determined by curve-fitting. The constants σcc（m） of the meta- and para-substituents were compared with their Hammett constants σ. The results indicated that σcc（m） and a express the substituent electrostatic effects in the excited- and ground-states, respectively. In addition, 10 samples of aryl Schiff bases and 14 samples of 3,3＇-disubstituted stilbenes with meta-substituents X were synthesized, and their λmax.pred were predicated based on the obtained constants σcc（m）. These results showed that the λmax.pred values agreed well with the experimental values, and confirmed the reliability of the obtained σcc（m） values. We also collected vmax values of 225 samples of disubstituted stilbenes and disubstituted benzenes and established a general quantitative equation to express the change regularity of their Vmax.