Effects of single bond-ion and single bond-diradical form on the stretching vibration of C=N bridging bond in 4,4′-disubstituted benzylidene anilines
Effects of single bond-ion and single bond-diradical form on the stretching vibration of C=N bridging bond in 4,4′-disubstituted benzylidene anilines
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DOI：
10.1016/j.saa.2016.03.021
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发表时间：
2016-06-15
影响因子：
4.4
通讯作者：
Cao, Chenzhong
中科院分区：
文献类型：
--
作者：
Cao, Chao-Tun;Bi, Yakun;Cao, Chenzhong
合成了57个模型化合物4，4 ′-二取代苯亚甲基苯胺p-X-ArCH = NAr-p-Y。记录了它们的红外吸收光谱，测定了C=N桥键的伸缩振动频率nu（C=N）。通过对影响nu（C=N）的因素的分析，提出了新的伸缩振动模式，即C=N键的伸缩振动主要有三种模式：（I）极性双键形式C=N，（II）单键-离子形式C+-N-和（III）单键-双自由基形式C中心点-N中心点。形式（I）和（II）对nu（C=N）变化的贡献可以通过使用Hammett取代基常数（包括X和Y基团之间的取代基交叉相互作用效应）来量化，而形式（III）的贡献可以通过使用激发态取代基常数来量化。这三种形式中贡献最大的是形式（III），其次是形式（II），从振动能量需求的角度讨论了形式（III）和形式（II）对振动能量贡献的差异。(C)2016爱思唯尔B. V.保留所有权利。
Fifty-seven samples of model compounds, 4,4'-disubstituted benzylidene anilines, p-X-ArCH = NAr-p-Y were synthesized. Their infrared absorption spectra were recorded, and the stretching vibration frequencies nu(C=N) of the C=N bridging bond were determined. New stretching vibration mode was proposed by means of the analysis of the factors affecting nu(C=N), that is there are mainly three modes in the stretching vibration of C=N bond: (I) polar double bond form C=N, (II) single bond-ion form C+-N- and (III) single bond-diradical form C center dot-N center dot. The contributions of the forms (I) and (II) to the change of nu(C=N) can be quantified by using Hammett substituent constant (including substituent cross-interaction effects between X and Y groups), whereas the contribution of the form (III) can be quantified by employing the excited-state substituent constant. The most contribution of these three forms is the form (III), the next is the form (II), whose contribution difference was discussed with the viewpoint of energy requirements in vibration with the form (III) and form (II). (C) 2016 Elsevier B.V. All rights reserved.