Remarkable Solvatochromic Color Change via Proton Tautomerism of a Phenol-Linked Imidazole Derivative
作者:Hiroaki Yamashita、Jiro Abe
DOI:10.1021/jp5007928
日期:2014.2.27
closed-shell singlet character of 1_OH. In contrast 1_NH possesses partial single bond character that leads to the open-shell singlet biradical character and the decrease in the singlet–triplet energy gap. The twisting of the π-conjugated electron system induced by the proton tautomerization was found to be the origin of the open-shell biradical character of 1_NH and the enhanced solvatochromic color change.
合成了一种独特的溶剂化变色2-苯基-4,5-二芳基咪唑衍生物,在咪唑环的4位和5位与酚部分和对苯二甲酰甲基部分连接,通过质子互变异构显示出显着的颜色变化,并且研究了溶剂变色颜色变化的机理。黄色的OH互变异构形式(1_OH)在非极性溶剂中占主导地位,而蓝色的NH互变异构形式(1_NH)在极性溶剂中稳定。这些互变异构体的分子结构通过X射线晶体学分析确定。所述p -quinonemethide部分和的咪唑环1_OH彼此共面,并具有平面的奎诺尔结构。另一方面,1_NH具有非平面扭曲的quinoidal结构,引起可见吸收光谱中的大红移。此外,X射线晶体学分析和DFT计算支持1_OH的闭壳单重态特征。相反,1_NH具有部分单键特征,导致开壳单重态双自由基性和单重态-三重态能隙的减小。发现由质子互变异构引起的π共轭电子系统的扭曲是1_NH的开壳双自由基特征和增强的溶剂化变色的起源。