Photomodulation of ionic interaction and reactivity: reversible photoconversion between imidazolium and imidazolinium.
Photomodulation of ionic interaction and reactivity: reversible photoconversion between imidazolium and imidazolinium.
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DOI：
10.1021/ja802986y
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发表时间：
2008-10
影响因子：
15
通讯作者：
T. Nakashima;M. Gotô;Shigekazu Kawai;T. Kawai
中科院分区：
文献类型：
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作者：
T. Nakashima;M. Gotô;Shigekazu Kawai;T. Kawai
首次提出了一种咪唑啉盐与咪唑啉盐之间的相互转化体系。咪唑和咪唑啉阳离子表现出不同的反应性，由于芳香性和电荷局域化结构的差异，这是成功地控制通过在本系统中的光照射。合成并研究了一类新型的光致变色材料4，5-二噻唑基咪唑盐，该材料可调节静电相互作用和化学反应活性。光致变色的4，5-二噻唑基咪唑啉盐在紫外光和可见光的连续照射下表现出咪唑啉盐的开放形式和咪唑啉盐的封闭形式之间的可逆光转换。咪唑啉封闭形式表现出特征溶剂化和离子化，其中吸收最大值根据溶剂极性和抗衡阴离子而移动超过80 nm，而咪唑啉开放形式没有表现出这种溶剂依赖性。由于相应的非离子4，5-二噻唑基咪唑也没有表现出溶剂依赖性的吸收曲线，无论是在开放和封闭的形式，这些铬的外观在咪唑啉封闭形式是由于离子相互作用的程度的变化，这是由咪唑鎓的光转化为咪唑啉。咪唑啉与抗衡阴离子的光衍生强离子相互作用进一步应用于光控亲核反应体系。而咪唑鎓开放形式是惰性的亲核试剂，如甲醇钠，咪唑啉闭合形式是亲核反应，证明了一个光门控反应系统。
An interconversion system between imidazolium and imidazolinium has been proposed for the first time. Imidazolium and imidazolinium cations exhibit different reactivity due to the difference in the aromaticity and charge localization structure, which is successfully controlled by means of photoirradiation in the present system. A 4,5-dithiazolylimidazolium salt was prepared and studied as a new class of photochromic materials modulating electrostatic interactions and chemical reactivities. The photochromic 4,5-dithiazolylimidazolium showed reversible photoconversions between imidazolium open-form and imidazolinium closed-form upon successive irradiation with UV and visible light. The imidazolinium closed-form exhibited characteristic solvato- and ionochromisms in which the absorption maximum shifted by more than 80 nm depending on the solvent polarity and counteranions, whereas the imidazolium open-form showed no such solvent-dependent property. Because the corresponding nonionic 4,5-dithiazolylimidazole also did not exhibit the solvent-dependent absorption profile both in open- and closed-forms, the appearance of these chromisms in imidazolinium closed-form was attributed to the change in the extent of ionic interaction, which was brought about by the photoconversion of imidazolium to imidazolinium. The photoderived strong ionic interaction of imidazolinium with counteranion was further applied to the photocontrolled nucleophilic reaction system. Whereas the imidazolium open-form was inert to nucleophiles such as sodium methoxide, the imidazolinium closed-form was reactive to the nucleophilic reaction, demonstrating a photogated reaction system.