Synthesis and photochromic behaviour of a series of benzopyrans bearing an N-phenyl-carbazole moiety: photochromism control by the steric effect.,Photochemical & Photobiological Sciences

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Synthesis and photochromic behaviour of a series of benzopyrans bearing an N-phenyl-carbazole moiety: photochromism control by the steric effect.
Photochemical & Photobiological Sciences ( IF 2.7 ) Pub Date : 2020-07-21 , DOI: 10.1039/d0pp00202j
Michel Frigoli ₁ , Tanguy Jousselin-Oba , Masashi Mamada , Jérôme Marrot , Agnese Zangarelli , Danilo Pannacci , Chihaya Adachi , Fausto Ortica

Affiliation

Five new N-phenyl-carbazole benzopyrans bearing different substitutions on one of the phenyl rings at the sp3 carbon have been synthesized. Their molecular structures were investigated by X-ray and NMR analyses and through quantum chemical calculations. The photochromic mechanism under UV irradiation in toluene, consisting of the consecutive formation of transoid-cis (TC) and transoid-trans (TT) isomers, was studied by UV-vis spectral and kinetic analyses. These molecules have been specifically designed to ascertain the possibility of favouring the formation of the less thermodynamically stable TT at the photostationary state, upon exploiting steric hindrance effects on the diene part of the molecule. The spectrokinetic study allowed the estimation of most of the spectrokinetic parameters, such as molar extinction coefficients, quantum yields of UV colouration and visible photobleaching, and the rate constants of the fast and slow thermal bleaching processes. Peculiar effects of substituents with different donor strengths on one phenyl ring located at the 3-position were observed on the spectrokinetic properties.

中文翻译：

一系列带有N-苯基-咔唑部分的苯并吡喃的合成和光致变色行为：通过空间效应控制光致变色。

合成了五个新的N-苯基咔唑苯并吡喃，它们在sp3碳的一个苯环上带有不同的取代基。通过X射线和NMR分析以及通过量子化学计算研究了它们的分子结构。甲苯紫外线照射下的光致变色机理，包括连续的反式-顺式（TC）和反式-反式形成（TT）异构体，通过紫外可见光谱和动力学分析进行了研究。这些分子经过专门设计，可以确定在利用分子的二烯部分的空间位阻效应时，有利于在光平稳状态下形成热力学较不稳定的TT的可能性。光谱动力学研究可以估算大多数光谱动力学参数，例如摩尔消光系数，UV着色和可见光漂白的量子产率以及快速和慢速热漂白过程的速率常数。在光谱动力学性质上观察到具有不同给体强度的取代基对位于3-位的一个苯环的奇特效应。

更新日期：2020-07-21

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