Li Qi, Zhang Qian, Xue Zhen-Zhen, Hu Ji-Xiang, Wang Guo-Ming
College of Chemistry and Chemical Engineering, Qingdao University, Qingdao, Shandong 266071, China.
Inorg Chem. 2022 Jul 18;61(28):10792-10800. doi: 10.1021/acs.inorgchem.2c01019. Epub 2022 Jul 7.
Electron transfer photochromic materials with photo-triggered radicals have received huge interest from chemists due to their potentialities in anticounterfeiting, displays, energy conversion, and information storage. However, utilizing the sole carboxylic acid to synthesize novel electron transfer photochromic species is still confronted with huge challenges. Herein, an acentric three-dimensional network Cd(ADC)(DMF)(HO) (; ADC = anthracene-9,10-dicarboxylate; DMF = ,-dimethylformamide) and a two-dimensional layer Zn(ADC)(HO)·DMA·HO (; DMA = ,-dimethylacetamide) were synthesized and characterized via a photoactive HADC ligand. Both compounds exhibited electron transfer photochromism with the formation of radical photoproducts at the solid state, which was revealed by IR, UV-Vis absorption, photoluminescence and electron spin resonance spectra, and magnetic susceptibility measurements. Density functional theory calculations for showed that the coloration process is a metal-assisted ligand-to-ligand electron transfer process between adjacent ADC molecules, and photogenerated stable radicals are delocalized over the ADC components. Compared with , the shorter distances between ADC components via coordination bonds promoted to exhibit a higher coloration efficiency and larger quantity of photogenerated radicals. Furthermore, both compounds showed unexpected radical-actuated photochromism in aqueous solution. This work showed that the carboxylic acid ligands, without viologen acceptors, could construct the electron transfer photochromic complexes, showing a novel kind of ligand for the design of hybrid photochromic materials.
具有光触发自由基的电子转移光致变色材料因其在防伪、显示、能量转换和信息存储方面的潜力而受到化学家的广泛关注。然而，利用单一羧酸合成新型电子转移光致变色物种仍然面临巨大挑战。在此，通过光活性的HADC配体合成并表征了一种非中心三维网络Cd(ADC)(DMF)(HO)（；ADC = 蒽-9,10-二羧酸酯；DMF = N,N-二甲基甲酰胺）和一种二维层状Zn(ADC)(HO)·DMA·HO（；DMA = N,N-二甲基乙酰胺）。两种化合物在固态下均表现出电子转移光致变色现象，并形成了自由基光产物，这通过红外光谱、紫外-可见吸收光谱、光致发光光谱、电子自旋共振光谱和磁化率测量得以揭示。对[Cd(ADC)(DMF)(H2O)]的密度泛函理论计算表明，变色过程是相邻ADC分子之间的金属辅助配体到配体的电子转移过程，光生稳定自由基在ADC组分上离域。与[Zn(ADC)(H2O)2·DMA·H2O]相比，通过配位键连接的ADC组分之间较短的距离促使[Cd(ADC)(DMF)(H2O)]表现出更高的变色效率和更多的光生自由基。此外，两种化合物在水溶液中均表现出意想不到的自由基驱动的光致变色现象。这项工作表明，在没有紫精受体的情况下，羧酸配体可以构建电子转移光致变色配合物，为混合光致变色材料的设计展示了一种新型配体。
