The Tri(imidazole)-Derivative Moiety: A New Category of Electron Acceptors for the Design of Crystalline Hybrid Photochromic Materials

The intermarriage of neutral and tripodal imidazole ligand, tris(4-(1H-imidazol-1-yl)phenyl)amine (TIPA), with zinc phosphite yields two hybrid phosphites, [Zn-2(HPO3)(2)(TIPA)].2 H2O (1) and [Zn-3(HPO3)(3)(TIPA)].6 H2O (2). Compound 1 has a hybrid sheet with neutral zinc-phosphite chains as supramolecular building blocks (SBBs), whereas 2 exhibits a 3D hybrid architecture with other neutral zincophosphite chains as supramolecular building blocks. The structural discrepancy between 1 and 2 is mainly due to the distinct linkage modes between organic TIPA ligands and inorganic zincophosphite chains. Interestingly, compounds 1 and 2 feature fast photochromism in response to UV light irradiation under ambient conditions. The discrepancy of photochromic performance between 1 and 2 is mainly due to the different geometrical configuration of the TIPA ligand. Different to majority of reported hybrid photochromic compounds driven by photochromic active units, the photochromism in 1 and 2 is derived from the electron transfer (ET) between phosphite and non-photochromic triimidazole-derivative ligand TIPA. Compared with the widely explored nonphotochromic polypyridine-derivative as electron acceptors (EAs), our work provides a new EA model for the design of hybrid photochromic materials based on the ligand-to-ligand ET mechanism. A multiple anti-counterfeiting application based on 1 and 2 was investigated.

Automated summary

The text discusses the structural and performance differences between two hybrid phosphites formed by the interaction of neutral and tripodal imidazole ligands with zinc phosphite, highlighting the novelty of the ligand-to-ligand electron transfer mechanism for the design of hybrid photochromic materials.