Inserting protonated phenanthroline derivatives into the interchain voids of anionic halometallate units to generate hybrid materials with tunable photochromic performance

Hybrid photochromic materials (HPMs) have potential applications in numerous fields, such as display, protection, and information storage. The generation of HPMs with tunable photochromic performance is meaningful for the availability of smart photoresponsive materials. As a good platform, crystalline HPMs (CHPMs) provide possibilities to generate desirable products because of their synthetic tunability. To achieve this goal, how to introduce predesigned organic ligands as electron acceptors (EAs) into suitable electron donor (ED) systems is significant for yielding products with hybrid ED-EA structure triggering electron transfer (ET) after photo-stimulus. In this study, inserting protonated 1,10-phenanthroline (phen) (as EAs) and its monosubstituted derivatives 5-Cl-phen and 5-NH2-phen to the interchain voids of anionic halometallate units (as EDs) generated three CHPMs, namely [H-phen][BiCl4] (1), [H-5-Cl-phen][BiCl4]·H2O (2), and [H-5-NH2-phen][BiCl4]·H2O (3). The obtained products featured the same anionic inorganic chains with main differences in the protonated organic guests. As expected, compounds 1-3 displayed apparent photochromism because of the ET from the anionic chains to protonated organic units. Interestingly, the photochromic performance of complexes 1-3 could be tuned by inserting phenanthroline-derivative-guests. This research offers a universal way to engineer the photochromic performance of halometallate-based CHPMs under the guidance of the organic EA design.