Temperature-Driven Crystal-to-Crystal Transformations and Luminescence Properties of Coordination Polymers Built with Diphenyldibenzofulvene Based Ligand

A propeller-shaped ligand di­(4-carboxyphenyl)­dibenzofulvene (H2L) was used for the construction of coordination polymers. From a single starting material with only varying the temperature, four coordination polymers, formulated as [Zn­(L)­(H2O)]·2DMF (CP-1), [Zn­(L)­(H2O)]·2DMF·H2O (CP-2), [Zn­(L)­(H2O)]·DMF (CP-3), and [Zn3(L)2(μ3-OH)2]·4H2O (CP-4) have been successfully synthesized in the relatively low temperature range of 25 to 115 °C. The structural diversity can be ascribed to the temperature effect and the conformational flexibility of the ligand. Upon heating, CP-1 or CP-2 undergoes a series of solvent-associated crystal-to-crystal transformations successively to CP-3, and finally to the thermodynamically stable CP-4. In addition, [Zn2(L)2(BPY)]·DMF·3.5H2O (CP-5) can be synthesized in a crystal-to-crystal transformation manner from CP-2 with addition of the auxiliary ligand 4,4′-bipyridine (Bpy). Owing to the H2L ligand possessing the feature of aggregation-induced emission, the solid-state fluorescence of CP-1 to CP-5 has also been studied in detail.