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)]center dot 2DMF (CP-1), [Zn(L)(H2O)]center dot 2DMF center dot H2O (CP-2), [Zn(L)(H2O)]center dot DMF (CP-3), and [Zn-3(L)(2)(mu(3)-OH)(2)]center dot 4H(2)O (CP-4) have been successfully synthesized in the relatively low temperature range of 25 to 115 degrees 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, [Zn-2(L)(2)(BPY)]center dot DMF center dot 3.5H(2)O (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.