Cuprous Iodide Pseudopolymorphs Based on Imidazole Ligand and Their Luminescence Thermochromism

Two cuprous iodide pseudopolymorphs, formulated as [(Cu4I4)(MBI)2]∞ (MBI = 1,1′-methylene-bis(imidazole)) with an irregular cubane-like Cu4I4 cluster as tetrahedrally coordinated secondary building unit and imidazole derivative as bridging ligand, have been synthesized and characterized by single-crystal X-ray diffraction analysis. Both of two compounds only exhibited a single broad low-energy cluster-centered (3CC) triplet emission band between room temperature and 77 K. Of particular interest, these two Cu4I4-imidazole pseudopolymorphs still displayed thermochromic luminescence originating from a red shift of such tunable single cluster-centered triplet emission, being different from that observed in the previously reported Cu4I4-pyridine system by balancing temperature-dependent multiple emissions (high-energy and low-energy) derived from their energetically distinct triplet states.