Vitrification and Luminescence Properties of Metal–Organic Complexes

In coordination chemistry, crystalline inorganic-organic hybrids are new functional materials that combine inorganic and organic chemistry. Liquid and glass formation have been observed in hybrid materials (e.g., metal-organic frameworks and coordination polymers), while a little attention has been paid to the vitrification of metal-organic complexes (MOCs), in spite of their various functionalities. In this letter, we synthesize MOC crystals (i.e., MX2(HbIm)2, M = Zn and Co; X = Cl, Br, and I; HbIm = benzimidazole) that have accessible liquid states with low mass loss at their melting temperatures. After quenching the MX2(HbIm)2 liquids, a series of new hybrid glasses and fibers are obtained with large size. Based on the structural and calorimetry analysis, we found that the halide ions play a crucial role in the melting thermodynamics of the as-synthesized MOC crystals. Surprisingly, the ZnX2(HbIm)2 glasses are highly transparent in the visible and near-infrared regions (89%) and show an efficient luminescence after the network is doped by organic dyes. The luminescence efficiency of the dye-doped MOC glass is thickness-dependent. Our findings make the MX2(HbIm)2-based hybrid glass a promising material for photonic applications (e.g., lighting and lasers).