High-Tp-triggered phase transition exhibiting switchable dielectric–thermal responses and long photoluminescence lifetime in a novel inclusion luminophor.

Materials combining high-temperature phase transformation and fluorescence properties are not abundant, especially, stator–rotator-type inclusion compounds possessing excellent optical properties are extremely rare. In this study, a neoteric high-temperature crown ether inclusion luminophor: [(2,4,6-trifluoroanilinium)-(18-crown-6)][BF₄] (1) was constructed, undergoing a reversible phase transition near T_p = 364 K. Differential thermal analysis (DTA), specific heat capacity (C_p) and differential scanning calorimetry (DSC) tests disclosed a reversible first-order phase transformation behavior of 1. Multiple-temperature PXRD analyses further demonstrated a structural transition from low- to high-symmetry. Permittivity tests for 1 exhibited a prominent step-like dielectric response near T_p, indicating that it is a promising dielectric switching material. Besides, 1 occupies a broad optical energy band of ca. 4.45 eV. The photoluminescence tests for 1 display a strong luminescence emission peak at 368 nm. Further research and computational analysis showed that the luminescence lifetime of 1 reaches up to 43.998 μs. The investigation opens up an alternative avenue to construct and synthesize phase-transition compounds possessing high-T_p and superior optical properties. [ABSTRACT FROM AUTHOR]