アキラルハイブリッド塩化インジウムにおける効率的な狭帯域発光と大きな発光非対称性因子の同時達成

To achieve high contrast in three-dimensional display, circularly polarized luminescence (CPL) materials should simultaneously have narrow full width at half-maximum (FWHM), high photoluminescence quantum yield (PLQY), and large dissymmetry factor (g_lum). However, very few materials can fulfill it. Herein, we report a zero-dimensional hybrid indium chloride [BPy][InCl₄(dtbp)] (BPy = N-butylpyridinium, dtbp = 4,4'-di-tert-butyl-2,2'-dipyridyl). Although crystallizing in the achiral point group mm2, the compound demonstrates remarkable chiroptical activity. It shows efficient blue-green emission peaking at 481 nm with a FWHM of 49 nm. The coordination with In³⁺ in the inorganic unit, combined with abundant intermolecular interactions, effectively suppresses vibrational relaxation of the organic ligand dtbp, resulting in narrow-band emission. Moreover, owing to the synergy between this structural rigidity and the distortion of the InCl₄(dtbp) unit, this compound overcomes the trade-off between PLQY and g_lum, exhibiting a PLQY approaching 100% and a |g_lum| value of 0.283. Photophysical characterizations and density-functional theory calculations indicate that the high-efficiency emission originates from the ligand. As a rare example of optically active achiral crystals, this compound not only offers a promising candidate for CPL materials integrating narrow FWHM, high PLQY, and large g_lum, but also provides valuable insight into the chiroptical properties of achiral crystalline systems.