Tunable Luminescence of Nonaromatic Borate Esters

Nonaromatic borate esters exhibit distinct luminescence and even persistent room temperature phosphorescence at concentrated solutions or crystals. Moreover, the emission of these nonconventional luminophores can be easily regulated by different stimuli, such as excitation wavelength, compression, and oxygen. These intriguing photophysical properties are understandable in terms of the clustering-triggered emission mechanism.

Abstract

While the majority of nonconventional luminophores consist of electron-rich heteroatoms, an emerging category with electron-deficient atoms (e. g. boron) have gained much attention. In this work, we focused on one of the most common boron-containing substances, namely bis(pinacolato)diboron (BE1) and its analogue bis(2,4-dimethylpentane-2,4-glycolato)diboron (BE2), whose empty p-orbitals of boron atoms and p-orbitals with lone pairs of oxygens form π frameworks. Both compounds are nonemissive in dilute solutions but depict remarkable photoluminescence (PL) at aggregate states, featuring aggregation-induced emission characteristics. Additionally, their PL can be easily tuned by various external factors, such as excitation wavelength, compression, and oxygen. These photophysical properties could well be explained by the clustering-triggered emission (CTE) mechanism.

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