Reversible Vapochromic Luminescence Accompanied by Planar Half‐Chair Conformational Change of a Propeller‐Shaped Boron β‐Diketiminate Complex

Abstract

Leakage of volatile organic compounds (VOCs) is one of the most severe industrial problems, because it can cause environmental pollution, global warming, fire, and explosion. Hence, the visualization of leakage is an essential technology to detect it at an early stage. Molecular crystals, fluorescence color of which can be changed by the exposure to VOCs could potentially serve as the sensing materials for realizing rapid and facile VOC detection. However, these materials usually require harsh conditions, such as heating or a vacuum, to recover their initial phases for reuse. Therefore, it remains a challenge to obtain completely reversible sensing systems without such energy-consuming recycling processes.Herein, the reversible color change of fluorescence from the crystals of a propeller-shaped boron β-diketiminate complex is reported. The complex was crystallized in distinct crystalline phases having different luminescent colors. Importantly, these phases were interconverted very rapidly (time constant < 60 s) and repeatedly upon exposure to the vapors of the appropriate VOCs. The small energy differences between conformers of the complex could lead to this pseudopolymorphic behavior. This finding could be applied for the development of further eco-friendly reversible sensing materials based on four-coordinated boron complexes.

Recent development of the fluorescence-based detection of volatile organic compounds: a mechanistic overview

“…22). 84 The distinct crystalline phases of the complex have different luminescent colors, i.e., the pure pentaphenyl boron complex crystal (phase G) exhibits green color while another containing DCM molecules in the crystals (phase B) become blue fluorescent. Furthermore, the phase G crystals were interconverted very rapidly (time constant o60 s) to phase B crystals by the treatment of appropriate and different VOCs.…”

“…22). 84 The distinct crystalline phases of the complex have different luminescent colors, i.e. , the pure pentaphenyl boron complex crystal (phase G) exhibits green color while another containing DCM molecules in the crystals (phase B) become blue fluorescent.…”

Effects of Regioregularity of π‐Conjugated Polymers Composed of Boron β‐Diketiminate on Their Stimuli‐Responsive Luminescence

“…These significantly low quantum yields should be derived from the fast nonradiative quenching processes involved in the 𝛽-diketiminate moiety. [33,[40][41][42][43]…”

Modulation of Properties by Ion Changing Based on Luminescent Ionic Salts Consisting of Spirobi(boron ketoiminate)

“…For example, simply by connecting AIE-active boron complexes, AIE-active and solid-state luminescent polymers can be fabricated from heteroatom-containing molecules including boron complexes [ 18 , 19 , 20 , 21 , 22 ]. In particular, since stimuli responsiveness, such as luminochromism as well as intensity changes, was often observed, the series of luminescent sensors can be obtained [ 23 , 24 , 25 , 26 , 27 , 28 , 29 ]. By replacing boron with a different element, such as other group-13 elements, stimuli responsiveness and/or unique luminescent properties were observed [ 30 , 31 , 32 , 33 ].…”