Time‐Dependent Emission Enhancement of the Ethynylpyrene‐o‐Carborane Dyad and Its Application as a Luminescent Color Sensor for Evaluating Water Contents in Organic Solvents

Abstract

The time‐dependent emission enhancement (TDEE) phenomena of the 1‐(o‐carboran‐1‐yl)ethynylpyrene dyad were reported. It was found that the emission intensity from the dyad increased in tetrahydrofuran (THF), acetone and dichloromethane with increasing incubation time. From the mechanistic studies, it was suggested that agglomeration of the dyad gradually proceeded in these media, followed by expression of excimer luminescence. Additionally, it was shown that the rates of TDEE of the dyad were sensitively accelerated in the presence of a trace amount of water. Based on this fact, a detection system for water contents in acetone was constructed. Before and after incubation for 96 h at room temperature, time courses of changes in optical properties were monitored. Finally, water contents in acetone can be estimated by the degrees of TDEE and emission color changes in the range from 0.1 wt % to 2.0 wt % and from 2.0 wt % to 20 wt %, respectively.

Recent Progress in the Development of Solid‐State Luminescent o‐Carboranes with Stimuli Responsivity

“…It is proposed that electronic conjugation is drastically changed by the formation of a dative bond between fluoride and tricoordinate boron at the substituent. Modified o ‐carboranes having stimuli‐responsive luminochromism in the solid state have been reported ( 76 – 85 ) . The details will be discussed in Section 5.…”

“…The dyad 82 showed time‐dependent aggregation‐induced excimer emission in solution (Figure ) . In a good solvent, the LE emission from the anthracene moiety was observed.…”

“…Other types of AIE‐active o ‐carborane derivatives are listed in Table and Scheme . Influences on AIE properties were investigated by changing the substituents on the o ‐carborane unit ( 44 – 75 ) . For these compounds, solid‐state excimer emission, single‐molecule white emission, aggregation‐induced electrochemiluminescence, and thermally activated delayed fluorescence were observed.…”

Recent Progress in the Development of Solid‐State Luminescent o‐Carboranes with Stimuli Responsivity

“…The dyad 82 showed time-dependent aggregation-induced excimer emission in solution (Figure 9). [65] In the good solvent, the LE emission from the anthracene moiety was observed. Interestingly, emission intensity gradually increased and reached a plateau after the incubation for several hours even in the presence of a trace amount of water.…”

“…The modified o-carboranes having stimuli-responsive luminochromism in solid have been reported (76)(77)(78)(79)(80)(81)(82)(83)(84)(85)). [61][62][63][64][65][66][67][68] The details are explained later. AIE as well as solid state emission were observed similarly to o-carboranes (46, 90-92), while electronic conjugation is slightly extended through m-carborane and ACQ is often observed.…”