Rational design for thermochromic luminescence in amorphous polystyrene films with bis‐o‐carborane‐substituted enhanced conjugated molecule having aggregation‐induced luminochromism

Abstract

We designed the triad molecule, bis-o-carborane-substituted bis(thienylethynyl) benzene, as a filler for realizing thermochromic luminescent behaviors based on conventional polymer films, such as polystyrene. From the optical measurements, it was found that the triad can show solid-state emission and dual-luminescent properties with variable intensity ratios depending on media. From the mechanistic studies including the experiments with the methyl-substituted model compound, it was revealed that dual emission should be originated from the locally excited and twisted intramolecular charge transfer states, and the latter emission band is significantly enhanced in the solid states. We prepared amorphous films containing variable concentrations of the triad with the spin-coating method and investigated optical properties. It was found that intensity ratios were drastically changed by altering the concentration of the triad. By increasing the proportion of the triad, aggregation occurred, and emission color was apparently varied through the changes in intensity ratios of the dual emission property. Based on the aggregationinduced luminochromic property of the triad, thermochromic luminescence was finally realized by heating the amorphous films. The rational design for obtaining thermochromic luminescent amorphous films is illustrated in this paper.

Regulation of solid-state dual-emission properties by switching luminescence processes based on a bis-o-carborane-modified anthracene triad

“…30 Moreover, by introducing bis-o-carborane substituents, highly sensitive luminochromic behaviors were observed. 31,32 The bis-o-carboranesubstituted pyrene triad showed clear luminochromic behaviors just by touching the crystalline powder. 32 Because of steric hindrances of o-carboranes, defect sites in crystalline packing could be readily induced by weak stimuli.…”

Front Cover: Controlling the Dual‐Emission Character of Aryl‐Modified o‐Carboranes by Intramolecular CH⋅⋅⋅O Interaction Sites (Chem. Eur. J. 20/2022)

“…[20] More recently, we reported thermochromic luminescent behaviors of bis(thienylethynyl)benzene-based o-carborane in amorphous polystyrene films. [21] By the aggregation formation of o-carborane species in polymer matrices, luminescent chromic behaviors originating from the enhancement of ICT emission were observed. Although the changes in intensity ratio were slight, clear luminescent chromic behaviors can be exhibited owing to dual-luminescent nature.…”

Controlling the Dual‐Emission Character of Aryl‐Modified o‐Carboranes by Intramolecular CH⋅⋅⋅O Interaction Sites

“…Our group also reported that the triaryl‐substituted o ‐carborane derivative can show white‐light emission in the specific aggregation state [20] . More recently, we reported thermochromic luminescent behaviors of bis(thienylethynyl)benzene‐based o ‐carborane in amorphous polystyrene films [21] . By the aggregation formation of o ‐carborane species in polymer matrices, luminescent chromic behaviors originating from the enhancement of ICT emission were observed.…”

“…[20] More recently, we reported thermochromic luminescent behaviors of bis(thienylethynyl)benzene-based o-carborane in amorphous polystyrene films. [21] By the aggregation formation of o-carborane species in polymer matrices, luminescent chromic behaviors originating from the enhancement of ICT emission were observed. Although the changes in intensity ratio were slight, clear luminescent chromic behaviors can be exhibited owing to the dual-luminescent nature.…”