Conjugated heteroatom complexes are a versatile “element-block”, which is defined as a minimum functional unit composed of heteroatoms, for fabricating opto-electronic devices because of their superior properties such as light absorption property, emission, and electron-carrier ability. However, their emissions in the solid states were usually spoiled by undesired intermolecular π-π stacking interaction, called as aggregation-caused quenching (ACQ) effects. Therefore, applications of conventional complexes in the solid state are still limited by the ACQ effects. Especially, in order to obtain stimuli-responsive luminescent films, ACQ is one of critical problems to be solved. Aggregation-induced emission (AIE), which is observed only by aggregation formation, is a key phenomenon for overcoming the ACQ effect and obtaining highly-efficient light-emitting solid materials. We have found that ACQ-active organoboron dyes composed of the <i>β</i>-diketonate structure can be transformed to the AIE-active dyes by replacing the oxygen atoms to nitrogen to form the ketoiminate and diiminate structures. According to quantum calculation, it was proposed that these complexes should potentially show large degree of structural relaxation in the excited state. Furthermore, the series of AIE-active and stimuli-responsive film materials composed of conjugated polymers were able to be obtained. Therefore, we regarded as these flexible organoboron complexes as not only an AIE-inducible but also a stimuli-responsive luminescent “element-block”. In this presentation, recent progresses of the stimuli-responsive luminescent materials based on flexible boron “element-blocks” will be demonstrated. In particular, we mention the regulation of luminescent properties by the external stimulus in the film. In these studies, flexible complexes showed luminescent chromism triggered by temperature changes, mechanical stresses and vapor fuming. The mechanisms and design strategies will be explained in the presentation.

Development of stimuli-responsive luminescent polymers based on a flexible “element-block”

ACS Spring Meeting 2021

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