Heat-Resistant Mechanoluminescent Chromism of the Hybrid Molecule Based on Boron Ketoiminate Modified Octasubstituted Polyhedral Oligomeric Silsesquioxane.

The development of a heat-resistant mechanoluminescent chromic (MLC) dye based on an organic-inorganic hybrid molecular scaffold is reported. Luminescent organoboron complexes were introduced into polyhedral oligomeric silsesquioxane (POSS) at each vertex through the rigid linker structure in the Suzuki-Miyaura cross-coupling reaction. From optical measurements, it was found that the crystalline state of the modified POSS showed orange emission. By adding mechanical forces to the sample, regular structures collapsed. Correspondingly, the emission color turned to yellow. Interestingly, the yellow-emissive amorphous state can be preserved during heating. By radially distributing luminescent chromophores on the rigid cube, both optical and thermal properties can be modulated to realize heat- resistant MLC behavior. POSS can contribute not only to expressing the MLC behavior, but also to improving thermal stability in the amorphous state. This is the first example, to the best of our knowledge, to offer the rational design of a heat-resistant MLC material.