Synthesis of O-B N embedded molecules and studies on the B N cleavage-driven thermo- and solvatochromic properties

Three O -B <- N embedded molecules identified as 1, 2, and 3 with different substituents and B <- N locations are synthesized to study the firmness of intramolecular B <- N coordination. After X-ray diffraction crystallography, electrochemical, and photophysical tests, in-depth B <- N cleavage -driven thermoand solvatochromic studies were conducted. In contrast to compound 1 with phenyl side groups, compound 2 with bulky and electrondeficient perfluorophenyl substituents has twisted backbone, significantly increased fluorescence quantum yield (phi F = 27 % vs 85 %), and most importantly, enhanced stability of B <- N coordination. Comparison to 1 and 2, whose B <- N bonds are located on the edge of fused rings, compound 3 with extended backbone conjugation and B <- N bonds embedded inside fused rings exhibits red -shifted absorption/emission, decreased phi F = 7 %, and remarkably enhanced strength of B <- N coordination. This work discloses the effects of substituents and B <- N locations on firmness of intramolecular B <- N coordination, which are enlightening to understand the stability and application of these O -B <- N embedded molecules.