Emissive Liquid Crystalline Boron C,N-Chelates: Synthesis, Self-assembly, and Photophysical Properties

A library of novel phenylpyridine-based boron C,N-chelates bearing a mesogenic unit was synthesized and investigated to clarify how the chain type, length, and number, as well as the boron substitution (BH₂ vs. BMe₂) influence the mesomorphic and photophysical behavior. All BH₂ derivatives exhibited SmA or N phases even with short alkyl chains, whereas BMe₂ analogues remained nonmesomorphic unless a semi-perfluorinated chain was introduced, demonstrating the strong influence of boron substitution on mesophase formation. All compounds displayed intense blue emission in solution, with spectral properties primarily determined by the boron C,N core and only minor shifts induced by variation in the mesogenic unit in agreement with complementary DFT calculations. Quantum yields reached up to 100% in solution. These results demonstrate that mesomorphic behavior can be introduced and tuned while preserving the excellent photophysical performance of the boron-C,N-chelate system.