2,6- and 2,7-Diazatriptycene-Based Boron Complexes: Synthesis, Optical Properties, and Crystal Structures

Boron-bridged 2,6- and 2,7-diazatriptycene complexes were synthesized as fluorescent three-dimensional π-systems. Single-crystal X-ray analysis revealed distinct packing modes: the chiral 2,6-isomer formed loosely packed trimeric clusters with large solvent-accessible voids, whereas the 2,7-isomer adopted a denser herringbone-like packing structure. Both complexes exhibited blue fluorescence in solution with higher photoluminescence quantum yields than ppy-BMe2. TD-DFT calculations indicated that boron coordination suppresses the dark n–π* character of diazatriptycenes and converts the S1 state into an allowed π–π* transition. These findings establish boron coordination as an effective approach for developing photofunctional azatriptycene-based three-dimensional π-systems.