Triptycene is a compound in which three benzene rings are bridged by two methylene groups, giving rise to a propeller-like structure with unique electronic properties and assembly behaviors. Owing to these characteristics, triptycene has attracted considerable attention in the fields of electronic materials, sensing materials, and supramolecular chemistry.

　In contrast, heterotriptycenes, in which the aromatic rings of triptycene contain heteroatoms, have been little explored because of the difficulties associated with their synthesis. We have developed an important key precursor, “TCBO,” for the synthesis of heterotriptycenes, and successfully synthesized a novel compound incorporating two pyrrole rings.[1] This molecule was found to exhibit distinctive two-dimensional assembly behavior and optical properties arising from the unique structural features of heterotriptycene.　

[1] Eur. J. Org. Chem. 2022, e202200041.(Top Downloaded Article !!)

　Although “2-azatriptycene,” in which the 2-position of triptycene is replaced by nitrogen, has been reported in the past, its functionalization has not been explored. We have developed a facile synthetic method for optically active 2-azatriptycenes using TCBO as a precursor.[2] The resulting compounds exhibited solvatochromic circularly polarized luminescence (CPL) with a shift exceeding 170 nm.

　In the crystalline state, the salt formed with HBr, taking advantage of the basicity of the pyridine moiety, afforded a chiral cage-like tetrameric cluster capable of encapsulating guest molecules. Furthermore, the 2-azatriptycene platinum complexes obtained through metal coordination were found to display bright circularly polarized phosphorescence.

[2] Chem. Commun. 2023, 59, 5571-5574.

　We have, for the first time, successfully synthesized 2,6-diazatriptycene, in which two nitrogen atoms are chirally incorporated into the triptycene framework [3]. The resulting compounds exhibited intriguing properties and functions associated with cationic and dicationic states upon acid addition.

　Enantiopure (9S,10S)-1 was found to be non-emissive in solution. Upon the addition of 1 equiv of TfOH, it displayed green circularly polarized fluorescence (CPL) with a negative sign, whereas further addition of 3 equiv of TfOH induced CPL with a positive sign. Remarkably, these three emission states could be reversibly and completely switched by the controlled addition of triethylamine. Thus, we achieved, for the first time, ternary CPL switching within a single-molecule and single-solution system. Considering the importance of CPL switching in security communications and molecular sensing, this work presents a novel switching mechanism and a dimensional expansion of CPL modulation.

　Notably, the supramolecular assembly of this compound was also highly responsive to acid equivalents. Depending on the protonation state, the molecules assembled into a herringbone packing (no acid), trimeric clusters (0.33 equiv), chiral porous tubes (0.86 equiv), and two-dimensional charge-separated sheets (2 equiv). In addition, the AIEE (aggregation-induced emission enhancement) properties were progressively strengthened with increasing acid concentration, attributable to the enhanced ionic hydrogen-bonding interactions. These findings demonstrate that nitrogen doping into triptycene is a powerful strategy to unlock hidden optical functions and supramolecular assembly behaviors.　

[3] Angew. Chem. Int. Ed. 2025, 64, e202506733.