Authors: Yushi Ohno | Tsukasa Ehara | Kosuke Sato | Ryoyu Hifumi | Ikuyoshi Tomita | Shinsuke Inagi
Source: ECS Meeting Abstracts (article, 2025-07-11)
Field: Materials Science — Materials Chemistry

Orthogonal Synthesis of Cationic Azatriphenylene Derivatives for Optical Properties Switching Cationic nitrogen-doped PAHs ( N + -doped PAHs) have a significant potential for maximizing their photophysical properties based on their diverse molecular designs including cationic and anionic species. Recent efforts have focused on the precise synthesis of N + -doped PAHs for fine-tuning electronic structures [1] . In particular, orthogonal synthetic approach from specific single precursors has great advantages of providing controlled π-conjugated structures and physical properties [2,3] . However, this concept is still under development. Due to our continuous interest in N + -doped PAHs, we had previously developed two types of intramolecular selective S N Ar reactions induced by thermal and electro-oxidative treatments [4,5] . We therefore envisaged that the combination of these two protocols is an effective approach for the orthogonal synthesis of N + -doped PAHs. In this study, we demonstrate the orthogonal synthesis of cationic azatriphenylene derivatives to switch their optical properties such as aggregation-induced emission (AIE) and aggregation-caused quenching (ACQ). Phenylpyridine precursor 1 was designed for the orthogonal transformations. As a result of screening various reaction conditions in each thermal and electro-oxidative S N Ar reaction, we successfully obtained corresponding products 2 and 3 with complete selectivity. This result indicated that we achieved the selective synthesis of π-conjugated structures by orthogonal stimulus such as thermal and electro-oxidative treatments. Interestingly, the obtained products 2 and 3 showed the opposite emission behavior. The fluorescence measurement revealed that 2 exhibits the AIE property, while 3 exhibits the ACQ property. To elucidate these differences in detail, theoretical calculations and single-crystal X-ray diffraction analysis were performed. As a result of time-dependent DFT (TD-DFT), 3 has a higher oscillator strength of the S 1 →S 0 transition (approximately 5.7 times greater) than 2 , caused by the larger orbital overlap between the pyridinium moiety and the methoxyphenyl moiety. In the crystal state, 2 has more distorted triphenylene units than 3 . 2 also formed charge-by-charge assemblies with alternating stacking of oppositely charged species, while 3 formed charge-segregated assemblies with separating cationic and anionic species, respectively. These structural differences suggest that the distorted structure unit and anion-π interaction favorably prevents π-π stacking between cationic π-skeletons promoting quenching pathways. In conclusion, we successfully designed the orthogonal synthesis of cationic azatriphenylene derivatives for AIE and ACQ properties switching. This proposed protocol would have potential for application in sensing systems responsive to thermal and electro-stimuli. -----Reference-------------------------------------------------------------------------------------------------------------------------- (1) A. Borissov, Y. K. Maurya, L. Moshniaha, W. S. Wong, M. Z. Karwowska, M. Stepien, Chem. Rev . 2022 , 122 , 565−788. (2) X. Jiang, Z. Zeng, Y. Hua, B. Xu, Y. Shen, J. Xiong, H. Qiu, Y. Wu, T. Hu, Y. Zhang, J. Am. Chem. Soc . 2020 , 142 , 15585−15594. (3) A. C. Shaikh, S. Banerjee, R. D. Mule, S. Bera, N. T. Patil, J. Org. Chem . 2019 , 84 , 4120−4130. (4) Y. Asanuma, H. Eguchi, H. Nishiyama, I. Tomita, S. Inagi, Org. Lett . 2017 , 19 , 1824−1827. (5) Y. Ohno, S. Ando, D. Furusho, R. Hifumi, Y. Nagata, I. Tomita, S. Inagi, Org. Lett . 2023 , 25 , 3951−3955. Figure 1 Cationic polymerization ; Chemistry ; Materials science ; Polymer chemistry Photochromic and Fluorescence Chemistry ; Luminescence and Fluorescent Materials ; Chemical Synthesis and Analysis