Sulfur-Bridged Cationic Diazulenomethenes: Formation of Charge-Segregated Assembly with High Charge-Carrier Mobility

• Published in: Journal of the American Chemical Society 2024-08, Vol.146 (32), p.22642-22649
• Main Authors: Takahashi, Satoshi, Murai, Masahito, Hattori, Yusuke, Seki, Shu, Yanai, Takeshi, Yamaguchi, Shigehiro
• Format: Article
• Language: English
• ISSN: 0002-7863; 1520-5126; 1520-5126
• DOI: 10.1021/jacs.4c07122

Sulfur-bridged cationic diazulenomethenes were synthesized and exhibited high stability even under basic conditions due to the delocalization of positive charge over the whole π-conjugated skeleton. As a result of the effective delocalization and the absence of orthogonally oriented bulky substituents, the cationic π-conjugated skeletons formed a π-stacked array with short interfacial distances. A derivative with SbF6 – as a counter anion formed a charge-segregated assembly in the crystalline state, rather than the generally favored charge-by-charge arrangement of oppositely charged species based on electrostatic interactions. Theoretical calculations suggested that the destabilization caused by electrostatic repulsion between two positively charged π-conjugated skeletons is compensated by the dispersion forces. In addition, the counter anion SbF6 – played a role in regulating the molecular alignment through F⋯H–C and F–S interactions, which resulted in the charge-segregated alignment of the cationic π-skeletons. This characteristic assembled structure gave rise to a high charge-carrier mobility of 1.7 cm2 V–1 s–1 as determined using flash-photolysis time-resolved microwave conductivity.