Recognizing Through‐Bond and Through‐Space Self‐Exchange Charge/Spin Transfer Pathways in Bis(triarylamine) Radical Cations with Similar Geometrical Arrangements

Radical cations of bis(triarylamine)s, 3 and 4 , in which the triarylamine redox centers are bridged by an ortho ‐phenylene and ortho ‐carborane cluster, respectively, have been prepared to elucidate the difference in intramolecular charge/spin‐transfer (ICT/IST) pathway owing to the two different bridging units affording similar geometrical arrangements between the redox centers. Electrochemistry, absorption spectroscopy, VT‐ESR spectroscopy, and DFT calculations reveal that 3 ^.+ and 4 ^.+ are classified into class II and class I mixed‐valence systems, respectively, and therefore, through‐bond and through‐space mechanisms are dominant for the ICT/IST phenomena in 3 ^.+ and 4 ^.+, respectively. Moreover, SQUID measurements for dicationic species provide the fact that virtually no spin‐exchange interaction is observed for spins in 4 ²⁺, while the antiferromagnetic interaction for spins in 3 ²⁺, in accordance with the existence of a conjugation pathway for the ortho ‐phenylene bridge.