Radical Cation of Tris(Triarylamine) Connected through 1,2,3-Benzenetriyl Bridge: A Three-Redox-Center Organic Mixed-Valence System

To explore intramolecular charge-transfer (ICT) pathways in three-redox-center organic mixed-valence (MV) radical cation, a tris(triarylamine) (TTA), in which three triarylamine (TA) redox-active centers are connected in a side-by-side fashion via 1,2,3-benzenetriyl bridging unit, has been newly synthesized. The MV state of the TTA radical cation has been investigated by a combination of experimental and theoretical methods, and the ICT pathway between three redox-active centers has been revealed. The intervalence CT (IVCT) band analysis gave an electronic coupling value comparable to the 𝘰𝘳𝘵𝘩𝘰-phenylene-bridged bis(triarylamine) radical cation. Dynamic electron spin resonance studies clarified that the TTA radical cation was a nondegenerate MV system exhibiting ICT between the central TA and the peripheral TAs through the 𝘰𝘳𝘵𝘩𝘰-phenylene-bridge.