Trioxotriangulene with carbazole: a donor–acceptor molecule showing strong near-infrared absorption exceeding 1000 nm
A donor–acceptor type trioxotriangulene (TOT) neutral radical derivative having three carbazolyl groups as electron-donors was newly synthesized. The ESR spectrum showed that the electronic spin delocalized over both the TOT skeleton and three carbazolyl groups, causing high stability of the neutral radical species. In the cyclic voltammetry measurement, the adduct exhibited multiple redox waves from the redox processes of TOT from the monocation to radical tetraanion species and also from the oxidation of the carbazolyl groups. The UV-vis spectra showed a strong near-infrared photoabsorption band with an absorption maximum of 1028 nm, which was characterized as an intramolecular charge-transfer from the carbazolyl group to the TOT neutral radical core. In both solution and solid states, the neutral radical formed a π-dimer stabilized by the strong two-electron-multicenter bonding on the TOT skeleton.