Direct evidence for a carbon-carbon one-electron σ-bond.

Covalent bonds share electron pairs between two atoms and make up the skeletons of most organic compounds in single, double and triple bonds. In contrast, examples of one-electron bonds remain scarce, most probably due to their intrinsic weakness. Although several pioneering studies have reported one-electron bonds between heteroatoms, direct evidence for one-electron bonds between carbon atoms remains elusive.

The Impact of C Insertion into a Carbazole Donor on the Physicochemical Properties of Dibenzo[a,j]phenazine-Cored Donor-Acceptor-Donor Triads.

Novel electron donor-acceptor-donor (D-A-D) compounds comprising dibenzo[a,j]phenazine as the central acceptor core and two 7-membered diarylamines (iminodibenzyl and iminostilbene) as the donors have been designed and synthesized. Investigation of their physicochemical properties revealed the impact of C insertion into well-known carbazole electron donors on the properties of previously reported twisted dibenzo[a,j]phenazine-core D-A-D triads. Slight structural modification caused a drastic change in conformational preference, allowing unique photophysical behavior of dual emission derived from room-temperature phosphorescence and triplet-triplet annihilation.