ABSTRACT
On-surface synthesis is of importance to fabricate low dimensional carbon-based nanomaterials with atomic precision. Here, we synthesize nitrogen-doped nanographene with an [18]annulene pore and its dimer through sequential reactions of debromination, aryl-aryl coupling, cyclodehydrogenation and C-N coupling on Ag(111) from 3,12-dibromo-7,8-diaza[5]helicene. The inner structures of the products were characterized with scanning tunneling microscopy with a CO terminated tip at low temperature. Furthermore, the first four unoccupied electronic states of the nanographene were investigated with a combination of scanning tunneling spectroscopy and theoretical calculations. Except for the LUMO + 2 state observed at +1.3 V, the electronic states at 500 mV, 750 mV and 1.9 V were attributed to the superatom molecular orbitals at the [18]annulene pore, which were significantly shifted towards the Fermi level due to the hybridization with the confined surface state.
ABSTRACT
A dual-photofunctional organogermanium compound based on a donor-acceptor-donor architecture that exhibits thermally activated delayed fluorescence and mechano-responsive luminochromism has been developed. The developed compound was successfully applied as an emitter for efficient organic light-emitting diodes.
ABSTRACT
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 C2 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. Furthermore, electrochemical analysis suggested sigma-dimer formation and electrochemical polymerization on the electrode. Quantum chemical calculations also rationalized the experimental results.
ABSTRACT
A novel twisted donor-acceptor-donor (D-A-D) π-conjugated compound that contains flexible and moderately-electron-donating units has been designed and synthesized. It exhibited not only multi-color-changing mechanochromic luminescence and thermally activated delayed fluorescence, but also, unexpectedly, room-temperature phosphorescence in a host layer.
