Two positional isomers (regioisomers) through changing the substituted position of perylenetetracarboxylic diimide and benzanthrone moieties were designed and synthesized. These two regioisomers exhibit totally different aggregation behaviors. The meta (bay)-substituted...

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Three novel N-heteroacene molecules (SDNU-1, SDNU-2 and SDNU-3)b ased on tetraazachrysene units as cores have been designed, synthesized and fully characterized. Their photophysical, electrochemical and fluorescence properties were investigated, and they exhibited blue to green emission in the solid state. Interestingly, SDNU-2 exhibited high solid photoluminescence quantum efficiencies (75.3 %), which is the highest value of N-heteroacenes derivatives to date. Two-photon absorption studies have been conducted by using the open and close apertureZ -san tech-nique. SDNU-3 showed as ignificant enhancement in the two-photon absorption cross-section with magnitudes as high as about 700 GM (1 GM = 1 10 À50 cm 4 s/photon)w hen excited with 800 nm light, which is the largest value based on ah eteroacene system measured by using aZ -scan experiment so far.W ea ttribute the outcomet os ufficient electronic coupling between the strong charge transfer of quadrupolars ubstituents and the tetraazachrysenec ore. Our result would provide an ew guideline to design novel efficient two-photon materials based on N-heteroacene cores.

Layer-by-layer construction of diamond devices for spin-sensing calls for the atomistic understanding of the nitrogen species on diamond surfaces. Motivated by recent experiments, we used density functional theory simulations to examine the adsorption of nitrogen species (N, NH, and NH2) on bare and hydrogenated diamond(001) surfaces. On the bare substrate, we find that nitrogen species favor to attack the CC dimers at low coverages, forming N­(ad) and NH­(ad) in a bridge configuration and NH2(ad) in a terminal configuration. At increasing coverages up to one full monolayer, the computed adsorption geometries and energetics suggest that the adsorbate–adsorbate interactions are attractive for N­(ad), but repulsive for NH­(ad) and NH2(ad). On the hydrogenated substrate, the adsorbed nitrogen species are subject to structural modification, as resulted from the weakened adsorbate–substrate interactions. Further, we calculated the vibration of nitrogen species and the 1s core-level shift of surface carbons, providing atomistic insights into the nature of surface bonding. Lastly, we simulated images of representative nitrogen species adsorbed on diamond(001), guiding future work using scanning tunneling microscopy.

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