Cost-Effective Force Field Tailored for Solid-Phase Simulations of OLED Materials

A united atom force field is empirically derived by minimizing the difference between experimental and simulated crystal cells and melting temperatures for eight compounds representative of organic electronic materials used in OLEDs and other devices: biphenyl, carbazole, fluorene, 9,9′-(1,3-phenylene)bis(9H-carbazole)-1,3-bis(N-carbazolyl)benzene (mCP), 4,4′-bis(N-carbazolyl)-1,1′-biphenyl (pCBP), phenazine, phenylcarbazole, and triphenylamine. The force field is verified against dispersion-corrected DFT calculations and shown to also successfully reproduce the crystal structure for two larger compounds employed as hosts in phosphorescent and thermally activated delayed fluorescence OLEDs: N,N′-di(1-naphthyl)-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine (NPD), and 1,3,5-tri(1-phenyl-1H-benzo[d]imidazol-2-yl)phenyl (TPBI). The good performances of the force field coupled to the large computational savings granted by the united atom approximation make it an ideal choice for the simulation of the morphology of emissive layers for OLED materials in crystalline or glassy phases.

Photocatalytic Dehydrogenative Lactonization of 2-Arylbenzoic Acids

A metal-free dehydrogenative lactonization of 2-arylbenzoic acids at room temperature was developed. This work illustrates the first application of visible-light photoredox catalysis in the preparation of benzo-3,4-coumarins, an important structural motif in bioactive molecules. The combination of photocatalyst [Acr+-Mes] with (NH4)2S2O8 as a terminal oxidant provides an economical and environmentally benign entry to different substituted benzocoumarins. Preliminary mechanistic studies suggest that this reaction most likely occurs through a homolytic aromatic substitution pathway.