Structure and Conformational Analysis of 5,5-Bis(bromomethyl)-2,2-diphenyl-1,3-dioxane
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY
Authors: Khazhiev, Sh. Yu.; Khusainov, M. A.; Khalikov, R. A.; Kataev, V. A.; Tyumkina, T. V.; Meshcheryakova, E. S.; Khalilov, L. M.; Kuznetsov, V. V.
The structure of 5,5-bis(bromomethyl)-2,2-diphenyl-1,3-dioxane was studied by H-1 and C-13 NMR spectroscopy and X-ray analysis. Its molecules in crystal adopt a chair conformation, whereas equilibrium between energy-degenerate chair invertomers exists in solution at room temperature. According to the low-temperature NMR data, the interconversion barrier amounts to 8.9 kcal/mol. The ring inversion path was simulated by DFT quantum chemical calculations using PBE/3 xi and (in some cases) RI-MP2/lambda 2 approximations, and the potential barrier to interconversion in different solvents was estimated by the cluster model. The calculated geometric parameters of the title compound were consistent with the experimental X-ray diffraction data, and the calculated interconversion barrier matched a cluster containing 5 molecules of methylene chloride in the nearest solvation shell of the substituted 1,3-dioxane molecule.
Tetraphenylethylene-BODIPY aggregation-induced emission luminogens for near-infrared polymer light-emitting diodes
Authors: Baysec, Sebnem; Minotto, Alessandro; Klein, Patrick; Poddi, Simone; Zampetti, Andrea; Allard, Sybille; Cacialli, Franco; Scherf, Ullrich
The aggregation-induced emission (AIE) phenomenon provides a new direction for the development of organic light-emitting devices. Here, we present a new class of emitters based on 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY), functionalized at different positions with tetraphenylethylene (TPE), which is one of the most famous AIE luminogens. Thanks to this modification, we were able to tune the photoluminescence of the BODIPY moiety from the green to the near-infrared (NIR) spectral range and achieve PL efficiencies of similar to 50% in the solid state. Remarkably, we observed an enhancement of the AIE and up to similar to 100% photoluminescence efficiencies by blending the TPE-substituted BODIPY fluorophores with a poly[(9,9-di-n-octylfluorene-2,7-diyl)-alt-(benzo[2,1,3]thiadiazol-4,7-diyl)] (F8BT) matrix. By incorporating these blends in organic light-emitting diodes (OLEDs), we obtained electroluminescence peaked in the range 650-700 nm with up to 1.8% external quantum efficiency and similar to 2 mW/cm(2) radiance, a remarkable result for red/NIR emitting and solution-processed OLEDs.