2479-47-2Relevant articles and documents
Intermolecular London Dispersion Interactions of Azobenzene Switches for Tuning Molecular Solar Thermal Energy Storage Systems
Kunz, Anne,Heindl, Andreas H.,Dreos, Ambra,Wang, Zhihang,Moth-Poulsen, Kasper,Becker, Jonathan,Wegner, Hermann A.
, p. 1145 - 1148 (2019)
The performance of molecular solar thermal energy storage systems (MOST) depends amongst others on the amount of energy stored. Azobenzenes have been investigated as high-potential materials for MOST applications. In the present study it could be shown that intermolecular attractive London dispersion interactions stabilize the (E)-isomer in bisazobenzene that is linked by different alkyl bridges. Differential scanning calorimetry (DSC) measurements revealed, that this interaction leads to an increased storage energy per azo-unit of more than 3 kcal/mol compared to the parent azobenzene. The origin of this effect has been supported by computation as well as X-ray analysis. In the solid state structure attractive London dispersion interactions between the C?H of the alkyl bridge and the π-system of the azobenzene could be clearly assigned. This concept will be highly useful in designing more effective MOST systems in the future.
Comparison between SiMe2 and CMe2 spacers as σ-bridges for photoinduced charge transfer
Van Walree, Cornelis A.,Roest, Martin R.,Schuddeboom, Wouter,Jenneskens, Leonardus W.,Verhoeven, Jan W.,Warman, John M.,Kooijman, Huub,Spek, Anthony L.
, p. 8395 - 8407 (2007/10/03)
The potential of dimethylsilylene and isopropylidene σ-spacers as bridges for photoinduced charge transfer (CT) in 4-cyano-4'-(dimethylamino)- and 4-cyano-4'-methoxy-substituted diphenyldimethylsilanes and 2,2-diphenylpropanes was studied. Fluorescence solvatochromism and time-resolved microwave conductivity measurements show that upon photoexcitation a charge separated state (D.+σA.-)* is populated in all compounds. Excited state dipole moments for a given donor-acceptor combination are, irrespective of the bridge, equal. The CT states of the silanes are however lying at lower energies, implying that the presence of silicon thermodynamically facilitates the CT process. Cyclic voltammetry data of model compounds show that this is a consequence of the lowering of the acceptor reduction potential by the silicon bridge. It was however inferred from radiative decay rates that the electronic coupling between the CT and locally excited states as well as the coupling between the ground and CT state is larger for the carbon-bridged compounds. As shown by both solution and solid state electronic spectra and radiative decay rates, the photophysics of the DσA compounds are dominated by intensity borrowing of the CT transitions from transitions localized in the Dσ and σA chromophores.
Regioselective nitration of diphenyl compounds
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, (2008/06/13)
A regioselective nitration process for diphenyl compounds which can be carried out at about ambient temperature in which each ring of the diphenyl compound is selectively nitrated in the para position to form the corresponding di(4-nitrophenyl) compound. Such compounds as diphenyl carbonate, 2,2-diphenylpropane, 2,2-diphenylhexafluoropropane, diphenyl sulfide, diphenyl ketone, diphenyl sulfone, and the like can be converted to an isomeric mixture containing an enhanced amount of the corresponding di(4-nitrophenyl) compound, which mixture may be reduced or purified and reduced to the di(4-aminophenyl) analogues for use in the manufacture of polyamides, polyimides, and polyamide-imides.