3 research outputs found

    Crystal-to-Crystal Photoinduced Reaction of Dinitroanthracene to Anthraquinone

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    The photochemical reaction of 9,10-dinitroanthracene (DNO<sub>2</sub>A) to anthraquinone (AQ) + 2NO has been studied by means of lattice phonon Raman spectroscopy in the spectral region 10–150 cm<sup>–1</sup>. In fact, crystal-to-crystal transformations are best revealed by following changes in the lattice modes, as even small modifications in the crystal structure lead to dramatic changes in symmetry and selection rules of vibrational modes. While analysis of the lattice modes allowed for the study of the physical changes, the chemical transformation was monitored by measuring the intramolecular Raman-active modes of both reactant and product. On the basis of the experimental data it has been possible, at a microscopic level, to infer crucial information on the reaction mechanism by simultaneously detecting molecular (vibrational modes) and crystal structure (lattice phonons) modifications during the reaction. At a macroscopic level we have detected an intriguing relationship between incident photons and mechanical strain, which manifests itself as a striking bending and unfolding of the specimens under irradiation. To clarify the mechanisms underlying the relationship between incoming light and molecular environment, we have extended the study to high pressure up to 2 GPa. It has been found that above 1 GPa the photoreaction becomes inhibited. The solid-state transformation has also been theoretically modeled, thus identifying the reaction pathway along which the DNO<sub>2</sub>A crystal lattice deforms to finally become the crystal lattice of the AQ product

    Crystal-to-Crystal Photoinduced Reaction of Dinitroanthracene to Anthraquinone

    No full text
    The photochemical reaction of 9,10-dinitroanthracene (DNO<sub>2</sub>A) to anthraquinone (AQ) + 2NO has been studied by means of lattice phonon Raman spectroscopy in the spectral region 10–150 cm<sup>–1</sup>. In fact, crystal-to-crystal transformations are best revealed by following changes in the lattice modes, as even small modifications in the crystal structure lead to dramatic changes in symmetry and selection rules of vibrational modes. While analysis of the lattice modes allowed for the study of the physical changes, the chemical transformation was monitored by measuring the intramolecular Raman-active modes of both reactant and product. On the basis of the experimental data it has been possible, at a microscopic level, to infer crucial information on the reaction mechanism by simultaneously detecting molecular (vibrational modes) and crystal structure (lattice phonons) modifications during the reaction. At a macroscopic level we have detected an intriguing relationship between incident photons and mechanical strain, which manifests itself as a striking bending and unfolding of the specimens under irradiation. To clarify the mechanisms underlying the relationship between incoming light and molecular environment, we have extended the study to high pressure up to 2 GPa. It has been found that above 1 GPa the photoreaction becomes inhibited. The solid-state transformation has also been theoretically modeled, thus identifying the reaction pathway along which the DNO<sub>2</sub>A crystal lattice deforms to finally become the crystal lattice of the AQ product

    Epitaxial Growth of π‑Stacked Perfluoropentacene on Graphene-Coated Quartz

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    Chemical-vapor-deposited large-area graphene is employed as the coating of transparent substrates for the growth of the prototypical organic n-type semiconductor perfluoropentacene (PFP). The graphene coating is found to cause face-on growth of PFP in a yet unknown substrate-mediated polymorph, which is solved by combining grazing-incidence X-ray diffraction with theoretical structure modeling. In contrast to the otherwise common herringbone arrangement of PFP in single crystals and “standing” films, we report a π-stacked arrangement of coplanar molecules in “flat-lying” films, which exhibit an exceedingly low π-stacking distance of only 3.07 Å, giving rise to significant electronic band dispersion along the π-stacking direction, as evidenced by ultraviolet photoelectron spectroscopy. Our study underlines the high potential of graphene for use as a transparent electrode in (opto-)electronic applications, where optimized vertical transport through flat-lying conjugated organic molecules is desired
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