3 research outputs found
Crystal-to-Crystal Photoinduced Reaction of Dinitroanthracene to Anthraquinone
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
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
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