Efficient photogeneration of nonacene on nanostructured graphene

The on-surface photogeneration of nonacene from α-bisdiketone precursors deposited on nanostructured epitaxial graphene grown on Ru(0001) has been studied by means of low temperature scanning tunneling microscopy and spectroscopy. The presence of an unoccupied surface state, spatially localized in the regions where the precursors are adsorbed, and energetically accessible in the region of the electromagnetic spectrum where n-π* transitions take place, allows for a 100% conversion of the precursors into nonacenes. With the help of state-of-the-art theoretical calculations, we show that such a high yield is due to the effective population of the surface state by the incoming light and the ensuing electron transfer to the unoccupied states of the precursors through an inelastic scattering mechanism. Our findings are the experimental confirmation that surface states can play a prominent role in the surface photochemistry of complex molecular systems, in accordance with early theoretical predictions made on small molecules.

Electronic Properties of Sulfur Covered Ru(0001) Surfaces

The structural properties of sulfur superstructures adsorbed on Ru(0001) have been widely studied in the past. However, much less effort has been devoted to determine their electronic properties. To understand the connection between structural and electronic properties, we have carried out density functional theory periodic boundary calculations mimicking the four long-range ordered sulfur superstructures identified experimentally by means of scanning tunneling microscopy (STM) techniques. Our simulations allow us to characterize the nature of the sulfur-Ru bond, the charge transfer between the Ru substrate and the sulfur adlayers, the interface states, and a parabolic state recently identified in STM experiments. A simple analysis, based on a one-dimensional model, reveals that this parabolic state is related to a potential well state, formed in the surface when the concentration of sulfur atoms is large enough to generate a new minimum in the surface potential.

High yielding and extremely site-selective covalent functionalization of graphene

Gr/Ru(0001) can be functionalized covalently in high yield (92%) and selectivity (98%) with CH₂CN˙ and increasing the sample temperature during functionalization.

Organic Covalent Patterning of Nanostructured Graphene with Selectivity at the Atomic Level

Organic covalent functionalization of graphene with long-range periodicity is highly desirable-it is anticipated to provide control over its electronic, optical, or magnetic properties-and remarkably challenging. In this work we describe a method for the covalent modification of graphene with strict spatial periodicity at the nanometer scale. The periodic landscape is provided by a single monolayer of graphene grown on Ru(0001) that presents a moiré pattern due to the mismatch between the carbon and ruthenium hexagonal lattices. The moiré contains periodically arranged areas where the graphene-ruthenium interaction is enhanced and shows higher chemical reactivity. This phenomenon is demonstrated by the attachment of cyanomethyl radicals (CH2CN(•)) produced by homolytic breaking of acetonitrile (CH3CN), which is shown to present a nearly complete selectivity (>98%) binding covalently to graphene on specific atomic sites. This method can be extended to other organic nitriles, paving the way for the attachment of functional molecules.

Synthesis and pharmacology of two new histamine receptor antagonists related to ranitidine

Pyridyl and 1,6-dihydropyridyl ranitidine analogues 1 and 2 were obtained by applying an improved modification of ranitidine synthesis. Compound 1 shows a selective H2 antagonistic activity while compound 2 is a non-selective histamine antagonist.

[Hemangiopericytoma of the maxillary sinus: apropos of a case]

Haemangiopericytoma is a rare vascular tumour arising from the proliferation of pericytes which are cells surrounding the capillaries. Since 1949 only 54 cases of haemangiopericytomas of the nose and paranasal sinuses have been reported in the literature. Of the latter, only 8 cases originated from the maxillary sinus. We report a further case originated from the maxillary sinus.

[Chemodectomas of the carotid body. Apropos 2 cases]

The chemodectoma a paragangliomas of the carotid body are infrequent tumors in the daily medical practice, but they must be taken into account in the differential diagnosis of any lateral neck mass. We present two new cases, reconsidering the existing literature.