A unique trimeric triphenylene radical cation: stacking aggregation, bonding, and stability.

A new and unique π-stacking triphenylene trimer cation radical unit appears in the crystal structure of a newly synthesized salt with an oligomeric gallium(iii) chloride, [(CH)]˙(GaCl), which is the first triphenylene aggregate observed. The structure is attributed to a shared electron distributed over the trimer displaying π-stacking pancake bonding. Computational modeling rationalizes the appearance of a "chain-shaped" rather than a "star-shaped" gallium chloride anion as well as the reasons why the trimer, rather than a radical cation aggregate of different size, is preferred in this system.

Dibenzannulated -acenoacenes from anthanthrene derivatives.

A series of dibenzannulated phenyl-annulated [4,2]-acenoacenes have been synthesized in three straightforward steps from 4,10-dibromoanthanthrone (vat orange 3). The phenyl bisannulation of [4,2]-acenoacene provides extra stability by increasing the overall aromatic character of the molecules, and allows for a 45-80% increase of the molar extinction coefficient () compared to their [5,2]-acenoacene isomers. Depending on the substituents attached to the π-conjugated core, some derivatives exhibit strong aggregation in the solid state with association constant () up to 255 M, resulting in a significant broadening of the absorption spectrum and a substantial decrease of the bandgap value (more than 0.

Chemical reaction induced carrier localization in nanometer-thin Al/Ru, Al/Co, and Al/Mo superlattices.

It is well-known that the electrical conductivity of a metallic film reduces dramatically when the film becomes very thin. This effect is mainly attributed to surface scattering of the conducting carriers. In a multilayer structure, interface scattering also reduces the conductance, but chemical reactions at the interfaces can have equal or bigger effects.

Primate evolution - in and out of Africa.

A synthetic analysis of molecular, fossil and biogeographical data gives a remarkably consistent scenario for the evolution of the catarrhine primates - the hominoids and Old World monkeys. This analysis supports the African location of the common ancestor of the Old World monkeys, and suggests that the Asian colobine monkeys and macaques dispersed out of Africa into Eurasia within the past ten million years. More interestingly and controversially, this analysis further suggests that the lineage leading to the living hominoids dispersed out of Africa about twenty million years ago, and that the common ancestor of the living African apes, including humans, migrated back into Africa from Eurasia within about the past ten million years.