Acenaphthenoannulation Induced by the Dual Lewis Acidity of Alumina

We have discovered a dual (i. e., soft and hard) Lewis acidity of alumina that enables rapid one-pot π-extension through the activation of terminal alkynes followed by C−F activation. The tandem reaction introduces an acenaphthene fragment – an essential moiety of geodesic polyarenes. This reaction provides quick access to elusive non-alternant polyarenes such as π-extended buckybowls and helicenes through three-point annulation of the 1-(2-ethynyl-6-fluorophenyl)naphthalene moiety. The versatility of the developed method was demonstrated by the synthesis of unprecedented structural fragments of elusive geodesic graphene nanoribbons

500-Fold Amplification of Small Molecule Circularly Polarised Luminescence through Circularly Polarised FRET

Strongly dissymmetric circularly polarised (CP) luminescence from small organic molecules could transform a range of technologies, such as display devices. However, highly dissymmetric emission is usually not possible with small organic molecules, which typically give dissymmetric factors of photoluminescence (gPL) less than 10−2. Here we describe an almost 103-fold chiroptical amplification of a π-extended superhelicene when embedded in an achiral conjugated polymer matrix. This combination increases the |gPL| of the superhelicene from approximately 3×10−4 in solution to 0.15 in a blend film in the solid-state. We propose that the amplification arises not simply through a chiral environment effect, but instead due to electrodynamic coupling between the electric and magnetic transition dipoles of the polymer donor and superhelicene acceptor, and subsequent CP Förster resonance energy transfer. We show that this amplification effect holds across several achiral polymer hosts and thus represents a simple and versatile approach to enhance the g-factors of small organic molecules

Aluminum oxide mediated C–F bond activation in trifluoromethylated arenes

Thermally activated γ-aluminium oxide was found to be very effective for C–F bond activation in trifluoromethylated arenes. Depending on the activation degree the respective arenes can be converted either to cyclic ketones or to the respective carboxylic acids with good to excellent yields

Bottom up fabrication of (9,0) zigzag and (6,6) armchair carbon nanotube end-caps on the Rh(111) surface

The exploration and wide application of single walled carbon nanotubes (SWCNTs) require the development of new synthetic approaches enabling facile and fully rational CNT fabrication. In this communication the conversion of two precursors yielding the potential CNT seeds of (9, 0) zigzag and (6, 6) armchair nanotubes using surface-assisted cyclodehydrogenation on the Rh(111) single-crystal surface is reported. The conversion efficiency found is nearly 100% and the CNT-caps remain thermally stable on the Rh surface up to 820 K which is high enough for subsequent SWCNT growth. It is shown that Rh is a suitable catalyst for the controllable synthesis of SWCNTs by the surface assisted bottom-up strategy. (C) 2014 Elsevier Ltd. All rights reserved

The importance of grain boundaries for the time-dependent mobility degradation in organic thin-film transistors

The relationships between organic semiconductor morphology and device stability of organic field-effect transistors (FETs) are very complex and not yet fully understood. Especially For obtaining high-performance, air-stable n-channel FETs, gaining a deep insight into possible degradation mechanisms can help improve their air stability. Here, we investigate the performance and stability of organic n-channel FETs based on solution-grown single-crystalline ribbons of the conjugated semiconductor bis(1H, 1H-perfluorobutyl)-dicyano-perylene tetracarboxylic diimide (C3F7CH2- PTCDI-(CN)(2)). The FETs show an electron mobility of 0.25 cm(2)/(V S) in air and an on/off ratio up to 1 x 10(7). Their mobility does not significantly change when devices are stored in air for more than 5 weeks. This excellent air stability stands in contrast to FETs based on thin evaporated polycrystalline films of the same compound that degrade by more than an order of magnitude during the same 5 week period. We attribute this striking difference in air stability to the grain boundaries in the polycrystalline films and discuss different possible degradation mechanisms