A π-Extended Donor-Acceptor-Donor Triphenylene Twin linked via a Pyrazine-bridge

Beta-amino triphenylenes can be accessed via palladium catalyzed amination of the corresponding triflate using benzophe-none imine. Transformation of amine 6 to benzoyl amide 18 is also straightforward and its wide mesophase range demon-strates that the new linkage supports columnar liquid crystal formation. Amine 6 also undergoes clean aerobic oxidation to give a new twinned structure linked through an electron-poor pyrazine ring. The new discotic liquid crystal motif contains donor and acceptor fragments, and is more oval in shape rather than disk-like. It forms a wide range columnar mesophase. Absorption spectra are strong and broad; emission is also broad and occurs with a Stokes shift of ca. 0.7 eV, indicative of charge-transfer characte

Degradation of polymer banknotes through handling, and effect on fingermark visualisation

The surface structure of mint (as-issued) and handled polymer five pounds sterling banknotes was studied by atomic force microscopy and laser scanning confocal microscopy. A total of 1856 fingermarks on mint and handled banknotes from four different issuing banks (Bank of England, Bank of Scotland, Royal Bank of Scotland and Clydesdale Bank) were visualised with Vacuum Metal Deposition (VMD), Cyanoacrylate Fuming (CAF) and, on Clydesdale Bank notes, magnetic fluorescent powder. VMD was significantly more effective in developing fingermarks on handled banknotes, across all the banks studied, although effectiveness varied with issuing bank. For example, on handled Bank of England notes 45% of marks showed ridge detail with VMD development and 28% with CAF; for Bank of Scotland handled notes success rates were 17% with VMD and 1% with CAF. Microscopy of degraded banknotes showed the loss of intaglio printing and the formation of a cracked surface structure in the handled notes. These features can lead to the trapping of powder, or contaminants, increasing quantity of development agent in fingermark background between the ridges, decreasing contrast and decreasing performance of powder-based fingermark development techniques. These same features can restrict the migration of components of the fingermark, preventing fingermarks degrading through spread of material and thus reducing potential formation of empty prints, so that VMD development is not adversely affected

Tetrabenzoporphyrin and -mono-, - Cis -di- and tetrabenzotriazaporphyrin derivatives: Electrochemical and spectroscopic implications of meso CH Group replacement with nitrogen

Nonperipherally hexyl-substituted metal-free tetrabenzoporphyrin (2H-TBP, 1a) tetrabenzomonoazaporphyrin (2H-TBMAP, 2a), tetrabenzo-cis-diazaporphyrin (2H-TBDAP, 3a), tetrabenzotriazaporphyrin (2H-TBTAP, 4a), and phthalocyanine (2H-Pc, 5a), as well as their copper complexes (1b-5b), were synthesized. As the number of meso nitrogen atoms increases from zero to four, Îmax of the Q-band absorption peak becomes red-shifted by almost 100 nm, and extinction coefficients increased at least threefold. Simultaneously the blue-shifted Soret (UV) band substantially decreased in intensity. These changes were related to the relative electron-density of each macrocycle expressed as the group electronegativity sum of all meso N and CH atom groups, âχR. X-ray photoelectron spectroscopy differentiated between the three different types of macrocyclic nitrogen atoms (the Ninner, (NH)inner, and Nmeso) in the metal-free complexes. Binding energies of the Nmeso and Ninner,Cu atoms in copper chelates could not be resolved. Copper insertion lowered especially the cathodic redox potentials, while all four observed redox processes occurred at larger potentials as the number of meso nitrogens increased. Computational chemical methods using density functional theory confirmed 1b to exhibit a Cu(II) reduction prior to ring-based reductions, while for 2b, Cu(II) reduction is the first reductive step only if the nonperipheral substituents are hydrogen. When they are methyl groups, it is the second reduction process; when they are ethyl, propyl, or hexyl, it becomes the third reductive process. Spectro-electrochemical measurements showed redox processes were associated with a substantial change in intensity of at least two main absorbances (the Q and Soret bands) in the UV spectra of these compounds

Development of a Multigram Synthesis of URB937, a Peripherally Restricted FAAH Inhibitor

A new synthetic approach to URB937 was developed starting from the inexpensive and widely available 4-benzyloxyphenol. A reproducible four-step procedure, requiring no chromatographic purifications, was optimized that allowed the preparation of 100 g of URB937 in 45% overall yield. © 2013 American Chemical Society