Synthesis and crystal structure of 1,3-bis[(3,4-dicyano)phenoxy]-4,6-dinitro-benzene, C22H8N6O6

C22H8N6O6, monoclinic, P21/n (no. 14), a = 15.3939(6) Å, b = 7.3053(3) Å, c = 16.8282(6) Å, β = 91.567(3)°, V = 1891.74(13) Å3, Z = 4, Rgt(F) = 0.0510, wRref(F2) = 0.0867, T = 140(2) K

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

Compact modeling of organic thin film transistors with solution processed octadecyl substituted tetrabenzotriazaporphyrin as an active layer

Using 70nm thick spin-coated film of newly synthesized octadecyl substituted copper tetrabenzotriazaporphyrin (10CuTBTAP) as an active layer on a highly doped silicon (110) gate electrode substrates, output characteristics and transfer characteristics of bottom-gate bottom-contact organic thin film transistors have been measured at room temperature. A compact model for thin film transistors has been employed as a part of circuit design tool to extract device parameters such as the charge carrier mobility μ, the threshold voltage VT and the contact resistances. Parallel measurements and analysis were performed on similarly constructed devices with a copper phthalocyanine analogue (10CuPc). The results reveal that the 10CuPc layer is relatively more susceptible to trapping degradation near the gate region than a 10CuTBTAP layer, which is significant in order to achieve stability in these transistors. The application of the simple square law in the classical MOS model provides a quicker but approximate interpretation of the transistor performance without providing information on the gate voltage dependence of mobility and the effects of the contact regions. In this comparative study, the analysis of the contact regions is found to be very important for determining the difference in the performance of two transistors

Protomers of the green and cyan fluorescent protein chromophores investigated using action spectroscopy

The photophysics of biochromophore ions often depends on the isomeric or protomeric distribution, yet this distribution, and the individual isomer contributions to an action spectrum, can be difficult to quantify. Here, we use two separate photodissociation action spectroscopy instruments to record electronic spectra for protonated forms of the green (pHBDI+) and cyan (Cyan+) fluorescent protein chromophores. One instrument allows for cryogenic (T = 40±10 K) cooling of the ions, while the other offers the ability to perform protomer-selective photodissociation spectroscopy. We show that both chromophores are generated as two protomers when using electrospray ionisation, and that the protomers have partially overlapping absorption profiles associated with the S1 ← S0 transition. The action spectra for both species span the 340–460 nm range, although the spectral onset for the pHBDI+ protomer with the proton residing on the carbonyl oxygen is red-shifted by ≈40 nm relative to the lower-energy imine protomer. Similarly, the imine and carbonyl protomers are the lowest energy forms of Cyan+, with the main band for the carbonyl protomer red-shifted by ≈60 nm relative to the lower-energy imine protomer. The present strategy for investigating protomers can be applied to a wide range of other biochromophore ions

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

Selective synthesis of meso-naphthylporphyrins

A series of novel meso-(8-substituted naphth-1-yl)porphyrins has been synthesized creating derivatives with a tight recognition environment above the porphyrin plane. The selective synthesis of single atropisomers is discussed. Condensation of bisnaphthaldehyde 12 with phenyldipyrromethane unexpectedly led to selective synthesis of the alpha,alpha-5,10-bridged isomer 14. A mechanism is proposed for this unusual scrambling, and alternative syntheses of alpha,alpha-5,15-bisnaphthylporphyrins are described. Synthesis of 5,15-analogues can be achieved by employing (pentafluorophenyl)dipyrromethane or via presynthesis of a bis(dipyrromethane) derivative 22 (from bisnaphthaldehyde 12) and subsequent condensation with benzaldehyde

Synthesis and properties of mixed alkynyl-alkoxy-triphenylenes

The synthesis and liquid crystalline properties of some new multisubstituted triphenylenes are reported. The materials bear combinations of alkyne and alkoxy substituents and were designed to probe the structural factors controlling mesophase formation, type and stability in triphenylene discotics. A combination of factors contributes to mesophase stability in these systems. Compounds bearing two alkynes can support, and indeed enhance, columnar mesophase behaviour, but mesophase behaviour is completely suppressed when four or six alkynes are present. A twinned structure linked by a diacetylene bridge shows a stable nematic phase, but conversion to a saturated bridge destroys all mesophase behaviour

Functionalization of discotic liquid crystals by direct substitution into the discogen ring α-nitration of triphenylene-based discogens

It is demonstrated for the first time that discotic liquid crystals can be functionalized by direct substitution into the central ring (core) of the discogen. It is shown that hexahexyloxy-triphenylene (HAT6) can be easily nitrated to give the mono-α-nitrated product exclusively. This material, which has a discotic mesophase range between room temperature and 136°C, can be modified to give α-amino-, α-acetylamino- and α,α'-diazo-HAT6. These new materials all show enantiotropic mesophases, have permanent dipole moments and some of them are coloured. This generally applicable approach opens up a route to an enormous range of new discotic liquid crystals