A series of novel hexafluorophosphate salts, based on N,N¾-dialkylimidazolium and substituted N-alkylpyridinium cations, display liquid crystalline behaviour at temperatures above their melting point. The temperature range over which liquid crystalline behaviour is observed increases markedly with increasing alkyl chain length. Alkyl substitution at the 3- and 4-positions on the pyridinium ring results in a decrease in the melting point compared with the equivalent unsubstituted salt, but also leads to a large decrease in the tendency towards liquid crystalline behaviour (or mesogenicity). The salts prepared are fully characterised using a wide variety of techniques, including NMR and IR spectroscopy, DSC, and single crystal X-ray diffraction in the case of 1-dodecyl-3-methylimidazolium hexafluorophosphate. The effect of preparing mixtures containing different proportions of two cations is also reported

The last decade has witnessed drastic improvements of the electronic properties, environmental and operational stability, and processibility of organic semiconductors (OSCs). [1,2] Designing new materials with high carrier mobilities, μ, remains one of the main research objectives to enable faster operation and lower power consumption of circuits and addressing of advanced liquid crystal and organic lightemitting diode displays. [1,3] Yet despite exploring a wide range of material systems, charge carrier mobilities in excess of 10 cm 2 V −1 s −1 have only been achieved in very few molecular semiconductors and highly aligned polymers. [4][5][6] At present, despite significant general advances in the comprehension of transport physics, a Molecular vibrations play a critical role in the charge transport properties of weakly van der Waals bonded organic semiconductors. To understand which specific phonon modes contribute most strongly to the electron-phonon coupling and ensuing thermal energetic disorder in some of the most widely studied high-mobility molecular semiconductors, state-of-the-art quantum mechanical simulations of the vibrational modes and the ensuing electronphonon coupling constants are combined with experimental measurements of the low-frequency vibrations using inelastic neutron scattering and terahertz time-domain spectroscopy. In this way, the long-axis sliding motion is identified as a "killer" phonon mode, which in some molecules contributes more than 80% to the total thermal disorder. Based on this insight, a way to rationalize mobility trends between different materials and derive important molecular design guidelines for new high-mobility molecular semiconductors is suggested.

The synthesis of a new ligand, hydrotris(methimazolyl)borate, a soft analogue of hydrotris(pyrazolyl)borate, is reported; to demonstrate the coordination chemistry of this novel ligand, complexes of CuI and ZnII are prepared and characterised

Detailed kinetic studies of the reaction of a model Ni 0 complex with a range of aryl electrophiles have been conducted. The reactions proceed via a fast ligand exchange preequilibrium, followed by oxidative addition to produce either [Ni I X(dppf)] (and biaryl) or [Ni II (Ar)X(dppf)]; the ortho substituent of the aryl halide determines selectivity between these possibilities. A reactivity scale is presented in which a range of substrates is quantitatively ranked in order of the rate at which they undergo oxidative addition. The rate of oxidative addition is loosely correlated to conversion in prototypical cross-coupling reactions. Substrates that lead to Ni I products in kinetic experiments produce more homocoupling products under catalytic conditions.

Two crystal structures of 2-4-6 trinitrotoluene (TNT) are given, the monoclinic form (a 0 = 1.49113 (1) nm, b 0 = 0.60340 (1) nm, c 0 = 2.08815(3) nm, β = 110.365 (1)°, V = 1.76137 (4) nm3, space group = P21/a, T = 100 K) and the orthorhombic form (a 0 = 1.4910 (2) nm, b 0 = 0.6031 (2) nm, c 0 = 1.9680 (4) nm, V = 1.7706 (7) nm3, space group = Pca21, T = 123 K). Of these two forms, the most stable is the monoclinic and the less stable is the orthorhombic form. These two polymorphs are shown to be orientational, rather than configurational in character. Due to their restricted molecular motifs, no strong hydrogen bonding exists and the crystalline form is dominated by van der Waals type forces. The two structures are shown to be closely related and an analysis of the two structures shows that they are effectively large scale polytypes. Calorimetric studies show that the two polymorphs are monotropic and that the enthalpy of transformation is very low, concurring with the similarity shown by the diffraction data and calculated lattice energies. The thermal expansion coefficients are defined, and it is shown that both polymorphs have similar thermal expansions.