Characterization and properties of low-linear-density polyethylene/Typha latifolia composites

The characterization of the effects of different sizes and loadings of Typha latifolia on the tensile, thermal, and morphological properties of linear-low-density polyethylene (LLDPE)/T. latifolia composites were evaluated using tensile test, Fourier transform infrared spectroscopy, thermogravimetric analysis, and scanning electron microscopy analyses. Results indicated the tensile strength and elongation at break decreased as T. latifolia loading increased. However, T. latifolia fine size (fs) exhibited better tensile properties than coarse size at the same loading in the composite. T. latifolia (15%, fs) recorded higher thermal stability than LLDPE control and other T. latifolia loadings and sizes due to the strong interaction of T. latifolia (15%, fs) in LLDPE matrix as shown in morphology.     

cis‐Di­chloro­(di­methyl­aminomethyl­ene)­(tri­phenyl­phosphine)palladium(II) acetone solvate

The synthesis and X‐ray structural analysis of the title compound, [PdCl₂(C₃H₇N)(C₁₈H₁₅P)]·C₃H₆O, are described. The crystal structure contains discrete monomeric mol­ecules of the carbene complex and solvent mol­ecules separated by normal van der Waals distances. The Pd atom is four‐coordinate in an essentially square‐planar environment, with the chlorine ligands mutually cis; Pd—P = 2.2495 (7), Pd—Cl = 2.3508 (7) and 2.3600 (7), Pd—C 1.948 (2) and N—C(carbene) 1.274 (3) Å.     

High electrical conductivity for the partially oxidised d8 Ru–Ru bonded chain [Ru(bpy)(CO)2]n (bpy = 2,2′-bipyridine) and its wide range redox control

High, electrochemically controlled electrical conductivity (0.2–0.3 S cm^?1) was measured for the first time for the metal–metal bonded polymeric compound [Ru(bpy)(CO)₂]_n (bpy = 2,2′-bipyridine). The conductivity depended on the degree of partial oxidation of the initially zero-valent Ru to Ru^I in the chains and was found to increase by four orders of magnitude after 5% oxidative doping. Linear conductance vs. doping level dependence was found for low levels and the conductivity of films could repeatedly be switched on and off. The conduction process is ascribed to charge delocalisation on the Ru chains in analogy to that of other similar chains formed by stacking of planar transition metal d⁸ complexes.     

A hydrogen-bonded adduct containing seven-component supramolecular aggregates

The title compound is a salt, 3,6,9,16,19,22-hexaaza­tri­cyclo­[22.2.2.2^11,14]­triaconta-1(26),11(29),12,14(30),24,27-hexa­ene–3,5-di­nitro­benzoic acid–methanol (1/4/2), C₂₄H₄₂N₆⁴⁺·4C₇H₃N₂O₆⁻·2CH₄O, in which the cation lies across a centre of inversion and one of the two independent anions is positionally disordered over two sets of atom sites having equal occupancy. The components are linked by four types of N—H⃛O hydrogen bond [N⃛O 2.674 (2)–2.815 (2) Å; N—H⃛O 149–163°] and one type of O—H⃛O hydrogen bond in which the acceptor is disordered over two closely adjacent sites [O⃛O 2.67 (4) and 2.75 (4) Å; O—H⃛O 172 and 173°], forming centrosymmetric seven-component aggregates.     

Mutagenesis of morphinone reductase induces multiple reactive configurations and identifies potential ambiguity in kinetic analysis of enzyme tunneling mechanisms

We have identified multiple reactive configurations (MRCs) of an enzyme-coenzyme complex that have measurably different kinetic properties. In the complex formed between morphinone reductase (MR) and the NADH analogue 1,4,5,6-tetrahydro-NADH (NADH4) the nicotinamide moiety is restrained close to the FMN isoalloxazine ring by hydrogen bonds from Asn-189 and His-186 as determined from the X-ray crystal structure. Molecular dynamic simulations indicate that removal of one of these hydrogen bonds in the N189A MR mutant allows the nicotinamide moiety to occupy a region of configurational space not accessible in wild-type enzyme. Using stopped-flow spectroscopy, we show that reduction of the FMN cofactor by NADH in N189A MR is multiphasic, identifying at least four different reactive configurations of the MR-NADH complex. This contrasts with wild-type MR in which hydride transfer occurs by environmentally coupled tunneling in a single kinetic phase [Pudney et al. J. Am. Chem. Soc. 2006, 128, 14053-14058]. Values for primary and alpha-secondary kinetic isotope effects, and their temperature dependence, for three of the kinetic phases in the N189A MR are consistent with hydride transfer by tunneling. Our analysis enables derivation of mechanistic information concerning different reactive configurations of the same enzyme-coenzyme complex using ensemble stopped-flow methods. Implications for the interpretation from kinetic data of tunneling mechanisms in enzymes are discussed.     

Poly(diphenylacetylene)s with Electron‐Donating Alkoxy and Electron‐Withdrawing Fluoroalkyl Groups: Effect of the Substituent on Fluorescence

New poly(diphenylacetylene)s with alkoxy and fluoroalkyl groups as electron‐donating and electron‐withdrawing groups, respectively, were synthesized by using a WCl₆‐n‐Ph₄Sn catalyst. The polymer solutions emitted strong, bluish‐green lights when photo‐excited. The polymers that contained the electron‐donating alkoxy groups showed longer fluorescence‐maximum peaks when compared to the polymers that contained the electron‐withdrawing fluoroalkyl groups. However, such an effect of the substituent on the absorption property was not clearly seen. The emission bands of the solid films did not show any significant red shift, relative to that of the dilute solution.

     

Origin of the Correlation of the Rate Constant of Substrate Hydroxylation by Nonheme Iron(IV)–oxo Complexes with the Bond‐Dissociation Energy of the C?H Bond of the Substrate

A series of hydrogen‐abstraction barriers of a nonheme iron(IV)–oxo oxidant mimicking the active species of taurine/α‐ketoglutarate dioxygenase (TauD) are rationalized by using a valence‐bond curve‐crossing diagram (see figure). It is shown that the barriers correlate with the strength of the C? H bond. Furthermore, electronic differences explain the differences between nonheme and heme iron(IV)–oxo hydrogen‐abstraction barriers.

     

The origins of the colours of yellow,green and blue sapphires

The absorption spectra of natural yellow sapphires are shown to be due to single Fe³⁺ and Fe³⁺  O²⁻  Fe³⁺ pairs, with the latter dominant. Blue and green sapphires have spectra dominated by Fe³⁺  O²⁻  Ti⁴⁺ and Fe²⁺  O²⁻  Fe³⁺ pairs.