Effect of magnesium chloride (2:1 electrolyte) on the aqueous solution behavior of some saccharides over the temperature range of 288.15-318.15 K: a volumetric approach

Infinite-dilution standard partial molar volumes, , for various mono-, di-, and trisaccharides, and their derivatives (methyl glycosides) at molalities ranging from 0.04 to 0.12 mol kg⁻¹ in aqueous solutions of magnesium chloride of 0.5, 1.0, 2.0, and 3.0 mol kg⁻¹, have been evaluated over a range of temperatures from 288.15 to 318.15 K by density measurements employing a vibrating-tube densimeter. These data have been utilized to determine the corresponding standard partial molar volumes of transfer, , of saccharides and methyl glycosides from water to aqueous magnesium chloride solutions. The values have been found to be positive, and their magnitudes increase with an increasing concentration of magnesium chloride in all cases. Partial molar expansion coefficients, and second derivatives thereof, have been estimated. The magnitude of values increases with an increase in temperature, indicating that hydration effects in solutions are strongly sensitive to temperature. Pair and higher order volumetric interaction coefficients (V_AB, V_ABB) have also been obtained from values by using the McMillan-Mayer theory. The various parameters have been discussed in terms of the solute (saccharide or methyl glycoside)-co-solute (magnesium chloride) interactions and are thus used to understand the mixing effects due to these interactions. These results have been compared with those earlier reported in the presence of electrolytes. An attempt is made to interpret the volumetric properties data in terms of the stereochemistry of the solutes.     

Alkyl dehydrogenation in iridium tri-cyclopentyl phosphines

The iridium cyclooctadiene complex incorporating a tricyclopentyl phosphine ligand (PCyp₃), Ir(η²:η²-C₈H₁₂)(PCyp₃)Cl, has been prepared. Removal of the chloride from this complex using in CH₂Cl₂/arene solvent results in dehydrogenation (C-H activation followed by β-H transfer) of one of the alkyl phosphine rings and formation of the complexes (X = H, F) which contain a hybrid phosphine-alkene ligand. These complexes are formed alongside another product (5-20% yield) that has been identified as , which can be prepared in high yield by an alternative, and slightly modified, route. This complex is with a minor isomer that has been tentatively identified as , which results from allylic C-H activation of cyclooctadiene. Addition of H₂ to and its isomer in arene solvent (C₆H₅X, X = F, H) forms the dihydrido η⁶-arene Ir(III) complexes . In contrast, hydrogenation in CH₂Cl₂ alone results in the formation of in which the anion is now acting as a ligand through one of its aryl rings. The fluorobenzene complex can be cleanly converted to by addition of the hydrogen acceptor tert-butylethene (tbe).     

Superoxide scavenging activity of pirfenidone-iron complex

Pirfenidone (PFD) is focused on a new anti-fibrotic drug, which can minimize lung fibrosis etc. We evaluated the superoxide () scavenging activities of PFD and the PFD-iron complex by electron spin resonance (ESR) spectroscopy, luminol-dependent chemiluminescence assay, and cytochrome c reduction assay. Firstly, we confirmed that the PFD-iron complex was formed by mixing iron chloride with threefold molar PFD, and the complex was stable in distillated water and ethanol. Secondary, the PFD-iron complex reduced the amount of produced by xanthine oxidase/hypoxanthine without inhibiting the enzyme activity. Thirdly, it also reduced the amount of released from phorbor ester-stimulated human neutrophils. PFD alone showed few such effects. These results suggest the possibility that the scavenging effect of the PFD-iron complex contributes to the anti-fibrotic action of PFD used for treating idiopathic pulmonary fibrosis.     

Crystal structures and magnetic properties of Ni-bisdithiolene complexes with decamethylmetallocenium cations

Three new compounds of formula (1), (2), and (3) have been synthesised, and structurally and magnetically characterised (dmit²⁻ = 1,3-dithiol-2-thione-4,5-dithiolato; dmid²⁻ = 1,3-dithiol-2-one-4,5-dithiolato). Their structural features and magnetic behaviours are compared with those of and . The result of this is that the interactions between the Ni(dmit)₂ units in 1 are of ferromagnetic-type, as suggested previously for . The change from acetonitrile to acetone when going from to 2 results in stronger ferromagnetic intermolecular interactions. This better cooperativity is due to a significant increase of the number of contacts between the various moieties within the . On the contrary, the inclusion of larger solvents such as benzonitrile in this type of complexes results in a totally different structural arrangement, which leads to an antiferromagnetic behaviour for 3.     

Novel structural variation of silver(I)-pyridine complexes in nitromethane as studied by X-ray absorption spectroscopy

The XAFS spectra were measured at around the Ag K-edge of the Ag(I) ion in nitromethane (NM) with a variety of concentrations of pyridine (PY). In NM without PY, the Ag(I) ion is tetrahedrally solvated by four NM molecules similar to those in most solvents. The Ag-O bond length in NM solvent is longer than that in aqueous solution, indicating the low donating ability of NM. The mono-, bis-, tris-, and tetrakis-pyridine complexes are formed in NM by the addition of PY. The EXAFS analyses reveal that the structure of the formed PY complex in NM is linear for Ag(py)(nm)⁺, linear for , triangular for , and tetrahedral for . The longer Ag-O bond length for Ag(py)(nm)⁺ than that for and the release of bound NM molecules at the formation of Ag(py)(nm)⁺ are interpreted to be due to the strong σ donating property of PY. The Ag-N bond length (220 pm) for is intermediate between 216 pm for and 228 pm for . The formation equilibria of and are analyzed on the basis of the changeover of EXAFS spectra as a function of the total concentrations of Ag⁺ and PY in NM.     

Photocatalysis of chloroform degradation by μ-dichlorotetrachlorodipalladate(II)

Unlike other chlorometallate complexes that catalyze the photodecomposition of haloalkanes through photodissociation of a chlorine atom, both and catalyze chloroform decomposition through a process that appears to involve C-H bond breakage from an excited state association complex with chloroform. This would account for the greatly retarded rate of decomposition in CDCl₃ and for the generation of CCl₄ as a side product. In chloroform, and are in slow equilibrium with each other. The rate for the conversion of - in chloroform at 23 °C obeys the expression (0.03 M⁻¹ s⁻¹) [][Cl⁻]. The equilibrium constant, K = [][Cl⁻]²/[]², was estimated to be 3 × 10⁻³ M in CHCl₃.     

NAD(P)H- and superoxide-dependent nitric oxide degradation by rat liver mitochondria

Mitochondria consume nitric oxide (NO) mainly through reaction with superoxide anion (). Here, we analyzed the sources for NO degradation by isolated rat liver mitochondria. Electron leakage from complex III and reverse electron transport to complex I accounted for -dependent NO degradation by mitochondria in the presence of a protonmotive force. Mitochondria incubated with NAD(P)H also presented intense generation and NO degradation rates that were insensitive to respiratory inhibitors and abolished after proteinase treatment. These results suggest that an outer membrane-localized NAD(P)H oxidase activity, in addition to the electron leakage from the respiratory chain, promotes -dependent NO degradation in rat liver mitochondria.     

A trade-off relationship between energetic cost and entropic cost for in vitro evolution

In this paper, we consider two complementary cost functions for the landscape exploring processes to obtain the global optimum sequence through in vitro evolution protocol: one is the entropic cost C_etp, which is based on the deviation from the uniformity of a mutant distribution in sequence space, and the other is the energetic cost C_eng, which is based on the total number of sequences to be generated and evaluated. Based on a prior knowledge about the structure of a given fitness landscapes, the conductor of the experiment can think up the efficient search algorithm (ESA), which requires the minimum number of points (=sequences) to be searched up to the global optimum. For five typical fitness landscapes, we considered their respective (putative) ESA, and based on the ESA. As a result, we found a trade-off relationship between and for every case, that is, is approximately equal to the logarithm of the volume of the sequence space. and are interpreted in terms of the information-theoretic concepts.     

Investigation into the reaction of (t-BuC5H4)2Nb(η-Te2)H with CH3Li: Hydride abstraction versus telluride methylation

The reaction of (Cp′ = t-BuC₅H₄) with CH₃Li in THF was examined by variable temperature ¹H NMR, ESR and mass spectroscopic means. From these methods it is evident that the diamagnetic compounds and as well as the paramagnetic compound form simultaneously. In the subsequent reaction of the intermediate solution with [Co₂(CO)₈] compound 4 was consumed and the compound (5) formed in good yield. Complex 5 was characterized by IR and variable temperature ¹H NMR spectroscopies. Electrochemical two-electron reduction of 1 leads, in a quasi-reversible process, to products that are not stable in solution.     

Kinetics and mechanism of the oxidation of oxalic acid by tetrachloroaurate(III) ion

The oxidation of oxalic acid by tetrachloroaurate(III) ion in 0.005 ? [HClO₄] ? 0.5 mol dm⁻³ is first order in and a fractional order in [oxalic acid], the reactive entities being AuCl₃(OH)⁻ and ions. The pseudo first-order rate, k_obs, with respect to [Au(III)], is retarded by increasing [H⁺] and [Cl⁻]. The retardation by H⁺ ion is caused by the dissociation equilibrium . A mechanism in which a substitution complex, is formed from AuCl₃(OH)⁻ and ions prior to its rate limiting disproportionation into products is suggested. The rate limiting constant, k, has been evaluated and its activation parameters are reported. The equilibrium constant K₁ for the formation of the substitution complex and its thermodynamic parameters are also reported.     

Synthesis, structure and reactions of a series of 1,2-dicyanoethylenedithiolate coordinated dimeric Mo(V) complexes

(where mnt = 1,2-dicyanoethylenedithiolate) (1), reacts with HX (X = SPh, Cl, Br) to form a series of complexes, . In acidic-alcoholic medium 1 with thiophenol yields another series of compounds, . Under similar conditions tertiary-butanol does not coordinate where a complex can only be isolated in the presence of bromide as . The use of excess of methanesulfonic acid in the presence of HSPh or HSEt facilitates methanesulfonate coordination in complexes, . All these complexes are structurally characterized by single crystal X-ray study. These complexes show pH dependent hydrolytic reaction leading to quantitative reversal to the starting complex, 1. Complexes 2a-c respond to hydrolysis in CH₂Cl₂ with the intermediate formation of EPR active molybdenum(V) species.