New osmium cluster compounds containing the heterocyclic ligand 2,3-bis-(diphenylphosphino)quinoxaline (dppq): Ligand isomerization and crystal structures of dppq, the isomeric clusters Os3(CO)10(dppq), and HOs3(CO)9[μ-2,3-PhP(η-C6H4)(Ph2P)quinoxaline]

Treatment of the labile cluster 1,2-Os₃(CO)₁₀(MeCN)₂ (1) with the diphosphine ligand 2,3-bis(diphenylphosphino)quinoxaline (dppq) at room temperature affords 1,2-Os₃(CO)₁₀(dppq) (2b) as the kinetic product of ligand substitution in 84% yield. 2b isomerizes to the thermodynamically more stable dppq-chelated cluster 1,1-Os₃(CO)₁₀(dppq) (2c) as the sole observable product under CO at temperatures below 358 K. The kinetics for the conversion of 2b → 2c have been investigated by NMR spectroscopy in CDCl₃ over the temperature range 323-353 K, and the reaction was found to exhibit a rate law that is first order in 2b. The calculated activation parameters [ΔH^≠ = 25.4(4) kcal/mol; ΔS^≠ = −3(1) eu] support an intramolecular isomerization scenario, one that involves the migration of phosphine and CO groups about the cluster polyhedron. The disposition of the dppq ligand in the isomeric Os₃(CO)₁₀(dppq) clusters has been established by X-ray crystallography and ³¹P NMR spectroscopy. Photolysis of 2c at 366 nm leads to CO loss and ortho metalation of one of the aryl groups on the Ph₂P moiety to furnish the hydride cluster HOs₃(CO)₉[μ-PhP(η¹-C₆H₄)(Ph₂P)quinoxaline] (3). The isomerization behavior exhibited by 2b follows that of related diphosphine-substituted Os₃ clusters prepared by us.     

Redox-induced η5 ⇔ η3 haptotropy of the fluorenyl ligand in 9-substituted η5-fluorenylmanganesetricarbonyl complexes

It has been shown by cyclic voltammetry in THF within the –90 to 40 °C temperature range that fluorenyl (⁵-9-R-C₁₃H₈)Mn(CO)₃ complexes (R=Bu^t (3) and Ph (4)) undergo two-electron reduction to form allyl type [(³-9-R-C₁₃H₈)Mn(CO)₃]^2– dianions as final products. At low temperatures complexes3 and4 are reduced in two one-electron steps according to the EEC-scheme. The first step is reversible and corresponds to the formation of 19-radical anions 3^–. and 4^–.. TheE ⁰ values for redox pairs3 ^0/–. and4 ^0/–. are –1.88 and –1.73 V, respectively. The further reduction of radical anions3 ^–. and4 ^–. at more negative potentials is accompanied by fast ^{5 3} haptocoordination of the fluorenyl ligand to form 18-dianions [(³-9-R-C₁₃H₈)Mn(CO)₃]^2–. These dianions obtained by the reduction of complexes3 and4 by the radical anion of pyrene are stable at –80 °C and are characterized by their IR spectra. At room temperature the ^{5 3} hapticity change is a fast and reversible process occurring at the step of 19-radical anions3 ^–. and4 ^–. and leading to the electron deficient 17-species [(³-9-R-C₁₃H₈)Mn(CO)₃]^–., which are reduced easier than the initial complexes. As a result, complexes3 and4 are reduced to the corresponding dianions [(³-9-R-C₁₃H₈)Mn(CO)₃]^2– at room temperature in one reversible two-electron step according to the ECE-scheme. Reactivities of 19e^–-species of the isomeric ⁵- and ⁶-fluorenylmanganesetricarbonyl complexes are compared.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1347–1353, July, 1995.The work was financially supported by the Russian Foundation for Basic Research (Project No. 93-03-05209) and the International Science Foundation (Grant No. REV 000).     

Application of enzyme-field effect transistor sensor arrays as detectors in a flow-injection analysis system for simultaneous monitoring of medium components. Part II. Monitoring of cultivation processes

Glucose, maltose, sucrose, lactose, ethanol and urea concentrations were monitored simultaneously during the cultivation of Escherichia coli and Saccharomyces cerevisiae by means of enzyme field effect transistors (EnFETs) applying glucose dehydrogenase (GDH), maltase (MAL)/GDH, invertase (INV)/GDH, β-galactosidase (β-GAL)/galactosedehydrogenase (GALDH), alcoholdehydrogenase (ADH)/aldehydedehydrogenase (ALDH), and urease. These enzymes were (co)immobilized on the pH sensitive gates of an eight-FET array. The FET array was integrated in a commercial FIA system.     

Simultaneous measurement of glucose and glutamine in aqueous solutions by near infrared spectroscopy

A method is described for measuring the concentrations of both glucose and glutamine in binary mixtures from near infrared (NIR) absorption spectra. Spectra are collected over the range from 5000–4000/cm (2.0–2.5μm) with a 1-mm optical path length. Glucose absorbance features at 4710, 4400, and 4300/cm and glutamine features at 4700, 4580, and 4390/cm provide the analytical information required for the measurement. Multivariate calibration models are generated by using partial least squares (PLS) regression alone and PLS regression combined with a preprocessing digital Fourier filtering step. The ideal number of PLS factors and spectral range are identified separately for each analyte. In addition, the optimum Fourier filter parameters are established for both compounds. The best overall analytical performance is obtained by combining Fourier filtering and PLS regression. Glucose measurements are established over the concentration range from 1.66–59.91 mM, with a standard error of prediction (SEP) of 0.32 mM and a mean percent error of 1.84%. Glutamine can be measured over the concentration range from 1.10–30.65 mM with a SEP of 0.75 mM and a mean percent error of 6.67%. These results demonstrate the analytical utility of NIR spectroscopy for monitoring glucose and glutamine levels in mammalian and insect cell cultures.     

微透析液中葡萄糖的液相色谱—电化学测定

文介绍了一种灵敏测定大白鼠皮下微透析液中葡萄糖的液相色谱－电化学分析方法。本法用柱后葡萄糖氧化酶反应器将色谱分析柱中分离出的葡萄糖转化成过氧化氢，再用过氧化物酶电极检测生成的过氧化氢。     

载体的晶化对Ni/WO3-ZrO2催化剂结构及催化正庚烷异构化活性的影响

采用XRD、BET、IR、SEM、NH3-TPD方法对以无定形Zr(OH)4和已晶化的ZrO2为载体制备的Ni-WO3/ZrO2催化剂进行了表征,考察了载体晶化对催化剂结构、酸性及催化性能的影响。结果表明,载体晶化减弱了W与Zr间的相互作用,抑制了四方相ZrO2的生成,减少了催化剂上强酸中心的数目,从而降低了Pt-WO3/ZrO2催化剂上正庚烷异构化反应活性.     

3-[2-(Boronophenyl)benzoxazol-5-yl]alanine derivatives as fluorescent monosaccharide sensors

Two 3-[2-(boronophenyl)benzoxazol-5-yl]alanine derivatives were synthesized and their potential application as fluorescent monosaccharide sensors was studied. It was found that both non-proteinogenic amino acids bound glucose and fructose at physiological pH, however, the latter much stronger. As a result they are selective sensors for fructose. Moreover, one of them (3-[2-(3-boronophenyl)benzoxazol-5-yl]alanine methyl ester) can be used to quickly distinguish, which monosaccharide is present in the solution because of the different character of fluorescence intensity changes (increase in the presence of fructose and decrease in the presence of glucose).     

The effects of alkali metal(Na+,K+) on the exchange degree of Hβ zeolite and the catalytic properties of the alkalized zeolites

The effects of alkali metals (Na+,K+) on the exchange degree of Hβ zeolite under different conditions and the conversion of α(or β)-methylnaphthalene over the alkalized zeolites were studied. The results showed that the H+ of Hβ zeolite is totally replaced by the Na+ of NaCl solution, while partially exchanged by the K+ of KC1 solution, there is an exchange equilibrium between the H+ and K+ for Hβ zeolite (Si/Al=17.23) and the value of equilibrium is 88.39. The exchange degree also increases with increasing the Si/Al of the samples. It was suggested that these resluts are attributed to the electrostatic field in the pore of Hβ zeolite and the nature of zeolite and the properties of alkali metal. The isomerization of α(or β)-methylnaphthalene is the main reaction over the samples and it is more favour on the proper acid-base sites of KHβ zeolite.     

Mechanism of the molecular hysteresis

The redox behavior in acetone solution of (1,5-dithiacyclooctane 1-oxide)bis(pentaammineruthenium(II)) has been characterized, where the concept of “molecular hysteresis” is presented. Detailed thermodynamics for the complex are studied, in which intramolecular electron transfer rates for Ru³⁺OS/Ru²⁺→Ru²⁺SO/Ru³⁺ were determined as 0.12 sec^?1 and 0.055 sec^?1. The molecular hysteresis consists of two important factors: isomerizations for the sulfoxideruthenium complexes and the slow intramolecular electron transfer in the complex; both are examined. Isomerization rates for Ru³⁺S→O and Ru²⁺O→S determined range from 0.4 to 5000 sec^?1 and from 0.7 to 16 sec^?1, respectively, for [Ru(NH₃)₅(sulfoxide)]^2+/3+. A mechanism for the slow electron transfer in the complex is also presented. Features of molecular hysteresis are discussed.     

Multifunctionality in spin crossover materials

One of the most important trends in the spin crossover (SCO) field is focused on the synthesis of new molecule-based functional materials in which the SCO properties may be combined with other physical or chemical properties in a synergic fashion. The current stage of investigations regarding interplay and synergic effects between SCO, magnetic coupling, liquid crystalline properties, host-guest interactions, non-linear optical properties, electrical conductivity, and ligand isomerization is highlighted and discussed.