Macromolecular design and application using Mn2(CO)10‐based visible light photoinitiating systems

The environmentally friendly Mn₂(CO)₁₀‐based visible light photoinitiating system is a powerful method for the preparation of linear and crosslinked polymeric structures. From a practical point of view, the most important feature of this initiating system is its optical characteristics in the visible range with high quantum yield and good solubility properties. This photoinitiating system is applicable for a variety of monomers that can be polymerized via either radical or cationic mechanisms. Various complex macromolecular structures such as telechelic polymers, block and graft copolymers, polymer networks and surface modifications can be simply prepared by using halogenated precursors. This photoinitiating system is also combined with controlled radical polymerization techniques providing a mild and efficient method for polymer synthesis. © 2016 Society of Chemical Industry     

Poly(butyleneterephtalate) photolysis and photooxidation : Identification of the ir-absorbing products

Irradiations (λ≥300 nm) of poly(butyleneterphtalate) films were carried out in both vacum and air. Photoproducts were investigated by FTIR spectroscopy, chemical derivatization reactions and physical treatments. The repartition of photoproducts in the polymer was shown to be heterogeneous. A scheme accounting for the main routes of PBT photolysis was found on the basis of photoproducts identification. Most of oxidation products were analogous to vacum photolysis species; the mechanism of photooxidation proposed implied both pure photolytical processes and a photo-induced oxidation route.     

Metal-assisted syntheses and NMR characterization of square-planar Pd(II) and Pt(II) complexes with tridentate nitrogen-donor chelate ligands

The complexes [PtCl(NNN^H)](OTf) (1^H), [PdCl(NNN^H)](OTf) (2^H), [PdCl(NNN^Me)](OTf) (2^Me), [PdMe(NNN^H)](OTf) (3^H), [PdMe(NNN^Me)](OTf) (3^Me) and [PdMe(NNN^Ph)](OTf) (3^Ph) {NNN^H = (pyridin-2-ylmethylene)-quinolin-8-yl-amine; NNN^Me = (1-pyridin-2-yl-ethylidene)-quinolin-8-yl-amine; NNN^Ph = (phenyl-pyridin-2-yl-methylene)-quinolin-8-yl-amine} were prepared by reacting a stoichiometric methanolic mixture of 8-aminoquinoline and an ortho-substituted aldehydo- or keto-pyridine {2-pyridinecarboxaldehyde, 2-acetylpyridine or 2-benzoylpyridine} with the proper Pt(II) or Pd(II) precursor in methanol. In the case of the 2 ^Me derivative, the addition of a stoichiometric amount of a Ag(I) salt to the reaction mixture was necessary to obtain the desired product. Information about the formation of these complexes are reported. In particular, NMR experiments allowed to observe the different reactivity of 8-aminoquinoline towards aldehydo- and keto-pyridines and the formation of the emiaminal ligand pyridin-2-yl-(quinolin-8-ylamino)-methanol NNN(H₂O)^H 4. Finally, the methanesulphonato-complex [Pd(η¹-OSO₂CH₃)(NNN^Me)](OTf) (5^Me) was obtained by reacting the chloro-derivative 2^Me with a stoichiometric amount of AgSO₃CH₃ in nitromethane.     

流场对MEC生物阴极CO2还原性能与产物的影响

针对微生物电解池 （microbial electrolysis cell,MEC）CO₂还原过程阴极CO₂还原速率低的问题,本文通过改变阴极室的流场环境,探究流场对生物阴极启动、运行、产物及功能微生物的影响,阐明MEC生物阴极CO₂还原性能、产物转化、微生物群落对流场的响应关系。结果表明,流场不仅增强了生物阴极还原CO₂能力（电子消耗量提高了10%,其中CO₂产乙酸途径消耗电子量提高了30%）,还使生物阴极的CO₂还原途径由启动阶段的CO₂还原产甲烷转变为运行阶段产乙酸。高通量分析表明,流场改变了生物阴极和阴极液的微生物群落结构,使阴极生物膜的嗜氢型产甲烷菌（Methanobacterium）向嗜乙酸型产甲烷菌（Methanosaeta）主导的群落演变。产乙酸菌群落（Petrimonas、Candidatus_Caldatribacterium）丰度较对照组提高了3.8%,在CO₂产乙酸过程中起到重要作用。本研究可为MEC还原CO₂产乙酸的定向调控研究提供理论和技术支撑。     

Effect of CO2 on crystallization kinetics of poly(ethylene terephthalate)

The effect of CO₂ on the isothermal crystallization kinetics of poly(ethylene terephthalate), PET, was investigated using a high‐pressure differential scanning calorimeter (DSC), which performed calorimetric measurements while keeping the polymer in contact with presurized CO₂. It was found that the crystallization rate followed the Avrami equation with values of the crystallization kinetic constant dependent on the crystallization temperature and concentration of CO₂ in PET. The presence of CO₂ in the PET increased its overall crystallization rate. CO₂ also decreased the glass transition temperature, T_g, and the melting temperature, T_m. As a result, the observed changes in crystallization rate caused by CO₂ can be qualitatively predicted from the magnitude of T_g depression and that of the equilibrium melting temperature, T_m⁰.     

Effect of pressure on CO2 transport in poly(ethylene terephthalate)

The CO₂ solubility, permeability, and diffusion time lag in poly(ethylene terephthalate) are reported at 35° and 65°C for CO₂ pressures ranging from 0.07 to 20 atm. The subatmospheric time lag and permeability measurements were made with a glass system at North Carolina State University, while the measurements between 1 and 20 atmospheres, using an identical polymer sample, were made at The University of Texas with a metal system capable of tolerating gauge pressures up to 30 atm. The measured solubility, permeability, and time lag all show strong deviations from the well-known simple expressions for gases in rubbery polymers. The solubility isotherm is non-linear in pressure, and both θ and P are quite pressure dependent, with each showing tendencies to approach low and high pressure asymptotic limits. These effects decrease as temperature increases and would be expected to disappear at or near the glass transition where the amorphous regions become rubbery. The importance of reporting the pressure levels used in transport measurements is emphasized for gas/glassy polymer systems where transport process do not follow linear laws.     

A rod-spacer mixed ligands MOF [Mn3(HCOO)2(D-cam)2(DMF)2]n as coating material for gas chromatography capillary column

The interest in metal-organic frameworks (MOFs) is rapidly expanding because of their fascinating architectures and intriguing topologies which allowed for potential applications in gas storage, separation, heterogeneous catalysis, and several other areas. As suitable chromatographic separation media, several MOFs have been employed as stationary phase for gas chromatography and high-performance liquid chromatography. In this work we report the use of a mixed ligands rod-spacer MOF [Mn₃(HCOO)₂(D-cam)₂(DMF)₂]_n as coating material for capillary column of gas chromatographic separation of a series of biochemical important compounds having linear alkyl hydrocarbon (aldehyde, alcohol and ester), aromatic hydrocarbon with two phenyls (ether, ester and ester with alcohol) and aromatic hydrocarbon (ester, ester with amino and two esters). The mixture of functional ligands, good thermal and chemical stabilities and host-guest interaction sites of the MOF are attributes to the good efficiency in gas chromatographic separation.     

Effect of hydrolysis products and Mg2+, Mn2+ and Ca2+ ions on whey lactose hydrolysis and β‐galactosidase stability

BACKGROUND: Enzyme inhibition is one of the constraints of reactions catalysed by enzymes, and information is required on the inhibition mechanisms that affect the process yield. Therefore the aim of the present study was to investigate the effect of hydrolysis products and ions on the hydrolysis of lactose recovered from whey and enzyme inactivation during the reaction. The experiments were carried out in 250 mL of 25 mmol L^?1 phosphate buffer solution using β‐galactosidase from Kluyveromyces marxianus lactis in a batch reactor system. RESULTS : The degree of lactose hydrolysis (%) and the residual enzyme activity (%) in the presence and absence of lactose over time were investigated versus hydrolysate amount, glucose and galactose concentrations and Mg²⁺, Mn²⁺ and Ca²⁺ ion concentrations. The hydrolysis degree decreased with the addition of all hydrolysis products, as enzyme inhibition occurred. The residual enzyme activity increased with the addition of hydrolysate and glucose but decreased with the addition of galactose. It was observed that Mn²⁺ and Mg²⁺ ions activated the enzyme. It was also found that the hydrolysis degree was not affected by the addition of Mn²⁺ ions. On the other hand, the hydrolysis degree decreased with the addition of Ca²⁺ ions, as the enzyme was inactivated. CONCLUSION: Evaluation of the experimental data showed that both β‐galactosidase activity and lactose hydrolysis were affected by the addition of hydrolysis products and ions. Moreover, mathematical models proposed to predict the residual lactose concentration and residual enzyme activity were confirmed by the experimental results. Copyright © 2008 Society of Chemical Industry     

Zirconium complexes of amino(polyphenolic) ligands and their hydrolytic stability

Three amino(polyphenolic) ligands, N,N′-bis(5-tert-butyl-2-hydroxybenzyl)-1,2-diaminoethane 1, tris(5-tert-butyl-2-hydroxy-3-methylbenzyl)amine 3, its 3-chloro analogue 4 and their Zr^IV complexes have been synthesised. The crystal structure of the Zr^IV complex of tris(5-tert-butyl-3-chloro-2-hydroxybenzyl)amine, shows this to be [Zr(4-2H)₂] in which both ligands exists in a zwitterionic form with one alkylammonium and three phenolate groups. The complexes are stable in a two phase, chloroform/water, system at high pH, but the zirconium is stripped at pH < 2.5. The pH value needed to strip 50% of the Zr^IV from the complex [Zr(1-4H)] of the tetraphenolic ligand is ∼2.0 whilst the complexes [Zr(3-2H)₂] and [Zr(4-2H)₂] of the triphenolic ligands are slightly more stable with pH_1/2 values of ∼1.4. We were unable to use the ligands to extract zirconium from low pH aqueous zirconium oxychloride solutions into an organic phase under a variety of conditions.     

Effect of phase transfer catalyst on CO substitution of Mo(CO)6

The effect of Q⁺ OH^- was studied, which is formed in NaOH solution used for anion exchange with PTC, on CO substitution of molybdenum hexacarbonyl complex by strong electron donating ligand, 2,2’-bipyridine. The change of product yield was discussed according to the amount and types of solvent and PTC, their compositions, reaction temperature and time, and different cation and anion of PTC.     

How the electronic and steric properties of the ligand can determine the stability of the asymmetric dinuclear carbonyl-phosphite Rh(0) complex (CO)2(P(O-o-tBuPh)3)Rh-Rh(P(O-o-tBuPh)3)(CO)3

Theoretical studies have shown that the low basicity of the phosphite ligand P(O-o-^tBuPh)₃ in the Rh(0) complex (CO)₂(P(O-o-^tBuPh)₃)Rh-Rh(P(O-o-^tBuPh)₃)(CO)₃ favours the non-bridged structure over the bridged one, but is not responsible for the absence of the expected sixth carbonyl in the structure. The steric effects of the bulky ligand play an important role in the unusual stability of the asymmetric complex.     

Vapour phase deposition and thermal decarbonylation of Re2(CO)10 on gamma-alumina: infrared studies

Dirheniumdecacarbonyl vacuum sublimed onto mesoporous -alumina forms Lewis type adducts where an axial CO group is coordinated to an A1³⁺ ion at the metal oxide surface, as revealed by IR spectroscopy. Vacuum heating of the surface adduct at 773 K brings about decarbonylation, with intermediate formation of a surface-bound mononuclear tricarbonyl which was completely decarbonylated on prolonged heating at the same temperature. The resulting material strongly chemisorbs CO to yield mainly a surface-bound pentacarbonyl species. This suggests that the supported metal remains primarily in a zero-valent and well dispersed state.     

超声波在电解氧化Mn(Ⅱ)为Mn(Ⅲ)中的应用研究

以Pb基PbO2为阳极、Pb为阴极,超声电氧化Mn(Ⅱ)生成Mn(Ⅲ),比较了3种不同超声波频率下的电流效率,探讨了超声电解的机理,获得了超声电氧化的最佳反应条件。当电流密度为0.09 A/cm2,温度为20℃,硫酸锰浓度为0.4 mol/L,硫酸浓度为5.5 mol/L,电解时间为4100 s,超声波频率为59 kHz,超声波输出功率175 W时,电解氧化Mn(Ⅱ)为Mn(Ⅲ)的电流效率可达到84.79%。实验发现,施加超声波于电解过程,可保持电极表面活性,加快传质速率,降低氧化电位,提高电流效率,且较高频率的超声波具有更优的性能。     

Effects of potassium on the chemisorption of CO2 and CO on the Mo2C/Mo(100) surface

The interaction of CO₂ with K-promoted Mo₂C/Mo(100) has been studied with high-resolution electron energy loss spectroscopy, work function measurements and temperature-programmed desorption. Pre-adsorbed potassium dramatically affects the adsorption behavior of CO₂ on the Mo₂C/Mo(100) surface. It increases the rate of adsorption, the binding energy of CO₂ and it induces the dissociation of CO₂ through the formation of negatively charged CO₂. Potassium adatoms also promote the dissociation of adsorbed CO over Mo₂C. This revised version was published online in July 2006 with corrections to the Cover Date.     

The metal-chain complexes (X)[Os(CO)3(CNBut)]3Mn(CO)5 (X=Cl,Br, I)

In what is a new metal-chain forming reaction, (X)[Os(CO)₃(CNBu^t)]₃Mn(CO)₅ (X=Cl, Br, I) complexes have been prepared by the successive addition of Os(CO)₄(CNBu^t) to Mn(CO)₅(X) in hexane. The crystal structure of the iodo derivative reveals it to contain an approximately linear Os₃ Mn chain of metal atoms.     

Methanol Synthesis on Potassium-Modified Cu(100) from CO + H2 and CO + CO2 + H2

Methanol cannot be produced from CO + H₂ on a clean copper surface, but a promotional effect of potassium on methanol synthesis from mixtures of CO + H₂ and CO + CO₂ + H₂ at a total pressure of 1.5 bar on a Cu(100) surface is shown in this work. The experiments are performed in a UHV chamber connected with a high-pressure cell (HPC). The methanol produced is measured with a gas chromatograph and the surface is characterized with surface science techniques. The results show that potassium is a promoter for the methanol synthesis from CO + H₂, and that the influence of CO₂ is negligible. Investigation of the post-reaction surface with TPD indicates that potassium carbonate is present and plays an important role. The activation energy is determined as 42 ± 3 kJ/mol for methanol synthesis on K/Cu(100) from CO + H₂.