Aggregation behavior of acrylamide/2-phenoxyethyl acrylate and its interaction with sodium dodecyl sulfate in aqueous solution studied by proton 1D and 2D NMR

¹H NMR self-diffusion coefficient, spin-lattice relaxation time, spin-spin relaxation time, and two-dimensional nuclear Overhauser enhancement (2D NOESY) measurements have been used to study the association behavior of a novel hydrophobically associating copolymer composed of acrylamide (AM) and a small amount of 2-phenoxyethyl acrylate (POEA), and its interaction with the anionic surfactant sodium dodecyl sulfate (SDS). Three sets of copolymers with approximately the same composition but with different hydrophobic POEA contents were investigated. The POEA contents for these copolymers were about 1.41, 1.03, and 0.56 mol% respectively, as validated by ¹H NMR spectra. Self-diffusion coefficient measurements show that the aggregation process occurs in a relative narrow concentration range and the critical association concentrations (cacs), of these copolymers are within this narrow concentration range, which are in agreement with those measured by viscosity measurements (6 g L^–1). Above this concentration, the hydrophobic POEA moieties are found to associate and possibly build a transitory three-dimensional network along the polyacrylamide (PAM) backbones, which induces a strong decrease in NMR parameters including self-diffusion coefficients and relaxation times. The surfactant SDS showed a significant interaction with the copolymer in the dilute solution. Addition of SDS resulted in the binding of SDS on copolymer POEA-PAM segments and reinforced the interchain transient network formation of copolymer at a concentration below its cac. In the SDS/POEA-PAM mixed systems, the hydrophobic methylene groups of the SDS molecules were preferentially located in the vicinity of the phenoxy groups of the POEA hydrophobes.     

烯烃的有机催化不对称环氧化研究进展及催化剂设计

介绍了用氧杂氮杂环丙烷、手性亚胺盐、手性酮、手性胺为催化剂的烯烃有机催化不对称环氧化反应,对各种体系催化机理进行介绍,并就手性催化剂的设计提出了构想.     

配合物[Cu(NPA)2(Im)2(H2O)]·H2O的合成、晶体结构及电化学性质

铜是生物体内必需的微量元素,是一些重要酶的活性中心,其配合物在生命体系有着特殊的生物活性和催化作用[1,2]。铜的配合物由于具有特殊的磁     

Synthesis and characterization of reduced heme and heme/copper carbonmonoxy species

Carbon monoxide readily binds to heme and copper proteins, acting as a competitive inhibitor of dioxygen. As such, CO serves as a probe of protein metal active sites. In our ongoing efforts to mimic the active site of cytochrome c oxidase, reactivity toward carbon monoxide offers a unique opportunity to gain insight into the binding and spectroscopic characteristics of synthetic model compounds. In this paper, we report the synthesis and characterization of CO-adducts of ((5/6)L)Fe(II), [((5/6)L)Fe(II)...Cu(I)](B(C(6)F(5))(4)), and [(TMPA)Cu(I)(CH(3)CN)](B(C(6)F(5))(4)), where TMPA = tris(2-pyridylmethyl)amine and (5/6)L = a tetraarylporphyrinate tethered in either the 5-position ((5)L) or 6-position ((6)L) to a TMPA copper binding moiety. Reaction of ((5/6)L)Fe(II) [in THF (293 K): UV-vis 424 (Soret), 543-544 nm; (1)H NMR delta(pyrrole) 52-59 ppm (4 peaks); (2)H NMR (from ((5)L-d(8))Fe(II)) delta(pyrrole) 53.3, 54.5, 55.8, 56.4 ppm] with CO in solution at RT yielded ((5/6)L)Fe(II)-CO [in THF (293 K): UV-vis 413-414 (Soret), 532-533 nm; IR nu(CO)(Fe) 1976-1978 cm(-1); (1)H NMR delta(pyrrole) 8.8 ppm; (2)H NMR (from ((5)L-d(8))Fe(II)-CO) delta(pyrrole) 8.9 ppm; (13)C NMR delta((CO)Fe) 206.8-207.1 ppm (2 peaks)]. Experiments repeated in acetonitrile, acetone, toluene, and dichloromethane showed similar spectroscopic data. Binding of CO resulted in a change from five-coordinate, high-spin Fe(II) to six-coordinate, low-spin Fe(II), as evidenced by the upfield shift of the pyrrole resonances to the diamagnetic region ((1)H and (2)H NMR spectra). Addition of CO to [((5/6)L)Fe(II)...Cu(I)](B(C(6)F(5))(4)) [in THF (293 K): UV-vis ((6)L only) 424 (Soret), 546 nm; (1)H NMR delta(pyrrole) 54-59 ppm (multiple peaks); (2)H NMR (from [((5)L-d(8))Fe(II).Cu(I)](B(C(6)F(5))(4))) delta(pyrrole) 53.4 ppm (br)] gave the bis-carbonyl adduct [((5/6)L)Fe(II)-CO...Cu(I)-CO](B(C(6)F(5))(4)) [in THF (293 K): UV-vis ((6)L only) 413 (Soret), 532 nm; IR nu(CO)(Fe) 1971-1973 cm(-1), nu(CO)(Cu) 2091-2093 cm(-1), approximately 2070(sh) cm(-1); (1)H NMR delta(pyrrole) 8.7-8.9 ppm; (2)H NMR (from [((5)L-d(8))Fe(II)-CO...Cu(I)-CO](B(C(6)F(5))(4))) delta(pyrrole) 8.9 ppm; (13)C NMR delta((CO)Fe) 206.8-208.1 ppm (2 peaks), delta((CO)Cu) 172.4 ((5)L), 178.2 ((6)L) ppm]. Experiments in acetonitrile, acetone, and toluene exhibited spectral features similar to those reported. The [((5/6)L)Fe(II)-CO.Cu(I)-CO](B(C(6)F(5))(4)) compounds yielded (CO)(Fe) spectra analogous to those seen for ((5/6)L)Fe(II)-CO and (CO)(Cu) spectra similar to those seen for [(TMPA)Cu(I)-CO](B(C(6)F(5))(4)) [in THF (293 K): IR nu(CO)(Cu) 2091 cm(-1), approximately 2070(sh) cm(-1); (13)C NMR delta((CO)Cu) 180.3 ppm]. Additional IR studies were performed in which the [((5)L)Fe(II)-CO...Cu(I)-CO](B(C(6)F(5))(4)) in solution was bubbled with argon in an attempt to generate the iron-only mono-carbonyl [((5)L)Fe(II)-CO.Cu(I)](B(C(6)F(5))(4)) species; in coordinating solvent or with axial base present, decreases in characteristic IR-band intensities revealed complete loss of CO from copper and variable loss of CO from the heme.     

The Second Dissociation Constant of Carbonic Acid in Ethanol–Water Mixtures from 5 to 45°C

The determination of the second dissociation constant of carbonic acid K ₂ in 5, 15, and 25 mass% ethanol—water mixed solvents has been made using cell of the type:

Tuning copper-dioxygen reactivity and exogenous substrate oxidations via alterations in ligand electronics

Copper(I)-dioxygen adducts are important in biological and industrial processes. For the first time we explore the relationship between ligand electronics, CuI-O2 adduct formation and exogenous substrate reactivity. The copper(I) complexes [CuI(R-MePY2)]+ (1R, where R = Cl, H, MeO, Me2N) were prepared; where R-MePY2 are 4-pyridyl substituted bis[2-(2-pyridyl)ethyl]methylamine chelates. Both the redox potential of 1R (ranging from E1/2 = -270 mV for 1Cl to -440 mV for 1MeN vs FeCp2/FeCp2+) and nuCO of the CO adducts of 1R (ranging from 2093 cm-1 for 1Cl-CO to 2075 cm-1 for 1Me2N-CO) display modest but expected systematic shifts. Dioxygen readily reacts with 1H, 1MeO, and 1Me2N, forming the side-on peroxo-CuII2 complexes [{CuII(R-MePY2)}2(O2)]2+ (2R, also containing some bis-mu-oxo-CuIII2 isomer), but there is no reaction with 1Cl. Stopped-flow studies in dichloromethane show that the formation of 2Me2N from dioxygen and 1Me2N proceeds with a k = 8.2(6) x 104 M-2 s-1 (183 K, DeltaH = -20.3(6) kJ mol-1, DeltaS = -219(3) J mol-1 K-1). Solutions of 2R readily oxidize exogenous substrates (9,10-dihydroanthracene --> anthracene, tetrahydrofuran (THF) --> 2-hydroxytetrahydrofuran (THF-OH), N,N-dimethylaniline --> N-methylaniline and formaldehyde, benzyl alcohol --> benzaldehyde, benzhydrol --> benzophenone, and methanol --> formaldehyde), forming the bis-mu-hydroxo-CuII2 complexes [{CuII(R-MePY2)(OH)}2]2+ (3R). Product yields increase as the R-group is made more electron-donating, and in some cases are quantitative with 2Me2N. Pseudo-first-order rate constants for THF and methanol oxidation reactions demonstrate a remarkable R-group dependence, again favoring the strongest ligand donor (i.e., R = Me2N). For THF oxidation to THF-OH a nearly 1500-fold increase in reaction rate is observed (kobs = 2(1) x 10-5 s-1 for 2H to 3(1) x 10-2 s-1 for 2Me2N), while methanol oxidation to formaldehyde exhibits an approximately 2000-fold increase (kobs = 5(1) x 10-5 s-1 for 2H to 1(1) x 10-1 s-1 for 2Me2N).     

Airy光纤:基于阵列波导耦合的光场调控方法

近年来,Airy光束作为一种无衍射光束,其特性引起了研究者的广泛关注,人们对它的理论研究、实验验证、实际应用多个方面都取得了长足的进步.而Airy光纤作为一种可生成Airy光束的波导器件,结合其光纤自身优点可适用于多种应用领域,因此开展新型Airy光纤的探索研究、拓展Airy光束的应用范围具有重要现实意义.本文从Airy光束的原理、光纤结构设计、光纤内部光束生成机理、生成光束波长响应特性以及Airy光纤研究现状和应用五个方面展开了较系统的讨论.     

基于多层膜偏振元件的同步辐射光束线偏振特性测量研究

利用自行研制的同步辐射软X射线多层膜综合偏振测量装置, 对北京同步辐射装置(BSRF)的3W1B软X射线光束线的偏振特性进行了系统的研究. 给出了多层膜偏振元件起偏前后的测量结果, 测量能量为206eV时, 经反射镜、光栅等光束线光学元件后输出的线偏振度(起偏前)为0.585, 经多层膜偏振元件起偏后输出光的 线偏振度达到0.995.     

高性能透射式GaAs光电阴极量子效率拟合与结构研究

为了探索高性能透射式GaAs光电阴极的特征结构,对光电阴极量子效率公式进行了光谱反射率与短波截止限的修正,并利用修正后的公式对ITT透射式GaAs光电阴极量子效率(≈43%)曲线进行了拟合,得到拟合相对误差小于5%时的结构参数为:窗口层Ga_1-xAl_xAs的厚度介于0.3-0.5 μm,Al组分x值为0.7,发射层GaAs的厚度介于1.1-1.4 μm.另外,根据拟合结果讨论了均匀掺杂透射式GaAs光电阴极的优化结构参数,如果光电阴极具有0.4 μm厚的Ga_1-xAl_xAs(x=0.7)窗口层和1.1-1.5 μm厚的GaAs发射层,则积分灵敏度可以达到2350 μA/lm以上. 关键词： 透射式GaAs光电阴极 量子效率 积分灵敏度 光学性能     

Synthesis,structure and thermal properties of polynuclear complexes with a new multidentate ligand, N,N′-bis(5-ethyl-1,3,4-thiadiazol-2-yl)-2,6-pyridinedicarboxamide

Based on N,N′-bis(5-ethyl-1,3,4-thiadiazol-2-yl)-2,6-pyridinedicarboxamide (H₂L) and inorganic Zn^II and Cd^II salts, three polynuclear complexes [Zn₆(μ₄-O)₂(L)₄] (1), [Zn₃(μ₃-O)₂(L)₂(H₂L)] (2) and [Cd₅(μ₃-O)₂(L)₃(H₂L)(CH₃OH)(DMF)] (3) have been prepared and their crystal structures have been determined by single-crystal X-ray analysis. The thermal behaviors of these complexes in nitrogen and the thermal decomposition kinetics of complex 2 in the temperature range 350–540 °C have been studied, and kinetic parameters were also obtained. Kinetic results show that the decomposition of complex 2 is double-step reaction: a 1st-order reaction (F1) is followed by an nth-order reaction (Fn).