四(三苯基氧膦)高氯酸钕合乙醇配合物的合成及结构测定

合成了Nd(ClO_4)_3·4phP=O·C_2H_5OH配合物,用四园衍射仪测定了它的分子及晶体结构,此晶体属三斜晶系P1空间群,晶胞参数为:a=13.475(61)A;b=15.003(15)A;c=18.697(15)A;α=85.44(7);β=78.49(24)°;γ=83.13(26)°;V=3671.2A,分子由99个非氢原子组成,实际上分子可分为三个部分即:配阳离子[Nd(ClO_4)_2·4phPO]~+;阴离子ClO_4和溶剂合分子C_2H_5OH配阳离子的钕与八个氧配位,四个氧来自双齿配位的ClO_4,四个氧来自四个ph_3PO,八个配位氧组成三角十二面体。 中性膦(磷)类化合物包括(RO)_3P=O和R_3P=O是一类重要的萃取剂。工业上已应用的TBP和TOPO都属于这一类。为了研究这类萃取剂在不同底液中萃取行为之所以不同的内在因素,我们制备了不同希土盐类与三苯基氧膦的配合物,并对它们进行了结构测定。已知的中性氧膦希土配合物中进行过结构测定的有Ce(NO)·2phP=O、Nd(NO)_2·2php=O·C_2HOH、La(NO_3)_3·3php=O·C_2H_5OH·CHCl_3和Nd(NCS)·4php=O。这些配合物晶体及分子结构各异,这表明了三苯基氧膦在形成配合物时的复杂性。本文报导的Nd(ClO_4)·4phP=O·C_2H_5OH实际上是由三部分组成;即[Nd(ClO_4)_2·4phP=O]~+外界的ClO_4和溶剂合分子。这在中性配体与高氯酸希土形成的配合物中时有发现。已知结构的     

中性磷(膦)类稀土萃合物的结构研究(Ⅲ)——三(三苯基氧膦)合硝酸镧的合成及结构测定

合成了三(三苯基氧膦)合硝酸镧络合物, 经鉴定确定络合物化学式为La(NO_3)_3·3ph_3PO·C_2H_5OH·CHCl_3。其中C_2H_5OH和CHCl_3为溶剂化分子。经X射线单晶衍射, 测定了该络合物属单斜晶系P2_1/n空间群, 晶体学参数如下a=1.3111(5) nm Z=4b=2.5075(10) nm F(000)=2687.65c=1.8725(6) nm μ吸收系数=9.83(cm~(-1))β=98.53(3)° d计算=1.45 gcm~(-3)V=6.088 nm d实验=1.43 gcm~(-3)La与9个氧直接配位, 其中六个氧来自三个双卤配位硝酸根, 另三个氧分别由三个苯基氧膦上的膦酰基所提供。La-O平均键长0.2549 nm。     

2020 Roadmap on two-dimensional nanomaterials for environmental catalysis

This roadmap demonstrates a series of two-dimensional nanomaterials, such as graphene, black phosphorus, oxides, layered double hydroxides, chalcogenides, bismuth-based layered compounds, MXenes, metal organic frameworks, covalent organic frameworks, and others, for environmental catalysis.     

Synthesis and cofluorescence of Eu(Y) complexes with salicylic acid and o-phenanthroline

A series of dinuclear complexes of salicylic acid (HSal) and o-phenanthroline (Phen) with different molar ratios of Eu3+ to Y3+ have been synthesized. Their compositions are Eu(x)Y(1-x) (Sal)3(Phen) (x = 0 to approximately 1). Their UV spectra, IR spectra, and fluorescence spectra were studied. The UV spectra of the complexes reflect essentially absorption of the ligands for the fact that no obvious change of wavelength and band shape is found between the spectra of the complexes and that of the ligands except slight red shift. The IR absorption spectra indicate that salicylic acid is coordinated to the rare earth ions and chemical bonds are formed between rare earth ions and nitrogen atoms of o-phenanthroline. The fluorescence spectra of the complexes indicate that the fluorescence emission intensity of europium ion was enhanced by the addition of Y3+, which is referred to as cofluorescence. These facts show that not only the ligands but also the yttrium complex can transfer the absorbed energy to Eu3+ ion in the complexes. Formation of polynuclear complexes appears to be responsible for cofluorescence.     

How does huperzine A enter and leave the binding gorge of acetylcholinesterase? Steered molecular dynamics simulations

The entering and leaving processes of Huperzine A (HupA) binding with the long active-site gorge of Torpedo californica acetylcholinesterase (TcAChE) have been investigated by using steered molecular dynamics simulations. The analysis of the force required along the pathway shows that it is easier for HupA to bind to the active site of AChE than to disassociate from it, which for the first time interprets at the atomic level the previous experimental result that unbinding process of HupA is much slower than its binding process to AChE. The direct hydrogen bonds, water bridges, and hydrophobic interactions were analyzed during two steered molecular dynamics (SMD) simulations. Break of the direct hydrogen bond needs a great pulling force. The steric hindrance of bottleneck might be the most important factor to produce the maximal rupture force for HupA to leave the binding site but it has a little effect on the binding process of HupA with AChE. Residue Asp72 forms a lot of water bridges with HupA leaving and entering the AChE binding gorge, acting as a clamp to take out HupA from or put HupA into the active site. The flip of the peptide bond between Gly117 and Gly118 has been detected during both the conventional MD and SMD simulations. The simulation results indicate that this flip phenomenon could be an intrinsic property of AChE and the Gly117-Gly118 peptide bond in both HupA bound and unbound AChE structures tends to adopt the native enzyme structure. At last, in a vacuum the rupture force is increased up to 1500 pN while in water solution the greatest rupture force is about 800 pN, which means water molecules in the binding gorge act as lubricant to facilitate HupA entering or leaving the binding gorge.     

Dynamic Lie algebraic formulation of second‐order optical nonlinearity for substituted benzenes

A dynamic Lie algebraic (DLA) formulation is applied to the study of nonlinear optical properties of the substituted benzenes. We have described the generation of the dynamic Lie algebra for the model Hamiltonian used in the present study. In terms of these elements of the dynamic algebra we express the evolution operator as a function of the group parameters, which can be determined by means of solving a system of coupled nonlinear differential equations. Thus, in terms of the density matrix operator formalism in statistical mechanics we obtain the statistical averages of the electric polarization and then derive readily an expression for the hyperpolarizability of the paradisubstituted benzenes. Comparisons with experimental observations and other quantum calculations of the hyperpolarizabilities for the paradisubstituted benzenes are made qualitatively and quantitatively. These results imply that the DLA method appears useful in describing the nonlinear optical phenomena in the substituted benzene molecules. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 93: 335–343, 2003     

Enhancement of chiral recognition by formation of a sandwiched complex in capillary electrophoresis

For chiral primary amino compounds not separable by cyclodextrins alone, chiral recognition was successfully achieved by the formation of a sandwiched complex of the non-chiral 18-crown-6, the chiral amine and cyclodextrin (CD) [18-crown-6+amino compound+CD]. The separation of 1-methyl-3-phenylpropylamine and 1,2,3,4-tetrahydro-1-naphthylamine racemates showed the special function of the non-chiral 18-crown-6 on chiral recognition. By formation of the sandwiched complex, the chiral center of 1-methyl-3-phenylpropylamine was successfully recognized, and resolution of 1,2,3,4-tetrahydro-1-naphthylamine dramatically increased. In these studies, the mobility differences of the enantiomers were evaluated as a function of the concentration of cyclodextrins with and without the 18-crown-6, and as a function of the concentration of the 18-crown-6. In addition, the separations by this method were compared to those by the chiral 18-crown-6 reagent.     

Sensitively probing the cofactor redox species and photo-induced electron transfer of wild-type and pheophytin-replaced photosynthetic proteins reconstituted in self-assembled monolayers

An ultrathin, ordered, and packed protein film, consisting of the 2-mercaptoacetic acid (MAA), polydimethyldiallylammonium chloride (PDDA), and wild-type (WT) photosynthetic reaction center (RC; termed as WT-RC) or its pheophytin (Phe)-replaced counterpart (termed as Phe-RC), was fabricated by self-assembling technique onto gold electrode for facilitating the electron transfer (ET) between RC and the electrode surface. Near-infrared (NIR)-visible (Vis) absorption and fluorescence (FL) emission spectra revealed the influence of pigment substitution on the cofactors arrangement and excitation relaxation of the proteins, respectively. Square wave voltammetry (SWV) and photoelectric tests were employed to systematically address the differences between the WT-RC films and mutant ones on the direct and photo-induced ET. The electrochemical results demonstrated that ET initiated by the oxidation of the primary donor (P) was obviously slowed down, and the formed P⁺ had more population as well as more positive redox potential in the Phe-RC films compared with those in the WT ones. The photoelectrochemical results displayed the dramatically enhanced photoelectric performances of the mutant ones, further suggesting the slow-down formation of final charge-separated state in Phe-RC. The functionalized protein films introduced in this paper provided an efficient approach to sensitively probe the redox cofactors and ET differences resulting from only minor changes in pigment arrangement in the pigment–protein complex. The favored ET process observed for the membrane proteins RC was potentially valuable for a deep understanding of the multi-step biological ET process and development of versatile bioelectronic devices.     

Vacancy ion-exclusion chromatography of aromatic carboxylic acids on a weakly acidic cation-exchange resin

Determination of aromatic carboxylic acids by conventional ion-exclusion chromatography is relatively difficult and methods generally rely on hydrophobic interaction between the solute and the resin. To overcome the difficulties in determining aromatic carboxylic acids a new approach is presented, termed vacancy ion-exclusion chromatography, which is based on use of the sample as mobile phase and an injection of aqueous 10% methanol onto a weakly acidic cation-exchange column (TSKgel OApak-A). Highly sensitive conductivity detection occurred with sharp and well-shaped peaks, leading to very efficient separations. The effects of sulfuric acid concentration added to the mobile phase, flow-rate, and column temperature on the retention volume of tested aromatic carboxylic acids was investigated. Retention times were found to be affected by the concentration of the analytes in the mobile phase and to some extent also by the addition of an organic modifier such as methanol to the injected water sample. Separation of sulfuric acid (SA), naphthalenetetracarboxylic acid (NTCA), phthalic acid (PA) and benzoic acid (BA) was satisfactory using this new approach. Detection limits were 0.66, 0.67, 0.42 and 0.86 microM and detector responses were linear in the range 1-100, 1-80, 2.5-100 and 10-40 microM, for SA, NTCA, PA and BA, respectively. Precision for retention times was 0.36% and for peak areas was 1.5%.     

水中痕量镉的准液膜富集

准液膜法是在液膜法基础上提出的新分离方法，它保持了液膜法分离富集的高效能，但省去了液膜法的制乳与破乳过程，使操作更为简便易行。本文用此法富集了水及废水中痕量镉，富集倍数可达２３０倍，镉的回收率在９７％以上。