Design and synthesis of cage-like NADH model molecule intermediate with multi-chiral centers

Studying NADH molecules is one of the most active areas in biomimetic research. It is important to design novel and efficient chiral NADH model molecules. Herein, a cage-like NADH model with multi-chiral centers was designed, and key intermediates have been synthesized. In this study, we found that pentafluorophenoxy group is an excellent leaving group for our synthetic route.     

Potassium thiocarbonate as a complexing agent and précipitant

Efficient analytical separations of Mo(VI), Tl(I), Se(IV), Te(IV) and V(V) from various ions have been made possible by using potassium thiocarbonate (PTC) as a complexing and precipitating agent. For gravimetric estimations, thermogravimetric studies of the products have been used to determine the optimum temperature range of ignition.     

Structure and thermodynamic aspects of macrobicyclic polyether-metal ion interactions

The crystals structure of a K⁺-diptychand-15C5-18C6 iodide complex has been determined from X-ray data. The complexed bicyclic molecule crystallizes in the triclinic space group witha = 9.995(4) Å,b = 10.097(4) Å,c = 13.725(6) Å, = 90.12(3)°, = 93.62(4)°, = 97.56(3)°. The structure was solved using heavy atom methods and refined toR = 0.032 for 3262 independent reflections. In the crystal structure, the K⁺ lies between the two crown ether rings, and is coordinated by the nine donor atoms of the ligand molecule. The complexation properties of the ligand with K⁺ and Na⁺ were studied by titration calorimetry in 90% (v/v) MeOH/H₂O solution. The studies indicate the formation of 1 : 1 ligand : metal ion complexes in both solid state and solution.This paper is dedicated to the memory of the late Dr C. J. Pedersen.     

Kinetic model of copper electrodeposition in sulfate solution containing trisodium citrate complexing agent

Simultaneous solution of two kinetic models of electrodeposition of copper in sulfate solution is studied in this paper. Bulk concentration of species involved in the numerical solution was calculated using MATLAB software. COMSOL Multiphysics software was used for the numerical solution of copper electrodeposition. Numerical results were evaluated using experimental data obtained by linear sweep voltammetry technique. The experimental data was almost fitted using COMSOL optimization physic module. It was found that kinetic parameters of Cu²⁺ (k^1Cu), Cu¹⁺ (k_2Cu), and CuCitH (k_1CuCitH) and diffusion coefficient and charge transfer coefficient of Cu²⁺ (\({D_{C{u^{2 + }}}}\), α_Cu1), Cu¹⁺ (α_Cu2) and CuCitH (D_CuCitH, α_CuCitH) affect the fitting of the experimental data with the computed ones. The variables such as concentration profiles and optimum kinetic parameters that cannot be experimentally measured were achieved by analysis of the model. The parameters, that not affect the fitting, were recognized and kept constant when using the optimization.     

Synthesis and transport properties of 12-silacrown-3, a new type of anion complexing agent

The synthesis of 1,1,5,5,9,9-hexamethyl-1,5,9-trisilacyclododecanone, 1, a new anion complexing agent and its complexing ability for halide ions is described.     

The spectrophotometric determination of complexing agent in a polynitroaromatic molecular compound

A spectrophotometric method for quantitative determination of complcxing agent in polynitroaromatic molecular compounds of naphthalene and its derivativcs is described. The procedure involves comparison of the absorbances of solutions of the molecular compounds and its complexing agent over a range of wavelengths where absorption by the complexed moiety is negligible. An absolute accuracy of 2% or less is indicated     

1'-Phthalazinylhydrazone of acetylferrocene: Structure,properties, and complexing ability

1'-Phthalazinylhydrazone of acetylferrocene (HL) and copper(II) and nickel(II) complexes on its basis [CuL₂] and [NiL₂] have been synthesized and investigated. The structure of the hydrazine was determined by X-ray diffraction analysis. Quantum-chemical simulation of the tautomerism of the hydrazone was performed.     

99mTc-DL-Homocysteine, a potential tumor imaging agent

The usefulness of 99mTc-labeled DL-homocysteine as a tumor imaging agent was further supported by high concentration distribution into the tumors of human lung or stomach tumor-bearing nude mice.     

Au2、Au3小团族分子的结构和势能函数

原子团簇的结构和性质研究是当今物理学和材料学中的一个热门课题,过渡金属团簇特别是Au团簇,由于其独特的物理和化学性质而被广泛地应用于催化反应、材料吸附[1-2]和光的吸收中[3]。近年来,人们用不同的理论方法研究金原子团簇。H儯kkinen等人利用GGA方法研究了中性和阴离Au2-10团簇的性质[4];Bravo-P啨rez等人采用从头计算的HF和post-HF方法研究Au2-Au6小团簇[5],这些计算结果与实验值相比,相差较大。由于金团簇电子结构的复杂性,对Au体系考虑旋—轨耦合和电子相关效应是很重要的,这种计算的不确定性对Au的影响比IB簇的其它金属团…     

Synthesis of a new and versatile macrocyclic NADH model

A new macrocyclic NADH model 1 has been designed and synthesised. The new model consists of the same subunits as previously reported models. However, the present model is designed as such that the pyridine nitrogen of the nicotinamide units are not incorporated in the macrocyclic framework. Thus, properties such as solubility can easily be varied by alkylation with an appropriate agent. The macrocyclic framework was prepared in 7 steps. Methylation of the pyridine nitrogens followed by reduction gave the desired model. This model compound was found to reduce methyl benzoylformate stereoselectively in good yield with 48% enantiomeric excess.     

A study of the theoretical effect of a complexing agent in countercurrent extraction

A general relationship between the variables involved in the countercurrent extraction of a solute by the formation of a 1 : 1 complex in the extracting solution has been found. Equations were fitted to the results obtained when an electronic computer was used to calculate the equilibria at each stage of the extraction transfer processes. Combination of these has yielded a final expression of simple form.     

Synthesis of N-hydroxyenamide, a potential precursor of chartelline

In our synthetic plan for chartelline A-C, a compound including N-hydroxyenamide moiety was designed as an important intermediate. Synthesis of the required N-hydroxyenamide by N-acylation of a suitable oxime derivative has been developed using model compounds.     

Structure of the adiabatic ground-state potential surface for the ozone molecule

Institute for Physical and Organic Chemistry, Rostov University. Translated from Zhurnal Strukturnoi Khimii, Vol. 32, No. 6, pp. 15–20, November–December, 1991.     

Hydrazone as complexing agent: Synthesis,structural characterization and biological studies of some complexes

This paper deals with the synthesis, magnetic, spectral, thermal, and biological studies of Ti(III), VO(IV), Cr(III), Mn(III), Fe(III), and Zr(IV) complexes with chelating hydrazone derived from 2-hydroxy-5-methylacetophenone and furoic acid hydrazide. The acid hydrazone synthesized is 2-hydroxy-5-methylace-tophenone-furoylhydrazone. The ligand has been characterized on the basis of IR and ¹H NMR spectra. The presence of water molecules and thermal stabilities of the complexes are also reported. Solid-state electrical conductivity was measured over a 313–410-K temperature range, and the compounds show semiconducting behavior. The new complexes have been screened for their antibacterial and antifungal activity, and they show higher activity than free ligands.     

Solvent extraction of the lanthanide elements,scandium, uranium and thorium using tetracycline as complexing agent

Hydrogen ion dependence and extractant dependence of the extraction of the lanthanide elements, scandium, uranium and thorium into a solution of tetracycline in benzyl alcohol have been determined. Possiblity of using the tetracycline-benzyl alcohol system for separation of the lanthanide elements present in a mixture, as well as for the separation of uranium from those elements was tested. In the first case discontinuous countercurrent technique was used. In the second case a single step solvent extraction procedure was applied.     

Spectrophotometric determination of flucloxacillin in pharmaceutical preparations using some nitrophenols as a complexing agent

Some nitrophenols are proposed as chromogenic reagents for the spectrophotometric determination of flucloxacillin. The reagent forms a greenish yellow 1:1 complex with flucloxacillin at pH 9.0. This complex is stable for at least 3.0 h after its formation. The greenish yellow charge transfer complex species has an absorption maximum at 446, 435, 442, 473 and 439 nm for p-nitrophenol (I), 2,4-dinitrophenol (II), 3,5-dinitrosalycilic acid (III), picramic acid (IV) and picric acid (V), respectively, with a molar absorptivity between 1.43 x 10(4) and 2.59 x 10(4) l mol(-1) cm(-1). Beer's low is valid over the concentration range 2.0-40 microg ml(-1) of flucloxacillin. The detection and quantitation limits as well as relative standard deviation were also calculated. The reagents have been successfully used for the spectrophotometric determination of flucloxacillin in pure form and in pharmaceutical preparations.     

Ni(+) reactions with aminoacetonitrile, a potential prebiological precursor of glycine

The gas-phase reactions between Ni(+) ((2)D(5/2)) and aminoacetonitrile, a molecule of prebiological interest as possible precursor of glycine, have been investigated by means of mass spectrometry techniques. The mass-analyzed ion kinetic energy (MIKE) spectrum reveals that the adduct ions [NC--CH(2)--NH(2), Ni(+)] spontaneously decompose by loosing HCN, H(2), and H(2)CNH, the loss of hydrogen cyanide being clearly dominant. The structures and bonding characteristics of the aminoacetonitrile-Ni(+) complexes as well as the different stationary points of the corresponding potential energy surface (PES) have been theoretically studied by density functional theory (DFT) calculations carried out at B3LYP/6-311G(d,p) level. A cyclic intermediate, in which Ni(+) is bisligated to the cyano and the amino group, plays an important role in the unimolecular reactivity of these ions, because it is the precursor for the observed losses of HCN and H(2)CNH. In all mechanisms associated with the loss of H(2), the metal acts as hydrogen carrier favoring the formation of the H(2) molecule. The estimated bond dissociation energy of aminoacetonitrile-Ni(+) complexes (291 kJ mol(-1)) is larger than those measured for other nitrogen bases such as pyridine or pyrimidine and only slightly smaller than that of adenine.