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1.
An ab initio molecular orbital study was performed to determine the effects of anions and cations on the π-complexation of C2H4 on MX(M=Ag, Cu; X=F, Cl). The calculated results show the following order of adsorption strength: F->Cl- for anions; Cu >Ag for cations. The results can be explained by the detailed analysis of atomic charge, orbital energy and orbital population by using the natural bond orbital(NBO) theory: (1) anions with stronger electronegativity can attract more electrons from the s orbital of M, while at the same time it does not obviously weaken the d orbital occupation of M, thus the nearly vacant s orbital and the sufficiently filled d orbitals of M help with forming σ-donation and d-π* backdonation with the π orbital and the π* orbital of olefin, respectively; (2) a smaller energy gap of symmetry-adapted orbitals between olefin and a cation can favor the electron transfer, that is why Cu forms stronger adsorption with olefin than Ag does. 相似文献
2.
ZHOU Jin-xia ZHANG Yong-chun GUO Xin-wen * State Key Laboratory of Fine Chemical Dalian University of Technology Dalian P. R. China 《高等学校化学研究》2005,21(2):217-219
Introduction Separation,recoveryofolefinorremovalof tracequantitiesofolefinfromitsmixturesbyusing π-complexatonisamostpromisingsolution,com- paredwithenergy-intensivedistillationorotheral- ternatives.π-Complexationisasubgroupofchemi- calcomplexationwhereamixtureisbroughtinto contactwithasecondphasecontainingacomplex- ingagent[1].Forexample,theadsorbentscontain- ingAg+orCu+canselectivelyadsorbolefinfroman ethylene/ethaneorpropylene/propanemixture. Becausetheπ-complexationbondsarestronger th… 相似文献
3.
Synthesis and Crystal Structure of A New Armed-tetraazacrown Ether and Its Liquid Membrane Transport of Alkali Metal Cations 总被引:2,自引:0,他引:2
Introduction Transportofcationsacrossanorganicliquidmem branewhichseparatestwowaterphaseshasbeenexten sivelyinvestigated .1Thesyntheticmacrocyclicligands ,suchascrownethers ,areusuallyusedasmodelcarrierstomimicthenaturallyoccurringantibioticmacrocycleswhichhavebeenshowntoalterthepermeabilityofbiologicalmembranestocertaincations .2 ,3 Thus ,theyhaveimpor tantapplicationsinbothchemistryandbiologytoselectivecomplexationofvariousmetalcations .4 ,5Itwasreportedthatthedivalenttransition metalcomp… 相似文献
4.
Osburn S Berden G Oomens J O'Hair RA Ryzhov V 《Journal of the American Society for Mass Spectrometry》2012,23(6):1019-1023
The radical cations of Cys-Gly and Gly-Cys were studied using ion-molecule reactions (IMR), infrared multiple-photon dissociation
(IRMPD) spectroscopy, and density functional theory (DFT) calculations. Homolytic cleavage of the S–NO bond of nitrosylated
precursors generated radical cations with the radical site initially located on the sulfur atom. Time-resolved ion-molecule
reactions showed that radical site migration via hydrogen atom transfer (HAT) occurred much more quickly in Gly-Cys•+ than in Cys-Gly•+. IRMPD and DFT calculations indicated that for Gly-Cys, the radical migrated from the sulfur atom to the α-carbon of glycine,
which is lower in energy than the sulfur radical (–53.5 kJ/mol). This migration does not occur for Cys-Gly because the glycine
α-carbon is higher in energy than the sulfur radical (10.3 kJ/mol). DFT calculations showed that the highest energy barriers
for rearrangement are 68.2 kJ/mol for Gly-Cys and 133.8 kJ/mol for Cys-Gly, which is in agreement with both the IMR and IRMPD
data and explains the HAT in Gly-Cys. 相似文献
5.
Dr. Hidde Elferink Wouter A. Remmerswaal Kas J. Houthuijs Oscar Jansen Dr. Thomas Hansen Prof. Dr. Anouk M. Rijs Dr. Giel Berden Dr. Jonathan Martens Prof. Dr. Jos Oomens Prof. Dr. Jeroen D. C. Codée Dr. Thomas J. Boltje 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(63):e202201724
Uronic acids are carbohydrates carrying a terminal carboxylic acid and have a unique reactivity in stereoselective glycosylation reactions. Herein, the competing intramolecular stabilization of uronic acid cations by the C-5 carboxylic acid or the C-4 acetyl group was studied with infrared ion spectroscopy (IRIS). IRIS reveals that a mixture of bridged ions is formed, in which the mixture is driven towards the C-1,C-5 dioxolanium ion when the C-5,C-2-relationship is cis, and towards the formation of the C-1,C-4 dioxepanium ion when this relation is trans. Isomer-population analysis and interconversion barrier computations show that the two bridged structures are not in dynamic equilibrium and that their ratio parallels the density functional theory computed stability of the structures. These studies reveal how the intrinsic interplay of the different functional groups influences the formation of the different regioisomeric products. 相似文献
6.
Farid I. El-Dossoki 《Journal of solution chemistry》2010,39(9):1311-1326
The effect of the charge and the nature of both the cations and the anions of some electrolytic salts: sodium fluoride (NaF),
potassium fluoride (KF), sodium bromide (NaBr), potassium bromide (KBr), sodium iodide (NaI), potassium iodide (KI), sodium
sulfate (Na2SO4), potassium sulfate (K2SO4), calcium chloride (CaCl2), and barium chloride (BaCl2), on the solubility of zwitterionic amino acids (glycine, DL-alanine, DL-valine, and DL-serine) in aqueous solutions at 298.15 K
are studied and discussed. A salting-in effect is observed for all amino acids under investigation with all electrolytes used
in the present study, except for DL-alanine and DL-valine in aqueous solutions containing sodium fluoride where a salting-out
effect was observed. The orders of the effect of the nature and the charge of both the anions and the cations are: F- < Cl- < Br- < I- < NO3- < SO42-\mathrm{F}^{-}<{}\mathrm{Cl}^{-}<{}\mathrm{Br}^{-}<{}\mathrm{I}^{-}<\mathrm{NO}_{3}^{-}<{}\mathrm{SO}_{4}^{2-} with both sodium and potassium cations; Na+<K+<Ca2+<Ba2+ with chloride anion. 相似文献
7.
Themetalcarbenecations,esPeciallytransitionmetalcarbenecations,areaclass0funstableintermediateswithhighactivity.TheyareveryimPortamtothefieldoforganometallicchendstryandhavegreatlyattractedchemist'sattention.JacobsonlstUdiedthereactionsofFeCH, andCoCH, withalkanes"',olefms2ingasphase.Butsofarasweknow,thereisnosystematictheoreticalstUdyontheirsmictUresandstability.InthispaPer,westUdythestfUcturalcharacteristics,molecularorbitalsofXCHLi andrelationshiPbetweensubstituelltsandstability,tak… 相似文献
8.
Two new polyoxomolybdate compounds,namely(CuIIL2)2[CuⅡ(HL)2]2[Mo8O26(HL)2].(H2O)4(1) and [CuⅡ(HL)2]2[β-Mo8O26](HL)2(2)(HL=imidazole),were designed and synthesized under hydrothermal conditions.X-ray diffraction analyses reveal that compound 1 consists of one Mo8O26(HL)24-cluster,two CuL2,two Cu(HL)22+,and four disassociated water molecules;and compound 2 is constructed by one β-Mo8O264-cluster,two Cu(HL)22+,and two uncoordinated imidazole molecules. 相似文献
9.
A Mahjoub M Hochlaf GA Garcia L Nahon L Poisson 《The journal of physical chemistry. A》2012,116(34):8706-8712
The near threshold photofragmentation pattern of δ-valerolactam(+) and δ-valerolactam(2)(+) has been recorded combining electron/ion coincidence techniques and vacuum ultraviolet synchrotron radiation. The experimental method yields the fragment intensity as a function of the internal energy deposited into the parent cation, up to 3.1 eV above the first ionization threshold. In parallel, ab initio studies on the δ-valerolactam(+) and δ-valerolactam(2)(+) cations and their ionic and neutral fragmentation products have been performed with the aim of determining the isomers of the ionic products observed experimentally as well as of their neutral counterparts. These computations were performed using the PBE0 exchange-correlation functional and the aug-cc-pVDZ basis set. We found good agreement between the calculated reaction enthalpies and experimental appearance energies of the ions. More generally, our experimental and theoretical results reveal that the fragmentation of the ionic species of interest leads to a multitude of neutral and ionic fragments, which may be formed after intramolecular isomerization and complex decomposition processes. Multistep reaction pathways are expected. 相似文献
10.
Justin Kai-Chi Lau Seydina Lo Junfang Zhao K. W. Michael Siu Alan C. Hopkinson 《Journal of the American Society for Mass Spectrometry》2013,24(4):543-553
Radical cations [Met-Gly]?+, [Gly-Met]?+, and [Met-Met]?+ have been generated through collision-induced dissociation (CID) of [CuII(CH3CN)2(peptide)]?2+ complexes. Their fragmentation patterns and dissociation mechanisms have been studied both experimentally and theoretically using density functional theory at the UB3LYP/6-311++G(d,p) level. The captodative structure, in which the radical is located at the α-carbon of the N-terminal residue and the proton is on the amide oxygen, is the lowest energy structure on each potential energy surface. The canonical structure, with the charge and spin both located on the sulfur, and the distonic ion with the proton on the terminal amino group, and the radical on the α-carbon of the C-terminal residue have similar energies. Interconversion between the canonical structures and the captodative isomers is facile and occurs prior to fragmentation. However, isomerization to produce the distonic structure is energetically less favorable and cannot compete with dissociation except in the case of [Gly-Met]?+. Charge-driven dissociations result in formation of [b n – H]?+ and a 1 ions. Radical-driven dissociation leads to the loss of the side chain of methionine as CH3-S-CH?=?CH2 producing α-glycyl radicals from both [Gly-Met]?+ and [Met-Met]?+. For [Met-Met]?+, loss of the side chain occurs at the C-terminal as shown by both labeling experiments and computations. The product, the distonic ion of [Met-Gly]?+, NH3 +CH(CH2CH2SCH3)CONHCH?COOH dissociates by loss of CH3S?. The isomeric distonic ion NH3 +CH2CONHC?(CH2CH2SCH3)COOH is accessible directly from the canonical [Gly-Met]?+ ion. A fragmentation pathway that characterizes this ion (and the distonic ion of [Met-Met]?+) is homolytic fission of the Cβ–Cγ bond to lose CH3SCH2 ?. 相似文献
11.
A new fluorescent compound based on calix[4] arene skeleton was synthesized.Its complexation ability with transition metal ions,such as Fe^3 ,Co^2 ,Ni^2 ,Cu^2 ,Zn^2 and Ag^ ,Was investigated by UV-vis and fluorescent spectra. 相似文献
12.
Murat Erdemoğlu 《Journal of Dispersion Science and Technology》2013,34(5):689-695
Electrokinetic behavior of pyrophyllite in aqueous solutions of K+, Na+, Mg2+, and Ca2+ ions and effect of low‐molecular‐weight organic anions like acetate (C2H3O2 ?), oxalate (C2O4 2?), and citrate (C6H5O7 3?) on the zeta potential was investigated. Pyrophyllite has higher negative zeta potential values in the presence of alkaline metal cations than in water, and it comes close to positive values in the presence of alkaline earth metal cations at low pH values. Results revealed that presence of low‐molecular‐weight organic anions led to a decrease in the zeta potential in the order of acetate>citrate>oxalate. 相似文献
13.
Ahmad Rouhollahi Mohammad Reza Ganjali Abolghasem Moghimi Gerald W. Buchanan Mojtaba Shamsipur 《Journal of inclusion phenomena and macrocyclic chemistry》1999,33(4):361-376
A synthetic procedure has been developed for the preparation of 4-carboxy-benzo-30-crown-10. The formation of Na+, K+, Rb+, Cs+ and Tl+ complexes with the large crown ether was investigated conductometrically in acetonitrile solution at various temperatures. The formation constants of the resulting 1:1 complexes were determined from the molar conductance-mole ratio data. It was found that the stability of the complexes vary in the order Tl+ > K+ > Rb+ > Cs+ > Na+. The data obtained in this study support the existence of a wrap around structure for the above complexes in solution. The enthalpy and entropy of complexation reactions were determined from the temperature dependence of the formation constants. In all cases, the complexes were enthalpy stabilized but entropy destabilized. The resulting TS° vs. H°plot showed a fairly good linear correlation, indicating the existence of an entropy-enthalpy compensation in the large crown complexation reactions. 相似文献
14.
15.
We have developed two synthesis routes for 4-amino derivatives of 6-nitro--carbolines: 1) consecutive conversion of 1,2-dimethyl-3-formyl-5-nitroindole to the 3-cyano derivative, condensation of the latter with DMF diethyl acetal, and cyclization of the enamine formed in this case with ammonia and benzylamine; 2) N-oxidation of 9-substituted 6-nitro--carbolines, transformation of N-oxides to the corresponding -carbolin-4-ones, from which the target compounds are obtained through the 4-chloro derivatives.For Communication 72, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 502–505, April, 1992. 相似文献
16.
A new mellitate complex [Cu3(μ2-mellitate)(μ2-H2O)(H2O)2·H2O]n 1 has been synthesized by the reaction of mellitic acid and Cu(CH3COO)2·H2O in the presence of base. Crystallographic data for 1: C12H8O16Cu3, Mr = 598.80, orthorhombic, Pbcn, a = 8.4378(6), b = 10.0396(7), c = 17.6799(12)A, V = 1497.70(18)A^3, Z = 4, De = 2.656 g/cm^3, μ = 4.327 mm^-1, F(000) = 1180, R = 0.0431 and wR = 0.0964 for 1075 observed reflections (I 〉 2σ(I)). X-ray crystal structural analysis revealed that the mellitate anions behave as the bridging ligands and link eight copper atoms repeatedly to form a novel three-dimensional metal-organic coordination polymer with two different rhombic tunnels in the solid-state structure. 相似文献
17.
A new mellitate complex [Cu3(μ2-mellitate)(μ2-H2O)(H2O)2·H2O]n 1 has been synthesi- zed by the reaction of mellitic acid and Cu(CH3COO)2·H2O in the presence of base. Crystallogra- phic data for 1: C12H80O16Cu3, Mr = 598.80, orthorhombic, Pbcn, a = 8.4378(6), b = 10.0396(7), c = 17.6799(12) A, V = 1497.70(18) A3, Z = 4, Dc = 2.656 g/cm3,μ = 4.327 mm-1, F(000) = 1180, R = 0.0431 and wR = 0.0964 for 1075 observed reflections (Ⅰ> 2σ(Ⅰ)). X-ray crystal structural analysis revealed that the mellitate anions behave as the bridging ligands and link eight copper atoms repeatedly to form a novel three-dimensional metal-organic coordination polymer with two different rhombic tunnels in the solid-state structure. 相似文献
18.
Investigation on Mechanism for Separation of Alkali, Alkaline Metal and Ammonium Cations in Nonaqueous Capillary Electrophoresis 总被引:2,自引:0,他引:2
Capillary electrophoresis ( CE ) has rapidly gained great interests among researchers in many different fields. One of these areas is the separation of small ions such as inorganic cations, anions, and low Mr organic molecules However, as the separation of ions 相似文献
19.
Low-valent N-coordinated cations and dications of heavier group 14 elements are of great interest in recent years. Their unique electronic structure gives them an ambiphilic character, as they contain both a lone electron pair and an empty p-orbital on the central metal atom. Thanks to their nucleophilic character, these compounds can act as ligands in transition metal chemistry, and conversely, their electrophilic character allows them to interact with a wide range of organic substrates and thus replace catalysts based on transition metal complexes in many chemical transformations. The aim of this article is to summarize the synthesis of N-coordinated ionic compounds of heavier group 14 elements with their subsequent reactivity towards various nucleophiles and electrophiles. 相似文献
20.
Mekecha TT Amunugama R McLuckey SA 《Journal of the American Society for Mass Spectrometry》2006,17(7):923-931
Multiply protonated human hemoglobin alpha-chain species, ranging from [M + 4H]4+ to [M + 20H]20+, have been subjected to ion trap collisional activation. Cleavages at 88 of the 140 peptide bonds were indicated, summed over all charge states, although most product ion signals were concentrated in a significantly smaller number of channels. Consistent with previous whole protein ion dissociation studies conducted under similar conditions, the structural information inherent to a given precursor ion was highly sensitive to charge state. A strongly dominant cleavage at D75/M76, also noted previously in beam-type collisional activation studies, was observed for the [M + 8H]8+ to [M + 11H]11+ precursor ions. At lower charge states, C-terminal aspartic acid cleavages were also prominent but the most abundant products did not arise from the D75/M76 channel. The [M + 12H]12+-[M + 16H]16+ precursor ions generally yielded the greatest variety of amide bond cleavages. With the exception of the [M + 4H]4+ ion, all charge states showed cleavage at the L113/P114 bond. This cleavage proved to be the most prominent dissociation for charge states [M + 14H]14+ and higher. The diversity of dissociation channels observed within the charge state range studied potentially provides the opportunity to localize residues associated with variants via a top-down tandem mass spectrometry approach. 相似文献