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1.
The binding interactions of bis‐3‐benzo‐15‐crown‐5 ethers and bis‐3‐benzo‐18‐crown‐6 ethers (neutral hosts) with a series of alkali metal cations Na+, K+, Rb+ and Cs+ (charged guests) were investigated using quantum chemical density functional theory. Different optimized structures, binding energies and various thermodynamic parameters of free crown ethers and their metal cation complexes were obtained based on the Becke, three‐parameter, Lee–Yang–Parr functional using mixed basis set (C, H, O, Na+ and K+ using 6‐31 g, and the heavier cation Rb+ and Cs+ using effective core potentials). Natural bond orbital analysis is conducted on the optimized geometric structures. The main types of driving force host–guest interactions are investigated. The electron donating O offers a lone pair of electrons to the contacting LP* (1‐center valence antibond lone pair) orbitals of metal cations. The bis‐3‐benzocrown ethers are assumed to have sandwich‐like conformations, considering the binding energies to gauge the exact interactions with alkali cations. It is found that there are two different types of complexes: one is a tight ion pair and the other is a separated ion pair. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

2.

Abstract  

Lithium-7 nuclear magnetic resonance (NMR) measurements were used to investigate the stoichiometry and stability of Li+ complexes with 15-crown-5 (15C5), benzo-15-crown-5 (B15C5) and dibenzo-15-crown-5 (DB15C5) in a number of nitromethane (NM)–acetonitrile (AN) binary mixtures. In all cases, the exchange between the free and complexed lithium ion was fast on the NMR time scale and a single population average resonance was observed. While all crown ethers form 1:1 complexes with Li+ ion in the binary mixtures used, stepwise formation constants of the 1:1 (ligand/metal) complexes were evaluated from computer fitting of the NMR-mole ratio data to equations which relate the observed metal ion chemical shifts to formation constants. There is an inverse linear relationship between the logarithms of the stability constants and the mole fraction of AN in the solvent mixtures. The stability order of the 1:1 complexes was observed to be 15C5.Li+ > B15C5.Li+ > DB15C5.Li+. The optimized structures of the free ligands and their 1:1 complexes with the Li+ ion were predicted by ab initio theoretical calculations using the Gaussian 98 software. The results of calculations are discussed.  相似文献   

3.
本文基于密度泛函理论研究了在水溶液中不同结构冠醚对Li~+的选择性.通过对几何结构、结合能和热力学的计算,发现15-冠-5(15C5)对Li~+的选择性强于12-冠-4(12C4)和18-冠-6(18C6).苯并15-冠-5(B15C5)与Li~+的结合能小于15C5,但在溶液巾结合Li~+时具有更低的自山能.研究了B15C5和Li、Co、Ni水合离子之间的交换反应,表明B15C5与水合锂离子之间的反应占据优势.上述结果表明采用B15C5从废旧钾离子电池浸出液中回收锂具有一定的可行性.  相似文献   

4.
Çakil Erk 《光谱学快报》2013,46(9):723-730
Abstract

The association constants of Li+, Ca+2 and Mg+2 ions complexing with 1, 4, 7, 10-tetraoxcyclododecane in DHO were determined by the aid of 13C dipole-dipole relaxation time measurements. To obtain the Ka, association constant, the TO 1 values of the stoichiometric complex solutions and the T10 of the free molecules were applied to the equation derived, 1/Ka· Ao + 2 = 1/P + P, for the 1:1 ratio of the complexing and to the equation 1/2Ka·Ao + 3/2 = P + 1/2P for the 1:2 ratio of the complexing where P, is molar ratio of the crown complexed ions.

Accordingly we found that the binding ability of the macrocyclic ether towards to the cations is in the following order of Li+ < Mg+2 ? Ca+2 in DHO solutions.  相似文献   

5.
Chemosensors are molecules of abiotic origin that are able to bind selectively and reversibly the analyte of interest with a concomitant change in the property of the system. They find wide applications in lots of disciplines and our work is directed to develop new species for future applications. We present here the latest luminescent chemosensors studied in our laboratory. The chosen luminophore moieties are anthracene and dioxyxanthone derivatives that have been differently connected with receptor units such as crown ethers and thioethers. In solution a good selectivity and affinity was observed for different ions such as Na+, K+, Cs+, Ba2+, Sr2+, Ca2+ and Ag+. The binding is signaled in all cases by pronounced changes in the photophysical properties of the luminophore present in the structure of the chemosensor.  相似文献   

6.
Stability orderings of 150 stable complexes formed by metal ions (Na+, K+, Ca2+, Mg2+, and Zn2+) and 13 stable thymine tautomers in both solvent and gas phases are obtained, and the optimal binding site for a metal ion in a specific thymine tautomer is identified. Results indicate that the complex with the canonical thymine tautomer (T1) is more stable than those with the rare ones, and the monodentate complex M–T1o4(o2) are their ground‐state form in the solvent phase. The ground‐state thymine complexes bound by Ca2+, Mg2+, or Zn2+ become bidentate M–T3o4lo2,n3, which is derived from a rare thymine tautomer T3o4l, whereas those bound by Na+ and K+ are still monodentate complexes M–T1o4(o2), however, in the gas phase. The differences in stability are discussed in detail from the binding strength of metal ions, relative energy of the corresponding thymine tautomers, and solution effect. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

7.
A new derivative of the previously reported 1,2‐bis(benzimidazol‐2‐yl)ethane motif, cation [1H2]2+, was synthesized under microwave irradiation and fully characterized by solution NMR, high‐resolution mass spectrometry, cyclic voltammetry and X‐ray crystallography. This cation presents a linear geometry and incorporates nitro substituents as electrochemical handles. In solution, cation [1H2]2+, is capable of threading the cavity of dibenzo‐24‐crown‐8 ether host (DB24C8) giving rise to a [2]pseudorotaxane complex [1H2?DB24C8]2+, regardless of the counterion, [CF3SO3]? or [CF3COO] ?. The interpenetrated structure of [1H2?DB24C8]2+ was proven by solution NMR and X‐ray crystallography. This host–guest complex is held together by several non‐covalent interactions, such as hydrogen bonding and ion‐dipole. An electrochemical study of [1H2]2+ in the presence of variable amounts of DB24C8 was performed; due to the irreversible redox behavior of cation [1H2]2+, it was not possible to electrochemically control the association/dissociation process with DB24C8. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

8.
Three derivatives of alkyl anthracene covalently bonded to aza‐18‐crown‐6 at the nitrogen position, anthracene(CH2)n, (n = 1–3) which act as an on–off fluorogenic photoswitch have been theoretically studied using a computational strategy based on density functional theory at B3LYP/6‐31 + G(d,p) method. The fully optimized geometries have been performed with real frequencies which indicate the minima states. The binding energies, enthalpies and Gibbs free energies have been calculated for aza‐18‐crown‐6 ( L ) and their metal complexes. The natural bond orbital analysis is used to explore the interaction of host–guest molecules. The absorption spectra differences between L and their metal ligands, the excitation energies and absorption wavelength for their excited states have been studied by time‐dependent density functional theory with the basis set 6‐31 + G(d,p). These fluorescent sensors and switchers based on photoinduced electron transfer mechanism have been investigated. The PET process from aza‐crown ether to fluorophore can be suppressed or completely blocked by the entry of alkali metal cations into the aza‐crown ether‐based receptor. Such a suppression of the PET process means that fluorescence intensity is enhanced. The binding selectivity studies of the aza‐crown ether part of L indicate that the presence of the alkali metal cations Li+, Na+ and K+ play an important role in determining the internal charge transfer and the fluorescence properties of the complexes. In addition, the solvent effect has been investigated. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

9.
Benzothiazole type butadienyl dyes containing a dithia‐15‐crown‐5 ( 2a ) or dithia‐18‐crown‐6 ether ( 2b ) moieties were synthesized. The structures of dyes 2a , b and their complexes with Ag+ and Pb2+ were studied by an X‐ray crystallography. It was found that the conformations of dithiacrown–ether moieties of dyes 2a , b are unfavorable for complex formation and change significantly upon binding of Ag+ or Pb2+. The complexation of 2a , b with Ag+, Cd2+, Pb2+, and Hg2+ in water–acetonitrile mixtures with different contents of water (PW = 0–75%, v/v) was studied by 1H NMR, UV–Vis spectroscopy, and polarography. In anhydrous acetonitrile, the stability constants of 1:1 complexes change in the sequence Cd2+ < Pb2+ ≤ Ag+ << Hg2+ in the case of 2a and in the sequence Cd2+ < Ag+ < Pb2+ << Hg2+ in the case of 2b . As PW increases, the thermodynamic stability of Ag+ complexes increases. The opposite effect is observed for the complexes with Cd2+, Pb2+, and Hg2+. When PW ~ 50%, the stability constants of complexes with Cd2+ and Pb2+ become too small to be measured. The selectivity of ligands 2a , b toward Hg2+ versus Ag+ is very high at any PW values (selectivity coefficients > 104). The complexation of 2a , b with Hg2+ at PW ≤ 50% is accompanied by a substantial hypsochromic effect. This allows dithiacrown‐containing butadienyl dyes to be used as selective optical molecular sensors for heavy metal ions, in particular, in aqueous solutions. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

10.
The present study compared the interactions among Na +, K +, Mg2+ and Ca2+, thymine and its tautomers in the gas and solvent phase, an interaction dependent upon the electronic construction of the tautomers. Three types of cation interaction with thymine and its tautomers were observed. In the first one, the metal cations interacted with a lone pair of nitrogen or oxygen of the tautomers. In the second type, there was an interaction among the cations, nitrogen and oxygen at the same time; the last one was that of cations with the electron density of thymine π-system, where the cations were perpendicular to the ring of thymine. The interaction of metals cation with tautomers was studied in the gas and solvent phases; a comparison was then made between interactions in two phases. The interaction energy for all complexes indicated the stability of complexes, an energy which was higher in Ca2+ and Mg2+ compared with Na+ and K+. Concerning K+ and Na+, the stability of all complexes of tautomers was greater than that of thymine complexes; however, the stability of certain Ca2+ and Mg2+ complexes was lower than the complexes of thymine.  相似文献   

11.
A new pyrene-based chemosensor (1) exhibits excellent selectivity for Fe3+ ions over a wide range of tested metal ions Ag+, Ca2+, Cd2+, Co2+, Cu2+, Fe2+, Hg2+, K+, Mg2+, Mn2+, Ni2+, Pb2+, and Zn2+. The binding of Fe3+ to chemosensor 1 produces an emission band at 507 nm due to the formation of a Py-Py* excimer that is induced by Fe3+-binding. The binding ratio of 1-Fe3+ was determined to be 1:1 from a Job plot. The association constant of 1-Fe3+ complexes was found to be 1.27?×?104 M?1 from a Benesi-Hildebrand plot. In addition, fluorescence microscopy experiments show that 1 can be used as a fluorescent probe for detecting Fe3+ in living cells.  相似文献   

12.
The stability and the possible application of our recently reported SiC heterofullerenes inspire the investigation of their further stabilization through ion encapsulation. The endohedral complexes X@C12Si8, where X=Li+, Na+, K+, Be2+, Mg2+, Ca2+, Al3+, and Ga3+, are probed at the MPWB1K/6-311G? and B3LYP/6-311G* levels of theory. The optimized geometries show the expanding or contracting capability of C12Si8 in order to accommodate metal ion guests. The inclusion energies indicate the stability of the complexes compared to the components. Meanwhile, the calculated binding energies show the stabilization of C12Si8 through the inclusion of Be2+, Mg2+, Al3+, and Ga3+. The host-guest interaction that is probed through NBO atomic charges supports the obtained results. This study refers to “metal ion encapsulation” as a strategy for stabilization of SiC heterofullerenes.  相似文献   

13.
Equilibrium between synthetic ion exchangers and solutions of cations has been the subject of this investigation. Competitive ion exchange reactions were studied for two cation exchange membranes (CMX and CRP) involving K+, Na+, and Ca2+ ions. The ionic strength of the equilibrating solutions was maintained constant, but the molar fraction varied; all experiments were conduced with nitrate as nonexchanging anions at 25 °C. Adsorption isotherm for the three binaries systems: K+/Na+, K+/Ca2+, and Na+/Ca2+ were studied. The obtained results show that potassium was the most strongly sorbed and the selectivity order for CMX and CRP membranes is K+>Ca2+>Na+ at 0.1 M, under the experimental conditions. Selectivity coefficients , , and for the three binaries and for the two membranes were determined at an ionic strength of 0.1 M and at a constant temperature of 25 °C. We remark that all the selectivity coefficient values are quite different from the unit. Ternary equilibrium was taken for the Ca2+/K+/Na+ system. It was found that binary selectivity data could be successfully used to predict the ternary ion exchange equilibrium.  相似文献   

14.
The present work cites the investigation results of 19F NMR spectra in polyerystalline compounds of the Me n[PtF6]m type, where Me - Li+, Na+, K+, Ca2+, Sr2+, Ba2+, La3+ and Ag+. The use of a NMR spectrometer with high field stress (~24 kOe) made possible the observation of different chemical shifts in solids of NMR signals from two nonequivalent fluorine types in octahedric complexes of [PtF6]2-.19 NMR and Structure of Pt (IV) Hexafluorocomplexes  相似文献   

15.
Cellulose hydrogels are biodegradable materials that can be applied as accommodating hosts for various species. Here we report the preparation of novel thin films based on luminescent cellulose hydrogels. The spectroscopic behavior of these soft materials and their sensing effects are investigated. Interestingly, we found that these films only give selective signal changes in the presence of Cu2+ in water in comparison with Na+, K+, Ag+, Mn2+, Co2+, Ca2+, Cd2+, Hg2+, Pd2+, Mg2+, Ni2+, Fe2+, and Fe3+. High visible-light transmittance and good flexibility for these films can be observed. More importantly, the thermal stability of rare-earth complexes could be significantly enhanced in aqueous solution as result of the protection by hydrogel matrix.  相似文献   

16.
Quadrupole moment and dipole polarizability tensor components are calculated at the correlated complete-active-space self-consistent-field (CASSCF) and complete-active-space perturbation-theory (CASPT) levels for 2P states of O?, F, Ne+, Na2+, S?, Cl, Ar+, 98, K2+ , Se?, Br, Kr+, Rb2+ and 3P, 1D, 1S states of O?, F+, Ne2+, Na3+, S, Cl+, Ar2+, K3+, Se, Br+, Kr2+, Rb3+. Relativistic corrections are included perturbatively for the 34- and 35-electron systems.  相似文献   

17.
Persistent carbocations generated by the protonation of hetero‐polycyclic aromatic compounds with oxygen atom(s) were studied by experimental NMR and density function theory calculations. Benzo[kl]xanthene ( 1 ), dibenzo[d,d′]benzo[1,2‐b:4,3‐b′]difuran ( 2 ), and dibenzo[d,d′]benzo[1,2‐b:4,5‐b′]difuran ( 3 ) were synthesized by the annulation of arenediazonium salts. Compound 1 in FSO3H‐SbF5 (4:1)/SO2ClF and 3 in FSO3H‐SbF5 (1:1)/SO2ClF ionized to 1aH+ with protonation at C(4) and to 3aH+ with protonation at C(6), and these cations were successfully observed by NMR at low temperatures. The density function theory calculations indicated that 1aH+ and 3aH+ were the most stable protonated carbocations and that 2 should ionize to 2aH+ with protonation at C(6). According to the changes in 13C chemical shifts (Δδ13C), the positive charge was delocalized into the naphthalene unit for 1aH+ , into one benzo[b,d]furan unit for 2aH+ , and into one benzo[b,d]furan unit for 3aH+ . Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

18.
The branching ratio of the following three modes of K+-meaon decay K+→μ+0+ν K+→e+0+ν K+→μ++ν is calculated by using the theory of the universal Fermi weak interaction proposed by Feymann and others. Perturbation method with cut-off is used. The ratio obtained is 1:1.5:12, which is in fair agreement with the experimental value 1:1:15. It is shown, other conbinations of Fermi interactions can not give result in agreement with experiment.  相似文献   

19.
A new compound, 1-[p-(dimethylamino)benzoyl]-4′-phenyl-semicarbazide (1) was synthesized and showed highly selective response to Cu2+ over other metal ions such as Pb2+, Mg2+, Fe2+, Co2+, Zn2+, Cd2+, Hg2+, Ni2+, Ca2+, Ag+, Na+, K+, and Li+. The control compound, 1-[p-(dimethylamino)benzoyl]-4-phenyl-thiosemicarbazide (2), showed different fluorescence spectral response to Cu2+. A 1:1 complex between Cu2+ and 1 was formed while 1:1 and 1:2 complexes between Cu2+ and 2 were formed. The binding model between the receptor (1 or 2) and Cu2+ was supported by IR spectra, mass spectra, and computation model. 1 possessed higher selectivity towards Cu2+ compared with 2 owing to the difference of complexation ability between urea and thiourea groups.  相似文献   

20.
The experimental infrared (IR) spectrum of composite wax powder was investigated. The frequency shifts of the C=C anti-symmetrical stretching mode were observed and the experimental cooperativity effect involving Na+···π interaction was suggested. In order to further reveal the nature of cooperativity effect, the interaction energies in Mn+···coronene···CH4 (Mn+ = Li+, Na+, K+, Be2+, Mg2+ or Ca2+) as the model systems of composite wax powder were calculated by using the B3LYP, M06-2X and MP2 methods with 6-311++G** basis set. The results show that the Mn+···π interactions were strengthened upon the formation of ternary complexes. Although the changes of absolute values of the interactions between CH4 and coronene were not obvious, the relative values were considerably significant upon the formation of ternary complexes. The cooperativity effect was perhaps the reason for the formation of notable advantage of composite wax powder upon the introduction of surfactant with cation into wax powder. Reduced density gradient and atoms-in-molecules analysis confirm the cooperativity effect in Mn+···coronene···CH4, and reveal the nature of the formation of the predominant advantage of composite wax powder.  相似文献   

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