Charge Localisation in Heavy Alkali Metal Ion Complexes of 4,4'-Biphenyldicarboxylate

2016 ◽  
Vol 69 (5) ◽  
pp. 505 ◽  
Author(s):  
Jack Harrowfield ◽  
Pierre Thuéry
Keyword(s):  
Crystal Structure ◽  
Alkali Metal ◽  
Metal Ions ◽  
Metal Ion ◽  
Negative Charge ◽  
Hydrogen Atoms ◽  
Alkali Metal Ion ◽  
Tetrahedral Environment ◽  
Structure Determinations ◽  
Irregular Form

Crystal structure determinations on the isomorphous RbI and CsI complexes of 4,4′-biphenyldicarboxylate have shown the carboxylate entities to be coordinated in an unusual fashion where both oxygen atoms are in a tetrahedral environment indicative of negative charge localisation on each. The metal ions also show a highly irregular form of six-coordination, while the biphenyl units are planar, seemingly as a result of attractive interactions between the ortho hydrogen atoms.

The Impact of the Alkali Metal Ion on the Crystal Structure and (Mechano)luminescence of Terbium(III) Tetrakis(β-diketonates)

2019 ◽  
Vol 2020 (6) ◽  
pp. 523-531 ◽  
Author(s):  
Yulia S. Kudyakova ◽  
Pavel A. Slepukhin ◽  
Marina S. Valova ◽  
Yanina V. Burgart ◽  
Viktor I. Saloutin ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Alkali Metal ◽  
Metal Ion ◽  
Alkali Metal Ion ◽  
The Impact

Alkali metal ion catalysis in nucleophilic displacement by ethoxide ion on p-nitrophenyl phenylphosphonate: Evidence for multiple metal ion catalysis

2003 ◽  
Vol 81 (1) ◽  
pp. 53-63 ◽  
Author(s):  
Erwin Buncel ◽  
Ruby Nagelkerke ◽  
Gregory RJ Thatcher
Keyword(s):  
Alkali Metal ◽  
Transition State ◽  
Metal Ions ◽  
Metal Ion ◽  
Alkali Metal Ions ◽  
Phosphoryl Transfer ◽  
Alkali Metal Ion ◽  
Nucleophilic Displacement ◽  
Displacement Reactions ◽  
Metal Ion Catalysis

In continuation of our studies of alkali metal ion catalysis and inhibition at carbon, phosphorus, and sulfur centers, the role of alkali metal ions in nucleophilic displacement reactions of p-nitrophenyl phenylphosphonate (PNPP) has been examined. All alkali metal ions studied acted as catalysts. Alkali metal ions added as inert salts increased the rate while decreased rate resulted on M+ complexation with 18-crown-6 ether. Kinetic analysis indicated the interaction of possibly three potassium ions, four sodium ions, and five lithium ions in the transition state of the reactions of ethoxide with PNPP. Pre-association of the anionic substrate with two metals ions in the ground state gave the best fit to the experimental data of the sodium system. Thus, the study gives evidence of the role of several metal ions in nucleophilic displacement reactions of ethoxide with anionic PNPP, both in the ground state and in the transition state. Molecular modeling of the anionic transition state implies that the size of the monovalent cation and the steric requirement of the pentacoordinate transition state are the primary limitations on the number of cations that can be brought to bear to stabilize the transition state and catalyze nucleophilic substitution at phosphorus. The bearing of the present work on metal ion catalysis in enzyme systems is discussed, in particular enzymes that catalyze phosphoryl transfer, which often employ multiple metal ions. Our results, both kinetic and modeling, reveal the importance of electrostatic stabilization of the transition state for phosphoryl transfer that may be effected by multiple cations, either monovalent metal ions or amino acid residues. The more such cations can be brought into contact with the anionic transition state, the greater the catalysis observed.Key words: alkali metal ion catalysis, nucleophilic displacement at phosphorus, multiple metal ion catalysis, phosphoryl transfer.

Confined alkali metal ion in two-dimensional aluminum phosphate promoted activity for condensation of lactic acid to 2,3-pentanedione

2021 ◽  
Author(s):  
Xinli Li ◽  
Ju Zhang ◽  
Yunsheng Dai ◽  
Congming Tang ◽  
Chenglong Yang
Keyword(s):  
Lactic Acid ◽  
Alkali Metal ◽  
Metal Ions ◽  
Metal Ion ◽  
Aluminum Phosphate ◽  
Sustainable Production ◽  
Alkali Metal Ions ◽  
Two Dimensional ◽  
Alkali Metal Ion

The sustainable production of 2,3-pentanedione from bio-lactic acid was investigated over the alkali metal ion intercalated laminar aluminum phosphate. The confined alkali metal ions by the adjacent layers of aluminum...

Size effects in the alkali metal ion-templated formation of oligo(ethylene glycol)-containing [2]catenanes

2016 ◽  
Vol 14 (3) ◽  
pp. 1153-1160 ◽  
Author(s):  
Yong-Jay Lee ◽  
Tsung-Hsien Ho ◽  
Chien-Chen Lai ◽  
Sheng-Hsien Chiu
Keyword(s):  
Alkali Metal ◽  
Ethylene Glycol ◽  
Metal Ions ◽  
Size Effects ◽  
Metal Ion ◽  
Alkali Metal Ions ◽  
Alkali Metal Ion

The most suitable alkali metal ions for templating the assembly of various homo- and hetero-[2]catenanes from the diamines containing central di-, tri-, and tetra(ethylene glycol) motifs, and isophthalaldehyde are investigated.

scholarly journals N-Alkyl pyrrolidone ether podands as versatile alkali metal ion chelants

2014 ◽  
Vol 43 (8) ◽  
pp. 3153-3161 ◽  
Author(s):  
Andrea Perrin ◽  
Dominic Myers ◽  
Katharina Fucke ◽  
Osama M. Musa ◽  
Jonathan W. Steed
Keyword(s):  
Alkali Metal ◽  
Metal Ions ◽  
Metal Ion ◽  
Alkali Metal Ions ◽  
Carbonyl Groups ◽  
Alkali Metal Ion ◽  
Lactam Carbonyl

The highly polar nature of lactam carbonyl groups makes them potent chelators of alkali metal ions as part of a flexible podand ligand.

scholarly journals Ionic selectivity in L-type calcium channels by electrostatics and hard-core repulsion

2009 ◽  
Vol 133 (5) ◽  
pp. 497-509 ◽  
Author(s):  
Dezső Boda ◽  
Mónika Valiskó ◽  
Douglas Henderson ◽  
Bob Eisenberg ◽  
Dirk Gillespie ◽  
...  
Keyword(s):  
Alkali Metal ◽  
Calcium Channels ◽  
Metal Ions ◽  
Metal Ion ◽  
Hard Core ◽  
Ion Currents ◽  
Alkali Metal Ion ◽  
Well Pattern ◽  
Alkaline Earth Metal Ions ◽  
Model Pore

A physical model of selective “ion binding” in the L-type calcium channel is constructed, and consequences of the model are compared with experimental data. This reduced model treats only ions and the carboxylate oxygens of the EEEE locus explicitly and restricts interactions to hard-core repulsion and ion–ion and ion–dielectric electrostatic forces. The structural atoms provide a flexible environment for passing cations, thus resulting in a self-organized induced-fit model of the selectivity filter. Experimental conditions involving binary mixtures of alkali and/or alkaline earth metal ions are computed using equilibrium Monte Carlo simulations in the grand canonical ensemble. The model pore rejects alkali metal ions in the presence of biological concentrations of Ca2+ and predicts the blockade of alkali metal ion currents by micromolar Ca2+. Conductance patterns observed in varied mixtures containing Na+ and Li+, or Ba2+ and Ca2+, are predicted. Ca2+ is substantially more potent in blocking Na+ current than Ba2+. In apparent contrast to experiments using buffered Ca2+ solutions, the predicted potency of Ca2+ in blocking alkali metal ion currents depends on the species and concentration of the alkali metal ion, as is expected if these ions compete with Ca2+ for the pore. These experiments depend on the problematic estimation of Ca2+ activity in solutions buffered for Ca2+ and pH in a varying background of bulk salt. Simulations of Ca2+ distribution with the model pore bathed in solutions containing a varied amount of Li+ reveal a “barrier and well” pattern. The entry/exit barrier for Ca2+ is strongly modulated by the Li+ concentration of the bath, suggesting a physical explanation for observed kinetic phenomena. Our simulations show that the selectivity of L-type calcium channels can arise from an interplay of electrostatic and hard-core repulsion forces among ions and a few crucial channel atoms. The reduced system selects for the cation that delivers the largest charge in the smallest ion volume.

Molecular Switch Triggered by Solvent Polarity: Synthesis, Acid–Base Behavior, Alkali Metal Ion Complexation, and Crystal Structure

2003 ◽  
Vol 9 (3) ◽  
pp. 800-810 ◽  
Author(s):  
Gianluca Ambrosi ◽  
Paolo Dapporto ◽  
Mauro Formica ◽  
Vieri Fusi ◽  
Luca Giorgi ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Alkali Metal ◽  
Metal Ion ◽  
Solvent Polarity ◽  
Molecular Switch ◽  
Acid Base ◽  
Metal Ion Complexation ◽  
Alkali Metal Ion ◽  
Ion Complexation

scholarly journals Alkali-metal-ion- and H+-dependent activation and/or inhibition of intestinal brush-border sucrase. A model involving three functionally distinct key prototropic groups

1988 ◽  
Vol 251 (3) ◽  
pp. 667-675 ◽  
Author(s):  
M Vasseur ◽  
G Van Melle ◽  
R Frangne ◽  
F Alvarado
Keyword(s):  
Alkali Metal ◽  
Metal Ions ◽  
Brush Border ◽  
Metal Ion ◽  
Molecular Mechanisms ◽  
Competitive Inhibitor ◽  
Ionization Constants ◽  
Alkali Metal Ions ◽  
Alkali Metal Ion ◽  
Intestinal Brush Border

For rabbit intestinal brush-border sucrase, a model based on classical Michaelis-Dixon theory cannot fully explain the peculiar antagonistic relationship existing between the substrate and one key proton, Hx, which at acid pH values behaves as a fully competitive inhibitor. In the same pH range, a second proton, Hy, is responsible for changes in catalytic activity and behaves as a mixed-type partially non-competitive inhibitor [Vasseur, Tellier & Alvarado (1982) Arch. Biochem. Biophys. 218, 263-274]. Although involved in the same ionization reaction, these two protons have different kinetic functions, since they are responsible for affinity-type and capacity-type effects respectively. Depending on whether Hx is bound or not, we postulate the enzyme to alternate between two distinct forms differing in their binding properties. The alkali-metal ions Na+ and Li+ have a concentration-dependent biphasic effect on this equilibrium. At low concentrations they facilitate the release of Hx, resulting in K-type activation. At higher concentrations they favour enzyme reprotonation, causing K-type inhibition. On the basic side of the pH spectrum, our results confirm the existence of separate non-competitive effects of the alkali-metal ions, particularly Li+ [Alvarado & Mahmood (1979) J. Biol. Chem. 254, 9534-9541]. To explain the molecular mechanisms underlying the alkali-metal-ion- and H+-dependent effects, we formulate a sucrase model, the three-protons model, in which the acid and basic ionization constants involve respectively two and one key prototropic groups that are functionally distinguishable. A global iterative fit of the relevant general equation to our whole set of data has permitted us to estimate the numerical value of each of the constants constituting the model.

Impact Electrical Property of Alkali Metal Doped ZnO

2012 ◽  
Vol 468-471 ◽  
pp. 1501-1507 ◽  
Author(s):  
Hong Ling Tan ◽  
Cong Ying Jia ◽  
Chao Xiang ◽  
Ying Xiang Yang
Keyword(s):  
Alkali Metal ◽  
Metal Ions ◽  
Metal Ion ◽  
Density Functional ◽  
Alkali Metal Ions ◽  
Acceptor Level ◽  
Electronic Density ◽  
Alkali Metal Ion ◽  
Doped Zno ◽  
P Type

Calculate the electronic structure of alkali metal ion-doped Zn crystal, based on density functional theory (DFT) first-principles plane-wave ultra-soft pseudo-potential method. Analyze the band structure of alkali metal ion-doped ZnO crystal, and the electronic density of states. The results indicated that in theory, the doping of alkali metal ions are able to form a p-type ZnO semiconductor, and introduce in the deep acceptor levels. In the actual substitution process, the dopant ions may enter the interstitial site. Thus the alkali metal ions are tending to become donor interstitial impurities. In addition, since the ionic radius of K is larger than the ionic radiuses of Li and Na. And K+ formed the minimum acceptor level (0.078eV), which is a shallow acceptor level. K+ is better than Li+ and Na+ as a dopant. In short, they are not good p-type dopants.

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