Charge distribution in Adsorbates

1996 ◽  
Author(s):  
Wolfgang Schmickler
Keyword(s):  
Charge Distribution ◽  
Electrostatic Potential ◽  
Metal Ion ◽  
Fundamental Problem ◽  
Specific Model ◽  
Formal Similarity ◽  
Individual Adsorption ◽  
Solvent Molecules ◽  
Rearrangement Processes ◽  
Macroscopic Quantity

The distribution of charges on an adsorbate is important in several respects: It indicates the nature of the adsorption bond, whether it is mainly ionic or covalent, and it affects the dipole potential at the interface. Therefore, a fundamental problem of classical electrochemistry is: What does the current associated with an adsorption reaction tell us about the charge distribution in the adsorption bond? In this chapter we will elaborate this problem, which we have already touched upon in Chapter 4. However, ultimately the answer is a little disappointing: All the quantities that can be measured do not refer to an individual adsorption bond, but involve also the reorientation of solvent molecules and the distribution of the electrostatic potential at the interface. This is not surprising; after all, the current is a macroscopic quantity, which is determined by all rearrangement processes at the interface. An interpretation in terms of microscopic quantities can only be based on a specific model. There is a formal similarity between adsorption and reactions such as metal deposition which gives rise to the concept of electrosorption valence. Consider the deposition of a metal ion of charge number z on an electrode of the same material.

Square-grid coordination networks of (5,10,15,20-tetra-4-pyridylporphyrinato)zinc(II) in its clathrate with two guest molecules of 1,2-dichlorobenzene: supramolecular isomerism of the porphyrin self-assembly

2009 ◽  
Vol 65 (3) ◽  
pp. m139-m142 ◽  
Author(s):  
Rajesh Koner ◽  
Israel Goldberg
Keyword(s):  
Self Assembly ◽  
Metal Ion ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Coordination Networks ◽  
Guest Molecules ◽  
Square Grid ◽  
Supramolecular Isomerism ◽  
Self Assembled ◽  
Solvent Molecules

The title compound, (5,10,15,20-tetra-4-pyridylporphyrinato)zinc(II) 1,2-dichlorobenzene disolvate, [Zn(C40H24N8)]·2C6H4Cl2, contains a clathrate-type structure. It is composed of two-dimensional square-grid coordination networks of the self-assembled porphyrin moiety, which are stacked one on top of the other in a parallel manner. The interporphyrin cavities of the overlapping networks combine into channel voids accommodated by the dichlorobenzene solvent. Molecules of the porphyrin complex are located on crystallographic inversion centres. The observed two-dimensional assembly mode of the porphyrin units represents a supramolecular isomer of the unique three-dimensional coordination frameworks of the same porphyrin building block observed earlier. The significance of this study lies in the discovery of an additional supramolecular isomer of the rarely observed structures of metalloporphyrins self-assembled directly into extended coordination polymers without the use of external ligand or metal ion auxiliaries.

One-dimensional CuIand AgIladder-like coordination polymers supported by 2-ethyl-1-(pyridin-3-ylmethyl)-1H-benzimidazole

2013 ◽  
Vol 69 (9) ◽  
pp. 1017-1021
Author(s):  
Liu-cheng Gui ◽  
Guang-ming Liang ◽  
Hua-hong Zou ◽  
Zhong Hou
Keyword(s):  
Hydrogen Bonds ◽  
Metal Ion ◽  
Three Dimensional ◽  
Coordination Geometry ◽  
Tetrahedral Coordination ◽  
Asymmetric Unit ◽  
Counter Anion ◽  
One Dimensional ◽  
Solvent Molecules ◽  
Distorted Tetrahedral Coordination

The title complexes, poly[[bis[μ2-2-ethyl-1-(pyridin-3-ylmethyl)-1H-benzimidazole-κ2N1:N3]copper(I)] tetrafluoroborate acetonitrile monosolvate], {[Cu(C15H15N3)2]BF4·CH3CN}n, (I), and poly[[bis[μ2-2-ethyl-1-(pyridin-3-ylmethyl)-1H-benzimidazole-κ2N1:N3]silver(I)] perchlorate methanol monosolvate], {[Ag(C15H15N3)2]ClO4·CH3OH}n, (II), are isostructural and exhibit one-dimensional ladder-like structures in which each asymmetric unit contains one metal ion (Cu+or Ag+), two 2-ethyl-1-(pyridin-3-ylmethyl)-1H-benzimidazole (bep) ligands, one counter-anion (tetrafluoroborate or perchlorate) and one interstitial molecule (acetonitrile or methanol). Each metal ion exhibits a distorted tetrahedral coordination geometry consisting of two pyridyl and two benzimidazole N atoms from four distinct ligands. Two metal ions are linked by two bep ligands to form a centrosymmetric 18-memberedM2(bep)2metallacycle, while adjacentM2(bep)2metallacycles are further interlinked by another two bep ligands resulting in a ladder-like array. In the extended structure, four adjacent ladder-like arrays are connected together through C—H...F, O—H...O and C—H...O hydrogen bonds between bep ligands, solvent molecules and counter-anions into a three-dimensional supramolecular structure.

scholarly journals Crystal structure of d(CCGGGGTACCCCGG)2at 1.4 Å resolution

2017 ◽  
Vol 73 (5) ◽  
pp. 259-265
Author(s):  
Selvam Karthik ◽  
Arunachalam Thirugnanasambandam ◽  
Pradeep Kumar Mandal ◽  
Namasivayam Gautham
Keyword(s):  
Crystal Structure ◽  
Metal Ion ◽  
Double Helix ◽  
Barium Chloride ◽  
Base Pairs ◽  
X Ray ◽  
Density Map ◽  
Solvent Molecules ◽  
Electron Density Map ◽  
Phosphate Groups

The X-ray crystal structure of the DNA tetradecamer sequence d(CCGGGGTACCCCGG)2is reported at 1.4 Å resolution in the tetragonal space groupP41212. The sequence was designed to fold as a four-way junction. However, it forms an A-type double helix in the presence of barium chloride. The metal ion could not be identified in the electron-density map. The crystallographic asymmetric unit consists of one A-type double helix with 12 base pairs per turn, in contrast to 11 base pairs per turn for canonical A-DNA. A large number of solvent molecules have been identified in both the grooves of the duplex and around the backbone phosphate groups.

scholarly journals When spectroscopy fails: The measurement of ion pairing

2006 ◽  
Vol 78 (8) ◽  
pp. 1571-1586 ◽  
Author(s):  
Glenn Hefter
Keyword(s):  
Metal Ion ◽  
Chemical Speciation ◽  
Ion Pairs ◽  
Ion Association ◽  
Ion Pair ◽  
Association Constants ◽  
Spectroscopic Techniques ◽  
Association Equilibria ◽  
Solvent Molecules ◽  
Contact Ion Pairs

Spectroscopic techniques such as UV/vis, NMR, and Raman are powerful tools for the investigation of chemical speciation in solution. However, it is not widely recognized that such techniques do not always provide reliable information about ion association equilibria. Specifically, spectroscopic measurements do not in general produce thermodynamically meaningful association constants for non-contact ion pairs, where the ions are separated by one or more solvent molecules. Such systems can only be properly quantified by techniques such as dielectric or ultrasonic relaxation, which can detect all ion-pair types (or equilibria), or by traditional thermodynamic methods, which detect the overall level of association. Various types of quantitative data are presented for metal ion/sulfate systems in aqueous solution that demonstrate the inadequacy of the major spectroscopic techniques for the investigation of systems that involve solvent-separated ion pairs. The implications for ion association equilibria in general are briefly discussed.

scholarly journals Crystal structure of bis(tetraphenylphosphonium) bis(cyanido-κC)(29H,31H-tetrabenzo[b,g,l,q]porphinato-κ4N29,N30,N31,N32)ferrate(II) acetone disolvate

2015 ◽  
Vol 71 (2) ◽  
pp. m48-m49
Author(s):  
Miki Nishi ◽  
Masaki Matsuda ◽  
Norihisa Hoshino ◽  
Tomoyuki Akutagawa
Keyword(s):  
Molecular Structure ◽  
Crystal Structure ◽  
Metal Ion ◽  
Acetone Molecule ◽  
Deprotonated Form ◽  
Cyanide Anion ◽  
Compound C ◽  
Distorted Octahedral ◽  
Solvent Molecules ◽  
Octahedral Configuration

The crystal structure of the title compound, (C24H20P)2[Fe(C36H20N4)(CN)2]·2C3H6O, is constructed from a tetrahedral Ph4P+(tetraphenylphosphonium) cation, one [Fe(tbp)(CN)2]2−anion (tbp = tetrabenzoporphyrin in its doubly deprotonated form), located on a centre of inversion, and an acetone molecule as crystallization solvent. Since the molecular structure of theM(tbp) moiety is insensitive to the kind of metal ion and its oxidation state, bond lengths and angles in the [Fe(tbp)(CN)2]2−anion are similar to those in otherM(tbp) compounds. The Fe2+ion, located on a centre of inversion, is coordinated by four N atoms of tpb in the equatorial plane and by two C atoms of the cyanide anion at axial positions in a slightly distorted octahedral configuration. The packing is stabilized by C—H...N interactions between the Ph4P+cation and the CN−ligand of the [Fe(tbp)(CN)2]2−anion, and by C—H...π interactions between the Ph4P+cation, acetone solvent molecules and the [Fe(tbp)(CN)2]2−anion.

Charge Distribution and Surface Properties of the Tobacco Mosaic Virus 4-nm Central-Pore

2012 ◽  
Author(s):  
Nikolay I. Rodionov ◽  
Shalabh C. Maroo
Keyword(s):  
Amino Acids ◽  
Tobacco Mosaic Virus ◽  
Mosaic Virus ◽  
Charge Distribution ◽  
Electrostatic Potential ◽  
Model Organism ◽  
Surface Characteristics ◽  
Exterior Surface ◽  
Central Pore ◽  
Poisson Boltzmann Equation

The uniform distribution of charged amino acids along the exterior surface of the tobacco mosaic virus (TMV) along with its unusual structural stability over a large pH and temperature range has made it a model organism for inorganic deposition and nanostructure fabrication studies on biomolecules. However, the potential engineering applications of the virus’s central pore, which is about 300 nm long and 4 nm in diameter, has been overlooked. We aim to expand TMV applications by understanding the surface characteristics of its central pore. We have identified the set of amino acids and atoms that create the surface of the pore, mapped the partial charge distribution of the pore using AMBER9 force fields, and determined the electrostatic potential of the pore surface through Coulomb’s law and Poisson-Boltzmann Equation (PBE). Our analysis has revealed that the pore contains a dense helical distribution of negatively charged glutamic amino acid residues, which results in a strong negative electrostatic potential across the pore. This can potentially be used for water filtration by creating overlapping electric double layer within the central pore.

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