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Ligand Field Theory
Ligand field theory (LFT) describes the bonding, orbital arrangement, and other characteristics of coordination complexes. It represents an application of molecular orbital theory to transition metal complexes. A transition metal ion has nine valence atomic orbitals - consisting of five ''n''d, one (''n''+1)s, and three (''n''+1)p orbitals. These orbitals have the appropriate energy to form bonding interactions with ligands. The LFT analysis is highly dependent on the geometry of the complex, but most explanations begin by describing octahedral complexes, where six ligands coordinate with the metal. Other complexes can be described with reference to crystal field theory. Inverted ligand field theory (ILFT) elaborates on LFT by breaking assumptions made about relative metal and ligand orbital energies. History Ligand field theory resulted from combining the principles laid out in molecular orbital theory and crystal field theory, which describe the loss of degeneracy of metal d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coordination Complexes
A coordination complex is a chemical compound consisting of a central atom or ion, which is usually metallic and is called the ''coordination centre'', and a surrounding array of bound molecules or ions, that are in turn known as ''ligands'' or complexing agents. Many metal-containing compounds, especially those that include transition metals (elements like titanium that belong to the periodic table's d-block), are coordination complexes. Nomenclature and terminology Coordination complexes are so pervasive that their structures and reactions are described in many ways, sometimes confusingly. The atom within a ligand that is bonded to the central metal atom or ion is called the donor atom. In a typical complex, a metal ion is bonded to several donor atoms, which can be the same or different. A polydentate (multiple bonded) ligand is a molecule or ion that bonds to the central atom through several of the ligand's atoms; ligands with 2, 3, 4 or even 6 bonds to the central atom ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pi Backbonding Orbitals
The number (; spelled out as pi) is a mathematical constant, approximately equal to 3.14159, that is the ratio of a circle's circumference to its diameter. It appears in many formulae across mathematics and physics, and some of these formulae are commonly used for defining , to avoid relying on the definition of the arc length, length of a curve. The number is an irrational number, meaning that it cannot be expressed exactly as a ratio of two integers, although fractions such as \tfrac are commonly Approximations of π, used to approximate it. Consequently, its decimal representation never ends, nor repeating decimal, enters a permanently repeating pattern. It is a transcendental number, meaning that it cannot be a solution of an algebraic equation involving only finite sums, products, powers, and integers. The transcendence of implies that it is impossible to solve the ancient challenge of squaring the circle with a Compass-and-straightedge construction, compass and stra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molecular Orbital Theory
In chemistry, molecular orbital theory (MO theory or MOT) is a method for describing the electronic structure of molecules using quantum mechanics. It was proposed early in the 20th century. The MOT explains the paramagnetic nature of O2, which valence bond theory cannot explain. In molecular orbital theory, electrons in a molecule are not assigned to individual chemical bonds between atoms, but are treated as moving under the influence of the atomic nuclei in the whole molecule. Quantum mechanics describes the spatial and energetic properties of electrons as molecular orbitals that surround two or more atoms in a molecule and contain valence electrons between atoms. Molecular orbital theory revolutionized the study of chemical bonding by approximating the states of bonded electrons – the molecular orbitals – as linear combinations of atomic orbitals (LCAO). These approximations are made by applying the density functional theory (DFT) or Hartree–Fock (HF) models to the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ligand Dependent Pathway
There are two types of pathway for substitution of ligands in a complex. The ligand dependent pathway is the one whereby the chemical properties of the ligand affect the rate of substitution. Alternatively, there is the ligand independent pathway, which is where the ligand does not have an effect. This is of vital importance in the world of inorganic chemistry and complex ion A coordination complex is a chemical compound consisting of a central atom or ion, which is usually metallic and is called the ''coordination centre'', and a surrounding array of bound molecules or ions, that are in turn known as ''ligands'' or ...s. References Chemical bonding {{chemistry-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crystal Field Theory
In inorganic chemistry, crystal field theory (CFT) describes the breaking of degeneracies of electron orbital states, usually ''d'' or ''f'' orbitals, due to a static electric field produced by a surrounding charge distribution (anion neighbors). This theory has been used to describe various spectroscopies of transition metal coordination complexes, in particular optical spectra (colors). CFT successfully accounts for some magnetic properties, colors, hydration enthalpies, and spinel structures of transition metal complexes, but it does not attempt to describe bonding. CFT was developed by physicists Hans Bethe and John Hasbrouck van Vleck in the 1930s. CFT was subsequently combined with molecular orbital theory to form the more realistic and complex ligand field theory (LFT), which delivers insight into the process of chemical bonding in transition metal complexes. CFT can be complicated further by breaking assumptions made of relative metal and ligand orbital energies, req ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phenanthroline
1,10-Phenanthroline (phen) is a heterocyclic organic compound. It is a white solid that is soluble in organic solvents. The 1,10 refers to the location of the nitrogen atoms that replace CH's in the hydrocarbon called phenanthrene. Abbreviated "phen", or sometimes "o-phen" for ortho-phenanthroline, it is used as a ligand in coordination chemistry, forming strong complexes with most metal ions.Luman, C.R. and Castellano, F.N. (2003) "Phenanthroline Ligands" in Comprehensive Coordination Chemistry II. Elsevier. . It is often sold as the monohydrate. Synthesis Phenanthroline can be prepared by two successive Skraup reactions of glycerol with ''o''-phenylenediamine, catalyzed by sulfuric acid, and an oxidizing agent, traditionally aqueous arsenic acid or nitrobenzene. Dehydration of glycerol gives acrolein which condenses with the amine followed by a cyclization. Reactions Oxidation of 1,10-phenanthroline with a mixture of nitric and sulfuric acids gives 1,10-phenanthroline-5,6- ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
2,2'-bipyridine
The comma is a punctuation mark that appears in several variants in different languages. Some typefaces render it as a small line, slightly curved or straight, but inclined from the vertical; others give it the appearance of a miniature filled-in figure placed on the baseline. In many typefaces it is the same shape as an apostrophe or single closing quotation mark . The comma is used in many contexts and languages, mainly to separate parts of a sentence such as clauses, and items in lists mainly when there are three or more items listed. The word ''comma'' comes from the Greek (), which originally meant a cut-off piece, specifically in grammar, a short clause. A comma-shaped mark is used as a diacritic in several writing systems and is considered distinct from the cedilla. In Byzantine and modern copies of Ancient Greek, the " rough" and "smooth breathings" () appear above the letter. In Latvian, Romanian, and Livonian, the comma diacritic appears below the letter, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ethylenediamine
Ethylenediamine (abbreviated as en when a ligand) is the organic compound with the formula C2H4(NH2)2. This colorless liquid with an ammonia-like odor is a basic amine. It is a widely used building block in chemical synthesis, with approximately 500,000 tonnes produced in 1998. Ethylenediamine is the first member of the so-called polyethylene amines. Synthesis Ethylenediamine is produced industrially by treating 1,2-dichloroethane with ammonia under pressure at 180 °C in an aqueous medium (EDC process): : In this reaction hydrogen chloride is generated, which forms a salt with the amine. The amine is liberated by addition of sodium hydroxide and can then be recovered by fractional distillation. Diethylenetriamine (DETA) and triethylenetetramine (TETA) are formed as by-products. Another industrial route to ethylenediamine involves the reaction of ethanolamine and ammonia:Hans-Jürgen Arpe, Industrielle Organische Chemie, 6. Auflage (2007), Seite 275, Wiley VCH : Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pyridine
Pyridine is a basic (chemistry), basic heterocyclic compound, heterocyclic organic compound with the chemical formula . It is structurally related to benzene, with one methine group replaced by a nitrogen atom . It is a highly flammable, weakly alkaline, water-miscible liquid with a distinctive, unpleasant fish-like smell. Pyridine is colorless, but older or impure samples can appear yellow, due to the formation of extended, unsaturated Polymer, polymeric chains, which show significant electrical conductivity. The pyridine ring occurs in many important compounds, including agrochemicals, pharmaceuticals, and vitamins. Historically, pyridine was produced from coal tar. As of 2016, it is synthesized on the scale of about 20,000 tons per year worldwide. Properties Physical properties Pyridine is diamagnetism, diamagnetic. Its critical point (thermodynamics), critical parameters are: pressure 5.63 MPa, temperature 619 K and volume 248 cm3/mol. In the temperatur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spectrochemical Series
A spectrochemical series is a list of ligands ordered by ligand "strength", and a list of metal ions based on oxidation number, group and element. For a metal ion, the ligands modify the difference in energy Δ between the d orbitals, called the ligand-field splitting parameter in ligand field theory, or the crystal-field splitting parameter in crystal field theory. The splitting parameter is reflected in the ion's electronic and magnetic properties such as its spin state, and optical properties such as its color and absorption spectrum. Spectrochemical series of ligands The spectrochemical series was first proposed in 1938 based on the results of absorption spectra of cobalt complexes. A partial spectrochemical series listing ligands from small Δ to large Δ is given below. (For a table, see the ligand page.) : I− < Br− < S2− < SCN− (S–bonded) < Cl− < NO3– < [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Energy
Energy () is the physical quantity, quantitative physical property, property that is transferred to a physical body, body or to a physical system, recognizable in the performance of Work (thermodynamics), work and in the form of heat and light. Energy is a Conservation law, conserved quantity—the law of conservation of energy states that energy can be Energy transformation, converted in form, but not created or destroyed. The unit of measurement for energy in the International System of Units (SI) is the joule (J). Forms of energy include the kinetic energy of a moving object, the potential energy stored by an object (for instance due to its position in a Classical field theory, field), the elastic energy stored in a solid object, chemical energy associated with chemical reactions, the radiant energy carried by electromagnetic radiation, the internal energy contained within a thermodynamic system, and rest energy associated with an object's rest mass. These are not mutual ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Synergy
Synergy is an interaction or cooperation giving rise to a whole that is greater than the simple sum of its parts (i.e., a non-linear addition of force, energy, or effect). The term ''synergy'' comes from the Attic Greek word συνεργία ' from ', , meaning "working together". Synergy is similar in concept to emergence. History The words ''synergy'' and ''synergetic'' have been used in the field of physiology since at least the middle of the 19th century: SYN'ERGY, ''Synergi'a'', ''Synenergi'a'', (F.) ''Synergie''; from ''συν'', 'with', and ''εργον'', 'work'. A correlation or concourse of action between different organs in health; and, according to some, in disease. :—Dunglison, Roble''Medical Lexicon''Blanchard and Lea, 1853 In 1896, Henri Mazel applied the term "synergy" to social psychology by writing ''La synergie sociale'', in which he argued that Darwinian theory failed to account of "social synergy" or "social love", a collective evolutionary drive. The hi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
