
	Where results make sense

Topic: Ligand field theory

Related Topics

Crystal field theory

Pi backbonding

Molecular orbital

Complex (chemistry)

Transition metal

Electron configuration

Homo

In the News (Sun 29 Nov 09)

Northern Trust

Marvin Harrison

Peter Chernin

Gary Locke

Match Play

Penelope Cruz

Mickey Rourke

AR Rahman

Danny Boyle

Hugh Jackman

	Ligand field theory - Wikipedia, the free encyclopedia
		Ligand field theory was developed during the 1930s and 1940s as an expansion of the electrostatic crystal field theory, which offered a good description of the electronic structure of metal ions in coordination complexes but was not able to provide a proper explanation for their bonding.
		Like crystal field theory, ligand field theory is most easily understood by picturing ligands approaching a central metal ion and visualising the resulting orbital overlap.
		(O stands for octahedral) and is determined by strength of the interaction of the ligand orbitals with the d-orbitals on the central atom, as described in crystal field theory.
	en.wikipedia.org /wiki/Ligand_field_theory (1071 words)

	Ligand - Wikipedia, the free encyclopedia
		In chemistry, a ligand is an atom, ion, or molecule (see also: functional group) that generally donates one or more of its electrons through a coordinate covalent bond to, or shares its electrons through a covalent bond with one or more central atoms or ions (these ligands act as a Lewis base).
		The molecule resulting from the coordination of a ligand (or an array of ligands) to a central atom is termed a complex.
		In general, ligands donate electron density to the (electron deficient) central atom (that is, overlap between the highest occupied molecular orbital (HOMO) of the ligand with the lowest unoccupied molecular orbital (LUMO) of the central atom).
	en.wikipedia.org /wiki/Ligand (1568 words)

	Complex
		Some ligands are capable of forming multiple links to the same metal atom, and are described as bidentate, tridentate etc. EDTA is hexadentate, which accounts for the great stability of many of its complexes.
		Because of this, simple octet bonding theory fails in the case of complexes and to understand the chemistry of these systems, a deeper understanding of chemical bonding rules is necessary.
		Ligand field theory[?], introduced in 1935 and built from molecular orbital theory, can handle a broader range of complexes and can explain complexes in which the interactions are covalent.
	www.ebroadcast.com.au /lookup/encyclopedia/co/Complex.html (363 words)

	Ligand Information Center - ligand pharmaceuticals
		The charge ligand reactions on the central atom constrains the number of ligands that may be bonded, since each type of ligand donates a characteristic number ligand field theory of electrons and there is a requirement for overall neutrality.
		Ligands which bind to the central atom through more than one site of their own are termed polydentate; a ligand binding through two sites, ligand for example, is bidentate.
		The ligand field splitting ligand geometries are named and described as if the central atom were in the protein ligand binding bovine serum albumin middle of a polyhedron, and the corners of that shape were the locations of the ligands.
	www.scipeeps.com /Sci-Chemistry_Topics_Li_-_Me/Ligand.html (572 words)

	An Introduction to Ligand and Crystal Field Theory
		Ligand and Crystal Field theories are used to describe the nature of the bonding in transition metal complexes.
		Crystal Field Theory is based upon the effect of a perturbation of the d-orbitals consisting of electronic interaction between the metal cation nucleus and the negatively charged electrons of the ligands: the metal-ligand interactions are electrostatic only.
		Ligand Field Theory treats the metal-ligand interaction as a covalent bonding interaction, and depends upon considering the overlap between the d-orbitals on the metals and the ligand donor orbitals.
	www.everyscience.com /Chemistry/Inorganic/Crystal_and_Ligand_Field_Theories/a.1012.php (455 words)

	Ligand Field Theory Summary - Ligand Field Theory Information
		The ligand field theory is especially useful for explaining the spectroscopic, magnetic, and optical characteristics of ions in the transition- metal and rare-earth groups.
		The ligand field theory's main concern is the effects of ligands on the energy levels of the central atom or ion.
		Ligands are the ions, molecules, or atoms that surround a central ion in a complex.
	www.bookrags.com /sciences/chemistry/ligand-field-theory-woc.html (556 words)

	Glossary - L
		Ligand Field Splitting Parameter: This is the magnitude of the separation of the otherwise degenerate d-orbital levels when exposed to the ligand field.
		Ligand Field Stabilization Energy: The sum of the energies of the d-electrons in a transition metal ion complex compared to their energies in the uncomplexed metal ion.
		Ligand Field Theory: The description of the effect on the metal ion energy levels when in a complex, based on the molecular orbital description of covalent bond formation between the ligands and the metal ion center.
	www.everyscience.com /Chemistry/Glossary/L.php (447 words)

	Mineral Fluorescence: Crystal Field Theory cont'd (Site not responding. Last check: 2007-10-24)
		Crystal field theory suggests that the degenerate nature of the five d-orbitals for an isolated transition metal atom or ion will be altered when interacting with the anions composing the surrounding field.
		However, the orbitals that are aligned with the ligand's orbitals are raised in energy more than those between the ligands, resulting in an energy split between the five d-orbitals, thus preferred lower energy configurations for three of the d-orbital electrons are presented.
		A property of transition metal ions, particularly sensitive to the effects of crystal field interactions, is the interatomic distance in a crystal structure.
	www.sas.upenn.edu /~reillyka/SpecProj/spec_theory2.html (721 words)

	Crystal Field Theory (Site not responding. Last check: 2007-10-24)
		This theory tried to describe the effect of the electrical field of neighboring ions on the energies of the valence orbitals of an ion in a crystal.
		As a result, the splitting observed in a tetrahedral crystal field is the opposite of the splitting in an octahedral complex.
		The splitting of d orbitals in the crystal field model not only depends on the geometry of the complex, it also depends on the nature of the metal ion, the charge on this ion, and the ligands that surround the metal.
	chemed.chem.purdue.edu /genchem/topicreview/bp/ch12/crystal.php (1278 words)

	[No title] (Site not responding. Last check: 2007-10-24)
		In this theory the bonding is observed to be primarily electrostatic.
		Crystal field theory is employed to study the formation of many of the complexes observed with transition metals.
		Ligand- field theory is more sophisticated in that it accounts for covalent as well as ionic bonds and can better explain the behavior of complex ions.
	ed.augie.edu /~jpschwan/crystal.html (416 words)

	Carl J. Ballhausen : History of the Crystal Field Approach - Component of : Early Ideas in the History of Quantum ...
		Thus the best features of both the valence-bond picture and the crystal field theory are incorporated in the ligand field theory, and it is this theory with which we shall be mostly concerned.
		The basic idea of the crystal field theory, namely, that the metal ion in the complexes is subjected to an electric field originating from the ligands, is due to Becquerel
		Nearly all the results of the crystal field theory are also valid in the ligand field theory.
	www.quantum-chemistry-history.com /Ball_Dat/WhatsCFT.htm (1241 words)

	Ligand-Field Theory (Site not responding. Last check: 2007-10-24)
		The valence-bond model and the crystal field theory explain some aspects of the chemistry of the transition metals, but neither model is good at predicting all of the properties of transition-metal complexes.
		A third model, based on molecular orbital theory, was therefore developed that is known as ligand-field theory.
		Ligand-field theory enables the 3d, 4s, and 4p orbitals on the metal to overlap with orbitals on the ligand to form the octahedral covalent bond skeleton that holds this complex together.
	chemed.chem.purdue.edu /genchem/topicreview/bp/ch12/ligand.php (283 words)

	Ligand Field Theory (Site not responding. Last check: 2007-10-24)
		It has been established that the ability of ligands to cause a large splitting of the energy between the orbitals is essentially independent of the metal ion and the SPECTROCHEMICAL SERIES is a list of ligands ranked in order of their ability to cause large orbital separations.
		Ligand Field Theory can be considered an extension of Crystal Field Theory such that all levels of covalent interactions can be incorporated into the model.
		Returning to the problem of correctly placing ligands in the Spectrochemical series, the halides are examples of case A and groups like CN- and CO are examples of case B. It is possible then to explain the Spectrochemical series once covalent effects are considered.
	wwwchem.uwimona.edu.jm:1104 /courses/LFT.html (764 words)

	JCE 2002 (79) 1072 [Sep] Ligand Field Theory and Its Applications (by Brian N. Figgis and Michael A. Hitchman)
		Ligand Field Theory and Its Applications by Brian N. Figgis and Michael A. Hitchman is a welcome extension and reworking of Introduction to Ligand Fields.
		The basic physics of the transition metal ion is rounded off with a discussion of the energy levels and the effect of strong and weak ligand fields.
		Ligand Field Theory and Its Applications is an excellent addition to the literature and, coupled with a good molecular orbital text, will make a good text for a complete inorganic structure and bonding course.
	jchemed.chem.wisc.edu /Journal/Issues/2002/Sep/abs1072_2.html (621 words)

	MCD Spectroscopy (Site not responding. Last check: 2007-10-24)
		The MCD spectra of biological metal complexes can be understood in terms of a simple ligand field theory model.
		Ligand field theory basically describes the ligand multipole perturbation of the metal ion and is usually restricted to analysis of the d-orbital splitting in complexes as an aid to interpreting spectroscopic and magnetochemical experiments.
		The pattern of ligand interactions determines the splitting and mixing of electronic wavefunctions in the reduced symmetry of the complex.
	www.bmb.ogi.edu /users/JWW/MCD08.html (234 words)

	McGraw-Hill AccessScience: Ligand field theory
		Accordingly, the ligands are assumed to be sources of negative charge which perturb the energy levels of the central metal ion.
		In this respect the ligands subject the metal ion to an electric field which is analogous to the electric or crystal field produced by the regular distribution of nearest neighbors within an ionic crystalline lattice.
		The crystal field theory allows the energy levels to be calculated and related to experimental observation.
	www.accessscience.com /Encyclopedia/1/17/Est_171400_frameset.html (282 words)

	Module and Programme Catalogue
		On completion of this module the students will have gained an appreciation of the principles of molecular orbital theory, and how it is successful in explaining the many facets of chemical bonding in chemical compounds despite their great diversity.
		They will also be able to appreciate how the theory can be applied to explain chemical reactivity, and to understand the application of ligand field theory to the chemistry of transition metal compounds.
		Ligand field theory: molecular orbital treatment of transition metal complexes; the influence of coordination geometry.
	www.leeds.ac.uk /modules/200203/ug/chem3130.htm (175 words)

	Press Release: The 1977 Nobel Prize in Physics
		At first the electrons of such a perturbing ton feel the influence of the electric field - the crystal field - which is generated by the atomic nuclei and the electrons of the host crystal.
		The electric properties of crystals are described by the so-called band theory which gives a classification with respect to the conductivity in metals, semiconductors, and insulators.
		This theory is not universally valid, however, and a famous exception is provided by nickel oxide, which according to band theory ought to be a metallic conductor but in reality is an insulator.
	nobelprize.org /physics/laureates/1977/press.html (913 words)

	Wiley::Ligand Field Theory and Its Applications
		A complete, up-to-date treatment of ligand field theory and its applications Ligand Field Theory and Its Applications presents an up-to-date account of ligand field theory, the model currently used to describe the metal-ligand interactions in transition metal compounds, and the way it is used to interpret the physical properties of the complexes.
		It examines the traditional electrostatic crystal field model, still widely used by physicists, as well as covalent approaches such as the angular overlap model, which interprets the metal ligand interactions using parameters relating directly to chemical behavior.
		Written by internationally recognized experts in the field, this book provides a comparison between ligand field theory and more sophisticated treatments as well as an account of the methods used to calculate the energy levels in compounds of the transition metals.
	www.wiley.com /WileyCDA/WileyTitle/productCd-0471317764.html (345 words)

	DommiMOE (Site not responding. Last check: 2007-10-24)
		In addition to the computation of an energy contribution for the ligand field stabilisation energy, a Morse function for the treatment of M-L distances and a potential function for 1,3 non-bonded L-L interactions were also added, as they were not part of the original source code.
		The ligand field stabilisation energy is calculated in the original LFMM module of DOMMINO, which has been converted from FORTRAN to C. An API module acts as a translator between the SVL modules and LFMM C source code.
		The calculated ligand field stabilisation energy contribution is returned to SVL and fed into the existing MOE optimiser.
	www2.warwick.ac.uk /fac/sci/chemistry/iccg/research/dommimoe (1063 words)

	Carl J. Ballhausen : Introduction to Ligand Field Theory - Component of : Early Ideas in the History of Quantum ...
		However, the field is advancing so rapidly that a complete survey would be outdated before long.
		I have tried to present the case for the ligand field theory as it is now understood.
		It must always be remembered, however, that the ligand field theory offers only a model of nature, with all the inherent limitations of models.
	www.quantum-chemistry-history.com /Ball_Dat/IntroLF.htm (444 words)

	Coordination Complexes
		Because the six ligands are located at the corners of an octahedron centered around the metal ion, these electron pairs are equivalent to clouds of negative charge that are directed from near the central ion out toward the corners of the octahedron.
		Although the five d orbitals of the central atom all have the same energy in a spherically symmetric field, their energies will not all be the same in the octahedral field imposed by the presence of the ligands.
		Hemoglobin performs the essential task of transporting dioxygen molecules from the lungs to the tissues in which it is used to oxidize glucose, this oxidation serving as the source of free energy required for cellular metabolic processes.
	www.chem1.com /acad/webtext/chembond/cb09.html (2558 words)

Try your search on: Qwika (all wikis)