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Noninnocent Ligand
In chemistry, a (redox) non-innocent ligand is a ligand in a metal complex where the oxidation state is not clear. Typically, complexes containing non-innocent ligands are redox active at mild potentials. The concept assumes that redox reactions in metal complexes are either metal or ligand localized, which is a simplification, albeit a useful one. C.K. Jørgensen first described ligands as "innocent" and "suspect": "Ligands are innocent when they allow oxidation states of the central atoms to be defined. The simplest case of a suspect ligand is NO..." Redox reactions of complexes of innocent vs. non-innocent ligands Conventionally, redox reactions of coordination complexes are assumed to be metal-centered. The reduction of MnO4− to MnO42− is described by the change in oxidation state of manganese from +7 to +6. The oxide ligands do not change in oxidation state, remaining −2. Oxide is an innocent ligand. Another example of conventional metal-centered redox couple is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemistry
Chemistry is the scientific study of the properties and behavior of matter. It is a physical science within the natural sciences that studies the chemical elements that make up matter and chemical compound, compounds made of atoms, molecules and ions: their composition, structure, properties, behavior and the changes they undergo during chemical reaction, reactions with other chemical substance, substances. Chemistry also addresses the nature of chemical bonds in chemical compounds. In the scope of its subject, chemistry occupies an intermediate position between physics and biology. It is sometimes called the central science because it provides a foundation for understanding both Basic research, basic and Applied science, applied scientific disciplines at a fundamental level. For example, chemistry explains aspects of plant growth (botany), the formation of igneous rocks (geology), how atmospheric ozone is formed and how environmental pollutants are degraded (ecology), the prop ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nitric Oxide
Nitric oxide (nitrogen oxide, nitrogen monooxide, or nitrogen monoxide) is a colorless gas with the formula . It is one of the principal oxides of nitrogen. Nitric oxide is a free radical: it has an unpaired electron, which is sometimes denoted by a dot in its chemical formula (•N=O or •NO). Nitric oxide is also a heteronuclear diatomic molecule, a class of molecules whose study spawned early modern theories of chemical bonding. An important intermediate in industrial chemistry, nitric oxide forms in combustion systems and can be generated by lightning in thunderstorms. In mammals, including humans, nitric oxide is a signaling molecule in many physiological and pathological processes. It was proclaimed the " Molecule of the Year" in 1992. The 1998 Nobel Prize in Physiology or Medicine was awarded for discovering nitric oxide's role as a cardiovascular signalling molecule. Its impact extends beyond biology, with applications in medicine, such as the development of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dithiolene
Dithiolene metal complexes are complexes containing 1,2-dithiolene ligands. 1,2-Dithiolene ligands, a particular case of 1,2-dichalcogenolene species along with 1,2-diselenolene derivatives, are unsaturated bidentate ligand wherein the two donor atoms are sulfur. 1,2-Dithiolene metal complexes are often referred to as "metal dithiolenes", "metallodithiolenes" or "dithiolene complexes". Most molybdenum- and tungsten-containing proteins have dithiolene-like moieties at their active sites, which feature the so-called molybdopterin cofactor bound to the Mo or W. Dithiolene metal complexes have been studied since the 1960s when they were first popularized by Gerhard N. Schrauzer and Volker P. Mayweg, who prepared nickel bis(stilbene-1,2-dithiolate) () by the reaction of nickel sulfide and diphenylacetylene. The structural, spectroscopic, and electrochemical properties of many related complexes have been described. Structure Dithiolene metal complexes can be found in coordination co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Catechol
Catechol ( or ), also known as pyrocatechol or 1,2-dihydroxybenzene, is an organic compound with the molecular formula . It is the ''ortho'' isomer of the three isomeric benzenediols. This colorless compound occurs naturally in trace amounts. It was first discovered by destructive distillation of the plant extract catechin. About 20,000 tonnes of catechol are now synthetically produced annually as a commodity organic chemical, mainly as a precursor to pesticides, flavors, and fragrances. Small amounts of catechol occur in fruits and vegetables. Isolation and synthesis Catechol was first isolated in 1839 by Edgar Hugo Emil Reinsch (1809–1884) by distilling it from the solid tannic preparation catechin, which is the residuum of catechu, the boiled or concentrated juice of ''Mimosa catechu'' ('' Acacia catechu''). Upon heating catechin above its decomposition point, a substance that Reinsch first named ''Brenz-Katechusäure'' (burned catechu acid) sublimated as a white efflo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metal Acetylacetonates
Metal acetylacetonates are coordination complexes derived from the acetylacetone, acetylacetonate anion () and metal ions, usually transition metals. The bidentate ligand acetylacetonate is often abbreviated acac. Typically both oxygen atoms bind to the metal to form a six-membered chelate ring. The simplest complexes have the formula M(acac)3 and M(acac)2. Mixed-ligand complexes, e.g. VO(acac)2, are also numerous. Variations of acetylacetonate have also been developed with myriad substituents in place of methyl (RCOCHCO−). Many such complexes are soluble in organic solvents, in contrast to the related metal halides. Because of these properties, acac complexes are sometimes used as catalyst precursors and reagents. Applications include their use as NMR "shift reagents" and as catalysts for organic synthesis, and precursors to industrial hydroformylation catalysts. in some cases also binds to metals through the central carbon atom; this bonding mode is more common for the third-row ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NacNac
NacNac is a class of anionic bidentate ligands. 1,3-Diketimines are often referred to as "HNacNac", a modification of the abbreviation Hacetylacetone, acac used for 1,3-diketones. These species can exist as a mixture of tautomers. Preparation of ligands and complexes Acetylacetone and related 1,3-diketones Condensation reaction, condense with primary alkyl- or arylamines resulting in replacement of the carbonyl oxygen atoms with NR groups, where R = aryl, alkyl. To prepare 1,3-diketimines from Steric effects, bulky amines, e.g. 2,4,6-Trimethylaniline, 2,4,6-trimethylanilines, prolonged reaction times are required. 2,6-Diisopropylaniline is a common bulky building block. Deprotonation of HNacNac compounds affords anionic bidentate ligands that form a variety of coordination complexes. Some derivatives with large Side chain, R groups can be used to stabilize low valent p-block, main group and transition metal complexes. Unlike the situation for the acetylacetonates, the steric pro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aryl
In organic chemistry, an aryl is any functional group or substituent derived from an aromatic ring, usually an aromatic hydrocarbon, such as phenyl and naphthyl. "Aryl" is used for the sake of abbreviation or generalization, and "Ar" is used as a placeholder for the aryl group in chemical structure diagrams, analogous to “R” used for any organic substituent. “Ar” is not to be confused with the elemental symbol for argon. A simple aryl group is phenyl (), a group derived from benzene. Examples of other aryl groups consist of: * The tolyl group () which is derived from toluene (methylbenzene) * The xylyl group (), which is derived from xylene (dimethylbenzene) * The naphthyl group (), which is derived from naphthalene Arylation is the process in which an aryl group is attached to a substituent. It is typically achieved by cross-coupling reactions. Nomenclature The simplest aryl group is phenyl, which is made up of a benzene ring with one of its hydrogen atom ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alkyl
In organic chemistry, an alkyl group is an alkane missing one hydrogen. The term ''alkyl'' is intentionally unspecific to include many possible substitutions. An acyclic alkyl has the general formula of . A cycloalkyl group is derived from a cycloalkane by removal of a hydrogen atom from a Ring (chemistry), ring and has the general formula . Typically an alkyl is a part of a larger molecule. In structural formulae, the symbol R is used to designate a generic (unspecified) alkyl group. The smallest alkyl group is methyl, with the formula . Related concepts Alkylation is the addition of alkyl groups to molecules, often by alkylating agents such as Haloalkane, alkyl halides. Alkylating antineoplastic agents are a class of compounds that are used to treat cancer. In such case, the term alkyl is used loosely. For example, nitrogen mustards are well-known alkylating agents, but they are not simple hydrocarbons. In chemistry, alkyl is a group, a substituent, that is attached to ot ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Corrole
A corrole is an aromatic tetrapyrrole. The corrin ring is also present in cobalamin ( vitamin B12). The ring consists of nineteen carbon atoms, with four nitrogen atoms in the core of the molecule. In this sense, corrole is very similar to porphyrin. Preparation Corroles can be prepared by a two-step process, beginning with the condensation reaction of a benzaldehyde with pyrrole. The open-ring product, a bilane (or tetrapyrrane), is cyclized by oxidation, typically with ''p''-chloranil: Comparison with porphyrins Corrole and porphyrins differ in several ways. Corroles are triprotic, whereas porphyrins are diprotic. Because of the 3- charge of the triply deprotonated ligand, metallocorroles are formally high-valent. Several are redox-noninnocent, with a corrole radical-dianion ligand. A second difference between corroles and porphyrins is the size of the metal-binding cavity, i.e., 17- vs 18-membered rings. See "Porphyrins and similar compounds" in conjugated systems ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phthalocyanine
Phthalocyanine () is a large, aromatic, macrocyclic, organic compound with the formula and is of theoretical or specialized interest in chemical dyes and photoelectricity. It is composed of four isoindole units linked by a ring of nitrogen atoms. = has a two-dimensional geometry and a ring system consisting of 18 π-electrons. The extensive delocalization of the π-electrons affords the molecule useful properties, lending itself to applications in dyes and pigments. Metal complexes derived from , the conjugate base of , are valuable in catalysis, organic solar cells, and photodynamic therapy. Properties Phthalocyanine and derived metal complexes (MPc) tend to aggregate and, thus, have low solubility in common solvents. Benzene at 40 °C dissolves less than a milligram of or CuPc per litre. and CuPc dissolve easily in sulfuric acid due to the protonation of the nitrogen atoms bridging the pyrrole rings. Many phthalocyanine compounds are, thermally, very s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Porphyrin
Porphyrins ( ) are heterocyclic, macrocyclic, organic compounds, composed of four modified pyrrole subunits interconnected at their α carbon atoms via methine bridges (). In vertebrates, an essential member of the porphyrin group is heme, which is a component of hemoproteins, whose functions include carrying oxygen in the bloodstream. In plants, an essential porphyrin derivative is chlorophyll, which is involved in light harvesting and electron transfer in photosynthesis. The parent of porphyrins is porphine, a rare chemical compound of exclusively theoretical interest. Substituted porphines are called porphyrins. With a total of 26 π-electrons the porphyrin ring structure is a coordinated aromatic system. One result of the large conjugated system is that porphyrins absorb strongly in the visible region of the electromagnetic spectrum, i.e. they are deeply colored. The name "porphyrin" derives . Structure Porphyrin complexes consist of a square planar MN4 core. The p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metal Peroxide
A metal () is a material that, when polished or fractured, shows a lustrous appearance, and conducts electrical resistivity and conductivity, electricity and thermal conductivity, heat relatively well. These properties are all associated with having electrons available at the Fermi level, as against nonmetallic materials which do not. Metals are typically ductile (can be drawn into a wire) and malleable (can be shaped via hammering or pressing). A metal may be a chemical element such as iron; an alloy such as stainless steel; or a molecular compound such as polythiazyl, polymeric sulfur nitride. The general science of metals is called metallurgy, a subtopic of materials science; aspects of the electronic and thermal properties are also within the scope of condensed matter physics and solid-state chemistry, it is a multidisciplinary topic. In colloquial use materials such as steel alloys are referred to as metals, while others such as polymers, wood or ceramics are nonmetallic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
