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Charge Transfer Band
193px, The intense color of tris(bipyridine)ruthenium(II) arises from a metal-to-ligand charge-transfer band. Charge-transfer bands are a characteristic feature of the optical spectra of many compounds. These bands are typically more intense than d–d transitions. They typically exhibit solvatochromism, consistent with shifts of electron density that would be sensitive to solvation. CT absorptions bands are intense and often lie in the ultraviolet or visible portion of the spectrum. For coordination complexes, charge-transfer bands often exhibit molar absorptivities, ε, of about 50000 L mol−1 cm−1. By contrast ε values for d–d transitions are in the range of 20–200 L mol−1. CT transitions are spin-allowed and Laporte-allowed. The weaker d–d transitions are potentially spin-allowed but always Laporte-forbidden. Charge-transfer bands of transition metal complexes result from shift of charge density between molecular orbitals (MO) that are predominantly metal in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tris(bipyridine)ruthenium(II)-chloride-powder
Tris, or tris(hydroxymethyl)aminomethane, or known during medical use as tromethamine or THAM, is an organic compound with the formula (HOCH2)3CNH2, one of the twenty Good's buffers. It is extensively used in biochemistry and molecular biology as a component of buffer solutions such as in TAE and TBE buffers, especially for solutions of nucleic acids. It contains a primary amine and thus undergoes the reactions associated with typical amines, e.g. condensations with aldehydes. Tris also complexes with metal ions in solution. In medicine, tromethamine is occasionally used as a drug, given in intensive care for its properties as a buffer for the treatment of severe metabolic acidosis in specific circumstances. Some medications are formulated as the "tromethamine salt" including Hemabate (carboprost as trometamol salt), and "ketorolac trometamol". Buffering features The conjugate acid of tris has a p''K''a of 8.07 at 25 °C, which implies that the buffer has an effective pH r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solvatochromism
In chemistry, solvatochromism is the phenomenon observed when the colour due to a solute is different when that solute is dissolved in different solvents. The solvatochromic effect is the way the spectrum of a substance (the solute) varies when the substance is dissolved in a variety of solvents. In this context, the dielectric constant and hydrogen bonding capacity are the most important properties of the solvent. With various solvents there is a different effect on the electronic ground state and excited state of the solute, so that the size of energy gap between them changes as the solvent changes. This is reflected in the absorption or emission spectrum of the solute as differences in the position, intensity, and shape of the spectroscopic bands. When the spectroscopic band occurs in the visible part of the spectrum solvatochromism is observed as a change of colour. This is illustrated by Reichardt's dye, as shown in the image. Negative solvatochromism corresponds to a hypsoc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coordination Complex
A coordination complex consists 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 are common. These compl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Laporte Rule
The Laporte rule is a rule that explains the intensities of absorption spectra for chemical species. It is a selection rule that rigorously applies to chromophores that are centrosymmetric, i.e. with an inversion centre. It states that electronic transitions that conserve parity are forbidden. Thus transitions between states that are symmetric with respect to an inversion centre will not be observed. Transitions between states that are unsymmetric with respect to inversion are forbidden as well. In the language of symmetry, ''g'' (gerade = even (German)) → ''g'' and ''u'' (ungerade = odd) → ''u'' transitions are forbidden. Allowed transitions in such molecules must involve a change in parity, either ''g'' → ''u'' or ''u'' → ''g''. The Laporte rule stipulates that s to s, p to p, d to d, etc. transitions should not be observed in centrosymmetric compounds. Practically speaking, only d-d transitions occur in the visible region of the spectrum. Thus, the Laporte rule is mos ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molecular Orbitals
In chemistry, a molecular orbital is a mathematical function describing the location and wave-like behavior of an electron in a molecule. This function can be used to calculate chemical and physical properties such as the probability of finding an electron in any specific region. The terms ''atomic orbital'' and ''molecular orbital'' were introduced by Robert S. Mulliken in 1932 to mean ''one-electron orbital wave functions''. At an elementary level, they are used to describe the ''region'' of space in which a function has a significant amplitude. In an isolated atom, the orbital electrons' location is determined by functions called atomic orbitals. When multiple atoms combine chemically into a molecule, the electrons' locations are determined by the molecule as a whole, so the atomic orbitals combine to form molecular orbitals. The electrons from the constituent atoms occupy the molecular orbitals. Mathematically, molecular orbitals are an approximate solution to the Schrödin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Permanganate Spectrum
A permanganate () is a chemical compound containing the manganate(VII) ion, , the conjugate base of permanganic acid. Because the manganese atom is in the +7 oxidation state, the permanganate(VII) ion is a strong oxidizing agent. The ion is a transition metal oxo complex with tetrahedral geometry. Permanganate solutions are purple in color and are stable in neutral or slightly alkaline media. The exact chemical reaction is dependent upon the organic contaminants present and the oxidant utilized. For example, trichloroethane (C2H3Cl3) is oxidized by permanganate ions to form carbon dioxide (CO2), manganese dioxide (MnO2), hydrogen ions (H+), and chloride ions (Cl−). :8 + 3 → 6 + 8 + + 4 + 9 In an acidic solution, permanganate(VII) is reduced to the pale pink +2 oxidation state of the manganese(II) (Mn2+) ion. :8 + + 5 e− → Mn2+ + 4 H2O In a strongly basic solution, permanganate(VII) is reduced to the green +6 oxidation state of the manganate ion, . ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tris(bipyridine)ruthenium(II) Chloride
Tris(bipyridine)ruthenium(II) chloride is the chloride salt coordination complex with the formula u(bpy)3sup>2+ 2Cl−. This polypyridine complex is a red crystalline salt obtained as the hexahydrate, although all of the properties of interest are in the cation u(bpy)3sup>2+, which has received much attention because of its distinctive optical properties. The chlorides can be replaced with other anions, such as PF6−. Synthesis and structure left, 144px, Cis-Dichlorobis(bipyridine)ruthenium(II), ''cis''-Dichlorobis(bipyridine)ruthenium(II) is an intermediate in the synthesis of tris(bipyridine)ruthenium(II) chloride. This salt is prepared by treating an aqueous solution of ruthenium trichloride with 2,2'-bipyridine. In this conversion, Ru(III) is reduced to Ru(II), and hypophosphorous acid is typically added as a reducing agent. u(bpy)3sup>2+ is octahedral, containing a central low spin d6 Ru(II) ion and three bidentate bpy ligands. The Ru-N distances are 2.053(2), short ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pigment Berliner Blau
A pigment is a colored material that is completely or nearly Solubility, insoluble in water. In contrast, dyes are typically soluble, at least at some stage in their use. Generally dyes are often organic compounds whereas pigments are often inorganic compounds. Pigments of prehistoric and historic value include ochre, charcoal, and lapis lazuli. Economic impact In 2006, around 7.4 million tons of inorganic chemistry, inorganic, organic chemistry, organic, and special pigments were marketed worldwide. Estimated at around US$14.86 billion in 2018 and will rise at over 4.9% CAGR from 2019 to 2026. The global demand for pigments was roughly US$20.5 billion in 2009. According to an April 2018 report by ''Bloomberg Businessweek'', the estimated value of the pigment industry globally is $30 billion. The value of titanium dioxide – used to enhance the white brightness of many products – was placed at $13.2 billion per year, while the color Ferrari red is valued at $ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Intervalence Charge Transfer
192 px, The intense blue color of Prussian blue is a consequence of an intervalence charge transfer band. In chemistry, intervalence charge transfer, often abbreviated IVCT or even IT, is a type of charge-transfer band that is associated with mixed valence compounds. It is most common for systems with two metal sites differing only in oxidation state. Quite often such electron transfer reverses the oxidation states of the sites. The term is frequently extended to the case of metal-to-metal charge transfer between non-equivalent metal centres. The transition produces a characteristically intense absorption in the electromagnetic spectrum. The band is usually found in the visible or near infrared region of the spectrum and is broad. The process can be described as follows: :LnM+-bridge-M'Ln + hν → LnM-bridge-M'+Ln where L is a bridging ligand In coordination chemistry, a bridging ligand is a ligand that connects two or more atoms, usually metal ions. The ligand may be a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mixed-valence Compound
Mixed valence complexes contain an element which is present in more than one oxidation state. Well-known mixed valence compounds include the Creutz–Taube complex, Prussian blue, and molybdenum blue. Many solids are mixed-valency including indium chalcogenides. Robin–Day classification Mixed-valence compounds are subdivided into three groups, according to the Robin–Day classification: *Class I, where the valences are trapped—localized on a single site—such as Pb3O4 and antimony tetroxide. There are distinct sites with different specific valences in the complex that cannot easily interconvert. *Class II, which are intermediate in character. There is some localization of distinct valences, but there is a low activation energy for their interconversion. Some thermal activation is required to induce electron transfer from one site to another via the bridge. These species exhibit an intense Intervalence charge transfer (IT or IVCT) band, a broad intense absorption in t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Infrared
Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around 1 millimeter (300 GHz) to the nominal red edge of the visible spectrum, around 700 nanometers (430 THz). Longer IR wavelengths (30 μm-100 μm) are sometimes included as part of the terahertz radiation range. Almost all black-body radiation from objects near room temperature is at infrared wavelengths. As a form of electromagnetic radiation, IR propagates energy and momentum, exerts radiation pressure, and has properties corresponding to both those of a wave and of a particle, the photon. It was long known that fires emit invisible heat; in 1681 the pioneering experimenter Edme Mariotte showed that glass, though transparent to sunlight, obstructed radiant heat. In 1800 the astronomer Sir William Herschel discovered ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
