In chemistry, the oxidation state, or oxidation number, is the hypothetical charge of an atom if all of its bonds to other atoms were fully ionic. It describes the degree of oxidation of an atom in a chemical compound. Conceptually, the oxidation state may be positive, negative or zero. While fully ionic bonds are not found in nature, many bonds exhibit strong ionicity, making oxidation state a useful predictor of charge.
In chemistry, noble gas compounds are chemical compounds that include an element from the noble gases, group 18 of the periodic table. Although the noble gases are generally unreactive elements, many such compounds have been observed, particularly involving the element xenon.
A non-Kekulé molecule is a conjugated hydrocarbon that cannot be assigned a classical Kekulé structure.
Tetrazoles are a class of synthetic organic heterocyclic compound, consisting of a 5-member ring of four nitrogen atoms and one carbon atom. The name tetrazole also refers to the parent compound with formula CH2N4, of which three isomers can be formulated.
Pentacene is a polycyclic aromatic hydrocarbon consisting of five linearly-fused benzene rings. This highly conjugated compound is an organic semiconductor. The compound generates excitons upon absorption of ultra-violet (UV) or visible light; this makes it very sensitive to oxidation. For this reason, this compound, which is a purple powder, slowly degrades upon exposure to air and light.
Hexacene is an aromatic compound consisting of six linearly-fused benzene rings. It is a blue-green, air-stable solid with low solubility.
Phosphine oxides are phosphorus compounds with the formula OPX3. When X = alkyl or aryl, these are organophosphine oxides. Triphenylphosphine oxide is an example. An inorganic phosphine oxide is phosphoryl chloride (POCl3).
The Negishi coupling is a widely employed transition metal catalyzed cross-coupling reaction. The reaction couples organic halides or triflates with organozinc compounds, forming carbon-carbon bonds (C-C) in the process. A palladium (0) species is generally utilized as the metal catalyst, though nickel is sometimes used. A variety of nickel catalysts in either Ni0 or NiII oxidation state can be employed in Negishi cross couplings such as Ni(PPh3)4, Ni(acac)2, Ni(COD)2 etc.
In organic chemistry, the acenes or polyacenes are a class of organic compounds and polycyclic aromatic hydrocarbons made up of benzene rings which have been linearly fused. They follow the general molecular formula C4n+2H2n+4.
Bioconjugation is a chemical strategy to form a stable covalent link between two molecules, at least one of which is a biomolecule.
In chemistry, an oxocarbon or oxide of carbon is a chemical compound consisting only of carbon and oxygen. The simplest and most common oxocarbons are carbon monoxide (CO) and carbon dioxide. Many other stable or metastable oxides of carbon are known, but they are rarely encountered, such as carbon suboxide and mellitic anhydride.
Diborane(2), also known as diborene, is an inorganic compound with the formula B2H2. The number 2 in diborane(2) indicates the number of hydrogen atoms bonded to the boron complex. There are other forms of diborane with different numbers of hydrogen atoms, including diborane(4) and diborane(6).
A borylene is the boron analogue of a carbene. The general structure is R-B: with R an organic moiety and B a boron atom with two unshared electrons. Borylenes are of academic interest in organoboron chemistry. A singlet ground state is predominant with boron having two vacant sp2 orbitals and one doubly occupied one. With just one additional substituent the boron is more electron deficient than the carbon atom in a carbene. For this reason stable borylenes are more uncommon than stable carbenes. Some borylenes such as boron monofluoride (BF) and boron monohydride (BH) the parent compound also known simply as borylene, have been detected in microwave spectroscopy and may exist in stars. Other borylenes exist as reactive intermediates and can only be inferred by chemical trapping.
Holger Braunschweig is Head and Chair of Inorganic Chemistry at the Julius-Maximilians-University of Würzburg in Würzburg, Germany. He is best known for founding the field of transition metal-boron multiple bonding, the synthesis of the first stable compounds containing boron-boron and boron-oxygen triple bonds, the isolation of the first non-carbon/nitrogen main-group dicarbonyl, and the first fixation of dinitrogen at an element of the p-block of the periodic table. By modifying a strategy pioneered by Prof. Gregory Robinson of the University of Georgia, Braunschweig also discovered the first rational and high-yield synthesis of neutral compounds containing boron-boron double bonds (diborenes). In 2016 Braunschweig isolated the first compounds of beryllium in the oxidation state of zero.
In chemistry, aluminium(I) refers to monovalent aluminium (+1 oxidation state) in both ionic and covalent bonds. Along with aluminium(II), it is an extremely unstable form of aluminium.
(Pentamethylcyclopentadienyl)aluminium(I) is an organometallic compound with the formula Al(C5Me5) ("Me" is a methyl group; CH3). The compound is often abbreviated to AlCp* or Cp*Al, where Cp* is the pentamethylcyclopentadienide anion (C5Me5−). Discovered in 1991 by Dhmeier et al., AlCp* serves as the first ever documented example of a room temperature stable monovalent aluminium compound. In its isolated form, Cp*Al exists as the tetramer [Cp*Al]4, and is a yellow crystal that decomposes at temperatures above 100 °C but also sublimes at temperatures above 140 °C.
An oxyhydride is a mixed anion compound containing both oxide O2− and hydride ions H−. These compounds may be unexpected as the hydrogen and oxygen could be expected to react to form water. But if the metals making up the cations are electropositive enough, and the conditions are reducing enough, solid materials can be made that combine hydrogen and oxygen in the negative ion role.
A solid-state electrolyte (SSE) is a solid ionic conductor and electron-insulating material and it is the characteristic component of the solid-state battery. It is useful for applications in electrical energy storage (EES) in substitution of the liquid electrolytes found in particular in lithium-ion battery. The main advantages are the absolute safety, no issues of leakages of toxic organic solvents, low flammability, non-volatility, mechanical and thermal stability, easy processability, low self-discharge, higher achievable power density and cyclability. This makes possible, for example, the use of a lithium metal anode in a practical device, without the intrinsic limitations of a liquid electrolyte thanks to the property of lithium dendrite suppression in the presence of a solid-state electrolyte membrane. The utilization of a high capacity anode and low reduction potential, like lithium with a specific capacity of 3860 mAh g−1 and a reduction potential of -3.04 V vs SHE, in substitution of the traditional low capacity graphite, which exhibits a theoretical capacity of 372 mAh g−1 in its fully lithiated state of LiC6, is the first step in the realization of a lighter, thinner and cheaper rechargeable battery. Moreover, this allows the reach of gravimetric and volumetric energy densities, high enough to achieve 500 miles per single charge in an electric vehicle. Despite the promising advantages, there are still many limitations that are hindering the transition of SSEs from academia research to large-scale production, depending mainly on the poor ionic conductivity compared to that of liquid counterparts. However, many car OEMs (Toyota, BMW, Honda, Hyundai) expect to integrate these systems into viable devices and to commercialize solid-state battery-based electric vehicles by 2025.
Iridium compounds are compounds containing the element iridium (Ir). Iridium forms compounds in oxidation states between −3 and +9, but the most common oxidation states are +1, +3, and +4. Well-characterized compounds containing iridium in the +6 oxidation state include IrF6 and the oxides Sr2MgIrO6 and Sr2CaIrO6. iridium(VIII) oxide was generated under matrix isolation conditions at 6 K in argon. The highest oxidation state (+9), which is also the highest recorded for any element, is found in gaseous [IrO4]+.
Stable and persistent phosphorus radicals are phosphorus-centred radicals that are isolable and can exist for at least short periods of time. Radicals consisting of main group elements are often very reactive and undergo uncontrollable reactions, notably dimerization and polymerization. The common strategies for stabilising these phosphorus radicals usually include the delocalisation of the unpaired electron over a pi system or nearby electronegative atoms, and kinetic stabilisation with bulky ligands. Stable and persistent phosphorus radicals can be classified into three categories: neutral, cationic, and anionic radicals. Each of these classes involve various sub-classes, with neutral phosphorus radicals being the most extensively studied. Phosphorus exists as one isotope 31P (I = 1/2) with large hyperfine couplings relative to other spin active nuclei, making phosphorus radicals particularly attractive for spin-labelling experiments.
