In coordination chemistry, a coordinate covalent bond, also known as a dative bond, dipolar bond, or coordinate bond is a kind of two-center, two-electron covalent bond in which the two electrons derive from the same atom. The bonding of metal ions to ligands involves this kind of interaction. This type of interaction is central to Lewis acid–base theory.
Cubane is a synthetic hydrocarbon compound with the formula C8H8, and that consists of eight carbon atoms arranged at the corners of a cube, with one hydrogen atom attached to each carbon atom. A solid crystalline substance, cubane is one of the Platonic hydrocarbons and a member of the prismanes. It was first synthesized in 1964 by Philip Eaton and Thomas Cole. Before this work, Eaton believed that cubane would be impossible to synthesize due to the "required 90 degree bond angles". The cubic shape requires the carbon atoms to adopt an unusually sharp 90° bonding angle, which would be highly strained as compared to the 109.45° angle of a tetrahedral carbon. Once formed, cubane is quite kinetically stable, due to a lack of readily available decomposition paths. It is the simplest hydrocarbon with octahedral symmetry.
Cyclobutadiene is an organic compound with the formula C4H4. It is very reactive owing to its tendency to dimerize. Although the parent compound has not been isolated, some substituted derivatives are robust and a single molecule of cyclobutadiene is quite stable. Since the compound degrades by a bimolecular process, the species can be observed by matrix isolation techniques at temperatures below 35 K. It is thought to adopt a rectangular structure.
In organic chemistry, a carbene is a molecule containing a neutral carbon atom with a valence of two and two unshared valence electrons. The general formula is R−:C−R' or R=C: where the R represents substituents or hydrogen atoms.
A non-Kekulé molecule is a conjugated hydrocarbon that cannot be assigned a classical Kekulé structure.
In chemistry, a nitrene or imene is the nitrogen analogue of a carbene. The nitrogen atom is uncharged and univalent, so it has only 6 electrons in its valence level—two covalent bonded and four non-bonded electrons. It is therefore considered an electrophile due to the unsatisfied octet. A nitrene is a reactive intermediate and is involved in many chemical reactions. The simplest nitrene, HN, is called imidogen, and that term is sometimes used as a synonym for the nitrene class.
In chemistry, a diradical is a molecular species with two electrons occupying molecular orbitals (MOs) which are degenerate. The term "diradical" is mainly used to describe organic compounds, where most diradicals are extremely reactive and in fact rarely isolated. Diradicals are even-electron molecules but have one fewer bond than the number permitted by the octet rule.
Organic photochemistry encompasses organic reactions that are induced by the action of light. The absorption of ultraviolet light by organic molecules often leads to reactions. In the earliest days, sunlight was employed, while in more modern times ultraviolet lamps are employed. Organic photochemistry has proven to be a very useful synthetic tool. Complex organic products can be obtained simply.
Atomic carbon, systematically named carbon and λ0-methane, is a colourless gaseous inorganic chemical with the chemical formula C. It is kinetically unstable at ambient temperature and pressure, being removed through autopolymerisation.
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.
In chemistry, a radical, also known as a free radical, is an atom, molecule, or ion that has at least one unpaired valence electron. With some exceptions, these unpaired electrons make radicals highly chemically reactive. Many radicals spontaneously dimerize. Most organic radicals have short lifetimes.
In chemistry, π-effects or π-interactions are a type of non-covalent interaction that involves π systems. Just like in an electrostatic interaction where a region of negative charge interacts with a positive charge, the electron-rich π system can interact with a metal, an anion, another molecule and even another π system. Non-covalent interactions involving π systems are pivotal to biological events such as protein-ligand recognition.
Pentacarbon dioxide, officially penta-1,2,3,4-tetraene-1,5-dione, is an oxide of carbon (an oxocarbon) with formula C5O2 or O=C=C=C=C=C=O.
Tetracarbon dioxide is an oxide of carbon, a chemical compound of carbon and oxygen, with chemical formula C4O2 or O=C=C=C=C=O. It can be regarded as butatriene dione, the double ketone of butatriene — more precisely 1,2,3-butatriene-1,4-dione.
Cyclobutanetetrone, also called tetraoxocyclobutane, is an organic compound with formula C4O4 or (CO)4, the fourfold ketone of cyclobutane. It would be an oxide of carbon, indeed a tetramer of carbon monoxide.
In chemistry, peroxydicarbonate is a divalent anion with the chemical formula C
2O2−
6. It is one of the oxocarbon anions, which consist solely of carbon and oxygen. Its molecular structure can be viewed as two carbonate anions joined so as to form a peroxide bridge –O–O–.
A photooxygenation is a light-induced oxidation reaction in which molecular oxygen is incorporated into the product(s). Initial research interest in photooxygenation reactions arose from Oscar Raab's observations in 1900 that the combination of light, oxygen and photosensitizers is highly toxic to cells. Early studies of photooxygenation focused on oxidative damage to DNA and amino acids, but recent research has led to the application of photooxygenation in organic synthesis and photodynamic therapy.
Singlet fission is a spin-allowed process, unique to molecular photophysics, whereby one singlet excited state is converted into two triplet states. The phenomenon has been observed in molecular crystals, aggregates, disordered thin films, and covalently-linked dimers, where the chromophores are oriented such that the electronic coupling between singlet and the double triplet states is large. Being spin allowed, the process can occur very rapidly and out-compete radiative decay thereby producing two triplets with very high efficiency. The process is distinct from intersystem crossing, in that singlet fission does not involve a spin flip, but is mediated by two triplets coupled into an overall singlet. It has been proposed that singlet fission in organic photovoltaic devices could improve the photoconversion efficiencies.
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.
The phosphaethynolate anion, also referred to as PCO, is the phosphorus-containing analogue of the cyanate anion with the chemical formula [PCO]− or [OCP]−. The anion has a linear geometry and is commonly isolated as a salt. When used as a ligand, the phosphaethynolate anion is ambidentate in nature meaning it forms complexes by coordinating via either the phosphorus or oxygen atoms. This versatile character of the anion has allowed it to be incorporated into many transition metal and actinide complexes but now the focus of the research around phosphaethynolate has turned to utilising the anion as a synthetic building block to organophosphanes.
