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Non-Kekulé Molecule
A non-Kekulé molecule is a conjugated system, conjugated hydrocarbon that cannot be assigned a classical Kekulé structure. Since non-Kekulé molecules have two or more formal charges or radical (chemistry), radical centers, their Spin (physics), spin-spin interactions can cause electrical conductivity or ferromagnetism (molecule-based magnets), and applications to functional materials are expected. However, as these molecules are quite reactive and most of them are easily decomposed or Polymerization, polymerized at room temperature, strategies for stabilization are needed for their practical use. Synthesis and observation of these reactive molecules are generally accomplished by matrix-isolation methods. Biradicals The simplest non-Kekulé molecules are biradicals. A biradical is an even-electron chemical compound with two free radical centres which act ''independently'' of each other. They should not be confused with the more general class of diradicals. One of the first bir ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Triangulene
Triangulene (also known as Clar's hydrocarbon) is the smallest triplet-ground-state polybenzenoid. It exists as a biradical with the chemical formula . It was first hypothesized by Czech chemist Erich Clar in 1953. Its first confirmed synthesis was published in a February 2017 issue of '' Nature Nanotechnology'', in a project led by researchers David Fox and Anish Mistry at the University of Warwick in collaboration with IBM. Other attempts by Japanese researchers have been successful only in making substituted triangulene derivatives. A six-step synthesis yielded two isomers of dihydrotriangulene which were then deposited on xenon or copper base. The researchers used a combined scanning tunneling and atomic force microscope (STM/AFM) to remove individual hydrogen atoms. The synthesized molecule of triangulene remained stable at high-vacuum low-temperature conditions for four days, giving the scientists plenty of time to characterize it (also using STM/AFM). 'n''riangulene ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polynuclear Aromatic Hydrocarbons
A Polycyclic aromatic hydrocarbon (PAH) is any member of a class of organic compounds that is composed of multiple fused aromatic rings. Most are produced by the incomplete combustion of organic matter— by engine exhaust fumes, tobacco, incinerators, in roasted meats and cereals, or when biomass burns at lower temperatures as in forest fires. The simplest representative is naphthalene, having two aromatic rings, and the three-ring compounds anthracene and phenanthrene. PAHs are uncharged, non-polar and planar. Many are colorless. Many of them are also found in fossil fuel deposits such as coal and in petroleum. Exposure to PAHs can lead to different types of cancer, to fetal development complications, and to cardiovascular issues. Polycyclic aromatic hydrocarbons are discussed as possible starting materials for abiotic syntheses of materials required by the earliest forms of life. Nomenclature and structure The terms polyaromatic hydrocarbon, or polynuclear aromatic hydroc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quinodimethane
In organic chemistry, a xylylene (sometimes quinone-dimethide) is any of the constitutional isomers having the formula C6H4(CH2)2. These compounds are related to the corresponding quinones and quinone methides by replacement of the oxygen atoms by CH2 groups. ''ortho''- and ''para''-xylylene are best known, although neither is stable in solid or liquid form. The ''meta'' form is a diradical. Certain substituted derivatives of xylylenes are however highly stable, such as tetracyanoquinodimethane and the xylylene dichlorides. p-Xylylene ''p''-Xylylene forms upon pyrolysis of ''p''-xylene or, more readily, the α-substituted derivatives. ''p''-Xylylene dimerizes with moderate efficiency to give ''p''-cyclophane: Further heating of the ''p''-cyclophane gives poly(''para''-xylylene). o-Xylylenes o-Xylylenes (''o''-quinodimethanes) are often generated in situ, e.g., by the pyrolysis of the corresponding sulfone. Another method involves 1,4-elimination of ortho benzylic silanes. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Biradicaloid
Biradicaloids or diradicaloids are molecules with two radical electrons that have significant interaction with each other. The two unpaired electrons are coupled and can either form a singlet ground state ( antiferromagnetic coupling) or a triplet ground state ( ferromagnetic coupling) (Figure 1). This is in contrast to "disbiradicals," where the two radical electrons have no significant interaction and act independently as isolated radical species. Diradicals are characterized by their diradical character, commonly quantified using an indicator \gamma. In the limit of fully degenerate frontier molecular orbitals, \gamma approaches a value of 1, representing 100% diradical character. However, diradicaloids have a small gap between the highest occupied molecular orbital (HOMO) and the lowest occupied molecular orbital (LUMO) and thus can be described as having incomplete diradical character, generally corresponding to a value of \gamma between 0.20 and 0.80. Diradicals have hist ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electron Spin Resonance
Electron paramagnetic resonance (EPR) or electron spin resonance (ESR) spectroscopy is a method for studying materials that have unpaired electrons. The basic concepts of EPR are analogous to those of nuclear magnetic resonance (NMR), but the spins excited are those of the electrons instead of the atomic nuclei. EPR spectroscopy is particularly useful for studying metal complexes and organic radicals. EPR was first observed in Kazan State University by Soviet physicist Yevgeny Zavoisky in 1944, and was developed independently at the same time by Brebis Bleaney at the University of Oxford. Theory Origin of an EPR signal Every electron has a magnetic moment and spin quantum number s = \tfrac , with magnetic components m_\mathrm = + \tfrac or m_\mathrm = - \tfrac . In the presence of an external magnetic field with strength B_\mathrm , the electron's magnetic moment aligns itself either antiparallel ( m_\mathrm = - \tfrac ) or parallel ( m_\mathrm = + \tfrac ) to the fie ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trimethylenemethane
Trimethylenemethane (often abbreviated TMM) is a chemical compound with molecular formula, formula . It is a Charge (chemistry), neutral free molecule with two unsatisfied valence bonds, and is therefore a highly reactive free radical. Formally, it can be viewed as an isobutylene molecule with two hydrogen atoms removed from the terminal methyl groups. Structure The electronic structure of trimethylenemethane was discussed in 1948.C. A. Coulson (1948), Journal de Chimie Physique et de Physico-Chimie Biologique, volume 45, page 243. Cited by Slipchenko and Krylov (2003) It is a neutral four-carbon molecule containing four pi molecular orbitals. When trapped in a solid matrix at about , the six hydrogen atoms of the molecule are equivalent. Thus, it can be described either as zwitterion, or as the simplest conjugated system, conjugated hydrocarbon that non-Kekulé molecule, cannot be given a Kekulé structure. It can be described as the superposition of three states: It has a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coppinger Biradical
Coppinger is a surname of Norse origin historically associated with Ireland and the counties of Suffolk and Kent in England, and the seaboard of Northern France. While there are various spellings in historical documents, after more standardised spellings became established in the C18th the main variant was between Coppinger and Copinger. Whether an individual chose to use one or two ps seems to have been a question of personal preference which thereafter became a fixed tradition in their descendants. Notable people Notable people with the surname include: * Barry Coppinger, British politician * Charles Coppinger (1851–1877), English cricketer *Captain Cuthbert Coppinger, DSC, Royal Navy, Hero of the Battle of Jutland. * Edward Coppinger (1846–1927), English cricketer * Edward Coppinger (1972–), Massachusetts State Representative 2011–2023 * George Coppinger Ashlin (1837–1921), Irish architect *James Coppinger (born 1981), English professional footballer * John W. Cop ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Yang Biradical
Yang may refer to: * Yang, in yin and yang, one half of the two symbolic polarities in Chinese philosophy * Korean yang, former unit of currency of Korea from 1892 to 1902 * YANG, a data modeling language for the NETCONF network configuration protocol Geography * Yang County, in Shaanxi, China * Yangzhou (ancient China), also known as Yang Prefecture * Yang (state), ancient Chinese state * Yang, Iran, a village in Razavi Khorasan Province * Yang River (other) People * Yang, one of the names for the Karen people in the Thai language *Yang di-Pertuan Agong, the constitutional monarch of Malaysia * Andrew Yang, American Politician and Co-Founder of the Forward Party. * Yang (surname) (楊), a Chinese surname * Yang (surname 陽), a Chinese surname * Yang (surname 羊), a Chinese surname * Yang (Korean surname) * Yang Rong (businessman) (, born 1957), Chinese businessman Fictional characters * Cristina Yang, on the TV show ''Grey's Anatomy'' * Yang, from the show ''Yin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aleksei Chichibabin
Alekséy Yevgényevich Chichibábin (; – 15 August 1945) was a Soviet Union, Soviet Russian organic chemist. His name is also written ''Alexei Yevgenievich Chichibabin'' and ''Alexei Euguenievich Tchitchibabine''. Life Chichibábin was born at Kuzemin on March 17, 1871. He studied at the University of Moscow from 1888 until 1892, and received his PhD from the University of Saint Petersburg. In 1896, Chichibáin married Vera Vladimirovna as his wife. He became a professor at the Imperial College of Technology in Moscow in 1909, and remained there until 1929. After losing his daughter Natacha, a chemist, to an industrial oleum accident (explosion) that he deemed preventable, Chichibábin moved to Paris where he remained despite threat of and eventual stripping of his Soviet citizenship and his position in the Academy of Sciences (1936, Academy standing restored posthumously, 1990).David Lewis, 2012, Early Russian Organic Chemists and Their Legacy (Vol. 4, SpringerBriefs in Mole ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
