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Non-Kekulé Molecule
A non-Kekulé molecule is a conjugated hydrocarbon that cannot be assigned a classical Kekulé structure. Since non-Kekulé molecules have two or more formal charges radical centers, their 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 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 biradicals was synthesized by Wilhelm Schlenk in 1915 following the same met ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Erich Clar
Erich Clar (23 August 1902 in Hřensko – 27 March 1987 in Estepona) was an Austrian organic chemist who studied polycyclic aromatic hydrocarbon chemistry. He is considered as the father of that field. In 1941, he authored "Aromatische Kohlenwasserstoffe" (Springer-Verlag) and in 1964 the greatly expanded two-volume ''Polycyclic Hydrocarbons'', which described the syntheses, properties, and UV-visible absorption spectra of hundreds of PAHs. He discovered the Clar reaction of the cyclic ketone perinaphthenone to form dibenzo d,lmerylene in a 400 C melt of zinc dust, zinc (II) chloride, and sodium chloride. He created the Sextet Theory, now eponymously called ''Clar's rule'', to describe the behavior of polycyclic aromatic hydrocarbon isomers. This was described in his book ''The Aromatic Sextet''. He was awarded the August Kekulé Medal by the Chemical Society of the GDR in 1965, the highest award given by that society to foreign scientists, and the first Polycyclic Aromatic Hydroc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Triangulene
Triangulene (also known as Clar's hydrocarbon) is the smallest Triplet state, triplet-ground-state Polycyclic aromatic hydrocarbon, polybenzenoid. It exists as a biradical with the chemical formula . It was first hypothesized by Czech Republic, 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 microscope, scanning tunneling and Atomic-force microscopy, atomic force microscope (STM/AFM) to remove individual hydrogen atoms. The synthesized molecule of triangulene remained stable at high-vacuum low-Cryogenics, tempera ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polynuclear Aromatic Hydrocarbons
A polycyclic aromatic hydrocarbon (PAH) is a class of organic compounds that is composed of multiple aromatic rings. 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 found in coal and in oil deposits, and are also produced by the combustion of organic matter—for example, in engines and incinerators or when biomass burns in forest fires. 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 hydrocarbon are also used for this concept. By definition, polycyclic aromatic hydrocarbons have multiple rings, precluding benzene from being considered a PAH. Some sources, such as the US EPA and CDC, consider naphthalene to be the simplest PAH. Other ... [...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 fi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trimethylenemethane
Trimethylenemethane (often abbreviated TMM) is a chemical compound with formula . It is a 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 hydrocarbon that cannot be given a Kekulé structure. It can be described as the superposition of three states: It has a triplet ground state (3''A''2′/3''B''2), and is therefore a diradical i ... [...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 * George Coppinger Ashlin (1837–1921), Irish architect * James Coppinger (born 1981), English professional footballer *John W. Coppinger (1852–1900), American politician and lawyer *José María Coppinge ... [...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 * Yang (surname), Chinese surname * Yang (Korean surname) Fictional characters * Cristina Yang, on the TV show ''Grey's Anatomy'' * Yang, from the show '' Yin Yang Yo!'' * Yang, Experiment 502 in '' Lilo and Stitch: The Series'' * Yang Fang Leiden, from ''Final Fantasy IV'' * Yang Lee, in the ''Street Fighter III'' series of videogames * Mr. Yang, the Yin Yang serial killer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aleksei Chichibabin
Alekséy Yevgényevich Chichibábin (russian: Алексей Евгеньевич Чичибабин) was a Soviet Union, Soviet/Russian organic chemist, born , Kuzemin village, current Sumy Oblast, Ukraine, died in Paris, France, 15 August 1945. 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 st ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
