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NTCDI AFM2
Naphthalenetetracarboxylic diimide (NTCDI) is a solid organic compound and one of the simplest naphthalenediimides (NDIs). NTCDI is produced from the parent naphthalene via an intermediate compound naphthalenetetracarboxylic dianhydride. Properties NTCDI is redox-active, forming stable radical anions near -1.10 V vs. Fc/Fc+. Its ability to accept electrons reflects the presence of an extended conjugated ring system and the electron withdrawing groups (carbonyl centers). NDI is used in supramolecular chemistry owing to its tendency to form charge-transfer complexes with crown ethers, e.g., to give rotaxanes and catenanes. As another consequence of their planar structure and electron-acceptor properties, NDIs intercalate Intercalation may refer to: *Intercalation (chemistry), insertion of a molecule (or ion) into layered solids such as graphite * Intercalation (timekeeping), insertion of a leap day, week or month into some calendar years to make the calendar foll ... into D ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Non-contact Atomic Force Microscopy
Non-contact atomic force microscopy (nc-AFM), also known as dynamic force microscopy (DFM), is a mode of atomic force microscopy, which itself is a type of scanning probe microscopy. In nc-AFM a sharp probe is moved close (order of Angstroms) to the surface under study, the probe is then raster scanned across the surface, the image is then constructed from the force interactions during the scan. The probe is connected to a resonator, usually a silicon cantilever or a quartz crystal resonator. During measurements the sensor is driven so that it oscillates. The force interactions are measured either by measuring the change in amplitude of the oscillation at a constant frequency just off resonance (amplitude modulation) or by measuring the change in resonant frequency directly using a feedback circuit (usually a phase-locked loop) to always drive the sensor on resonance (frequency modulation). Modes of operation The two most common modes of nc-AFM operation, frequency modulation (F ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrogen Bonding
In chemistry, a hydrogen bond (or H-bond) is a primarily electrostatic force of attraction between a hydrogen (H) atom which is covalently bound to a more electronegative "donor" atom or group (Dn), and another electronegative atom bearing a lone pair of electrons—the hydrogen bond acceptor (Ac). Such an interacting system is generally denoted , where the solid line denotes a polar covalent bond, and the dotted or dashed line indicates the hydrogen bond. The most frequent donor and acceptor atoms are the second-row elements nitrogen (N), oxygen (O), and fluorine (F). Hydrogen bonds can be intermolecular (occurring between separate molecules) or intramolecular (occurring among parts of the same molecule). The energy of a hydrogen bond depends on the geometry, the environment, and the nature of the specific donor and acceptor atoms and can vary between 1 and 40 kcal/mol. This makes them somewhat stronger than a van der Waals interaction, and weaker than fully covalent or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organic Compound
In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. The study of the properties, reactions, and syntheses of organic compounds comprise the discipline known as organic chemistry. For historical reasons, a few classes of carbon-containing compounds (e.g., carbonate salts and cyanide salts), along with a few other exceptions (e.g., carbon dioxide, hydrogen cyanide), are not classified as organic compounds and are considered inorganic. Other than those just named, little consensus exists among chemists on precisely which carbon-containing compounds are excluded, making any rigorous definition of an organic compound elusive. Although organic compounds make up only a small percentage of Earth's crust, they are of central importance because all known life is based on organic compounds. Living t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Naphthalene
Naphthalene is an organic compound with formula . It is the simplest polycyclic aromatic hydrocarbon, and is a white crystalline solid with a characteristic odor that is detectable at concentrations as low as 0.08 ppm by mass. As an aromatic hydrocarbon, naphthalene's structure consists of a fused pair of benzene rings. It is best known as the main ingredient of traditional mothballs. History In the early 1820s, two separate reports described a white solid with a pungent odor derived from the distillation of coal tar. In 1821, John Kidd cited these two disclosures and then described many of this substance's properties and the means of its production. He proposed the name ''naphthaline'', as it had been derived from a kind of naphtha (a broad term encompassing any volatile, flammable liquid hydrocarbon mixture, including coal tar). Naphthalene's chemical formula was determined by Michael Faraday in 1826. The structure of two fused benzene rings was proposed by Emil Erlenmeye ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Naphthalenetetracarboxylic Dianhydride
Naphthalenetetracarboxylic dianhydride (NTDA) is an organic compound related to naphthalene. The compound is a beige solid. NTDA is most commonly used as a precursor to naphthalenediimides (NDIs) (such as napthalenetetracarboxylic diimide), a family of compounds with many uses. Synthesis and structure Naphthalenetetracarboxylic dianhydride is prepared by oxidation of pyrene. Typical oxidants are chromic acid and chlorine. The unsaturated tetrachloride hydrolyzes to enols that tautomerize to the bis-dione, which in turn can be oxidized to the tetracarboxylic acid.F. Röhrscheid "Carboxylic Acids, Aromatic" in ''Ullmann's Encyclopedia of Industrial Chemistry'', Wiley-VCH, Weinheim, 2012. Naphthalene diimides Symmetrical naphthalene diimides are synthesized by the condensation reaction of primary amines and the dianhydride. Unsymmetrical derivatives, i.e. those derived from two different amines, are obtained by hydrolysis of one of the two anhydride groups prior to the conde ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radical Anion
In organic chemistry, a radical anion is a free radical species that carries a negative charge. Radical anions are encountered in organic chemistry as reduced derivatives of polycyclic aromatic compounds, e.g. sodium naphthenide. An example of a non-carbon radical anion is the superoxide anion, formed by transfer of one electron to an oxygen molecule. Radical anions are typically indicated by M^. Polycyclic radical anions Many aromatic compounds can undergo one-electron reduction by alkali metals. The electron is transferred from the alkali metal ion to an unoccupied antibonding p-p п* orbital of the aromatic molecule. This transfer is usually only energetically favorable if the aprotic solvent efficiently solvates the alkali metal ion. Effective solvents are those that bind to the alkali metal cation: diethyl ether < < [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ferrocenium
Ferrocenium tetrafluoroborate is an organometallic compound with the formula e(C5H5)2F4. This salt is composed of the cation e(C5H5)2sup>+ and the tetrafluoroborate anion (). The related hexafluorophosphate is also a popular reagent with similar properties. The cation is often abbreviated Fc+ or Cp2Fe+. The salt is deep blue in color and paramagnetic. Ferrocenium salts are sometimes used as one-electron oxidizing agents, and the reduced product, ferrocene, is inert and readily separated from ionic products. The ferrocene–ferrocenium couple is often used as a reference in electrochemistry. The standard potential of ferrocene-ferrocenium is 0.400 V vs. the normal hydrogen electrode (NHE) and is often assumed to be invariant between different solvents. Preparation Commercially available, this compound may be prepared by oxidizing ferrocene typically with ferric salts followed by addition of fluoroboric acid. A variety of other oxidants work well also, such as nitrosyl tetr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Conjugated System
In theoretical chemistry, a conjugated system is a system of connected p-orbitals with delocalized electrons in a molecule, which in general lowers the overall energy of the molecule and increases stability. It is conventionally represented as having alternating single and multiple bonds. Lone pairs, radicals or carbenium ions may be part of the system, which may be cyclic, acyclic, linear or mixed. The term "conjugated" was coined in 1899 by the German chemist Johannes Thiele. Conjugation is the overlap of one p-orbital with another across an adjacent σ bond (in transition metals, d-orbitals can be involved). A conjugated system has a region of overlapping p-orbitals, bridging the interjacent locations that simple diagrams illustrate as not having a π bond. They allow a delocalization of π electrons across all the adjacent aligned p-orbitals. The π electrons do not belong to a single bond or atom, but rather to a group of atoms. Molecules containing conjugated syst ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electron Withdrawing Group
In chemistry, an electron-withdrawing group (EWG) is a substituent that has some of the following kinetic and thermodynamic implications: *with regards to electron transfer, electron-withdrawing groups enhance the oxidizing power tendency of the appended species. Tetracyanoethylene is an oxidant because the alkene is appended to four cyano substituents, which are electron-withdrawing. *with regards to acid-base reactions, acids with electron-withdrawing groups species have low acid dissociation constants. For EWG's attached to benzene, this effect is described by the Hammett equation, which allows EWGs to be discussed quantitatively. *with regards to nucleophilic substitution reactions, electron-withdrawing groups are susceptible to attack by weak nucleophiles. For example, compared to chlorobenzene, chlorodinitrobenzene is susceptible to reactions that displace chloride.{{cite journal , author=J. F. Bunnett, R. M. Conner, doi=10.15227/orgsyn.040.0034, title=2,4-Dinitroiodobe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Supramolecular Chemistry
Supramolecular chemistry refers to the branch of chemistry concerning chemical systems composed of a discrete number of molecules. The strength of the forces responsible for spatial organization of the system range from weak intermolecular forces, electrostatic charge, or hydrogen bonding to strong covalent bonding, provided that the electronic coupling strength remains small relative to the energy parameters of the component. While traditional chemistry concentrates on the covalent bond, supramolecular chemistry examines the weaker and reversible non-covalent interactions between molecules. These forces include hydrogen bonding, metal coordination, hydrophobic forces, van der Waals forces, pi–pi interactions and electrostatic effects. Important concepts advanced by supramolecular chemistry include molecular self-assembly, molecular folding, molecular recognition, host–guest chemistry, mechanically-interlocked molecular architectures, and dynamic covalent chemistry. The st ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Charge-transfer Complexes
In chemistry, a charge-transfer (CT) complex or electron-donor-acceptor complex describes a type of supramolecular assembly of two or more molecules or ions. The assembly consists of two molecules that self-attract through electrostatic forces, i.e., one has at least partial negative charge and the partner has partial positive charge, referred to respectively as the electron acceptor and electron donor. In some cases, the degree of charge transfer is "complete", such that the CT complex can be classified as a salt. In other cases, the charge-transfer association is weak, and the interaction can be disrupted easily by polar solvents. Examples Electron donor-acceptor complexes A number of organic compounds form charge-transfer complex, which are often described as electron-donor-acceptor complexes (EDA complexes). Typical acceptors are nitrobenzenes or tetracyanoethylene. The strength of their interaction with electron donors correlates with the ionization potentials of the c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
