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F Bonds (f + bond)
Selected AbstractsTransition Metal Catalyzed Cross-Coupling of Aryl Grignard Reagents with Aryl Fluorides via Pd- or Ni-Activation of the C,F Bond: An Efficient Synthesis of Unsymmetrical Biaryls , Application of Microwave Technology in Ligand and Catalyst Screening.CHEMINFORM, Issue 27 2005John W. Dankwardt Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: The Short N,F Bond in N2F+ and How Pauli Repulsion Influences Bond Lengths.CHEMINFORM, Issue 19 2002NF3X+, NH3X+ (X: F, Theoretical Study of N2X+ Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Isolation and Spectroscopic Characterization of C60F17CF2CF3 and Isomers of C60F17CF3; Insertion of :CF2 into Fluorofullerene C,F Bonds.CHEMINFORM, Issue 12 2001Olga V. Boltalina Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Photochemistry of Oxazolidinone Antibacterial Drugs,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 4 2009Elisa Fasani The photochemistry of six N3-(3-fluoro-4-dialkylaminophenyl)-oxazolidinones known for their antimicrobial activity has been examined. All of these compounds are defluorinated in water (,dec , 0.25) and in methanol (,dec , 0.03), reasonably via the triplet. The chemical processes observed are reductive defluorination and solvolysis, depending on the structural variation introduced (thus, tethering the dialkylamino group to the aromatic ring and introducing a highly polar group in the oxazolidinone moiety have an effect). A likely mechanism involves the fragmentation of the C,F bond yielding the corresponding triplet phenyl cation. This intermediate either is reduced or, under appropriate conditions, intersystem crosses to the singlet state that adds the solvent. These data demonstrate a sizeable photodecomposition of these drugs that causes a decrease in the therapeutic activity. Furthermore, the likely formation of phenyl cations may cause a photogenotoxic effect. [source] Molecular Self-Recognition: Rotational Spectra of the Dimeric 2-Fluoroethanol ConformersCHEMISTRY - A EUROPEAN JOURNAL, Issue 1 2009Xunchen Liu Abstract Fluoroalcohols show competitive formation of intra- and intermolecular hydrogen bonds, a property that may be crucial for the protein-altering process in a fluoroalcohol/water solution. In this study, we examine the intra- and intermolecular interactions of 2-fluoroethanol (FE) in its dimeric conformers by using rotational spectroscopy and ab initio calculations. Three pairs of homo- and heterochiral dimeric FE conformers are predicted to be local minima at the MP2/6-311++G(d,p) level of theory. They are solely made of the slightly distorted most stable G+g,/G,g+ FE monomer units. Jet-cooled rotational spectra of four out of the six predicted dimeric conformers were observed and unambiguously assigned for the first time. All four observed dimeric conformers have compact geometries in which the fluoromethyl group of the acceptor tilts towards the donor and ensures a large contact area. Experimentally, the insertion of the OH group of one FE subunit into the intramolecular OH,,,F bond of the other was found to lead to a higher stabilisation than the pure association through an intermolecular OH,,,OH link. The hetero- and homochiral combinations were observed to be preferred in the inserted and the associated dimeric conformers, respectively. The experimental rotational constants and the stability ordering are compared with the ab initio calculations at the MP2 level with the 6-311++G(d,p) and aug-cc-pVTZ basis sets. The effects of fluorination and the competing inter- and intramolecular hydrogen bonds on the stability of the dimeric FE conformers are discussed. [source] Hierarchical Porous, Self-Supporting La- and F-Codoped TiO2 with High Durability for Continuous-Flow Visible Light PhotocatalysisJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2010Guangxiu Cao Hierarchical porous, self-supporting La- and F-codoped TiO2 with high durability was prepared using a simple polymer template gel. The TiO2 foams were in the anatase phase, with a specific surface area of up to 88 m2/g, and showed a network-like structure containing meso-/macropores. The macropores had a diameter of ca. 300 nm and a wall thickness of 100,300 nm, while the mesopores were narrowly distributed with a mean diameter of around 5.4 nm. The UV-vis diffuse reflection spectra of the sample showed that the presence of intraband gap states was likely responsible for its absorption of visible light. X-ray photoelectron spectroscopy revealed that La2O3 and O,Ti,F bonds were formed. The sample showed an excellent visible light photocatalytic activity and a high durability of photocatalytic activity for the degradation of methylene blue solution. [source] Bond analyses of borates from the Inorganic Crystal Structure DatabaseACTA CRYSTALLOGRAPHICA SECTION B, Issue 5 2006Daqiu Yu Various fundamental building blocks (FBBs) are observed in the crystallographic structures of oxoborates available in the Inorganic Crystal Structure Database, Version 1.3.3 (2004); the occurrence of borate groups with low complexity is dominant. Bond-valence parameters d0 of B,O bonds in 758 oxoborates with various FBBs have been calculated using the bond-valence sum model. Some discrepancies in the d0 values obviously occur if the detailed configurations of FBBs in borate crystals are considered; d0 is sensitive to the chemical bonding structure of B atoms in the crystallographic framework. Moreover, d0 values are affected by the existence of interstitial atoms and the substitution of other anionic groups. In addition, the d0 parameters for B,N, B,S, B,P and B,F bonds are also calculated statistically. Some suitable d0 data for various borate FBBs are recommended according to their particular configurations, especially for those with low complexity. On the basis of the proposed linear relationship between calculated nonlinear optical (NLO) coefficients of borates and the current d0 values for various FBBs, it is found that the d0 values may be regarded as a useful parameter for pre-investigating the NLO properties of borates, leading to an efficient structural evaluation and design of novel borates. [source] New vanadium(IV) and titanium(IV) oxyfluorotellurates(IV): V2Te2O7F2 and TiTeO3F2ACTA CRYSTALLOGRAPHICA SECTION C, Issue 1 2009Jean Paul Laval As part of a continuing study of oxyfluorotellurates(IV), materials likely to present interesting nonlinear optical properties, two new phases, titanium(IV) tellurium(IV) trioxide difluoride, TiTeO3F2, and divanadium(IV) ditellurium(IV) heptaoxide difluoride, V2Te2O7F2, have been characterized and present, respectively, titanium and vanadium in the tetravalent state. The TiTeO3F2 structure is based on linear double rows of TiO3F3 polyhedra sharing vertices. These rows are connected to adjacent rows via two vertices of Te2O5 bipolyhedra. The Te, Ti, one F and two O atoms are on general positions, with one O and F statistically occupying the same site with half-occupancy for each anion. One O and one F occupy sites with .m. symmetry. The V2Te2O7F2 structure consists of zigzag chains of VO4F2 octahedra alternately sharing O,O and F,F edges. These chains are connected via Te2O5 bipolyhedra, forming independent mixed layers. The Te, V, one F and three O atoms are on general positions while one O atom occupies a site of symmetry. In both phases, the electronic lone pair E of the TeIV atom is stereochemically active. A full O/F anionic ordering is observed in V2Te2O7F2, but in TiTeO3F2 one of the six anionic sites is occupied by half oxygen and half fluorine, all the others being strictly ordered. These compounds represent new members of a growing family of oxyfluorotellurates(IV), including the recently characterized members of formula MTeO3F, M being a trivalent cation. As was true for the previous members, they are characterized by an unusually high thermal and chemical stability in relation to the absence of direct Te,F bonds. [source] | ||||||||||