Search results for "molecule"
showing 10 items of 5162 documents
N-(2,3,5,6-Tetrafluoropyridyl)sulfoximines: synthesis, X-ray crystallography, and halogen bonding
2020
In the presence of KOH, NH-sulfoximines react with pentafluoropyridine to give N-(tetrafluoropyridyl)sulfoximines (NTFP-sulfoximines) in moderate to excellent yields. Either a solution-based or a superior solvent-free mechanochemical protocol can be followed. X-Ray diffraction analyses of 26 products provided insight into the bond parameters and conformational rigidity of the molecular scaffold. In solid-state structures, sulfoximines with halo substituents on the S-bound arene are intermolecularly linked by C–X⋯OS (X = Cl, Br) halogen bonds. Hirshfeld surface analysis is used to assess the type of non-covalent contacts present in molecules. For mixtures of three different S-pyridyl-substit…
Bis-macrocyclic Ligands with Two Ferrocenyl End Groups, and Their Tetranuclear Dicopper(I) Compounds
1999
A series of bismacrocyclic ligands with two ferrocenyl groups, exo/endo-1,1‘:1‘ ‘,1‘ ‘‘-[1,2,4,5-tetrakis(5-aza-2-thiahexa-5-enyl)benzene]bisferrocene (exo/endo-FeBeFe), 1,1‘:1‘ ‘,1‘ ‘‘-[1,2:1‘,2‘-tetrakis(5-aza-2-thiahexa-5-enyl)ethene]bisferrocene (1,2-FeEnFe), 1,1‘:1‘ ‘,1‘ ‘‘-[1,1‘:2,2‘-tetrakis(5-aza-2-thiahexa-5-enyl)ethene]bisferrocene (1,1-FeEnFe), 1,1‘:1‘ ‘,1‘ ‘‘-[tetrakis(5-aza-2-thiahexa-5-enyl)methane]bisferrocene (FeMeFe), and their dicopper(I) compounds have been synthesized and characterized (electrochemistry, IR, NMR and Mossbauer spectroscopy). The molecular structure of endo-FeBeFe has been determined by X-ray structure analysis and the copper(I)-induced discrimination of t…
Automorphisms of 2–dimensional right-angled Artin groups
2007
We study the outer automorphism group of a right-angled Artin group AA in the case where the defining graph A is connected and triangle-free. We give an algebraic description of Out.AA/ in terms of maximal join subgraphs in A and prove that the Tits’ alternative holds for Out.AA/. We construct an analogue of outer space for Out.AA/ and prove that it is finite dimensional, contractible, and has a proper action of Out.AA/. We show that Out.AA/ has finite virtual cohomological dimension, give upper and lower bounds on this dimension and construct a spine for outer space realizing the most general upper bound. 20F36; 20F65, 20F28
Anilato-based multifunctional molecular materials
2018
En esta Tesis presentamos varias series de compuestos moleculares basados en el ligando anilato (anilato = C6O4X22- = 2,5-disustituida-3,6-dihidroxi-1,4-benzoquinona) y diferentes átomos metálicos incluyendo metales de los bloques s, p, d y f. En el capítulo uno presentamos la síntesis y caracterización de nuevas sales precursoras, basadas en el ligando anilato, con fórmula general A3[M(C6O4X2)3]; (MIII = Fe, Cr y Ga; X = Cl, Br and NO2). Hemos usado diferentes cationes A+ (A = K+, [PPh3Et]+, [PPh3Pr]+, [PBu4]+, [NBu4]+, [NHep4]+, [PPh4]+ y K+, compuestos 1-20) para estudiar el papel que juega la forma y el tamaño del catión en la estructura y simetría de las correspondientes sales. Este es…
Advances in plant materials, food by-products, and algae conversion into biofuels: use of environmentally friendly technologies
2019
Green technologies have emerged as useful tools for the generation of clean fuels with the potential to minimize the effect of human activity on the environment. Currently, these fuels are mainly composed of hydrocarbons obtained from crude oil. Over the past two decades, biomass has gained significant attention as a renewable feedstock for more sustainable biofuel production and has been a great candidate to replace fossil fuels. The principal components of most of the available biomass are cellulose, hemi-cellulose, and lignin. Although the available green technologies for biofuel production are progressing rapidly, productivity and chemical yield from these techniques are still below the…
π-Stacked polymers in drug delivery applications
2016
Abstract Polybenzofulvenes are π-stacked polymers, which can be synthesized by spontaneous polymerization of the corresponding monomers without the use of catalysts or initiators. Therefore, they can be obtained completely free from byproducts, impurities, or harmful substances. The absence of any relevant toxic effects and cell viability impairments allows PEGylated polybenzofulvene brushes to be potentially functional in a wide range of biological, biomedical, and biotechnological applications. Moreover, the properties of these polymers, in terms of interaction with pharmacological active agents and the ability to self-assemble into nanoaggregates or a quite compact physical gel useful as…
“Twin” phosphorous atoms of tetraethyl 2-methyl-piperyd-1-ylmethylenebisphosphonates
2007
Recently, bisaminophosphonates found applications as therapeutic agents for curing bone disorders. When trying to relate the structures of substituted piperid-1-ylmethylenebisphosphonic with their biological properties, non-typical findings that in 31P NMR spectra of 2-methyl-piperid-1-ylmethylenebisphosphonic and 2-ethyl-piperid-1-ylmethylenebisphosphonic acids, two separate singlets from each of the phosphonic groups were observed, while their analogues bearing substituent in position 3 exhibit only one signal. Their presence was explained by freezing of the molecular motions by strong hydrogen bonding between NH and P = O atoms. In this work, synthesis as well as spectroscopic and theore…
Trap-assisted spectroscopy with REXTRAP
2007
International audience; As one of the fashionable techniques for nuclear spectroscopy experiments, the beam manipulation in gas-filled Penning traps permits the accurate measurement of some of the ground state properties of exotic nuclides. It was recently applied using REXTRAP for the measurement of the half-life of 38Ca, one of the 0+ → 0+ β-decaying nuclide of interest for the determination of the Ft value for super-allowed transitions, and the test of the unitarity of the CKM matrix. The experimental setup and the original method of beam purification adopted for this measurement is presented.
Mossbauer spectroscopic study of the thermal spin crossover in [Fe(II)(isoxazole)(6)](ClO(4))(2)
2008
The (57)Fe Mossbauer spectroscopy of mononuclear [Fe(II)(isoxazole)(6)](ClO(4))(2) has been studied to reveal the thermal spin crossover of Fe(II) between low-spin (S = 0) and high-spin (S = 2) states.Temperature-dependent spin transition curves have been constructed with the least-square fitted data obtained from the Mossbauer spectra measured at various temperatures between 84 and 270 K during a cooling and heating cycle. This compound exhibits an unusual temperature-dependent spin transition behaviour with T(C)(down arrow) = 223 and T(C)(up arrow) = 213 K occurring in the reverse order in comparison to those observed in SQUID observation and many other spin transition compounds. The comp…
Identification and characterization of aging products in the glyoxal/ammonium sulfate system – implications for light-absorbing material in atmospher…
2012
Abstract. In this study we report the identification of bicyclic imidazoles in aqueous aerosol mimics using HPLC-ESI-MS/MS. 2,2´-Biimidazole was identified to be a major contributor to the 280 nm absorbance band observed in mixtures of glyoxal and ammonium sulfate, despite the fact that its production rate is two orders of magnitude lower than the previously reported production rates of imidazole or imidazole-2-carboxaldehyde. The molar absorptivity of 2,2´-biimidazole was determined to be (36 690±998) M−1 cm−1. This demonstrates the necessity of molecular product identification at trace levels to enable a better understanding of relevant absorbing species. Additionally the forma…