Search results for "bond"
showing 10 items of 3527 documents
Hydrogen bonding and proton transfer involving the trihydride complexes Cp*M(dppe)H 3 (M = Mo, W) and fluorinated alcohols: the competitive role of t…
2003
International audience; The protonation of complexes Cp*M(dppe)H3 (dppe is ethylenebis(diphenylphosphine), M = Mo (1), W (2)) by a variety of fluorinated alcohols of different acid strength (FCH2CH2OH, CF3CH2OH, (CF3)2CHOH, and (CF3)3COH) was investigated experimentally by the variable temperature spectroscopic methods (IR, NMR) and stopped-flow technique (UV-Vis). The structures of the hydrogen-bonded and proton transfer products were studied by DFT calculations. In agreement with the calculation results, the IR data suggest that the initial hydrogen bond is established with a hydride site for complex 1 and with the metal site for complex 2. However, no intermediate dihydrogen complex foun…
Crystal structures of 2,2′-bipyridin-1-ium 1,1,3,3-tetracyano-2-ethoxyprop-2-en-1-ide and bis(2,2′-bipyridin-1-ium) 1,1,3,3-tetracyano-2-(dicyanometh…
2015
In each of the title compounds, the anion shows evidence of extensive electronic delocalization. A combination of N—H⋯N and X—H⋯N hydrogen bonds links the ions in (I) into a ribbon of alternating centrosymmetric (18) and (26) rings, and those in (II) into simple (7) chains of alternating cations and anion with further cations pendent from the chain.
Reversible Supracolloidal Self-Assembly of Cobalt Nanoparticles to Hollow Capsids and Their Superstructures
2017
| openaire: EC/FP7/291364/EU//MIMEFUN The synthesis and spontaneous, reversible supracolloidal hydrogen bond-driven self-assembly of cobalt nanoparticles (CoNPs) into hollow shell-like capsids and their directed assembly to higher order superstructures is presented. CoNPs and capsids form in one step upon mixing dicobalt octacarbonyl (Co2CO8) and p-aminobenzoic acid (pABA) in 1,2-dichlorobenzene using heating-up synthesis without additional catalysts or stabilizers. This leads to pABA capped CoNPs (core ca. 5nm) with a narrow size distribution. They spontaneously assemble into tunable spherical capsids (d≈50-200nm) with a few-layered shells, as driven by inter-nanoparticle hydrogen bonds th…
Molecular dynamics simulations of elementary chemical processes in liquid water using combined density functional and molecular mechanics potentials.…
1997
The first molecular dynamics (MD) simulation of a chemical process in solution with an ab initio description of the reactant species and a classical representation of the solvent is presented. We study the dynamics of proton (deuterium) transfer in strongly hydrogen-bonded systems characterized by an energy surface presenting a double well separated by a low activation barrier. We have chosen the hydroxyl-water complex in liquid water to analyze the coupling between the reactive system and the environment. The proton is transferred from one well to the other with a frequency close to 1 ps−1 which is comparable to the low-frequency band associated to hindered translations, diffusional transl…
Vibrational Signature of Water Molecules in Asymmetric Hydrogen Bonding Environments
2013
The O–H stretching vibrational modes of water molecules are sensitive to their local environments. Here, we applied effective normal-mode analysis to isolate contributions of each of the two hydrogen atoms to the vibrational modes ν1 and ν3 of water molecules in the liquid phase. We demonstrate that the decoupling of the two contributions fd and the frequency splitting of the vibrational modes Δω13 are inextricably related to the symmetry of the hydrogen bonding environment. We show that ambient liquid water modeled at the density functional level of theory exhibits the characteristics of an asymmetric environment with an average decoupling of 0.82 and a splitting of 137 inverse centimeters…
Hydrogen-Bonded Analogues of Cavitands
2000
Regioselective acylation of aminoresorcinarenes
2007
Abstract The acid catalyzed hydrolytic cleavage of the oxazine rings in the readily available tetraoxazine derivatives of resorcinarenes results in tetraaminoresorcinarenes. A similar process applied to C2-symmetrical bisoxazine resorcinarene tetratosylates affords C2v-symmetrical resorcinarenediamines. The mild acylation of these resorcinareneamines with BOC-anhydride or para-nitrophenyl ester proceeds selectively at the nitrogen atoms without affecting the hydroxyl groups. Most of the resulting resorcinareneamides are thus obtained in preparative yields and can be easily purified by simple crystallizations. In the crystalline state the compounds obtained are found to bind chloride anions …
[Bis(dimethylsulphoxide) protium][trans-bisdimethylsulphoxidetetrachloroiridate(III)]
1988
Abstract [(DMSO)2H]trans-[IrCl4(DMSO)2] (DMSO = dimethylsulphoxide) has been structurally characterized. The hydrogen bonded cation [DMSOHDMSO]+ has a very short OHO bond distance (2.405 A) which compares well with that in the known rhodium analogue. The two DMSO ligands are trans on iridium and coordinate via the sulphur atoms. Earlier work had assigned the cis structure to the anion in this compound.
Self-Assembled Hydrogen-Bonded Dimeric Capsules with High Kinetic Stability
2000
Gas-phase H/D-exchange reactions on resorcinarene and pyrogallarene capsules: Proton transport through a one-dimensional Grotthuss mechanism
2011
Hydrogen/deuterium exchange (HDX) experiments can be used to examine the gas-phase structure of hydrogen-bonded dimeric resorcinarene and pyrogallarene capsules. Already the qualitative comparison of the isotope exchange rates of different host–guest complexes with Cs+, tetramethyl ammonium (TMA+) and tetraethyl ammonium (TEA+) as the guest cations provides insight into the H/D-exchange mechanisms and with it, into the capsules' gas-phase ion structures. The smaller Cs+cations bind inside dimeric capsules with an intact seam of hydrogen bonds between the two monomers. Larger cations such as TEA+ lead to capsules with partially disrupted seams of hydrogen bonds. A fast isotope exchange is on…