A Triphenylphoshine Oxide−Water Aggregate Facilitates an Exceptionally Short C−H···O Hydrogen Bond

Kariuki, Benson M.; Harris, Kenneth D. M.; Philp, and Douglas; Robinson, James M.

doi:10.1021/ja973506z

Cited by 79 publications

(63 citation statements)

References 12 publications

(9 reference statements)

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“…Solid-state NMR experiments were also performed on a home-built 400 MHz NMR spectrometer utilizing a Tecmag Libra system for pulse programming and signal digitization. The static magnetic field strength of the spectrometer is 9.4 T, corresponding to resonance frequencies for the 1 H, 31 P, and 27 Al species of 399.995, 161.927, and 104.229 MHz, respectively. Spectra were acquired using a Chemagnetics 5.0 mm tripleresonance CPMAS NMR probe with rotor frequencies between 5 and 10 kHz.…”

Section: Methodsmentioning

confidence: 99%

“…A TRAPDOR NMR signal is obtained as the difference of the signals from two separate NMR experiments: The first is a spin-echo MAS signal obtained from the 31 P spins after initial cross-polarization from the 1 H nuclei. In a second experiment, the 31 P spin-echo is formed in an analogous manner, but during this time a long radio-frequency pulse is applied at the Larmor frequency of the 27 Al nuclei. The interaction between the nuclear electric quadrupole moment of the 27 Al nuclei and local gradients in the electric field causes a time-dependent change in the spin energy levels under MAS conditions, and the long radiofrequency pulse causes mixing and scrambling of coherences among these energy levels.…”

Section: Methodsmentioning

confidence: 99%

“…Samples containing Brønsted acid sites have also been characterized by 31 P MAS NMR of TMPO probes. A sample of ultrastable Y zeolite was further characterized using triple-resonance 1 H/ 31 P/ 27 Al NMR experiments to confirm a number of the specific assignments. Quantification of spectral intensities of resonances assigned to Brønsted sites is used to calculate the concentration of Brønsted acidity in the solids, and these results are compared with those obtained using IPA/TPD.…”

Section: Introductionmentioning

confidence: 99%

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Characterization of Acid Sites in Zeolitic and Other Inorganic Systems Using Solid-State ³¹P NMR of the Probe Molecule Trimethylphosphine Oxide

Rakiewicz¹,

Peters²,

Wormsbecher³

et al. 1998

J. Phys. Chem. B

162

231

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The ability to determine the types and concentrations of acid sites in zeolites and fluid-catalytic cracking systems is important for an increased understanding of structure/performance relationships in these materials. Currently, a variety of thermal methods exist that allow quantitative measurement of the Brønsted acid site concentration. In addition, numerous spectroscopic methods using probe molecules are available for qualitative and quantitative detection of both Brønsted and Lewis acid sites. In studies utilizing solid-state NMR spectroscopy, probe molecules containing 31 P nuclei present substantial advantages over probes isotopically enriched with 13 C and 15 N nuclei. These advantages include increased sensitivity and chemical shift dispersion. While a number of phosphorus-based experiments have probed the interaction of trimethylphosphine with solid acid catalysts, initial studies of the more stable trimethylphosphine oxide (TMPO) have only been reported on amorphous silica-alumina surfaces. We now report the successful completion of TMPO studies of acid sites in several systems including γ-alumina; HY, USY, and dealuminated Y zeolites; and a silica-alumina catalyst with an aluminum concentration of 13%. Comprehensive and consistent assignments to particular types of sites are made for all resonance lines in the 31 P MAS NMR signals from TMPO. Based on results from dehydroxylated γ-alumina, new chemical shift assignments are made for the TMPO/Lewis acid complex. The assignments of 31 P resonances from molecules not directly associated with nearby 27 Al nuclei (such as crystalline or physisorbed TMPO species) are supported using 1 H/ 31 P/ 27 Al triple-resonance NMR methods. The concentrations of Brønsted acid sites from the NMR results are compared with concentrations obtained from isopropylamine/temperature-programmed-desorption measurements, and substantial agreement between the methods is found.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Characterization of Acid Sites in Zeolitic and Other Inorganic Systems Using Solid-State ³¹P NMR of the Probe Molecule Trimethylphosphine Oxide

Rakiewicz¹,

Peters²,

Wormsbecher³

et al. 1998

J. Phys. Chem. B

162

231

View full text Add to dashboard Cite

show abstract

“…When first proposed many years ago (Glasstone, 1937;Dippy, 1939), there was some resistance due to the low electro negativity of C which was presumed to make it a weak proton donor. However, Support was later added to this idea on the basis of IR data (Allerhand and Schleyer, 1953;DeLaat and Ault, 1987;Kariuki et al, 1997) and the geometry of molecular complexes in the gas phase (Astrup and Aomar, 1975;Peterson and Klemperer, 1984;Fujii et al, 1998) and in crystalline environment (Sutor, 1962;Kaufmann et al, 1977). This CH.…”

Section: Introductionmentioning

confidence: 99%

Contribution of unconventional C-H…O bonds to the structural stability of Antimicrobial peptides

Ramanathan

Shanthi

Sethumadhavan

2009

Interdiscip Sci Comput Life Sci

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The native structure of Antimicrobial peptides is stabilized by a large number of individually weak forces; a complete understanding of folding implies the need to evaluate the contribution of each of these, including nonconventional hydrogen bonds. In this work, we have analyzed the influence of C-H...O interactions in the structural stability of Antimicrobial peptides by comparison with conventional hydrogen bond. There are a number of amino acid residues that can form hydrogen bonds via their side chains in addition to their peptide group. Perhaps highest contribution in this category is polar residue (Cys) and charged residues such as Lys and Arg. A total of 2513 C-H...O interactions were found in a data set of 53 Antimicrobial peptides. Among the 2513 nonconventional interactions observed in the data set, 40% of interactions are bonded to alpha carbon. This is consistent with the fact that the hydrogens are more acidic than others. Most prominent were side-chain to main-chain C-H...O interactions (SM-C-H...O). 92% of the stabilizing centers in the Antimicrobial peptides were found to be involved in C-H...O interactions. These interactions are mainly formed by short range contacts. Moreover, the study shows that, there is an average of more than one C-H...O interactions observed for every single residue in the Antimicrobial peptides data set. It is concluded that the C-H...O interaction can, indeed, be categorized as a true stabilizing force like hydrogen bond in Antimicrobial peptides.

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“…O contact between 1,2-diethylnylbenzene and a triphenylphosphine-water aggregate, l eq,CHO ¼ 3.02 Å , achieved through the polarization of the water molecule by its hydrogen bonding to two triphenylphosphine oxide molecules. [33] According to the LS potential, this should correspond to D 0,CHO ¼ 1.5 kcal/mol. The (C-H .…”

Section: Theoretical Methodology Ism/sctst Calculationsmentioning

confidence: 99%

A chemical understanding for the enhanced hydrogen tunnelling in hydroperoxidation of linoleic acid catalysed by soybean lipoxygenase‐1

Barroso

Arnaut

Formosinho

2008

J of Physical Organic Chem

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The reaction path of the Interacting-State Model (ISM) is used with the Transition-State Theory (TST) and the semiclassical correction for tunnelling (ISM/scTST) to calculate the rates of H-atom abstraction from C(11) of linoleic acid catalysed by soybean lipoxygenase-1 (SLO), as well as of an analogous uncatalysed reaction in solution. The calculated hydrogen-atom transfer rates, their temperature dependency and kinetic isotope effect (KIE) are in good agreement with the experimental data. ISM/scTST calculations reveal the hypersensitivity of the rate to protein dynamics when the hydrogen bonding to a carbon atom is present in the reaction coordinate.

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A Triphenylphoshine Oxide−Water Aggregate Facilitates an Exceptionally Short C−H···O Hydrogen Bond

Cited by 79 publications

References 12 publications

Characterization of Acid Sites in Zeolitic and Other Inorganic Systems Using Solid-State ³¹P NMR of the Probe Molecule Trimethylphosphine Oxide

Characterization of Acid Sites in Zeolitic and Other Inorganic Systems Using Solid-State ³¹P NMR of the Probe Molecule Trimethylphosphine Oxide

Contribution of unconventional C-H…O bonds to the structural stability of Antimicrobial peptides

A chemical understanding for the enhanced hydrogen tunnelling in hydroperoxidation of linoleic acid catalysed by soybean lipoxygenase‐1

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A Triphenylphoshine Oxide−Water Aggregate Facilitates an Exceptionally Short C−H···O Hydrogen Bond

Cited by 79 publications

References 12 publications

Characterization of Acid Sites in Zeolitic and Other Inorganic Systems Using Solid-State 31P NMR of the Probe Molecule Trimethylphosphine Oxide

Characterization of Acid Sites in Zeolitic and Other Inorganic Systems Using Solid-State 31P NMR of the Probe Molecule Trimethylphosphine Oxide

Contribution of unconventional C-H…O bonds to the structural stability of Antimicrobial peptides

A chemical understanding for the enhanced hydrogen tunnelling in hydroperoxidation of linoleic acid catalysed by soybean lipoxygenase‐1

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Product

Resources

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Characterization of Acid Sites in Zeolitic and Other Inorganic Systems Using Solid-State ³¹P NMR of the Probe Molecule Trimethylphosphine Oxide

Characterization of Acid Sites in Zeolitic and Other Inorganic Systems Using Solid-State ³¹P NMR of the Probe Molecule Trimethylphosphine Oxide