The relative stability of hydrogen-bonded of Molybdate-Phosphonic Acid (MPA) complex (1:2) ingas phase has been carried out using Density Functional Theory (DFT) methods. The methods are usedfor calculations are B3LYP, BP86 and B3PW91 that have been studied in two series of basis sets: D95**and 6-31+G(d,p) for hydrogen and oxygen atoms; LANL2DZ for Mo and Phosphorus. Predictedhydrogen-bond geom...

The effects of fluorinated hydroxy compounds and naphthalene on the fluorescence of N-(4-pyridyl)-1,2-naphthalimide (PyNI) have been studied in toluene. The interaction of the pyridyl moiety of PyNI with hexafluoro-2-propanol (HFIP) gave rise to a hydrogen-bonded complex, whereas a more stable, hydrogen-bonded ion pair was formed with trifluoroacetic acid (TFA). Time-resolved fluorescence measu...

High quality reference data from diffusion Monte Carlo calculations are presented for bulk sI methane hydrate, a complex crystal exhibiting both hydrogen-bond and dispersion dominated interactions. The performance of some commonly used exchange-correlation functionals and all-atom point charge force fields is evaluated. Our results show that none of the exchange-correlation functionals tested a...

Methanol is a versatile chemical feedstock, fuel source, and energy storage material. Many reactions involving methanol are catalyzed by transition metal surfaces, on which hydrogen-bonded methanol overlayers form. As with water, the structure of these overlayers is expected to depend on a delicate balance of hydrogen bonding and adsorbate-substrate bonding. In contrast to water, however, relat...

Intermolecular hydrogen bond librational modes in cyclic trimers and tetramers of methanol and t-butyl alcohol isolated at low temperature in pulsed supersonic jet expansions are observed by direct absorption spectroscopy in the far-infrared region. The large amplitude librational modes probe the strength and directionality of the intermolecular hydrogen bonds. In addition, their frequency and ...

In the title salt, C(6)H(9)N(2) (+)·C(8)H(5)O(4) (-), the hydrogen phthalate anion is essentially planar, with a maximum deviation of 0.011 (2) Å. In the crystal structure, the protonated N atom of the pyridine ring and the 2-amino group of the cation are hydrogen bonded to the carboxyl-ate O atoms of the anion via a pair of N-H⋯O hydrogen bonds, forming an R(2) (2)(8) ring motif. In the hydrog...

For blue-shifted hydrogen-bonded systems, the hydrogen stretching frequency increases rather than decreases on complexation. In computations at various levels of theory, the blue-shift in the archetypical system, F(3)C-H.FH, is reproduced at the Hartree-Fock level, indicating that electron correlation is not the primary cause. Calculations also demonstrate that a blue-shift does not require eit...

The presence of bound water in the solution structure of the IgG binding domain of streptococcal protein G has been investigated by nuclear magnetic resonance using three-dimensional 1H rotating frame Overhauser 1H-15N multiple quantum coherence spectroscopy. The backbone amide protons of three residues, Ala20, Gln32 and Tyr33, are found to be in close proximity to bound water. Examination of t...

Protonation of the Ca ligands of the SR Ca-ATPase (SERCA1a) was studied by a combination of rapid scan FTIR spectroscopy and electrostatic calculations. With FTIR spectroscopy, we investigated the pH dependence of C1⁄4O bands of theCa-free phosphoenzyme (E2P) and obtained direct experimental evidence for the protonation of carboxyl groups uponCa release. At least three of the infrared signals f...

Raman spectroscopic studies of compound II of horseradish peroxidase show that the oxygen atom in the FeIV = O group of the heme is rapidly exchanged in H2O at pH 7.0 but not in an alkaline solution (pH 11.0). This conclusion is based on studies of shift in the FeIV = O stretching mode of compound II in H2(18)O; further studies show that the FeIV = O heme is hydrogen-bonded to an amino acid res...