Atom Of H2O Research Articles

Long‐range π‐type hydrogen bond in the dimers CH2OHF, CH2OH2O, and CH2ONH3

AbstractUsing four basis sets, 6‐311G(d,p), 6‐31+G(d,p), 6‐311++G(2d,2p), and 6‐311++G(3df,3pd), the optimized structures with all real frequencies were obtained at the MP2 level for dimers CH2OHF, CH2OH2O, CH2ONH3, and CH2OCH4. The structures of CH2OHF, CH2OH2O, and CH2ONH3 are cycle‐shaped, which result from the larger bend of σ‐type hydrogen bonds. The bend of σ‐type H‐bond O…HY (YF, O, N) is illustrated and interpreted by an attractive interaction of a chemically intuitive π‐type hydrogen bond. The π‐type hydrogen bond is the interaction between one of the acidic H atoms of CH2O and lone pair(s) on the F atom in HF, the O atom in H2O, or the N atom in NH3. By contrast with above the three dimers, for CH2OCH4, because there is not a π‐type hydrogen‐bond to bend its linear hydrogen bond, the structure of CH2OCH4 is a noncyclic shaped. The interaction energy of hydrogen bonds and the π‐type H‐bond are calculated and discussed at the CCSD(T)/6‐311++G(3df,3pd) level. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005

Novel Cytotoxic Copper(II) Complexes of 8‐Aminoquinoline Derivatives: Crystal Structure and Different Reactivity towards Glutathione

AbstractTwo novel CuII complexes [Cu(CMQA)(H2O)] (1) (CMQA = N‐carboxymethyl‐L‐methionine‐N′‐8‐quinolylamide) and [Cu(MQA)(OAc)] (2) (MQA = L‐methionine‐N′‐8‐quinolylamide, OAc = CH3COO−) have been synthesized and structurally characterized. Complex 1 crystallizes in the orthorhombic system with space group P212121 [a = 5.556(1) Å, b = 15.002(3) Å, c = 20.886(4) Å] while complex 2 crystallizes in the monoclinic system with space group C2 [a = 28.463(6) Å, b = 5.264(1) Å, c = 13.345(3) Å, β = 109.142(3)°]. In both complexes the CuII center is coordinated by three N atoms of the ligand and one O atom of H2O (1) or OAc (2). The in vitro cytotoxicity of both complexes and their corresponding ligands have been tested against the murine leukemia P‐388 and lung adenocarcinoma A‐549 cell lines. Complex 2 shows a potent activity against both cell lines with an inhibitory rate of 100% for the murine leukemia P‐388 cell line and 93.4% for the lung adenocarcinoma A‐549 cell line at a concentration of 10−6 mol·L−1, while complex 1 shows only a marginal activity against the same cell lines. The reactivity of the two complexes towards γ‐glutathione (GSH) has been investigated and is discussed in association with their different cytotoxicity. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

O atom sites in natural kaolinite and muscovite:17O MAS and 3QMAS NMR study

The layer silicates are among the most common minerals in the Earth’s surface environment, play important roles in many geological processes, and have diverse technological applications. While it has been suggested that O isotope exchange and dissolution kinetics in aqueous solutions are controlled by chemical bonding and local atomic structures, the effect of atomic environment around O atom sites in clay minerals on their site-specific reactivities with H2O are not well known, mainly because direct experimental evidence is lacking. Here, we present for the first time detailed high-resolution 17O NMR data for 17O-exchanged natural kaolinite [Al2Si2O5(OH)4] and muscovite [KAl2(AlSi3)O10(OH)2] using 17O triple quantum magic angle spinning (3QMAS) and MAS NMR at high fields. At least two basal O atom sites in kaolinite are resolved: O4, and (O3 + O5). Apical O atoms ([4]Si-O-2[6]Al) and hydroxyl groups are also shown in these spectra. The 17O 3QMAS spectrum for muscovite shows improved resolution over the 17O MAS NMR spectrum, allowing us to resolve several basal O atoms, including ([4]Si-O-[4]Al), as well as hydroxyl groups. The fraction of each O atom appears to deviate somewhat from the stoichiometric value, suggesting that each crystallographically distinct site may have a different rate of exchange with the O atom in H2O.

The complex of HF2− and H2O: A theoretical study

The complex of HF2− and H2O is studied using B3LYP, MP2, and QCISD methods. Energetics, geometries, and vibrational frequencies of the equilibrium structure and two transition states are calculated using 6-311++G(d,p), 6-311++G(2d,2p), and 6-311++G(2df,2pd) basis sets. For the equilibrium structure there is a hydrogen bond between one of the F atoms of HF2− and one of the H atoms of H2O. The two transition states are only about 0.5 kcal/mol higher. The HF2−–H2O equilibrium structure is planar and, at the B3LYP/6-311++G(2df,2pd) level, the F–H–O bond angle is nearly linear at 174.4° and the F–O distance is 2.59 Å. With zero point energy and counterpoise correction, the binding energy is 14.9 kcal/mol and the strong hydrogen bond of HF2− is weakened by 11.3 kcal/mol (25%). In HF2− the experimental F–F distance is 2.28 Å and the F–H–F bond angle is 180°. The most intense IR vibration is the F–H–F asymmetric stretch at 1331 cm−1. In HF2− the calculated F–F distance is 2.30 Å and in the HF2−–H2O equilibrium structure the F–H distance for the hydrogen bonded F atom is longer by 0.13 Å but the F–H distance for the free F atom is shorter by 0.10 Å and the F–F distance is only 0.03 Å longer. The F–H–F bond angle is very close to linear at 179.4°. The most intense IR vibration remains the F–H–F asymmetric stretch, blueshifted by 648 cm−1. The F–H–O asymmetric stretch is also an intense IR vibration, redshifted by 729 cm−1 from the O–H local mode stretch for H2O.

Measurements and Calculations of the Halfwidth of Two Rotational Transitions of Water Vapor Perturbed by N2, O2, and Air

In this paper we report the results of both an experimental and theoretical study of the halfwidths of two transitions of water vapor. Measurements on the lines of the H216O and H218O isotopomers located at 325.1 and 203.4 GHz, respectively, were carried out in the temperature range 300–393 K, with N2and O2as perturbing gases. The foreign-broadening coefficients and their temperature-dependence parameters were determined assuming a Voigt profile and the usual temperature dependence for the halfwidth. The retrieved values are compared to values calculated using the complex semiclassical formalism of Robert and Bonamy. The assumed intermolecular potential is a combination of electrostatic and atom–atom components. This last contribution is defined as the sum of pairwise Lennard–Jones 6–12 interactions between the atoms of H2O and the atoms of the perturbing molecules expanded to eighth order. Also calculated are the pressure-induced shifts of the spectral lines for temperatures from 200 to 400 K. Calculated and experimental results are in good agreement, within ±3.2%, except for the N2-broadening temperature coefficients, for which there are discrepancies as high as 23%. Air-broadening parameters are determined following the classical relation: γ (air) = 0.79γ (N2) + 0.21γ (O2).

Identification of the Limiting Species in the Plutonium(IV) Carbonate System. Solid State and Solution Molecular Structure of the [Pu(CO3)5]6- Ion

The identity of the limiting Pu(IV) species under high carbonate concentrations has been determined to be Pu(CO3)56-. Single crystals of [Na6Pu(CO3)5]2·Na2CO3·33H2O were obtained from a 0.15 M solution of Pu(IV) in 2.6M Na2CO3. The asymmetric unit contains a complex network consisting of [Pu(CO3)5]6- anions and Na+ cations which are linked through interactions with CO32- and H2O ligands. Each Na+ ion is coordinated to the O atoms of H2O or CO32- ligands such that the Na+ ions achieve either octahedral or square-based pyramidal coordination. The [Pu(CO3)5]6- anion can be viewed as a pseudohexagonal bipyramid with three CO32- ligands in a equatorial plane and two in axial positions. EXAFS data for Pu(IV) in 2.5M Na2CO3 solution were collected at the Pu LIII edge. Curve fitting reveals three shells in the FT spectrum. The first shell contains ten O atoms with Pu−O = 2.42(2) A; the second shell was fit with five C atoms with Pu- - -C = 2.89(2) A; and the third shell was fit with five O atoms with Pu- - -O = 4...

An ab initio study on Penning ionization of a polyatomic target: H2O–He* (2 3S)

An ab initio calculation is carried out for the system H2O–He* (2 3S) →H2O+(2B1,2A1,2B2)+He+e−. Not only the potential for the resonance H2O–He* (2 3S) state and for the ionized H2O+–He, but also the widths into three different ionized states are calculated with the Feshbach projection operator method. The resonance potential has an attractive well in the direction of lone pairs of the O atom of H2O. The well depth is estimated to be about 450 meV. The potential is compared with those for the same or similar system. The widths obtained reflect distributions of the molecular orbital of the target molecule concerned with the relevant ionization and that ionization into totally symmetric states is favored. The analyses of partial waves of emitted electrons leads to the conclusion that the σ electrons are mainly emitted in regard to the H2O–He pseudoaxis. The obtained results are consistent with results of Penning ionization electron spectroscopy.

Ab initio study of the intermolecular potential of the water–carbon monoxide complex

The combination of the supermolecular Mo/ller–Plesset scheme with the perturbation theory of intermolecular forces is applied in the analysis of the potential energy surface (PES) of the H2O...CO complex. We located three low-energy configurations on the potential energy surface corresponding to two isomeric H-bonded complexes OC...HOH (C structure), CO...HOH (O structure), and a T-shaped structure with CO bonded to the O atom of H2O. The absolute minimum corresponds to the C configuration OC...HOH, involving a nonlinear C...H–O bond. The tilt from the linearity is 11 deg, in agreement with the value derived from the experimental data. The computed binding energies on the fourth-order perturbation theory level are 651 cm−1 for the C configuration, 301 cm−1 for T, and 256 cm−1 for O. The anisotropy of the potential energy surface is analyzed using the perturbation theory. The absolute minimum results from the attractive electrostatic contribution and dispersion energy, which overcome considerable exchange repulsion. A small tilt of 11 deg from the linear H bond is due to the balance of the electrostatic and exchange repulsion terms; the repulsive Heitler–London term is minimal when the angle between the C2V axis of the water molecule and the intermolecular axis is equal to 63.0 deg. The bonding in the T configuration is due largely to the dispersion energy which overcomes strong exchange repulsion. The third O configuration is more stable on the SCF level than on the MP2 level, because of the reversal of the sign of the dipole moment of the CO molecule. The tunneling motion of the water molecule around its c inertial axis was studied and the barrier to exchange of the bound and the free hydrogen atom was determined as 280 cm−1 (1289.470 μhartree).

Proton–donor properties of water and ammonia in van der Waals complexes with rare-gas atoms. Kr–H2O and Kr–NH3

The perturbation theory of intermolecular forces in conjunction with the supermolecular Mo/ller–Plesset perturbation theory is applied to the analysis of the potential-energy surfaces of Kr–H2O and Kr–NH3 complexes. The valleylike minimum region on the potential-energy surface of Kr–H2O ranges from the coplanar geometry with the C2 axis of H2O nearly perpendicular to the O–Kr axis (T structure) to the H-bond structure in which Kr faces the H atom of H2O. Compared to the previously studied Ar–H2O [J. Chem. Phys. 94, 2807 (1991)] the minimum has more of the H-bond character. The minimum for Kr–NH3 corresponds to the T structure only, in accordance to the result for Ar–NH3 [J. Chem. Phys. 91, 7809 (1989)]. The minima in Kr–H2O and Kr–NH3 are roughly 27% and 19%, respectively, deeper than for the analogous Ar complexes. To examine the proton–donor abilities of O–H and N–H bonds the ratios of the deformation energy to dispersion energy are considered. They reflect fundamental differences between the two bonds and explain why NH3 is not capable of forming the H-bond structures to rare-gas atoms.

MOLECULAR STRUCTURE OF AQUAETHYLENEDIAMINETETRAACETATOOSMIUM(IV) MONOHYDRATE: [Os (edta) (H2O)]·H2O

Abstract The title complex, obtained as the first characterized solid Os(IV)-edta complex, crystallizes in the monoclinic space group P21/a with a=14.956(7), b=8.181(3), c=14.600(7) Å, β=126.64(3)°, and Z=4. In the complex molecule [Os(edta)(H2O)], the seven-coordinate Os(IV) sits in a monocapped trigonal prism formed with two N and four O atoms of sexidentate edta and with an O atom of H2O.

Ab initio valence-bond calculations of H2O

A new technique for the determination of atomic valence states and their energies has been developed and applied to the water molecule and hydroxyl radical. This method is applicable to valence-bond studies involving a large number of resonance structures rather than simply a one structure perfect pairing approach. The original basis of resonance structures is transformed into a basis of approximate composite functions which are orthogonal and non-interacting for the separated atoms. The equilibrium molecular eigenfunction is analyzed in terms of the composite functions by means of structure projections. A description of the valence states and the promotional energies of each of the component atoms in H2O and OH is obtained.