Hydrogen-bonded OH Research Articles

Neutral and cationic ruthenium carbonyl complexes [Ru(CO)(2,2′-dipyridylamine)(PR3)Cl2] and [Ru(CO)(N–N)(PPh3)2(H)]Cl: synthesis, structural characterization and transfer-hydrogenation

The neutral complexes [Ru(CO)(dpa)(PR3)Cl2] (R = Ph (1) or p-tol (2); dpa = 2,2′-dipyridylamine) were synthesized by the reaction of [Ru(CO)(dmf)(PR3)2Cl2] (dmf = N,N-dimethylformamide) and the dpa ligand, while the cationic carbonyl hydride complexes [Ru(CO)(N–N)(PPh3)2(H)]Cl were synthesized by reaction of [Ru(CO)(PPh3)3Cl(H)] and the appropriate N–N ligand [N–N = 2,2′-bipyridine = bipy (3), 2,2′-4,4′dimethyl-bipyridine = dmb (4) and 2,2′-dipyridylamine = dpa (5)]. The complexes were characterized by NMR (31P, 1H and HMBC 1H-31P), FTIR, elemental analysis and X-ray diffraction. The molecular structure of [Ru(CO)(dpa)(PPh3)Cl2] (1) was determined by X-ray crystallography. The crystal packing is stabilized by strong (CH3)O–H···Cl and N–H···OH(CH3) hydrogen bonds between symmetry-related molecules leading to the formation of dimers. Complexes 1–6 were evaluated as pre-catalysts for the reduction of acetophenone under transfer-hydrogenation conditions using isopropanol as hydrogen source, and conversions up to 86 % in 4 h were achieved.

Growth and characterization of L-prolinium phosphite

Single crystal of L-prolinium phosphite was grown by evaporation method from aqueous solution. It crystallizes in the orthorhombic system (space group P212121, Z=4). The asymmetric unit contains one L-prolinium cation and one phosphite (HPO2(OH))− anion. The phosphite anions form a chain by hydrogen bond OH…O with O…O distance 2.5601(15)Å parallel [010]. The L-prolinium cations bridge two chains of anions by OH…O and NH…O hydrogen bonds with O…O and N…O distances 2.505(2)Å and 2.718(2)Å respectively. The infrared and Raman spectra are registered and discussed. Thermal behavior was studied. Phase-matched SHG was observed.

Crystal structure, IR spectroscopic and optical properties of the two (C11N4H10)4·H2O and (C11N4H10)2·H2O compounds

The crystallization of (C11N4H10)2·H2O (I) and (C11N4H10)4·H2O (II) is made by slow evaporation from aqueous solutions. The structures of these compounds have been solved and refined by single-crystal X-ray diffraction data. The compound (I) is centrosymmetric (space group C2/c) with lattice parameters: a=14.118 (2)Å, b=7.399 (1)Å, c=21.982 (3)Å and β=107.80 (1)°. The compound (II) crystallizes in the same space group (C2/c) with lattice parameters: a=28.976 (2)Å, b=7.593 (2)Å, c=21.724 (2)Å and β=115.819 (2)°. The cohesion in both structures is provided by two types of bonds: hydrogen bonds OH⋯N and NH⋯O involving water molecules and organic molecules, and Van der Waals bonds for the connection between the organic molecules. The IR spectra shows an enlargement of the band between 3300 and 2800cm−1, due to the presence of water molecules and the overlap of vibration modes ν (OH) and ν (CH, NH). The optical band gap is determined to be 4.07eV by UV–Vis–T90+ absorption spectra, which revealed the nature of insulator.

X-ray single crystal, thermal analysis and vibrational study of (NH4)2(SO4)0.92H(AsO4)0.08⋅Te(OH)6

The crystal structure of (NH4)2(SO4)0.92H(AsO4)0.08⋅Te(OH)6 [NSAsTe] crystallizes in the monoclinic system P21/c with the following parameters: a=11.382(5) Å, b=6.615(5) Å, c=13.707(5) Å, β=106.731(5)° and Z=4. The structure is formed by a set of anions (TeO6-6, SO42- and HAsO42-) and NH4+ groups connected by two types of hydrogen bonds OH⋯O and NH⋯O which make the building of the crystal. The differential scanning calorimetry (DSC) analysis has shown three-phase transitions before the decomposition at 399K, 466K and 471K. The thermal analyses (DTA) and (TG) of the title compound has proven that the decomposition of this material starts at a temperature equal to 475K. The Raman spectroscopy at various temperatures, it has confirmed the presence of the phase transitions shown in DSC and DTA. The vibrational study at room temperature shows the presence and the independence of anionic groups, ammonium groups and gives more importance to the strong hydrogen bonds.

TDDFT study on intermolecular hydrogen bond of photoexcited hydroxy coumarin/methyl imidazole

The excited hydrogen bonding between hydroxy coumarin (HC) and hydroxy coumarin/methyl imidazole (HCMI) has been studied using TDDFT method. The intermolecular hydrogen bond OH⋯NH is strengthened upon intramolecular electron transfer (ICT) excitation. The calculated ultraviolet absorption spectrum is in good agreement with the experimental data, and the experimental peak at 310 nm is predicted to be the excited S1 state. From the frontier molecular orbitals of HCMI, the HOMO and the LUMO are of π and π* character and the transition from the ground state to the S1 state is a local exciting process. The intramolecular electron transfer of π electron from the OH group to an π* orbital of C8CF3 group not to CO group is found upon ICT excitation. The calculated gap between HOMO and LUMO shows that HCMI can be more easily excited than free HC. The hydrogen bonding can modulate the internal conversion rate of HCMI.

Insights into a highly conserved network of hydrogen bonds in the agonist binding site of nicotinic acetylcholine receptors: a structural and theoretical study.

Structural and theoretical studies on the geometrical features of a hydrogen-bond network occurring in the binding site of nicotinic acetylcholine receptors (nAChRs) and composed of interconnected WxPD (Trp-x-Pro-Asp) and SWyz (Ser-Trp-yz) sequences from loops A and B, respectively, have been carried out. Multiple sequence alignments using as template the sequence of the apoform of Aplysia californica acetylcholine binding protein (Ac-AChBP) show the strict conservation of serine and tryptophan residues of the loop B SWyz sequence. Considering a sample of 19 high resolution AChBP structures, the strong conformational preferences of the key tryptophan residue has been pointing out, whatever the form, free or bounded, of AChBP. The geometry of the motif hydrogen-bond network has been characterized through the analyses of seven distances. The robustness of the various hydrogen-bond interactions is pointed out, the one involving the aspartate carboxylate group and the serine residue being the shortest of the network. The role of a cooperative effect involving a NH(His145)…OH (Ser142) hydrogen bond is highlighted. Density functional theory calculations on several simplified models based on the motif hydrogen-bond network allow probing the importance of the various hydrogen-bond interactions. The removal of the Ser142 hydroxyl group induces strong structural rearrangements, in agreement with the structural observations. Molecular electrostatic potential calculations on model systems highlight the importance of a cooperative effect in the whole hydrogen-bond network. More precisely, the key role of the Ser142 hydroxyl group, involved in several hydrogen bonds, is underlined.

Aqueous heterogeneity at the air/water interface revealed by 2D-HD-SFG spectroscopy.

Water molecules interact strongly with each other through hydrogen bonds. This efficient intermolecular coupling causes strong delocalization of molecular vibrations in bulk water. We study intermolecular coupling at the air/water interface and find intermolecular coupling 1) to be significantly reduced and 2) to vary strongly for different water molecules at the interface--whereas in bulk water the coupling is homogeneous. For strongly hydrogen-bonded OH groups, coupling is roughly half of that of bulk water, due to the lower density in the near-surface region. For weakly hydrogen-bonded OH groups that absorb around 3500 cm(-1), which are assigned to the outermost, yet hydrogen-bonded OH groups pointing towards the liquid, coupling is further reduced by an additional factor of 2. Remarkably, despite the reduced structural constraints imposed by the interfacial hydrogen-bond environment, the structural relaxation is slow and the intermolecular coupling of these water molecules is weak.

Polar and stereoelectronic effects on the structural and spectroscopic properties of halomethanols

Halogenated methanol derivatives (halogen=F, Cl and Br) were theoretically studied and the gauche conformer relative to the X–C–O–H torsional angle was the single energy minimum found at the MP2/6-311G++(d,p) and B3LYP/6-311G++(d,p) levels in the gas phase, implicit and explicit aqueous solution. The generalized anomeric effect is operative, since the structure (gauche) with an electron lone pair in the anti orientation relative to the halogen is the stable conformation. Natural bond orbital calculations show that this conformational preference, in comparison with the stationary anti structure that exhibits imaginary frequency, is due to hyperconjugation rather than electrostatic effects, while internal hydrogen bond OH⋯X does not operate. However, the 1JC,F coupling constant for the fluorinated derivative is exponentially dependent on the molecular dipole moment and linearly correlated with the C–F distance, but a correlation with the nO→σ∗CF hyperconjugation was not observed. Thus, the generalized anomeric effect in some model systems agrees with the hyperconjugation model, while the Perlin-like effect does not appear to have hyperconjugative dependence, but a polar instead.

TDDFT study on intramolecular hydrogen bond of photoexcited methyl salicylate

The equilibrium geometries, IR-spectra and transition mechanism of intramolecular hydrogen-bonded methyl salicylate in excited state were studied using DFT and TDDFT with 6-31++G (d, p) basis set. The length of hydrogen bond OH⋯OC is decreased from 1.73Å in the ground state to 1.41 and 1.69Å in the excited S1 and S3 states. The increase of bond length for HO and CO group also indicates that in excited state the hydrogen bond OH⋯OC is strengthened. IR spectra show HO and CO stretching bands are strongly redshifted by 1387 and 67cm−1 in the excited S1 and S3 states comparing to the ground state. The excitation energy and the absorption spectrum show the S3 state is the main excited state of the low-lying excited states. By analyzing the frontier molecular orbitals, the transition from the ground state to the excited S1 and S3 states was predicted to be the π→π∗ mode.

Communication: Ultrafast vibrational dynamics of hydrogen bond network terminated at the air/water interface: A two-dimensional heterodyne-detected vibrational sum frequency generation study

Ultrafast vibrational dynamics of hydrogen bond network at the air∕water interface is revealed by two-dimensional heterodyne-detected vibrational sum frequency generation (2D HD-VSFG) spectroscopy. Three diagonal peaks are clearly observed in the 2D HD-VSFG spectrum, which correspond to the negative and positive hydrogen-bonded OH stretch bands and the positive "free" OH stretch band in the steady-state HD-VSFG spectrum. A diagonally elongated bleaching lobe of the hydrogen-bonded OH at 0 ps indicates that it is partly inhomogeneously broadened. This diagonal elongation vanishes in a few hundred femtoseconds, implying the ultrafast spectral diffusion in the hydrogen-bonded OH band. Off-diagonal cross peaks between each OH oscillator are clearly observed instantaneously within the time resolution of 0.2 ps, suggesting that they are vibrationally coupled through anharmonicity and∕or energy transfer.

Brønsted acidity of H-MCM-22 as probed by variable-temperature infrared spectroscopy of adsorbed CO and N2

Brønsted acidity is a key factor controlling catalytic performance of zeolites in many technological processes, and hence the need to find a reliable means for measuring acidity strength. The enthalpy change, ΔH0, involved in the hydrogen bonding interaction between a weak base, such as carbon monoxide or dinitrogen, and the Brønsted acid [Si(OH)Al] hydroxyl groups should correlate with the zeolite acid strength. However, on account of simplicity, the red shift of the OH stretching frequency, ΔνOH, in the hydrogen-bonded OH⋯CO or OH⋯N2 complexes is frequently measured (instead of ΔH0) and correlated with acid strength; and in fact it is often found that ΔH0 and ΔνOH correlate among themselves, but this might not always be the case. We report herein on a variable-temperature IR (VTIR) spectroscopic study of the interaction of CO and N2 with the protonic zeolite H-MCM-22 (structure type MWW). From series of infrared spectra taken over a temperature range, the standard enthalpy of formation of the OH⋯CO and OH⋯N2 complexes was found to be −23.5(±2) and −14.5(±2)kJmol−1, respectively. Corresponding ΔνOH values are −321 and −123cm−1, respectively. Comparison with corresponding ΔH0 and ΔνOH values reported in the literature for other Brønsted-acid zeolites shows strong evidence of a limited validity of the rule correlating ΔνOH with ΔH0 for both probe molecules, which gives a clear warning about the risk of using the magnitude of ΔνOH as a measure of zeolite acidity.

Conformational analysis and intramolecular interactions in monosubstituted phenylboranes and phenylboronic acids

A 1TSJF,H(O) coupling pathway, dictated by a hydrogen bond, in some 2-fluorobenzoic acids has been observed, while such an interaction does not occur in 2-fluorophenol. Thus, this work reports the conformational analysis of 2-fluorophenylboronic acid (1), in order to evaluate a possible intramolecular OH∙∙∙F hydrogen bond in comparison to an nF→pB interaction, which mimics the quantum nF→σ*OH hydrogen bond that would be expected in 2-fluorophenol. 2-Fluorophenylborane (3), which does not experience hydrogen bonding, was used to verify whether nF→pB interaction governs the conformational equilibrium in 1 due to a predominant OH∙∙∙F hydrogen bond or to other effects. A series of 2-X-phenylboranes (X = Cl, Br, NH2, PH2, OH and SH) were further computationally analyzed to search for electron donors to boron, capable of influencing the conformational equilibrium. Overall, the intramolecular OH∙∙∙F hydrogen bond in 1 is quite stabilizing and dictates the 1hJF,H(O) coupling constant. Moreover, electron donation to the empty p orbital of boron (for noncoplanar BH2 moiety relative to the phenyl ring) is also significantly stabilizing for the NH2 and PH2 derivatives, but not enough to make the corresponding conformers appreciably populated, because of steric effects and the loss of πCC→pB resonance. Thus, the results found earlier for 2-fluorophenol about the lack of intramolecular hydrogen bonding are now corroborated.

Experimental Evidence of Fermi Resonances in Isotopically Dilute Water from Ultrafast Broadband IR Spectroscopy

The vibrational dynamics of liquid water, which result from a complex interplay between internal molecular vibrations and the fluctuating hydrogen bond network, are fundamental to many physicochemical and biological processes. Using a new ultrafast broadband mid-infrared light source with over 2000 cm(-1) of bandwidth, we performed ultrafast time-resolved infrared spectroscopy to study the vibrational couplings and relaxation dynamics of the stretching and bending vibrations of the mixed isotopologue, HOD, in D2O. Analysis of cross-peaks and induced absorptions in the two-dimensional infrared spectrum and transient absorption spectrum shows that the hydroxyl stretch of HOD is coupled to the HOD bending mode via Fermi resonance, with a 70° angle between their transition dipole moments. We see that HOD is also anharmonically coupled to the D2O solvent modes. From transient absorption spectra, we conclude that vibrational relaxation occurs through a number of paths. The strongly hydrogen-bonded OH oscillators have the highest propensity to relax through the bending mode, while the weakly hydrogen bonded oscillators relax through other modes.

Direct Dynamics Simulations of the Product Channels and Atomistic Mechanisms for the OH–+ CH3I Reaction. Comparison with Experiment

Electronic structure and direct dynamics calculations were used to study the potential energy surface and atomic-level dynamics for the OH(-) + CH3I reactions. The results are compared with crossed molecular beam, ion imaging experiments. The DFT/B97-1/ECP/d level of theory gives reaction energetics in good agreement with experiment and higher level calculations, and it was used for the direct dynamics simulations that were performed for reactant collision energies of 2.0, 1.0, 0.5, and 0.05 eV. Five different pathways are observed in the simulations, forming CH3OH + I(-), CH2I(-) + H2O, CH2 + I(-) + H2O, IOH(-) + CH3, and [CH3--I--OH](-). The SN2 first pathway and the proton-transfer second pathway dominate the reaction dynamics. Though the reaction energetics favor the SN2 pathway, the proton-transfer pathway is more important except for the lowest collision energy. The relative ion yield determined from the simulations is in overall good agreement with experiment. Both the SN2 and proton-transfer pathways occur via direct rebound, direct stripping, and indirect mechanisms. Except for the highest collision energy, 70-90% of the indirect reaction for the SN2 pathway occurs via formation of the hydrogen-bonded OH(-)---HCH2I prereaction complex. For the proton-transfer pathway the indirect reaction is more complex with the roundabout mechanism and formation of the OH(-)---HCH2I and CH2I(-)---HOH complexes contributing to the reaction. The majority of the SN2 reaction is direct at 2.0, 1.0, and 0.5 eV, dominated by stripping. At 0.05 eV the two direct mechanisms and the indirect mechanisms have nearly equal contributions. The majority of the proton-transfer pathway is direct stripping at 2.0, 1.0, and 0.5 eV, but the majority of the reaction is indirect at 0.05 eV. The product relative translational energy distributions are in good agreement with experiment for both the SN2 and proton-transfer pathways. For both, direct reaction preferentially transfers the product energy to relative translation, whereas transfer to product vibration is more important for the indirect reactions. For the proton-transfer reactions the velocity scattering angle distribution is peaked in the forward direction and in quite good agreement with experiment. However, for the SN2 reaction, the experimental scattering is isotropic in nature whereas forward scattering dominates the simulation distributions. The implication is that the simulations give too much stripping, which leads to forward scattering. The dynamics for the OH(-) + CH3I SN2 pathway are similar to those found previously for the F(-) + CH3I SN2 reaction.

Cellulose polymorphism study with sum-frequency-generation (SFG) vibration spectroscopy: identification of exocyclic CH2OH conformation and chain orientation

Sum-frequency-generation (SFG) vibration spectroscopy is a technique only sensitive to functional groups arranged without centrosymmetry. For crystalline cellulose, SFG can detect the C6H2 and intra-chain hydrogen-bonded OH groups in the crystal. The geometries of these groups are sensitive to the hydrogen bonding network that stabilizes each cellulose polymorph. Therefore, SFG can distinguish cellulose polymorphs (Iβ, II, IIII and IIIII) which have different conformations of the exocyclic hydroxymethylene group or directionalities of glucan chains. The C6H2 asymmetric stretching peaks at 2,944 cm−1 for cellulose Iβ and 2,960 cm−1 for cellulose II, IIII and IIIII corresponds to the trans-gauche (tg) and gauche-trans (gt) conformation, respectively. The SFG intensity of the stretch peak of intra-chain hydrogen-bonded O–H group implies that the chain arrangement in cellulose crystal is parallel in Iβ and IIII, and antiparallel in II and IIIII.

Synthesis and study of tetramethylammonium hexafluoridozirconate and hexafluoridohafnate solvated by H2O·HF adducts and [N(CH3)4]2ZrF6

A new type of zirconium and hafnium fluoride complexes of the composition [N(CH3)4]2AF6·(H2O·HF) (A=Zr, Hf) solvated by H2O·HF adducts and the compound [N(CH3)4]2ZrF6 have been synthesized. The synthesized compounds were studied by X-ray diffraction, vibrational spectroscopy, quantum chemical calculations and differential thermal analysis. The crystal structures of [N(CH3)4]2AF6·(H2O·HF) (A=Zr, Hf) are built up from N(CH3)4+ cations, octahedral complex anions [AF6]2−, and solvate adducts H2O·HF linked by strong hydrogen bonds FH⋯O. The compound [N(CH3)4]2ZrF6 is built up from N(CH3)4+ cations and complex anions [ZrF6]2−. In the investigated structures, the complex anions, cations, and adducts are linked by ionic interactions and a branched system of hydrogen bonds OH⋯F and СH⋯F.

Photoresponsive two-component organogelators based on trisphenylisoxazolylbenzene

Photochromic tris(phenylisoxazolyl)benzene 1 and bispyridine derivatives 2a–e were mixed in a certain ratio to generate stable gels in benzyl alcohol, 4-methoxybenzyl alcohol, and aniline. Supramolecular assembly of 1 in solution was confirmed by 1H NMR study. The Tgel value was saturated in a 2 : 3 ratio of 1 and 2c. The intermolecular hydrogen bonds OH···N and salt bridge O(−)···H(–)N(+) between 1 and 2c coexisted evidently, and these hydrogen bonds contributed to the stabilization of the gel networks. The lengths of alkyl chains of 2a–e governed the stabilities of the gels. The gel formations were driven by the morphological transition of 1 before and after the addition of 2a–e. Mixtures of 1 and 2a–e led to the well developed fibrillar networks, generating a lot of voids that are responsible for immobilizing solvent molecules. When the benzyl alcohol gel was irradiated at 360 nm, the gel turned to the sol. The sol was reversed to the gel by warming. This gel-to-sol phase transition was completely reversible.

The x-ray absorption spectroscopy model of solvation about sulfur in aqueous L-cysteine

The environment of sulfur in dissolved aqueous L-cysteine has been examined using K-edge x-ray absorption spectroscopy (XAS), extended continuum multiple scattering (ECMS) theory, and density functional theory (DFT). For the first time, bound-state and continuum transitions representing the entire XAS spectrum of L-cysteine sulfur are accurately reproduced by theory. Sulfur K-edge absorption features at 2473.3 eV and 2474.2 eV represent transitions to LUMOs that are mixtures of S-C and S-H σ∗ orbitals significantly delocalized over the entire L-cysteine molecule. Continuum features at 2479, 2489, and 2530 eV were successfully reproduced using extended continuum theory. The full L-cysteine sulfur K-edge XAS spectrum could not be reproduced without addition of a water-sulfur hydrogen bond. Density functional theory analysis shows that although the Cys(H)S⋯H-OH hydrogen bond is weak (∼2 kcal) the atomic charge on sulfur is significantly affected by this water. MXAN analysis of hydrogen-bonding structures for L-cysteine and water yielded a best fit model featuring a tandem of two water molecules, 2.9 Å and 5.8 Å from sulfur. The model included a S(cys)⋯H-O(w1)H hydrogen-bond of 2.19 Å and of 2.16 Å for H(2)O(w1)⋯H-O(w2)H. One hydrogen-bonding water-sulfur interaction alone was insufficient to fully describe the continuum XAS spectrum. However, density functional theoretical results are convincing that the water-sulfur interaction is weak and should be only transient in water solution. The durable water-sulfur hydrogen bond in aqueous L-cysteine reported here therefore represents a break with theoretical studies indicating its absence. Reconciling the apparent disparity between theory and result remains the continuing challenge.

Solvation Effect on the NH Stretching Vibrations of Solvated Aminopyrazine, 2-Aminopyridine, and 3-Aminopyridine Clusters

The vibrational spectra of the hydrated and methanol-solvated aminopyrazine, 2-aminopyridine and 3-aminopyridine in supersonic jets have been measured in terms of IR-UV double-resonance spectroscopy. Comparing the IR spectrum of aminopyrazine with those of 2-aminopyridine and 3-aminopyridine clusters, we determine the solvation structure of aminopyrazine to be a similar cyclic structure as hydrated 2-aminopyridine clusters [Wu, et al., Phys. Chem. Chem. Phys. 2004, 6, 515]. In the case of monohydrated aminopyrazine cluster, one of the normal modes composed of the hydrogen-bonded OH and NH stretching local modes gives the anomalously weak IR intensity, which is ascribed to the cancellation of the dipole moment change between the OH and NH stretching local modes. The solvated 3-aminopyridine clusters forms the hydrogen-bond between the pyridyl nitrogen atom and the OH group, but the amino group is indirectly affected to induce slight blue shift of the NH(2) stretches. This phenomenon is explained by inductive effect where the electron withdrawing from the amino group upon the solvation results in a "quinoid-like" structure of the amino group.

Experimental and Theoretical Investigations of Energy Transfer and Hydrogen-Bond Breaking in the Water Dimer

The hydrogen bonding in water is dominated by pairwise dimer interactions, and the predissociation of the water dimer following vibrational excitation is reported here. Velocity map imaging was used for an experimental determination of the dissociation energy (D(0)) of (D(2)O)(2). The value obtained, 1244 ± 10 cm(-1) (14.88 ± 0.12 kJ/mol), is in excellent agreement with the calculated value of 1244 ± 5 cm(-1) (14.88 ± 0.06 kJ/mol). This agreement between theory and experiment is as good as the one obtained recently for (H(2)O)(2). In addition, pair-correlated water fragment rovibrational state distributions following vibrational predissociation of (H(2)O)(2) and (D(2)O)(2) were obtained upon excitation of the hydrogen-bonded OH and OD stretch fundamentals, respectively. Quasi-classical trajectory calculations, using an accurate full-dimensional potential energy surface, are in accord with and help to elucidate experiment. Experiment and theory find predominant excitation of the fragment bending mode upon hydrogen bond breaking. A minor channel is also observed in which both fragments are in the ground vibrational state and are highly rotationally excited. The theoretical calculations reveal equal probability of bending excitation in the donor and acceptor subunits, which is a result of interchange of donor and acceptor roles. The rotational distributions associated with the major channel, in which one water fragment has one quantum of bend, and the minor channel with both water fragments in the ground vibrational state are calculated and are in agreement with experiment.