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Title: Observation of a remarkable temperature effect in the hydrogen bonding structure and dynamics of the CN-(H2O) cluster

Abstract

The CN-(H2O) cluster represents a model diatomic monohydrate with multiple solvation sites. We report joint experimental and theoretical studies of its structure and dynamics using temperature-controlled photoelectron spectroscopy (PES) and ab-initio electronic structure calculations. The observed PES spectra of CN-(H2O) display a remarkable temperature effect, namely that the T=12 K spectrum shows an unexpectedly large blue shift of 0.25 eV in the electron binding energy relative to the Room Temperature (RT) spectrum. Extensive theoretical analysis of the potential energy function (PEF) of the cluster at the CCSD(T) level of theory reveal the existence of two nearly isoenergetic isomers corresponding to H2O forming a H-bond with either the C or the N atom, respectively. This results in four topologically distinct minima, i.e., CN-(HaOHb), CN-(HbOHa), NC-(HaOHb) and NC-(HbOHa). There are two main pathways connecting these minima: (i) CN- tumbling relative to water and (ii) water rocking relative to CN-. The relative magnitude of the barriers associated with these two motions reverses between low [pathway (i) is preferred] and high [pathway (ii) is preferred] temperatures. As a result, at T=12 K the cluster adopts a structure that is close to the minimum energy CN-(H2O) configuration, while at RT it can effectively access regionsmore » of the PEF close to the transition state for pathway (ii), explaining the surprisingly large spectral shift between the 12 K and RT PES spectra. This work was supported by the Division of Chemical Sciences, Geosciences and Biosciences, Office of Basic Energy Sciences, US Department of Energy. Battelle operates Pacific Northwest National Laboratory for the US Department of Energy.« less

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE
OSTI Identifier:
973994
Report Number(s):
PNNL-SA-67173
30794; KC0301020; TRN: US201007%%174
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Physical Chemistry A, 113(35):9579-9584; Journal Volume: 113; Journal Issue: 35
Country of Publication:
United States
Language:
English
Subject:
08 HYDROGEN; BINDING ENERGY; BONDING; CONFIGURATION; ELECTRONIC STRUCTURE; ELECTRONS; HYDROGEN; ISOMERS; PHOTOELECTRON SPECTROSCOPY; POTENTIAL ENERGY; SOLVATION; SPECTRA; SPECTRAL SHIFT; TEMPERATURE DEPENDENCE; WATER; http://pubs.acs.org/doi/abs/10.1021/jp9034002; Environmental Molecular Sciences Laboratory

Citation Formats

Wang, Xue B., Werhahn, Jasper C., Wang, Lai S., Kowalski, Karol, Laubereau, Alfred, and Xantheas, Sotiris S. Observation of a remarkable temperature effect in the hydrogen bonding structure and dynamics of the CN-(H2O) cluster. United States: N. p., 2009. Web. doi:10.1021/jp9034002.
Wang, Xue B., Werhahn, Jasper C., Wang, Lai S., Kowalski, Karol, Laubereau, Alfred, & Xantheas, Sotiris S. Observation of a remarkable temperature effect in the hydrogen bonding structure and dynamics of the CN-(H2O) cluster. United States. doi:10.1021/jp9034002.
Wang, Xue B., Werhahn, Jasper C., Wang, Lai S., Kowalski, Karol, Laubereau, Alfred, and Xantheas, Sotiris S. 2009. "Observation of a remarkable temperature effect in the hydrogen bonding structure and dynamics of the CN-(H2O) cluster". United States. doi:10.1021/jp9034002.
@article{osti_973994,
title = {Observation of a remarkable temperature effect in the hydrogen bonding structure and dynamics of the CN-(H2O) cluster},
author = {Wang, Xue B. and Werhahn, Jasper C. and Wang, Lai S. and Kowalski, Karol and Laubereau, Alfred and Xantheas, Sotiris S.},
abstractNote = {The CN-(H2O) cluster represents a model diatomic monohydrate with multiple solvation sites. We report joint experimental and theoretical studies of its structure and dynamics using temperature-controlled photoelectron spectroscopy (PES) and ab-initio electronic structure calculations. The observed PES spectra of CN-(H2O) display a remarkable temperature effect, namely that the T=12 K spectrum shows an unexpectedly large blue shift of 0.25 eV in the electron binding energy relative to the Room Temperature (RT) spectrum. Extensive theoretical analysis of the potential energy function (PEF) of the cluster at the CCSD(T) level of theory reveal the existence of two nearly isoenergetic isomers corresponding to H2O forming a H-bond with either the C or the N atom, respectively. This results in four topologically distinct minima, i.e., CN-(HaOHb), CN-(HbOHa), NC-(HaOHb) and NC-(HbOHa). There are two main pathways connecting these minima: (i) CN- tumbling relative to water and (ii) water rocking relative to CN-. The relative magnitude of the barriers associated with these two motions reverses between low [pathway (i) is preferred] and high [pathway (ii) is preferred] temperatures. As a result, at T=12 K the cluster adopts a structure that is close to the minimum energy CN-(H2O) configuration, while at RT it can effectively access regions of the PEF close to the transition state for pathway (ii), explaining the surprisingly large spectral shift between the 12 K and RT PES spectra. This work was supported by the Division of Chemical Sciences, Geosciences and Biosciences, Office of Basic Energy Sciences, US Department of Energy. Battelle operates Pacific Northwest National Laboratory for the US Department of Energy.},
doi = {10.1021/jp9034002},
journal = {Journal of Physical Chemistry A, 113(35):9579-9584},
number = 35,
volume = 113,
place = {United States},
year = 2009,
month = 9
}
  • The authors have incorporated the flexible RWK2 water potential into the parameterization of a chloride-water interaction potential from first principles calculations and used it to investigate the temperature effects in the infrared (IR) spectrum of Cl{sup {minus}}(H{sub 2}O){sub 2}. They have found that spectral signatures of hydrogen bonding between the two water molecules in the cluster disappear with increasing temperature, a consequence of the weak water-water interaction in the cluster.
  • No abstract prepared.
  • The excitation energy in the multiphoton ionization spectrum of the trans-1-naphthol/N2 cluster shows only a small red-shift with respect to isolated naphthol, indicating a van-der-Waals ?-bound structure rather than a hydrogen bonded one. In order to confirm this interpretation, high-level electronic structure calculations were performed for several ?- and hydrogen-bonded isomers of this cluster. The calculations were carried out at the second order Moeller Plesset (MP2) level of perturbation theory with the family of correlation consistent basis sets up to quintuple-? quality including corrections for the basis set superposition error and extrapolation to the MP2 complete basis set (CBS) limit.more » We report the optimal geometries, vibrational frequencies and binding energies (De), also corrected for harmonic zero-point energies (D0), for three energetically low-lying isomers. In all calculations the lowest energy structure was found to be an isomer with the N2 molecule bound to the ?-system of the naphthol ring carrying the OH-group. In the CBS limit its dissociation energy was computed to be D0=2.67 kcal/mol (934 cm-1) as compared to D0=1.28 kcal/mol (448 cm-1) for the H-bound structure. The electronic structure calculations therefore confirm the assignment of the experimental electronic spectrum corresponding to a van-der-Waals ?-bound structure. The energetic stabilization of the ?-bound isomer with respect to the hydrogen bonded one is rather unexpected when compared with previous findings in related systems, in particular phenol/N2.« less
  • The effect of strong intermolecular hydrogen bonding on torsional degrees of freedom is investigated by far-infrared absorption spectroscopy for different methanol dimer isotopologues isolated in supersonic jet expansions or embedded in inert neon matrices at low temperatures. For the vacuum-isolated and Ne-embedded methanol dimer, the hydrogen bond OH librational mode of the donor subunit is finally observed at ∼560 cm{sup −1}, blue-shifted by more than 300 cm{sup −1} relative to the OH torsional fundamental of the free methanol monomer. The OH torsional mode of the acceptor embedded in neon is observed at ∼286 cm{sup −1}. The experimental findings are heldmore » against harmonic predictions from local coupled-cluster methods with single and double excitations and a perturbative treatment of triple excitations [LCCSD(T)] and anharmonic. VPT2 corrections at canonical MP2 and density functional theory (DFT) levels in order to quantify the contribution of vibrational anharmonicity for this important class of intermolecular hydrogen bond vibrational motion.« less
  • Aqua ligands can undergo rapid internal rotation about the M-O bond. For magnetic resonance contrast agents, this rotation results in diminished relaxivity. Herein, we show that an intramolecular hydrogen bond to the aqua ligand can reduce this internal rotation and increase relaxivity. Molecular modeling was used to design a series of four Gd complexes capable of forming an intramolecular H-bond to the coordinated water ligand, and these complexes had anomalously high relaxivities compared to similar complexes lacking a H-bond acceptor. Molecular dynamics simulations supported the formation of a stable intramolecular H-bond, while alternative hypotheses that could explain the higher relaxivitymore » were systematically ruled out. Finally, intramolecular H-bonding represents a useful strategy to limit internal water rotational motion and increase relaxivity of Gd complexes.« less