Joanna Sadlej

Definition of the hydrogen bond (IUPAC Recommendations 2011)

A novel definition for the hydrogen bond is recommended here. It takes into account the theoretical and experimental knowledge acquired over the past century. This definition insists on some evidence. Six criteria are listed that could be used as evidence for the presence of a hydrogen bond.

Defining the hydrogen bond: An account (IUPAC Technical Report)

The term “hydrogen bond” has been used in the literature for nearly a century now. While its importance has been realized by physicists, chemists, biologists, and material scientists, there has been a continual debate about what this term means. This debate has intensified following some important experimental results, especially in the last decade, which questioned the basis of the traditional view on hydrogen bonding. Most important among them are the direct experimental evidence for a partial covalent nature and the observation of a blue-shift in stretching frequency following X–H···Y hydrogen bond formation (XH being the hydrogen bond donor and Y being the hydrogen bond acceptor). Considering the recent experimental and theoretical advances, we have proposed a new definition of the hydrogen bond, which emphasizes the need for evidence. A list of criteria has been provided, and these can be used as evidence for the hydrogen bond formation. This list is followed by some characteristics that are observed in typical hydrogen-bonding environments.

Discrete stages in the solvation and ionization of hydrogen chloride adsorbed on ice particles

Ionization and dissociation reactions play a fundamental role in aqueous chemistry. A basic and well-understood example is the reaction between hydrogen chloride (HCl) and water to form chloride ions (Cl-) and hydrated protons (H3O+ or H5O2+). This acid ionization process also occurs in small water clusters and on ice surfaces, and recent attention has focused on the mechanism of this reaction in confined-water media and the extent of solvation needed for it to proceed. In fact, the transformation of HCl adsorbed on ice surfaces from a predominantly molecular form to ionic species during heating from 50 to 140 K has been observed. But the molecular details of this process remain poorly understood. Here we report infrared transmission spectroscopic signatures of distinct stages in the solvation and ionization of HCl adsorbed on ice nanoparticles kept at progressively higher temperatures. By using Monte Carlo and ab initio simulations to interpret the spectra, we are able to identify slightly stretched HCl molecules, strongly stretched molecules on the verge of ionization, contact ion pairs comprising H3O+ and Cl-, and an ionic surface phase rich in Zundel ions, H5O2+.

THE ASYMMETRIC CAGE STRUCTURE OF (H2O)7 FROM A COMBINED SPECTROSCOPIC AND COMPUTATIONAL STUDY

The vibrational OH stretch spectra have been measured for the size-selected pure water clusters (H2O)7. In contrast to (H2O)n, n=8–10 clusters, which exhibit three distinct bands corresponding to three distinct types of OH bonds, the heptamer spectrum displays seven bands spanning the range from 2935 to 3720 cm−1. Calculations suggest that the spectra originate from two isomers, derived from the S4 octamer cube by removal of either one double donor or one double acceptor water molecule.

Ab initio study of van der Waals interaction of CO2 with Ar

The ab initio potential energy surface of the ArCO2 cluster is calculated using the supermolecular Mo/ller–Plesset perturbation theory (S‐MPPT) and dissected into its fundamental components; electrostatic, exchange, induction, and dispersion energies. The surface contains a single minimum for the perpendicular approach of Ar toward the C atom which has a well depth of ∼210 cm−1 at R=6.5 a0. This value is obtained using an extended basis set supplied with the bond functions and the fourth order supermolecular Mo/ller–Plesset calculations, and is expected to be accurate to within ±5%. The areas of the surface corresponding to the collinear approach of Ar to CO2 contain an extended plateau. The saddle point in this region for R=9.0 a0 is stabilized by 117 cm−1. The analytical pair potential for Ar–CO2 obtained by fitting to the individual interaction components is provided. The three‐body effects in the related cluster, Ar2CO2, are examined for two configurations of the Ar2CO2 cluster. The overall nonadditiv...

The importance of high-order correlation effects for the CO-CO interaction potential

Abstract The CO–CO interaction energy is calculated for several geometries, both by the supermolecule MP4 and CCSD(T) methods, and by symmetry-adapted perturbation theory. Relatively large differences between the MP4 and CCSD(T) results are explained by means of a diagrammatic analysis of electron correlation effects, supported by quantitative calculations of the fifth-order contributions to the electrostatic interaction energy. It follows from this analysis that the calculation of an accurate intermolecular potential for CO is a particularly difficult problem: even the CCSD(T) method is not sufficiently reliable since it lacks important fifth-order correlation contributions.

Characterization of dihydrogen-bonded D-H...H-A complexes on the basis of infrared and magnetic resonance spectroscopic parameters

The structural, energetic, and spectroscopic properties of the dihydrogen-bonded complexes LiH⋯H2, LiH⋯CH4, LiH⋯C2H6, and LiH⋯C2H2 are investigated. In particular, the interaction energy is decomposed into physically meaningful contributions, and the calculated vibrational frequencies, the magnetic resonance shielding constants, and inter- and intramolecular spin–spin coupling constants are analyzed in terms of their correlation with the interaction energy. Unlike the other three complexes, which can be classified as weak van der Waals complexes, the LiH⋯C2H2 complex resembles a conventional hydrogen-bonded system. The complexation-induced changes in the vibrational frequencies and in the magnetic resonance shielding constants correlate with the interaction energy, as does the reduced coupling 2hJHX between the proton of LiH and hydrogen or carbon nucleus of the proton donor, while 1hJHH do not correlate with the interaction energy. The calculations have been carried out using Moller–Plesset perturbation ...

DFT study of vibrational circular dichroism spectra of D-lactic acid-water complexes

This paper presents a discussion of the interaction energies, conformations, vibrational absorption (VA, harmonic and anharmonic) and vibrational circular dichroism (VCD) spectra for conformers of monomeric chiral d(-)-lactic acid and their complexes with water at the DFT(B3LYP)/aug-cc-pVDZ and DFT(B3LYP)/aug-cc-pVTZ levels. A detailed analysis has been performed principally for the two most stable complexes with water, differing by lactic acid conformation. The VCD spectra were found to be sensitive to conformational changes of both free and complexed molecules, and to be especially useful for discriminating between different chiral forms of intermolecular hydrogen bonding complexes. In particular, we show that the VCD modes of an achiral water molecule after complex formation acquire significant rotational strengths whose signs change in line with the geometry of the complex. Using the theoretical prediction, we demonstrate that the VCD technique can be used as a powerful tool for structural investigation of intermolecular interactions of chiral molecules and can yield information complementary to data obtained through other molecular spectroscopy methods.

Symmetry-Adapted Perturbation-Theory Interaction-Energy Decomposition for Hydrogen-Bonded and Stacking Structures.

This letter reports the computational ab initio studies on the stacked and hydrogen-bonded geometries of the uracil dimer and pyrimidine···p-benzoquinone complex with a special regard to the ratios of different interaction-energy terms calculated by means of the symmetry-adapted perturbation theory (SAPT). In the hydrogen-bonded systems the absolute value of the dispersion term constitutes approximately half of the absolute value of the total SAPT0 interaction energy, while in the stacking complexes the ratio of the dispersion to the total interaction energy is much larger, ca. 1.2-2.0. Our SAPT results are compared with the DFT-SAPT results published recently by the Hobza group (J. Chem. Phys. 2007, 127, 075104), and the role of the dispersion contribution in stacking and hydrogen-bonded arrangements is discussed. The methodological part of this letter presents the influence of counterpoise corrections in the optimization procedure on the geometries of the systems and the calculated SAPT contributions.

AB INITIO STUDY OF ENERGY, STRUCTURE AND DYNAMICS OF THE WATER-CARBON DIOXIDE COMPLEX

The supermolecular Moller–Plesset perturbation theory (MPPT) is applied to calculate and analyze selected portions of the potential-energy surface (PES) of the H2O⋯CO2 complex. Two kinds of minima have been found. The global minimum, which corresponds to the T-shaped structure with the C atom bonded to the O atom, and the local minimum for the H-bonded arrangement OCO⋯HOH. The global minimum was estimated to be 920 cm−1 deep at the fourth order of MPPT combined with the extended spdf-quality basis set supplemented with bond functions. At the same level of theory the optimal H-bonded structure is 357 cm−1 higher in energy, and reveals a small 10° departure from the collinear arrangement OCO⋯H–O. Both the T-shaped and H-bonded forms are primarily bound by the electrostatic term, which is twice as large as the dispersion component. One-dimensional sections of the potential-energy surface were subsequently used to calculate vibrational energy levels for the wagging motion of the water moiety in the T-shaped a...