Noncovalent interactions: a challenge for experiment and theory

Molecular Clusters of π-Systems: Theoretical Studies of Structures, Spectra, and Origin of Interaction Energies

Infrared Spectroscopy of Size-Selected Water and Methanol Clusters

1.1. Historical Background Hydrogen bonds1,2 are one of the principal intermolecular forces. A special class are ionic hydrogen bonds (IHBs) that form between ions and molecules with bonds strengths of 5-35 kcal/mol, up to a third of the strength of covalent bonds. These strong interactions are critical, for example, in ionic clusters and nucleation, in electrolytes, ion solvation, and acid-base chemistry, in the structures of ionic crystals, surfaces, silicates, and clays, in surface adsorption, and in self-assembly in supramolecular chemistry and molecular crystals.3 IHBs are also important in bioenergetics including protein folding, enzyme active centers, formation of membranes and proton transport, and biomolecular recognition. With such wide-ranging roles, the fundamental properties of IHB interactions need to be understood. The energetics of IHB interactions cannot be isolated and quantified in the condensed phase. However, these interactions can be isolated and studied quantitatively in gas phase. These studies lead to a fundamental understanding of relations between IHB bond strengths and molecular structure, the solvation of ions, especially in the critical inner shells, and acid-based phenomena and bioenergetics. This review will present the basic insights that have been obtained in the past four decades. It will present a comprehensive review of the thermochemistry and its structural implications obtained from ab initio calculations. Relevant recent results from spectroscopy will be also illustrated. The advent of variable temperature high-pressure mass spectrometry (HPMS) introduced by Field and co-workers in the 1960s4 and pulsed high-pressure mass spectrometry (PHPMS) introduced by Kebarle in the late 1960s5 have been particularly significant. These workers realized that at pressures of several torrs and gas densities of 1016-1017 cm-3 in ion sources, ions can undergo 103-106 collisions with neutral molecules during typical residence times of 0.1-10 ms and establish thermal ion populations and * E-mail: m.mautner@solis1.com. 213 Chem. Rev. 2005, 105, 213−284

http://www.astro-ecology.com/PDFTheIonicHydrogenBondChemicalReviews2005Paper.pdf

The Ionic Hydrogen Bond

Extensive ab initio calculations have been performed using the 6-31G(d,p) and 6-311++G(2d,2p) basis sets for several possible structures of water clusters (H2O)n, n = 8−20. It is found that the most stable geometries arise from a fusion of tetrameric or pentameric rings. As a result, (H2O)n, n = 8, 12, 16, and 20, are found to be cuboids, while (H2O)10 and (H2O)15 are fused pentameric structures. For the other water clusters (n = 9, 11, 13, 14, and 17−19) under investigation, the most stable geometries can be thought of as arising from either the cuboid or the fused pentamers or a combination thereof. The stability of some of the clusters, namely, n = 8−16, has also been studied using density functional theory. An attempt has been made to estimate the basis set superposition error and zero-point energy correction for such clusters at the Hartree−Fock (HF) level using the 6-311++G(2d,2p) basis set. To ensure that a minimum on the potential-energy surface has been located, frequency calculations have been c...

/pdf/structure-and-stability-of-water-clusters-h2o-n-n-8-20-an-ab-zl3uiva3sq.pdf

Structure and Stability of Water Clusters (H2O)n, n ) 8-20: An Ab Initio Investigation

The vibronic spectra of jet cooled phenol(H2O)7,8 clusters were analyzed with mass selective resonance enhanced two photon ionization (R2PI) and ultraviolet-ultraviolet spectral hole burning (UV-UV SHB) A double resonance technique with an infrared (IR) laser as burn laser (IR-UV SHB) was used to measure the intramolecular OH stretching vibrations of the mass- and isomer-selected clusters Two isomers of phenol(H2O)7 and three isomers of phenol(H2O)8 could be distinguished via SHB and their IR spectra recorded The red- or blueshift of the electronic origin relative to the phenol monomer gives valuable hints on the hydrogen bonding between phenol and the water moiety All IR spectra contain four characteristic groups of OH stretching vibrations which give insight into the structure of the H bonded network The ab initio calculations show that the minimum energy structures for phenol(H2O)7,8 are very similar to the corresponding water clusters which are based on regular (H2O)8 cubes Comparison between experiment and calculation for phenol(H2O)8 shows that phenol can attach to and insert itself in the water network

Structure and vibrations of phenol(H2O)7,8 studied by infrared-ultraviolet and ultraviolet-ultraviolet double-resonance spectroscopy and ab initio theory

The structure of phenol in the S1-state determined by high resolution UV-spectroscopy

The intermolecular vibrations of jet-cooled phenol(H2O)2-5 and phenol(D2O)2-5-d1 were investigated in the S0 and S1 electronic states by using mass-selective UV spectral hole burning (SHB) and sing...

Intermolecular vibrations of phenol(h2o)2-5 and phenol(d2o)2-5-d1 studied by uv double-resonance spectroscopy and ab initio theory

The infrared spectra of (phenol)(H2O)n+ cluster ions (n = 1−4, 7, 8) have been recorded in the region from 2850 to 3800 cm-1. The method developed for this study (IR-PARI = infrared photodissociation after resonant ionization) allows sensitive IR spectroscopy of cluster ions from size-selected neutral precursors. The three-color laser scheme used for ion selection and dissociation consists of a two-color S0 → S1 → D0 ionization of a mass-selected cluster followed by IR photodissociation of the cluster ion. The IR spectra were taken by monitoring the photodissociation dip of the parent ion signal and by recording the rise of the −H2O fragment signal. The experimentally observed frequencies are compared to the results of ab initio calculations. No proton transfer is observed for the (phenol)(H2O)1,2+ clusters. In contrast to the S0 state, the structure of (phenol)(H2O)2+ turns out to be linear. In the case of the (phenol)(H2O)3,4+ clusters, linear and solvated structures are discussed. Within the solvated s...

D. Spangenberg

Papers

Structure and vibrations of phenol(H2O)7,8 studied by infrared-ultraviolet and ultraviolet-ultraviolet double-resonance spectroscopy and ab initio theory

The structure of phenol in the S1-state determined by high resolution UV-spectroscopy

Intermolecular vibrations of phenol(h2o)2-5 and phenol(d2o)2-5-d1 studied by uv double-resonance spectroscopy and ab initio theory

Infrared spectroscopy of resonantly ionized (phenol)(h2o)n

Determination of the structures and barriers to hindered internal rotation of the phenol–methanol cluster in the S0 and S1 states