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Journal ArticleDOI

Infrared photodissociation spectroscopy of [Aniline-(Water)n]+ (n = 1-8): Structural change from branched and cyclic to proton-transferred forms

29 May 2003-Journal of Physical Chemistry A (American Chemical Society)-Vol. 107, Iss: 21, pp 4230-4237
TL;DR: In this article, the infrared photodissociation spectra of [aniline−(H2O)n]- (n = 1−8) are measured in the 2700−3800 cm-1 region.
Abstract: Infrared photodissociation spectra of [aniline−(H2O)n]+ (n = 1−8) are measured in the 2700−3800 cm-1 region. The spectra are interpreted with the aid of density functional theory calculations. The n = 1 ion has an N−H···O hydrogen bond. The spectrum of the n = 2 ion demonstrates a large perturbation to both of the NH oscillators, indicating the 1−1 structure where each NH bond is bound to a water molecule. For the n = 3 ion, the calculated spectrum of the 2−1 branched structure coincides well with the observed one. For the n = 4 ion, there exist three strong bands at 2960, 3100, and 3430 cm-1, as well as a very weak one at 3550 cm-1. The observed spectrum in the 3600−3800 cm-1 region is decomposed into four bands centered at 3640, 3698, 3710, and 3734 cm-1. The 2−2 branched isomer is responsible for all the features except the 3550 and 3710 cm-1 bands. These two bands are due to another isomer with a five-membered ring. An infrared band characteristic of the n = 5 ion appears at 3684 cm-1, which is not se...

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TL;DR: This paper will focus on the major areas of research initiated by the Yuan T. Lee group and how these studies stimulated and influenced others in what is currently a vibrant and growing field of ionic clusters.
Abstract: Beginning in the mid-1980s, a number of innovative experimental studies on ionic clusters emerged from the laboratory of Yuan T. Lee combining infrared laser spectroscopy and tandem mass spectrometry. Coupled with modern electronic structure calculations, this research explored many facets of ionic clusters including solvation, structure, and dynamics. These efforts spawned a resurgence in gas-phase cluster spectroscopy. This paper will focus on the major areas of research initiated by the Lee group and how these studies stimulated and influenced others in what is currently a vibrant and growing field.

86 citations

Journal ArticleDOI
TL;DR: In this paper, the utilization of light irradiation to tune the photothermal catalysis has been investigated, which couples both solar and thermal energies, has burgeoned as a promising approach to drive catalytic reactions.
Abstract: Photothermal catalysis, which couples both solar and thermal energies, has burgeoned as a promising approach to drive catalytic reactions. However, the utilization of light irradiation to tune the ...

65 citations

Journal ArticleDOI
TL;DR: In this paper, cluster geometries are optimized and vibrational frequencies are evaluated by density functional theory calculation, and the most stable isomer of [Mg·(H2O)4]- has a six-membered ring composed of the Mg+ ion, two of the three water molecules in the first solvation shell; the fourth molecule is bonded to the first Solvation shell.
Abstract: Infrared photodissociation spectra of [Mg·(H2O)1-4]+ and [Mg·(H2O)1-4·Ar]+ are measured in the 3000−3800 cm-1 region For [Mg·(H2O)1-4]+, cluster geometries are optimized and vibrational frequencies are evaluated by density functional theory calculation We determine cluster structures of [Mg·(H2O)1-4]+ by comparison of the infrared photodissociation spectra with infrared spectra calculated for optimized structures of [Mg·(H2O)1-4]+ In the [Mg·(H2O)1-3]+ ions, all the water molecules are directly bonded to the Mg+ ion The infrared photodissociation spectra of [Mg·(H2O)4]+ and [Mg·(H2O)4·Ar]+ show bands due to hydrogen-bonded OH stretching vibrations in the 3000−3450 cm-1 region In the [Mg·(H2O)4]+ ion, three water molecules are attached to the Mg+ ion, forming the first solvation shell; the fourth molecule is bonded to the first solvation shell As a result, the most stable isomer of [Mg·(H2O)4]+ has a six-membered ring composed of the Mg+ ion, two of the three water molecules in the first solvation sh

57 citations

Journal ArticleDOI
TL;DR: In this paper, the authors measured the infrared spectra of [Mg·-H2O)1,2]- and [Al·−(H 2O)2]- ion and assigned a band at 3200-3800 cm−1.

52 citations

Journal ArticleDOI
TL;DR: The potential of the ABN(+)-H2O dimer is characterized in detail and supports the cluster growth derived from the IRPD spectra, and the formation of a solvent network stabilized by strong cooperative effects is favored over interior ion hydration which is destabilized by noncooperative effects.
Abstract: Infrared photodissociation (IRPD) spectra of mass-selected 4-aminobenzonitrile-(water)n cluster cations, ABN+-(H2O)n with n ≤ 4, recorded in the N–H and O–H stretch ranges are analyzed by quantum chemical calculations at the M06-2X/aug-cc-pVTZ level to determine the evolution of the initial microhydration process of this bifunctional aromatic cation in its ground electronic state. IRPD spectra of cold clusters tagged with Ar and N2 display higher resolution and allow for a clear-cut structural assignment. The clusters are generated in an electron impact source, which generates predominantly the most stable isomers. The IRPD spectra are assigned to single isomers for n = 1–3. The preferred cluster growth begins with sequential hydration of the two acidic NH protons of the amino group (n = 1–2), which is followed by attachment of secondary H2O ligands hydrogen-bonded to the first-shell ligands (n = 3–4). These symmetric and branched structures are more stable than those with a cyclic H-bonded solvent network. Moreover, in the size range n ≤ 4 the formation of a solvent network stabilized by strong cooperative effects is favored over interior ion hydration which is destabilized by noncooperative effects. The potential of the ABN+-H2O dimer is characterized in detail and supports the cluster growth derived from the IRPD spectra. Although the N–H bonds are destabilized by stepwise microhydration, which is accompanied by increasing charge transfer from ABN+ to the solvent cluster, no proton transfer to the solvent is observed for n ≤ 4.

30 citations

References
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Journal ArticleDOI
TL;DR: In this paper, the infrared spectrum of the benzene-water cation, C6H6+−H2O, was recorded in the O−H stretch region to obtain the first experimental information about its geometry and interaction strength.

82 citations

Journal ArticleDOI
Abstract: Infrared (IR) spectra of benzene–(water)n cluster cations (Bz–Wn)+ (n=1–6) in the OH and CH stretching vibrational region were observed in order to investigate their structure and reactivity The cluster cations were prepared by two different production methods: one is due to collision between bare benzene cations and water clusters; and the other utilizes resonance enhanced multiphoton ionization (REMPI) of neutral clusters The former method prefers the production of the most stable isomer cluster cations, while the latter would reflect the Franck-Condon restriction in the ionization process The structures of the n=1 and n=2 clusters were determined on the basis of the comparison between the IR spectra and density functional theory (DFT) calculations In the n=1 cluster cation, the oxygen atom of the water molecule is located in the benzene ring plane and coordinates to the benzene moiety by two identical CH–O hydrogen bonds The IR spectra of the n=2 cluster cation showed absorption bands arising from two different types of isomers: one has a hydrogen-bonded water dimer interacting with the benzene cation; in the other isomer two water molecules are independently bound to the benzene cation The production ratio between the isomers was found to strongly depend on the cluster ion preparation methods Except for the case of the n=2 cluster, the cluster cations prepared by the two different methods gave identical IR spectra This means that quite extensive rearrangements of the cluster structure occur upon ionization of the neutral clusters, leading to the most stable form of the cluster cations The spectral features of the n=3 cluster cation are very similar to the n=2 cluster, suggesting similar structures among these clusters Higher clusters larger than the n=3 cluster showed quite different IR spectra from those of the n≤3 clusters, but their spectral features are very similar to those of hydrated clusters of protonated species, X–H+–(H2O)n, indicating that proton transfer reactions from the benzene cation to the water moiety occur in the larger clusters than those with n=3

71 citations

Journal ArticleDOI
TL;DR: In this paper, a vibrational predissociation spectroscopy of water on protonated molecular ions has been investigated by vibrational pre-collapse spectra, and it has been shown that 2-and 3-coordinated H2O is present in the water clusters.
Abstract: Clustering of water on protonated molecular ions has been investigated by vibrational predissociation spectroscopy. Systematic measurements at different cluster sizes reveal a close resemblance of the OH stretch spectra between NH4+(H2O)n, CH3NH3+(H2O)n, and H3O+(H2O)n. Particularly at n⩾6, a sharp feature, identical to that found on ice and water surfaces, emerges at 3690 cm−1 for free-OH stretching. The feature is distinguished from the other free-OH absorption, commonly observed for small- and medium-sized (H2O)n clusters at 3715 cm−1. The results, in conjunction with ab initio calculations, provide compelling evidence for 2- and 3-coordinated H2O in the protonated ion–water clusters.

65 citations

Journal ArticleDOI
TL;DR: In this paper, the authors measured the IRPD spectra of benzene (Bz )−H 2 O + + in the 3 μm region and found that the most stable isomer cluster cation was generated by resonant photoionization of the neutral cluster and collisions of bare benzene cation with water molecules.

57 citations

Journal ArticleDOI
TL;DR: In this article, the authors investigated the behavior of an excess proton in solute-containing water clusters using infrared spectroscopy and ab initio calculations and provided compelling evidence for the coexistence of two distinct structural isomers, CH3OH2+ and H3O+ in a supersonic expansion.
Abstract: Behaviors of an excess proton in solute-containing water clusters were investigated using infrared spectroscopy and ab initio calculations. This investigation characterized the structures of protonated methanol-water clusters, H+(CH3OH)(H2O)n with n=2–6, according to their nonhydrogen-bonded and hydrogen-bonded OH stretches in the frequency range of 2700–3900 cm−1. Ab initio calculations indicated that the excess proton in these clusters can be either localized at a site closer to methanol, forming a methyloxonium ion core (CH3OH2+), or at a site closer to water, forming a hydronium ion core (H3O+). Infrared spectroscopic measurements verified the calculations and provided compelling evidence for the coexistence of two distinct structural isomers, CH3OH2+(H2O)3 and H3O+(CH3OH)(H2O)2, in a supersonic expansion. The spectral signatures of them (either CH3OH2+ or H3O+ centered) are the free-OH stretching absorption band at 3706 cm−1 of a single-acceptor-single-donor H2O, and the band at 3673 cm−1 of a single...

53 citations