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: Vibrational predissociation spectra of aniline(pyrrole)(water) 2 + and pyrrole(water) 3 + clusters were taken at 2700-4000 cm −1 to verify their most stable structures.
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TL;DR: The most stable structure of [(aniline)-(methanol)-(water)2]+ is suggested through infrared photodissociation spectra supported by the density functional theory calculations at the level of ωB97X-D/cc-pVQZ.
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TL;DR: In this paper , infrared photodissociation spectra of amantadineH+(H2O)n = 1-4 clusters in the sensitive OH, NH, and CH stretch range were analyzed.
Abstract: Solvation of pharmaceutical drugs has an important effect on their structure and function. Analysis of infrared photodissociation spectra of amantadineH+(H2O)n=1-4 clusters in the sensitive OH, NH, and CH stretch range by quantum chemical calculations (B3LYP-D3/cc-pVTZ) provides a first impression of the interaction of this pharmaceutically active cation with water at the molecular level. The size-dependent frequency shifts reveal detailed information about the acidity of the protons of the NH3+ group of N-protonated amantadineH+ (AmaH+) and the strength of the NH⋯O and OH⋯O hydrogen bonds (H-bonds) of the hydration network. The preferred cluster growth begins with sequential hydration of the NH3+ group by NH⋯O ionic H-bonds (n = 1-3), followed by the extension of the solvent network through OH⋯O H-bonds. However, smaller populations of cluster isomers with an H-bonded solvent network and free N-H bonds are already observed for n ≥ 2, indicating the subtle competition between noncooperative ion hydration and cooperative H-bonding. Interestingly, cyclic water ring structures are identified for n ≥ 3, each with two NH⋯O and two OH⋯O H-bonds. Despite the increasing destabilization of the N-H proton donor bonds upon gradual hydration, no proton transfer to the (H2O)n solvent cluster is observed up to n = 4. In addition to ammonium cluster ions, a small population of microhydrated iminium isomers is also detected, which is substantially lower for the hydrophilic H2O than for the hydrophobic Ar environment.
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TL;DR: In this paper, the authors used the Perdew-Burke-Ernzerhof (PBE) method with aug-cc-PVTZ, 6-311++G**, and Def2-TZVP large basis sets to study the hydrogen bond interactions between oxygen lone pair as a donor electron with hydrogen atom connected to the aniline's nitrogen as an electron acceptor (H2O·HNH-Ph), and nitrogen lone pair with hydrogen of water molecule (Ph-H2N···HOH), both in the gas phase.
Abstract: DFT-GGA method of Perdew-Burke-Ernzerhof (PBE) is used with aug-cc-PVTZ, 6-311++G**, and Def2-TZVP large basis sets to study the hydrogen bond interactions between oxygen lone pair as a donor electron with hydrogen atom connected to the aniline’s nitrogen as an electron acceptor (H2O···HNH-Ph), and nitrogen lone pair with hydrogen of water molecule (Ph-H2N···HOH), both in the gas phase. In some cases, MP2/Def2-TZVP is also carried out to test the results of DFT. To analyze donor-acceptor interactions of two above hydrogen bonds, natural bond orbital (NBO), natural energy decomposition analysis (NEDA), natural population analysis (NPA), and quantum theory of atoms in molecules (QTAIM) methods have been used in a detailed manner. Results show that the hydrogen bond in PhH2N···HOH is partially covalent, while hydrogen bond in PhHNH···OH2 is totally electrostatic. For the PhHNH···OH2 complex, there is a large gap between MP2 and PBE results which can be filled by incorporating dispersion terms in the DFT calculations. In all calculations, nitrogen atom of aniline is an stronger electron donor than the oxygen atom of water in the gas phase. PhH2N···HOH has higher electron density than PhHNH···OH2. NBO data shows that the stabilization energy due to the charge transfer for HOH···NH2Ph complex is more than that in H2O···HNHPh complex. The inversion barrier energy was also calculated at the level of PBE/Def2-TZVP without and with dispersion term, and results show that the barrier energy for PhH2N···HOH and PhHNH···OH2 complexes, are about 104 and 103 kcal mol-1, without, and 8.14 and 7.03 kcal mol-1, with dispersion, respectively.
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Cites methods from "Infrared photodissociation spectros..."
...Inokuchi and co-workers used DFT method to interpret measured infrared photodissociation spectra of [aniline-(H2O)n], n = 1-8 [10]....
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TL;DR: In this article, the aniline-HCl-A complexes were studied using DFT (B3LYP) method and 6-31+G (d,p) basis set.
Abstract: The aniline–HCl–A complexes are studied using DFT (B3LYP) method and 6-31+G (d,p) basis set. A is a catalyst molecule such as H 2 SO 4 , H 2 SO 3 , HCOOH, HNO 3 , HF, CH 3 OH, H 2 O, H 2 O 2 , HNO 2 (b), HNO 2 (a), NH 3 , HCOH, HCN, HCl, H 2 S and PH 3 . We found that the proton transfer take place in 12 structures in which A = H 2 SO 4 , H 2 SO 3 , HCOOH, HF, HNO 2 (a), HNO 3 , H 2 O 2 , H 2 O, NH 3 , HNO 2 (b), HCl, CH 3 OH and not occurred in another 4 structures with A = HCOH, HCN, H 2 S and PH 3 . The interaction energies ( E int ) of the complexes are computed and correlation between E int and the extent of proton transfer is investigated. The atoms in molecules theory (AIM) of Bader is also applied to study the intra-cluster hydrogen bonds in the aniline–HCl–A clusters. Additionally, the influence of phenyl ring on the proton transfer reaction is computed with the complexes structures without the phenyl ring (NH 3 –HCl–catalyst).
1 citations
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TL;DR: In this paper, a two color laser scheme consisting of a tunable cw infrared laser with 0.5 cm^−1 resolution used to excite the O−H stretching vibrations and a cw CO2 laser that dissociates the vibrationally excited cluster ion through a multiphoton process is presented.
Abstract: The gas phase infrared spectra of the hydrated hydronium cluster ions H3O+·(H2O)n(n=1, 2, 3) have been observed from 3550 to 3800 cm^−1. The new spectroscopic method developed for this study is a two color laser scheme consisting of a tunable cw infrared laser with 0.5 cm^−1 resolution used to excite the O–H stretching vibrations and a cw CO2 laser that dissociates the vibrationally excited cluster ion through a multiphoton process. The apparatus is a tandem mass spectrometer with a radio frequency ion trap that utilizes the following scheme: the cluster ion to be studied is first mass selected; spectroscopic interrogation then occurs in the radio frequency ion trap; finally, a fragment ion is selected and detected using ion counting techniques. The vibrational spectra obtained in this manner are compared with that taken previously using a weakly bound H2 "messenger." A spectrum of H7 O + 3 taken using a neon messenger is also presented. Ab initio structure and frequency predictions by Remington and Schaefer are compared with the experimental results.
459 citations
TL;DR: In this article, a vibrational predissociation spectroscopy and ab initio calculations of protonated water clusters from a supersonic expansion were performed at the B3LYP/6-31+G* level.
Abstract: Protonated water clusters, H+(H2O)n (n = 5−8), from a supersonic expansion have been investigated by vibrational predissociation spectroscopy and ab initio calculations. The experimental spectra were obtained at an estimated cluster temperature of 170 ± 20 K. Recorded absorption bands at the frequency range of 2700−3900 cm-1 are attributed to the free- and hydrogen-bonded-OH stretches of the ion core and the surrounding solvent molecules. Ab initio calculations, performed at the B3LYP/6-31+G* level, indicate that geometries of the H+(H2O)5-8 isomers are close in energy, with the excess proton either localized on a single water molecule, yielding H3O+(H2O)n-1, or equally shared by two molecules, yielding H5O2+(H2O)n-2. Systematic comparison of the experimental and computed spectra provides compelling evidence for both cases. The unique proton-transfer intermediate H5O2+(H2O)4 was identified, for the first time, by its characteristic bonded-OH stretching absorptions at 3178 cm-1. The existence of five-membe...
313 citations
TL;DR: In this paper, a vibrational predissociation spectroscopy (VPS) was used to identify cyclic and noncyclic isomers in the supersonic jet.
Abstract: The NH4+(H2O)3-6 cluster ions synthesized by a free jet expansion contain a variety of structural isomers. This investigation identifies some of these isomers by employing vibrational predissociation spectroscopy (VPS) in conjunction with ab initio calculations. The NH4+(H2O)n ions are produced by corona discharge of NH3/H2O seeded in a H2 beam. They are mass-selected and then vibrationally cooled in an octopole ion trap for infrared spectroscopic measurements. In the VPS, four distinct stretching vibrations (hydrogen-bonded and non-hydrogen-bonded NH and OH) are closely examined. The characteristic absorptions of these stretches, together with systematic temperature dependence measurements of their band intensities, allow us to identify both cyclic and noncyclic isomers in the supersonic jet. Such identification is corroborated by ab initio calculations performed at the B3LYP and MP2 levels using the 6-31+G* basis set. The satisfactory agreement in both vibrational frequencies and absorption intensities ...
105 citations
TL;DR: In this article, the HO stretching vibrations of hydrogen-bonded cluster ions of phenol (PhOH), [PhOH−(H2O)n]- (n = 1−4), (PhO−methanol)+ and [PhO+−H3O+n−1]- were observed with infrared photodissociation spectroscopy in combination with an ion-trapping technique.
Abstract: OH stretching vibrations of hydrogen-bonded cluster ions of phenol (PhOH), [PhOH−(H2O)n]+ (n = 1−4), (PhOH)2+, and (PhOH−methanol)+ have been observed with infrared photodissociation spectroscopy in combination with an ion-trapping technique. Cluster ions were efficiently generated by ionization of phenol followed by a jet expansion and were mass-selectively stored by the radio frequency ion trap method, which allows us to observe infrared multiphoton dissociation yield spectra of size-selected cluster ions. For [PhOH−(H2O)n]+, the OH stretching vibrations of the water moieties strongly suggested that the n ≥ 3 cluster ions exhibit the proton-transferred form, [PhO−H3O+(H2O)n-1], while the n = 1 and 2 ions are of the nontransferred form, [PhOH+−(H2O)n]. As for (PhOH)2+, the infrared spectra indicate that the dimer ion is characterized as the open form, in which the phenol ion acts as a proton donor and the neutral phenol as an acceptor through their single hydrogen bond. The similar open form is also foun...
87 citations
TL;DR: In this article, 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.
Abstract: 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...
82 citations