1
|
Valadbeigi Y, Gal JF. Noble gas cations as Lewis acids: Adduct formation with Lewis bases with high ionization energies. Chem Phys 2023. [DOI: 10.1016/j.chemphys.2023.111918] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/03/2023]
|
2
|
Vitalis F, Muncan J, Anantawittayanon S, Kovacs Z, Tsenkova R. Aquaphotomics Monitoring of Lettuce Freshness during Cold Storage. Foods 2023; 12:foods12020258. [PMID: 36673350 PMCID: PMC9858011 DOI: 10.3390/foods12020258] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Revised: 12/21/2022] [Accepted: 12/26/2022] [Indexed: 01/09/2023] Open
Abstract
Fresh-cut leafy vegetables are one of the most perishable products because they readily deteriorate in quality even during cold storage and have a relatively short shelf life. Since these products are in high demand, methods for rigorous quality control and estimation of freshness that are rapid and non-destructive would be highly desirable. The objective of the present research was to develop a rapid, non-destructive near-infrared spectroscopy (NIRS)-based method for the evaluation of changes during cold storage of lettuce using an aquaphotomics approach to monitor the water molecular structure in lettuce leaves. The reference measurements showed that after 6 days of dark, cold storage, the weight and water activity of lettuce leaves decreased and β-carotene decreased, while chlorophylls slightly increased. Aquaphotomics characterization showed large differences in the lettuce leaves' spectra depending on their growth zone. Difference spectra, principal component analysis (PCA) and linear discriminant analysis (LDA) confirmed the differences in the inner and outer leaves and revealed that spectra change as a function of storage time. Partial least squares regression (PLSR) allowed the prediction of the time spent in storage with a coefficient of determination of R2 = 0.80 and standard error of RMSE = 0.77 days for inner, and R2 = 0.86 and RMSE = 0.66 days for outer leaves, respectively. The following water absorbance bands were found to provide the most information in the spectra: 1348, 1360, 1373, 1385, 1391, 1410, 1416, 1422, 1441, 1447, 1453, 1466, 1472, 1490, 1503, 1515, 1521, 1534 and 1571 nm. They were further used as water matrix coordinates (WAMACs) to define the water spectral patterns (WASPs) of lettuce leaves. The WASPs of leaves served to succinctly describe the state of lettuces during storage. The changes in WASPs during storage reveled moisture loss, damage to cell walls and expulsion of intracellular water, as well as loss of free and weakly hydrogen-bonded water, all leading to a loss of juiciness. The WASPs also showed that damage stimulated the defense mechanisms and production of vitamin C. The leaves at the end of the storage period were characterized by water strongly bound to collapsed structural elements of leaf tissues, mainly cellulose, leading to a loss of firmness that was more pronounced in the outer leaves. All of this information was reflected in the changes of absorbance in the identified WAMACs, showing that the water molecular structure of lettuce leaves accurately reflects the state of the lettuce during storage and that WASPs can be used as a multidimensional biomarker to monitor changes during storage.
Collapse
Affiliation(s)
- Flora Vitalis
- Department of Measurements and Process Control, Institute of Food Science and Technology, Hungarian University of Agriculture and Life Sciences, Somlói Street 14-16, H-1118 Budapest, Hungary
| | - Jelena Muncan
- Aquaphotomics Research Department, Graduate School of Agricultural Science, Kobe University, 1-1, Rokkodai, Nada, Kobe 657-8501, Japan
| | - Sukritta Anantawittayanon
- Aquaphotomics Research Department, Graduate School of Agricultural Science, Kobe University, 1-1, Rokkodai, Nada, Kobe 657-8501, Japan
| | - Zoltan Kovacs
- Department of Measurements and Process Control, Institute of Food Science and Technology, Hungarian University of Agriculture and Life Sciences, Somlói Street 14-16, H-1118 Budapest, Hungary
| | - Roumiana Tsenkova
- Aquaphotomics Research Department, Graduate School of Agricultural Science, Kobe University, 1-1, Rokkodai, Nada, Kobe 657-8501, Japan
- Correspondence: ; Tel.: +81-78-803-5911
| |
Collapse
|
3
|
Muncan J, Anantawittayanon S, Furuta T, Kaneko T, Tsenkova R. Aquaphotomics monitoring of strawberry fruit during cold storage - A comparison of two cooling systems. Front Nutr 2022; 9:1058173. [PMID: 36570127 PMCID: PMC9780392 DOI: 10.3389/fnut.2022.1058173] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Accepted: 11/21/2022] [Indexed: 12/13/2022] Open
Abstract
The objective of this study was to use aquaphotomics and near-infrared (NIR) spectroscopy to follow the changes in strawberries during cold storage in the refrigerator with an electric field generator (supercooling fridge, SCF) and without it (control fridge, CF). The NIR spectra of strawberries stored in these refrigerators were collected over the course of 15 days using a portable mini spectrometer and their weight was measured daily. The spectral data in the region of the first overtone of water (1,300-1,600 nm) were analyzed using aquaphotomics multivariate analysis. The results showed a decrease in weight loss of strawberries, but the loss of weight was significantly lower in SCF, compared to the CF. The reduction of weight loss due to exposure to an electric field was comparable to the use of coatings. The aquaphotomics analysis showed that the NIR spectra adequately captured changes in the fruit over the storage period, and that it is possible to predict how long the fruit spent in storage, regardless of the storage type. During aquaphotomics analysis, 19 water absorbance bands were found to be consistently repeating and to have importance for the description of changes in strawberries during cold storage. These bands defined the water spectral pattern (WASP), multidimensional biomarker that was used for the description of the state and dynamics of water in strawberries during time spent in storage. Comparison of WASPs of strawberries in CF and SCF showed that exposure to an electric field leads to a delay in ripening by around 3 days. This was evidenced by the increased amount of structural, strongly bound water and vapor-like trapped water in the strawberries stored in SCF. This particular state of water in strawberries stored in SCF was related to the hardening of the strawberry skin and prevention of moisture loss, in agreement with the results of significantly decreased weight loss.
Collapse
Affiliation(s)
- Jelena Muncan
- Aquaphotomics Research Department, Graduate School of Agricultural Science, Kobe University, Kobe, Japan
| | - Sukritta Anantawittayanon
- Aquaphotomics Research Department, Graduate School of Agricultural Science, Kobe University, Kobe, Japan
| | | | | | - Roumiana Tsenkova
- Aquaphotomics Research Department, Graduate School of Agricultural Science, Kobe University, Kobe, Japan,*Correspondence: Roumiana Tsenkova,
| |
Collapse
|
4
|
Müller D, Dopfer O. Microsolvation of H 2O +, H 3O +, and CH 3OH 2+ by He in a cryogenic ion trap: structure of solvation shells. Phys Chem Chem Phys 2022; 24:11222-11233. [PMID: 35481676 DOI: 10.1039/d2cp01192a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Due to the weak interactions of He atoms with neutral molecules and ions, the preparation of size-selected clusters for the spectroscopic characterization of their structures, energies, and large amplitude motions is a challenging task. Herein, we generate H2O+Hen (n ≤ 9) and H3O+Hen (n ≤ 5) clusters by stepwise addition of He atoms to mass-selected ions stored in a cryogenic 22-pole ion trap held at 5 K. The population of the clusters as a function of n provides insight into the structure of the first He solvation shell around these ions given by the anisotropy of the cation-He interaction potential. To rationalize the observed cluster size distributions, the structural, energetic, and vibrational properties of the clusters are characterized by ab initio calculations up to the CCSD(T)/aug-cc-pVTZ level. The cluster growth around both the open-shell H2O+ and closed-shell H3O+ ions begins by forming nearly linear and equivalent OH⋯He hydrogen bonds (H-bonds) leading to symmetric structures. The strength of these H-bonds decreases slightly with n due to noncooperative three-body induction forces and is weaker for H3O+ than for H2O+ due to both enhanced charge delocalization and reduced acidity of the OH protons. After filling all available H-bonded sites, addition of further He ligands around H2O+ (n = 3-4) occurs at the electrophilic singly occupied 2pz orbital of O leading to O⋯He p-bonds stabilized by induction and small charge transfer from H2O+ to He. As this orbital is filled for H3O+, He atoms occupy in the n = 4-6 clusters positions between the H-bonded He atoms, leading to a slightly distorted regular hexagon ring for n = 6. Comparison between H3O+Hen and CH3OH2+Hen illustrates that CH3 substitution substantially reduces the acidity of the OH protons, so that only clusters up to n = 2 can be observed. The structure of the solvation sub-shells is visible in both the binding energies and the predicted vibrational OH stretch and bend frequencies.
Collapse
Affiliation(s)
- David Müller
- Institut für Optik und Atomare Physik, Technische Universität Berlin, Hardenbergstr. 36, 10623 Berlin, Germany.
| | - Otto Dopfer
- Institut für Optik und Atomare Physik, Technische Universität Berlin, Hardenbergstr. 36, 10623 Berlin, Germany.
| |
Collapse
|
5
|
Liu JM, Nishigori T, Maeyama T, Huang QR, Katada M, Kuo JL, Fujii A. Infrared Spectroscopy and Anharmonic Vibrational Analysis of (H 2O-Kr n) + ( n = 1-3): Hemibond Formation of the Water Radical Cation. J Phys Chem Lett 2021; 12:7997-8002. [PMID: 34433278 DOI: 10.1021/acs.jpclett.1c02164] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The hemibond is a nonclassical covalent bond formed between a radical (cation) and a closed shell molecule. The hemibond formation ability of water has attracted great interest, concerning its role in ionization of water. While many computational studies on the water hemibond have been performed, clear experimental evidence has been hardly reported because the hydrogen bond formation overwhelms the hemibond formation. In the present study, infrared photodissociation spectroscopy is applied to (H2O-Krn)+ (n = 1-3) radical cation clusters. The observed spectra of (H2O-Krn)+ are well reproduced by the anharmonic vibrational simulations based on the hemibonded isomer structures. The firm evidence of the hemibond formation ability of water is revealed.
Collapse
Affiliation(s)
- Jing-Min Liu
- Institute of Atomic and Molecular Sciences, Academia Sinica, 1 Roosevelt Rd., Sec. 4, Taipei 10617, Taiwan
| | - Tomoki Nishigori
- Department of Chemistry, Graduate School of Science, Tohoku University, Aramaki-Aza-Aoba 6-3, Aoba-Ku, Sendai 980-8578, Japan
| | - Toshihiko Maeyama
- Department of Chemistry, Graduate School of Science, Tohoku University, Aramaki-Aza-Aoba 6-3, Aoba-Ku, Sendai 980-8578, Japan
| | - Qian-Rui Huang
- Institute of Atomic and Molecular Sciences, Academia Sinica, 1 Roosevelt Rd., Sec. 4, Taipei 10617, Taiwan
| | - Marusu Katada
- Department of Chemistry, Graduate School of Science, Tohoku University, Aramaki-Aza-Aoba 6-3, Aoba-Ku, Sendai 980-8578, Japan
| | - Jer-Lai Kuo
- Institute of Atomic and Molecular Sciences, Academia Sinica, 1 Roosevelt Rd., Sec. 4, Taipei 10617, Taiwan
| | - Asuka Fujii
- Department of Chemistry, Graduate School of Science, Tohoku University, Aramaki-Aza-Aoba 6-3, Aoba-Ku, Sendai 980-8578, Japan
| |
Collapse
|
6
|
Garand E. Spectroscopy of Reactive Complexes and Solvated Clusters: A Bottom-Up Approach Using Cryogenic Ion Traps. J Phys Chem A 2018; 122:6479-6490. [DOI: 10.1021/acs.jpca.8b05712] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Etienne Garand
- Department of Chemistry, University of Wisconsin—Madison, 1101 University Avenue, Madison, Wisconsin 53706, United States
| |
Collapse
|
7
|
Huang QR, Nishigori T, Katada M, Fujii A, Kuo JL. Fermi resonance in solvated H3O+: a counter-intuitive trend confirmed via a joint experimental and theoretical investigation. Phys Chem Chem Phys 2018; 20:13836-13844. [DOI: 10.1039/c8cp02151a] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
In this work, we combine both experimental and theoretical approaches to jointly investigate Ne-tagged and Ar-tagged H3O+ (with n = 1, 2, and 3) to gain a better understanding of the Fermi resonance in solvated H3O+.
Collapse
Affiliation(s)
- Qian-Rui Huang
- Institute of Atomic and Molecular Sciences
- Academia Sinica
- Taipei 10617
- Taiwan
| | - Tomoki Nishigori
- Department of Chemistry
- Graduate School of Science
- Tohoku University
- Sendai 980-8578
- Japan
| | - Marusu Katada
- Department of Chemistry
- Graduate School of Science
- Tohoku University
- Sendai 980-8578
- Japan
| | - Asuka Fujii
- Department of Chemistry
- Graduate School of Science
- Tohoku University
- Sendai 980-8578
- Japan
| | - Jer-Lai Kuo
- Institute of Atomic and Molecular Sciences
- Academia Sinica
- Taipei 10617
- Taiwan
| |
Collapse
|
8
|
Wagner JP, McDonald DC, Duncan MA. Near-infrared spectroscopy and anharmonic theory of the H2O+Ar1,2 cation complexes. J Chem Phys 2017; 147:104302. [DOI: 10.1063/1.4998419] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Affiliation(s)
- J. Philipp Wagner
- Department of Chemistry, University of Georgia, 140 Cedar Street, Athens, Georgia 30602, USA
| | - David C. McDonald
- Department of Chemistry, University of Georgia, 140 Cedar Street, Athens, Georgia 30602, USA
| | - Michael A. Duncan
- Department of Chemistry, University of Georgia, 140 Cedar Street, Athens, Georgia 30602, USA
| |
Collapse
|
9
|
Ziemkiewicz MP, Pluetzer C, Wojcik M, Loreau J, van der Avoird A, Nesbitt DJ. Near infrared overtone (vOH = 2 ← 0) spectroscopy of Ne–H2O clusters. J Chem Phys 2017; 146:104204. [DOI: 10.1063/1.4977061] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Michael P. Ziemkiewicz
- JILA, National Institute of Standards and Technology, University of Colorado and Department of Chemistry and Biochemistry, University of Colorado at Boulder, Boulder, Colorado 80309, USA
| | - Christian Pluetzer
- JILA, National Institute of Standards and Technology, University of Colorado and Department of Chemistry and Biochemistry, University of Colorado at Boulder, Boulder, Colorado 80309, USA
| | - Michael Wojcik
- JILA, National Institute of Standards and Technology, University of Colorado and Department of Chemistry and Biochemistry, University of Colorado at Boulder, Boulder, Colorado 80309, USA
| | - Jérôme Loreau
- Service de Chimie Quantique et Photophysique, Université Libre de Bruxelles, 50 av. F.D. Roosevelt, CP 160/09, 1050 Brussels, Belgium
| | - Ad van der Avoird
- Theoretical Chemistry, Institute for Molecules and Materials, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - David J. Nesbitt
- JILA, National Institute of Standards and Technology, University of Colorado and Department of Chemistry and Biochemistry, University of Colorado at Boulder, Boulder, Colorado 80309, USA
| |
Collapse
|
10
|
Lee HM, Youn IS, Kim KS. CO Capture and Conversion to HOCO Radical by Ionized Water Clusters. J Phys Chem A 2014; 118:7274-9. [DOI: 10.1021/jp410927a] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Affiliation(s)
- Han Myoung Lee
- Department
of Chemistry, School of Natural Science, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, Korea
- Center for Superfunctional Materials, Department of Chemistry, Pohang University of Science and Technology, Pohang 790-784, Korea
| | - Il-Seung Youn
- Department
of Chemistry, School of Natural Science, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, Korea
- Center for Superfunctional Materials, Department of Chemistry, Pohang University of Science and Technology, Pohang 790-784, Korea
| | - Kwang S. Kim
- Department
of Chemistry, School of Natural Science, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, Korea
- Center for Superfunctional Materials, Department of Chemistry, Pohang University of Science and Technology, Pohang 790-784, Korea
| |
Collapse
|
11
|
Fujii A, Mizuse K. Infrared spectroscopic studies on hydrogen-bonded water networks in gas phase clusters. INT REV PHYS CHEM 2013. [DOI: 10.1080/0144235x.2012.760836] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
|
12
|
Lee HM, Kim KS. Dynamics and structural changes of small water clusters on ionization. J Comput Chem 2013; 34:1589-97. [DOI: 10.1002/jcc.23296] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2013] [Revised: 03/19/2013] [Accepted: 03/22/2013] [Indexed: 01/02/2023]
Affiliation(s)
- Han Myoung Lee
- Department of Chemistry; Center for Superfunctional Materials, Pohang University of Science and Technology; San 31, Hyojadong; Namgu; Pohang; 790-784; Korea
| | - Kwang S. Kim
- Department of Chemistry; Center for Superfunctional Materials, Pohang University of Science and Technology; San 31, Hyojadong; Namgu; Pohang; 790-784; Korea
| |
Collapse
|
13
|
|
14
|
Mizuse K, Fujii A. Infrared photodissociation spectroscopy of H+(H2O)6·Mm (M = Ne, Ar, Kr, Xe, H2, N2, and CH4): messenger-dependent balance between H3O+ and H5O2+ core isomers. Phys Chem Chem Phys 2011; 13:7129-35. [DOI: 10.1039/c1cp20207c] [Citation(s) in RCA: 96] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
15
|
Inokuchi Y, Kobayashi Y, Muraoka A, Nagata T, Ebata T. Structures of water-CO2 and methanol-CO2 cluster ions: [H2O•(CO2)n]+ and [CH3OH•(CO2)n]+ (n=1–7). J Chem Phys 2009; 130:154304. [DOI: 10.1063/1.3116144] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
|
16
|
Lee HM, Kim KS. Water Dimer Cation: Density Functional Theory vs Ab Initio Theory. J Chem Theory Comput 2009; 5:976-81. [DOI: 10.1021/ct800506q] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Han Myoung Lee
- Center for Superfunctional Materials and Center for Basic Sciences, Department of Chemistry, Pohang University of Science and Technology, Pohang 790-784, Korea
| | - Kwang S. Kim
- Center for Superfunctional Materials and Center for Basic Sciences, Department of Chemistry, Pohang University of Science and Technology, Pohang 790-784, Korea
| |
Collapse
|
17
|
Walker NR, Walters RS, Tsai MK, Jordan KD, Duncan MA. Infrared photodissociation spectroscopy of Mg(+)(H2O)Ar(n) complexes: isomers in progressive microsolvation. J Phys Chem A 2007; 109:7057-67. [PMID: 16834068 DOI: 10.1021/jp051877t] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Ion-molecule complexes of the form Mg(H2O)Ar(n)+ (n = 1-8) are produced by laser vaporization in a pulsed-nozzle cluster source. These complexes are mass-selected and studied with infrared photodissociation spectroscopy in the O-H stretch region. The spectra are interpreted with the aid of ab initio calculations on the n = 1-5 complexes, including examination of various isomeric structures. The combined spectroscopic and theoretical studies reveal the presence of multiple isomeric structures at each cluster size, as the argon atoms assemble around the Mg(+)(H2O) unit. Distinct infrared resonances are measured for argon-on-metal, argon-on-OH and argon-on-two-OH isomers.
Collapse
Affiliation(s)
- N R Walker
- Department of Chemistry, University of Georgia, Athens, Georgia 30602-2556, USA
| | | | | | | | | |
Collapse
|
18
|
Pasker FM, Solcà N, Dopfer O. Spectroscopic Identification of Carbenium and Ammonium Isomers of Protonated Aniline (AnH+): IR Spectra of Weakly Bound AnH+−Ln Clusters (L = Ar, N2). J Phys Chem A 2006; 110:12793-804. [PMID: 17125293 DOI: 10.1021/jp064571a] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Infrared photodissociation (IRPD) spectra of mass-selected clusters composed of protonated aniline (C6H8N+ = AnH+) and a variable number of neutral ligands (L = Ar, N2) are obtained in the N-H stretch range. The AnH+ -Ln complexes (n < or = 3) are produced by chemical ionization in a supersonic expansion of An, H2, and L. The IRPD spectra of AnH+-Ln feature the unambiguous fingerprints of at least two different AnH+ nucleation centers, namely, the ammonium isomer (5) and the carbenium ions (1 and/or 3) corresponding to protonation at the N atom and at the C atoms in the para and/or ortho positions, respectively. Protonation at the meta and ipso positions is not observed. Both classes of observed AnH+-Ln isomers exhibit very different photofragmentation behavior upon vibrational excitation arising from the different interaction strengths of the AnH+ cores with the surrounding neutral ligands. Analysis of the incremental N-H stretch frequency shifts as a function of cluster size shows that microsolvation of both 5 and 1/3 in Ar and N2 starts with the formation of intermolecular H bonds of the ligands to the acidic NH protons and proceeds by intermolecular pi bonding to the aromatic ring. The analysis of both the photofragmentation branching ratios and the N-H stretch frequencies demonstrates that the N-H bonds in 5 are weaker and more acidic than those in 1/3, leading to stronger intermolecular H bonds with L. The interpretation of the spectroscopic data is supported by density functional calculations conducted at the B3LYP level using the 6-31G* and 6-311G(2df,2pd) basis sets. Comparison with clusters of neutral aniline and the aniline radical cation demonstrates the drastic effect of protonation and ionization on the acidity of the N-H bonds and the topology of the intermolecular potential, in particular on the preferred aromatic substrate-nonpolar ligand recognition motif.
Collapse
Affiliation(s)
- Felix M Pasker
- Institut für Optik und Atomare Physik, Technische Universität Berlin, Hardenbergstrasse 36, D-10623 Berlin, Germany
| | | | | |
Collapse
|
19
|
Walters RS, Pillai ED, Duncan MA. Solvation dynamics in Ni+ (H2O)n clusters probed with infrared spectroscopy. J Am Chem Soc 2006; 127:16599-610. [PMID: 16305249 DOI: 10.1021/ja0542587] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Infrared photodissociation spectroscopy is reported for mass-selected Ni+ (H2O)n complexes in the O-H stretching region up to cluster sizes of n = 25. These clusters fragment by the loss of one or more intact water molecules, and their excitation spectra show distinct bands in the region of the symmetric and asymmetric stretches of water. The first evidence for hydrogen bonding, indicated by a broad band strongly red-shifted from the free OH region, appears at the cluster size of n = 4. At larger cluster sizes, additional red-shifted structure evolves over a broader wavelength range in the hydrogen-bonding region. In the free OH region, the symmetric stretch gradually diminishes in intensity, while the asymmetric stretch develops into a closely spaced doublet near 3700 cm(-1). The data indicate that essentially all of the water molecules are in a hydrogen-bonded network by the size of n = 10. However, there is no evidence for the formation of clathrate structures seen recently via IR spectroscopy of protonated water clusters.
Collapse
Affiliation(s)
- Richard S Walters
- Department of Chemistry, University of Georgia, Athens, Georgia 30602-2556, USA
| | | | | |
Collapse
|
20
|
Walters RS, Pillai ED, Schleyer PVR, Duncan MA. Vibrational Spectroscopy and Structures of Ni+(C2H2)n (n =1−4) Complexes. J Am Chem Soc 2005; 127:17030-42. [PMID: 16316250 DOI: 10.1021/ja054800r] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Nickel cation-acetylene complexes of the form Ni(+)(C(2)H(2))(n), Ni(+)(C(2)H(2))Ne, and Ni(+)(C(2)H(2))(n)Ar(m) (n = 1-4) are produced in a molecular beam by pulsed laser vaporization. These ions are size-selected and studied in a time-of-flight mass spectrometer by infrared laser photodissociation spectroscopy in the C-H stretch region. The fragmentation patterns indicate that the coordination number is 4 for this system. The n = 1-4 complexes with and without rare gas atoms are also investigated with density functional theory. The combined IR spectra and theory show that pi-complexes are formed for the n = 1-4 species, causing the C-H stretches in the acetylene ligands to shift to lower frequencies. Theory reveals that there are low-lying excited states nearly degenerate with the ground state for all the Ni(+)(C(2)H(2))(n) complexes. Although isomeric structures are identified for rare gas atom binding at different sites, the attachment of rare gas atoms results in only minor perturbations on the structures and spectra for all complexes. Experiment and theory agree that multiple acetylene binding takes place to form low-symmetry structures, presumably due to Jahn-Teller distortion and/or ligand steric effects. The fully coordinated Ni(+)(C(2)H(2))(4) complex has a near-tetrahedral structure.
Collapse
Affiliation(s)
- Richard S Walters
- Department of Chemistry, University of Georgia, Athens, 30602-2556, USA
| | | | | | | |
Collapse
|
21
|
Zhou H, Yang R, Jin X, Zhou M. Infrared Spectra of the OH+ and H2O+ Cations Solvated in Solid Argon. J Phys Chem A 2005; 109:6003-7. [PMID: 16833936 DOI: 10.1021/jp0511808] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Infrared spectra of various OH+ and H2O+ isotopomers solvated in solid argon are presented. The OH+ and H2O+ cations were produced by co-deposition of H2O/Ar mixture with high-frequency discharged Ar at 4 K. Detailed isotopic substitution studies confirm the assignments of absorptions at 3054.9 and 3040.0 cm(-1) to the antisymmetric and symmetric H-O-H stretching vibrations of H2O+ and 2979.6 cm(-1) to the O-H stretching vibration of OH+. The frequencies of H2O+ solvated in solid argon are red-shifted, whereas the frequency of OH+ is blue-shifted with respect to the gas-phase fundamentals. On the basis of previous gas-phase studies and quantum chemical calculations, the OH+ and H2O+ cations solvated in solid argon may be regarded as the OH+-Ar5 and H2O+-Ar4 complexes isolated in the argon matrix.
Collapse
Affiliation(s)
- Han Zhou
- Department of Chemistry & Laser Chemistry Institute, Shanghai Key Laboratory of Molecular Catalysts and Innovative Materials, Fudan University, Shanghai 200433, People's Republic of China
| | | | | | | |
Collapse
|
22
|
Solcà N, Dopfer O. Spectroscopic Identification of Oxonium and Carbenium Ions of Protonated Phenol in the Gas Phase: IR Spectra of Weakly Bound C6H7O+−L Dimers (L = Ne, Ar, N2). J Am Chem Soc 2004; 126:1716-25. [PMID: 14871102 DOI: 10.1021/ja0305858] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Structural isomers of isolated protonated phenol (C(6)H(7)O(+)) are characterized by infrared (IR) photodissociation spectroscopy of their weakly bound complexes with neutral ligands L (L = Ne, Ar, N(2)). IR spectra of C(6)H(7)O(+)-L recorded in the vicinity of the O-H and C-H stretch fundamentals carry unambiguous signatures of at least two C(6)H(7)O(+) isomers: the identified protonation sites of phenol include the O atom (oxonium ion, O-C(6)H(7)O(+)) and the C atoms of the aromatic ring in the ortho and/or para position (carbenium ions, o/p-C(6)H(7)O(+)). In contrast, protonation at the meta and ipso positions is not observed. The most stable C(6)H(7)O(+)-L dimer structures feature intermolecular H-bonds between L and the OH groups of O-C(6)H(7)O(+) and o/p-C(6)H(7)O(+). Extrapolation to zero solvation interaction yields reliable experimental vibrational frequencies of bare O-C(6)H(7)O(+) and o/p-C(6)H(7)O(+). The interpretation of the C(6)H(7)O(+)-L spectra, as well as the extrapolated monomer frequencies, is supported by B3LYP and MP2 calculations using the 6-311G(2df,2pd) basis. The spectroscopic and theoretical results elucidate the effect of protonation on the structural properties of phenol and provide a sensitive probe of the activating and ortho/para directing nature of the OH group observed in electrophilic aromatic substitution reactions.
Collapse
Affiliation(s)
- Nicola Solcà
- Institute for Physical Chemistry, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | | |
Collapse
|
23
|
Dopfer O, Engel V. Infrared spectrum and predissociation dynamics of H[sub 2]O[sup +]–Ar. J Chem Phys 2004; 121:12345-52. [PMID: 15606253 DOI: 10.1063/1.1825998] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The infrared (IR) spectrum and vibrational predissociation of the proton-bound H(2)O(+)-Ar ionic complex are investigated within an ab initio and quantum dynamical study. For this purpose, a two-dimensional potential energy surface (2D PES) is determined as a function of the HO-H and OH-Ar coordinates. This PES is then employed in a wave-packet calculation to determine spectral properties of the system and to calculate the IR absorption spectrum. The vibrational energy levels and relative IR intensities agree well with the experimental spectrum reported earlier. On the other hand, the predissociation lifetimes in the nanosecond regime derived from the 2D PES are in disagreement with the experimental observations, indicating the importance of the neglected degrees of freedom for a correct description of the dynamics of the complex.
Collapse
Affiliation(s)
- O Dopfer
- Institut für Physikalische Chemie, Universität Würzburg Am Hubland, D-97074 Würzburg, Germany.
| | | |
Collapse
|
24
|
Andrei HS, Solcà N, Dopfer O. Ionization-induced switch in aromatic molecule–nonpolar ligand recognition: Acidity of 1-naphthol+(1-Np+) rotamers probed by IR spectra of 1-Np+–Lncomplexes (L = Ar/N2, n ≤ 5). Phys Chem Chem Phys 2004. [DOI: 10.1039/b403970j] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
25
|
Dopfer O, Solcà N, Olkhov RV, Maier JP. Microsolvation of the ammonia cation in argon: II. IR photodissociation spectra of NH3+–Arn (n=1–6). Chem Phys 2002. [DOI: 10.1016/s0301-0104(02)00497-4] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
|
26
|
|
27
|
|