301
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Raynaud C, del Rosal I, Jolibois F, Maron L, Poteau R. Multicentered effective group potentials: ligand-field effects in organometallic clusters and dynamical study of chemical reactivity. Theor Chem Acc 2009. [DOI: 10.1007/s00214-009-0615-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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302
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Durlak P, Latajka Z. Car–Parrinello molecular dynamics and density functional theory simulations of infrared spectra for acetic acid monomers and cyclic dimers. Chem Phys Lett 2009. [DOI: 10.1016/j.cplett.2009.07.010] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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303
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Durlak P, Latajka Z, Berski S. A Car–Parrinello and path integral molecular dynamics study of the intramolecular lithium bond in the lithium 2-pyridyl-N-oxide acetate. J Chem Phys 2009; 131:024308. [DOI: 10.1063/1.3175797] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
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304
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Jezierska A, Panek JJ. Investigations of an O-H...S hydrogen bond via Car-Parrinello and path integral molecular dynamics. J Comput Chem 2009; 30:1241-50. [PMID: 18988272 DOI: 10.1002/jcc.21158] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The presence of intramolecular hydrogen bonds influences the binding energy, tautomeric equilibrium, and spectroscopic properties of various classes of organic molecules. This article discusses the O-H...S bridge, one of the less commonly investigated types of intramolecular interactions. 3-mercapto-1,3-diphenylprop-2-en-1-one was considered as the model structure. This compound exhibits photochromic properties. Car-Parrinello molecular dynamics (CPMD) was applied to investigate the spectroscopic and molecular properties of this compound in the gas phase and in the solid state. The second part of the study is devoted to the effects of the quantization of nuclear motions, with special attention to the O-H...S moiety. Path integral molecular dynamics (PIMD) of the molecular crystal of 3-mercapto-1,3-diphenylprop-2-en-1-one was carried out for this purpose. The employment of this fully quantum mechanical technique enables one to study, in a time-averaged sense, the zero-point motion important for flat potential energy surfaces. Finally, the potentials of mean force (Pmfs) were calculated from the CPMD and PIMD data obtained for the solid-state calculations. The effect of including quantum nuclear motion was investigated. In the studied compound, quantum effects shortened the H-bridge and provided a better description of the free energy minimum. The computational results place this uncommon intramolecular H-bonding among the class of strong hydrogen bonds with large red shifts of O-H stretching modes, which correspond well with previously presented experimental data in the literature concerning this structure.
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Affiliation(s)
- Aneta Jezierska
- Faculty of Chemistry, University of Wrocław, ul. F. Joliot-Curie 14, 50-383 Wrocław, Poland.
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305
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Vest B, Klinkhammer K, Thierfelder C, Lein M, Schwerdtfeger P. Kinetic and Thermodynamic Stability of the Group 13 Trihydrides. Inorg Chem 2009; 48:7953-61. [DOI: 10.1021/ic900997p] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Brian Vest
- Centre for Theoretical Chemistry and Physics (CTCP), New Zealand Institute for Advanced Study (NZIAS), Massey University Albany, Private Bag 102904, North Shore MSC, Auckland, New Zealand
| | - Karl Klinkhammer
- Institut für Anorganische und Analytische Chemie, Johannes-Gutenberg-Universität Mainz, Duesbergweg 10-14, D-55128 Mainz, Germany
| | - Christian Thierfelder
- Centre for Theoretical Chemistry and Physics (CTCP), New Zealand Institute for Advanced Study (NZIAS), Massey University Albany, Private Bag 102904, North Shore MSC, Auckland, New Zealand
| | - Matthias Lein
- Centre for Theoretical Chemistry and Physics (CTCP), New Zealand Institute for Advanced Study (NZIAS), Massey University Albany, Private Bag 102904, North Shore MSC, Auckland, New Zealand
| | - Peter Schwerdtfeger
- Centre for Theoretical Chemistry and Physics (CTCP), New Zealand Institute for Advanced Study (NZIAS), Massey University Albany, Private Bag 102904, North Shore MSC, Auckland, New Zealand
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306
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Rastoltseva EV, Bataev VA, Godunov IA. Structure and conformational dynamics of the cyclopropyl methyl ketone molecule in the ground electronic state. ACTA ACUST UNITED AC 2009. [DOI: 10.1016/j.theochem.2009.03.016] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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307
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Wang H, Zhu C, Yu JG, Lin SH. Anharmonic Franck−Condon Simulation of the Absorption and Fluorescence Spectra for the Low-Lying S1 and S2 Excited States of Pyridine. J Phys Chem A 2009; 113:14407-14. [DOI: 10.1021/jp903585c] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Huan Wang
- Department of Applied Chemistry, Institute of Molecular Science and Center for Interdisciplinary Molecular Science, National Chiao-Tung University, Hsinchu 30050, Taiwan, and Department of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
| | - Chaoyuan Zhu
- Department of Applied Chemistry, Institute of Molecular Science and Center for Interdisciplinary Molecular Science, National Chiao-Tung University, Hsinchu 30050, Taiwan, and Department of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
| | - Jian-Guo Yu
- Department of Applied Chemistry, Institute of Molecular Science and Center for Interdisciplinary Molecular Science, National Chiao-Tung University, Hsinchu 30050, Taiwan, and Department of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
| | - Sheng Hsien Lin
- Department of Applied Chemistry, Institute of Molecular Science and Center for Interdisciplinary Molecular Science, National Chiao-Tung University, Hsinchu 30050, Taiwan, and Department of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
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308
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Thorwirth S, Harding ME. Coupled-cluster calculations of C2H2Si and CNHSi structural isomers. J Chem Phys 2009; 130:214303. [DOI: 10.1063/1.3142702] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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309
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Petković M, Novak J, Došlić N. Shaping the infrared spectrum of the acetic acid dimer in the OH-stretching range: Multiple conformers and anharmonic coupling. Chem Phys Lett 2009. [DOI: 10.1016/j.cplett.2009.04.014] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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310
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Wilke JJ, Lind MC, Schaefer HF, Császár AG, Allen WD. Conformers of Gaseous Cysteine. J Chem Theory Comput 2009; 5:1511-23. [DOI: 10.1021/ct900005c] [Citation(s) in RCA: 112] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Jeremiah J. Wilke
- Department of Chemistry and Center for Computational Chemistry, University of Georgia, Athens, Georgia 30602, and Laboratory of Molecular Spectroscopy, Institute of Chemistry, Eötvös University, H-1518 Budapest 112, P.O. Box 32, Hungary
| | - Maria C. Lind
- Department of Chemistry and Center for Computational Chemistry, University of Georgia, Athens, Georgia 30602, and Laboratory of Molecular Spectroscopy, Institute of Chemistry, Eötvös University, H-1518 Budapest 112, P.O. Box 32, Hungary
| | - Henry F. Schaefer
- Department of Chemistry and Center for Computational Chemistry, University of Georgia, Athens, Georgia 30602, and Laboratory of Molecular Spectroscopy, Institute of Chemistry, Eötvös University, H-1518 Budapest 112, P.O. Box 32, Hungary
| | - Attila G. Császár
- Department of Chemistry and Center for Computational Chemistry, University of Georgia, Athens, Georgia 30602, and Laboratory of Molecular Spectroscopy, Institute of Chemistry, Eötvös University, H-1518 Budapest 112, P.O. Box 32, Hungary
| | - Wesley D. Allen
- Department of Chemistry and Center for Computational Chemistry, University of Georgia, Athens, Georgia 30602, and Laboratory of Molecular Spectroscopy, Institute of Chemistry, Eötvös University, H-1518 Budapest 112, P.O. Box 32, Hungary
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311
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Calvo F, Parneix P, Basire M. Quantum densities of states of fluxional polyatomic systems from a superposition approximation. J Chem Phys 2009; 130:154101. [DOI: 10.1063/1.3115178] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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312
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Buemi G. DFT study of the hydrogen bond strength and IR spectra of formic, oxalic, glyoxylic and pyruvic acids in vacuum, acetone and water solution. J PHYS ORG CHEM 2009. [DOI: 10.1002/poc.1543] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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313
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Irikura KK, Johnson RD, Kacker RN, Kessel R. Uncertainties in scaling factors forab initiovibrational zero-point energies. J Chem Phys 2009; 130:114102. [DOI: 10.1063/1.3086931] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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314
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Zhu C, Liang KK, Hayashi M, Lin SH. Theoretical treatment of anharmonic effect on molecular absorption, fluorescence spectra, and electron transfer. Chem Phys 2009. [DOI: 10.1016/j.chemphys.2009.01.006] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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315
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Figgen D, Schwerdtfeger P. Structures, inversion barriers, and parity violation effects in chiral SeOXY molecules (X,Y=H, F, Cl, Br, or I). J Chem Phys 2009; 130:054306. [DOI: 10.1063/1.3072370] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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316
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Reilly AM, Wann DA, Rankin DWH. What makes the huge 31P-31P coupling constants in S(PF2)2 and Se(PF2)2 vary so much with temperature? J Phys Chem A 2009; 113:938-42. [PMID: 19175336 DOI: 10.1021/jp8100078] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The enormous temperature dependence of the (2)J(PP) coupling constants in S(PF(2))(2) and Se(PF(2))(2) has been explained by a theoretical investigation of their conformations and NMR coupling constants. In contrast, the coupling in O(PF(2))(2) is almost invariant. Gas electron diffraction data for S(PF(2))(2) have been reinterpreted. The results show that two conformers, with C(s) and C(2v) symmetry, exist for the S and Se compounds. The C(s) and C(2v) conformers have very different (2)J(PP) coupling constants (-12.6 and 395.2 Hz for S(PF(2))(2) at B3LYP/aug-cc-pVQZ) and thermal interconversion of these conformers explains the experimental behavior.
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Affiliation(s)
- Anthony M Reilly
- School of Chemistry, University of Edinburgh, West Mains Road, Edinburgh EH9 3JJ, UK
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317
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Aldridge S, Downs AJ, Tang CY, Parsons S, Clarke MC, Johnstone RDL, Robertson HE, Rankin DWH, Wann DA. Structures and Aggregation of the Methylamine−Borane Molecules, MenH3−nN·BH3 (n = 1−3), Studied by X-ray Diffraction, Gas-Phase Electron Diffraction, and Quantum Chemical Calculations. J Am Chem Soc 2009; 131:2231-43. [PMID: 19170515 DOI: 10.1021/ja807545p] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Simon Aldridge
- Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QR, U.K., and School of Chemistry, University of Edinburgh, West Mains Road, Edinburgh EH9 3JJ, U.K
| | - Anthony J. Downs
- Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QR, U.K., and School of Chemistry, University of Edinburgh, West Mains Road, Edinburgh EH9 3JJ, U.K
| | - Christina Y. Tang
- Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QR, U.K., and School of Chemistry, University of Edinburgh, West Mains Road, Edinburgh EH9 3JJ, U.K
| | - Simon Parsons
- Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QR, U.K., and School of Chemistry, University of Edinburgh, West Mains Road, Edinburgh EH9 3JJ, U.K
| | - Michael C. Clarke
- Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QR, U.K., and School of Chemistry, University of Edinburgh, West Mains Road, Edinburgh EH9 3JJ, U.K
| | - Russell D. L. Johnstone
- Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QR, U.K., and School of Chemistry, University of Edinburgh, West Mains Road, Edinburgh EH9 3JJ, U.K
| | - Heather E. Robertson
- Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QR, U.K., and School of Chemistry, University of Edinburgh, West Mains Road, Edinburgh EH9 3JJ, U.K
| | - David W. H. Rankin
- Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QR, U.K., and School of Chemistry, University of Edinburgh, West Mains Road, Edinburgh EH9 3JJ, U.K
| | - Derek A. Wann
- Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QR, U.K., and School of Chemistry, University of Edinburgh, West Mains Road, Edinburgh EH9 3JJ, U.K
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318
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Bokareva OS, Bataev VA, Godunov IA. A quantum-chemical study of the structure and conformational dynamics of the acrolein molecule in the ground electronic state. RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A 2009. [DOI: 10.1134/s0036024409010178] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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319
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Torrent-Sucarrat M, Anglada JM, Luis JM. Role of vibrational anharmonicity in atmospheric radical hydrogen-bonded complexes. Phys Chem Chem Phys 2009; 11:6377-88. [DOI: 10.1039/b904736k] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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320
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Puzzarini C, Barone V. The role of accurate quantum mechanical computations in the assignment of vibrational spectra for unstable free radicals: H2CN and F2CN as test cases. Chem Phys Lett 2009. [DOI: 10.1016/j.cplett.2008.11.067] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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321
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Zierkiewicz W, Komorowski L, Michalska D, Cerny J, Hobza P. The Amino Group in Adenine: MP2 and CCSD(T) Complete Basis Set Limit Calculations of the Planarization Barrier and DFT/B3LYP Study of the Anharmonic Frequencies of Adenine. J Phys Chem B 2008; 112:16734-40. [DOI: 10.1021/jp8058118] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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322
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Feller D, Peterson KA, Dixon DA. A survey of factors contributing to accurate theoretical predictions of atomization energies and molecular structures. J Chem Phys 2008; 129:204105. [DOI: 10.1063/1.3008061] [Citation(s) in RCA: 312] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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323
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Dobrowolski JC, Jamróz MH, Kołos R, Rode JE, Sadlej J. IR Low-Temperature Matrix and ab Initio Study on β-Alanine Conformers. Chemphyschem 2008; 9:2042-51. [DOI: 10.1002/cphc.200800383] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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324
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Hou Y, Woo HK, Wang P, Xing X, Ng CY, Lau KC. Vacuum ultraviolet pulsed field ionization-photoelectron and infrared-photoinduced Rydberg ionization study of trans-1,3-butadiene. J Chem Phys 2008; 129:114305. [DOI: 10.1063/1.2973635] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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325
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Filippov OA, Tsupreva VN, Epstein LM, Lledos A, Shubina ES. Intermolecular HH vibrations of dihydrogen bonded complexes H3EH(-)...HOR in the low-frequency region: theory and IR spectra. J Phys Chem A 2008; 112:8198-204. [PMID: 18698750 DOI: 10.1021/jp804303j] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The results of DFT calculations of harmonic and anharmonic frequencies of the dihydrogen bonded (DHB) complexes H 3EH (-)...HOR (E = B, Al, Ga and HOR = CH 3OH, CF 3CH 2OH) in gas phase and in low polar medium (by CPCM model) in comparison with the partners are presented. Normal coordinate analysis of the low-frequency modes was carried out to assign the new vibrations induced by DHB formation by the potential energy distribution values. Among them, the intermolecular H...H stretching vibrations only have individual modes. The influence of central atom mass and isotope and the strength of the proton donor effects were determined. The systems convenient for IR studies were chosen from the calculation predictions. The spectral investigation was made on the BH 4 (-)/ROH complexes (ROH = CH 2FCH 2OH (MFE), CF 3CH 2OH (TFE), (CF 3) 2CHOH (HFIP)). The results of temperature dependence, isotope substitution, and influence of the proton-donor strength studies agree with the theoretical conclusions. Combination of experimental and theoretical approaches allowed determining for the first time the intermolecular stretching mode characterizing intrinsic DHB vibrations.
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Affiliation(s)
- Oleg A Filippov
- A.N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilov Street 28, 119991 Moscow, Russia
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326
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Iterative active-space selection for vibrational configuration interaction calculations using a reduced-coupling VSCF basis. Chem Phys Lett 2008. [DOI: 10.1016/j.cplett.2008.05.001] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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327
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Hermoso W, Ornellas FR. Predicting new molecular species of potential interest to atmospheric chemistry: The isomers HSI and HIS. Chem Phys Lett 2008. [DOI: 10.1016/j.cplett.2008.05.063] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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328
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Beste A, Buchanan AC, Harrison RJ. Computational Prediction of α/β Selectivities in the Pyrolysis of Oxygen-Substituted Phenethyl Phenyl Ethers. J Phys Chem A 2008; 112:4982-8. [DOI: 10.1021/jp800767j] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Affiliation(s)
- Ariana Beste
- Computer Science and Mathematics Division, Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, Tennessee 37831-6367, Chemical Sciences Division, Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, Tennessee 37831-6197, and Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996
| | - A. C Buchanan
- Computer Science and Mathematics Division, Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, Tennessee 37831-6367, Chemical Sciences Division, Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, Tennessee 37831-6197, and Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996
| | - Robert J. Harrison
- Computer Science and Mathematics Division, Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, Tennessee 37831-6367, Chemical Sciences Division, Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, Tennessee 37831-6197, and Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996
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329
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Hansen MB, Christiansen O, Toffoli D, Kongsted J. A virtual vibrational self-consistent-field method for efficient calculation of molecular vibrational partition functions and thermal effects on molecular properties. J Chem Phys 2008; 128:174106. [DOI: 10.1063/1.2912184] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
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330
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Bounouar M, Scheurer C. The impact of approximate VSCF schemes and curvilinear coordinates on the anharmonic vibrational frequencies of formamide and thioformamide. Chem Phys 2008. [DOI: 10.1016/j.chemphys.2007.12.002] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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331
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Franco ML, Ferreira DEC, Santos HFD, De Almeida WB. Ab Initio Highly Correlated Conformational Analysis of 1,2-Difluorethane and 1,2-Dichloroethane. J Chem Theory Comput 2008; 4:728-39. [DOI: 10.1021/ct800014w] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Affiliation(s)
- Mauro L. Franco
- Laboratório de Química Computacional e Modelagem Molecular (LQC-MM), Departamento de Química, ICEx, Universidade Federal de Minas Gerais (UFMG), Campus Universitário, Pampulha, Belo Horizonte, MG, 31270-901, Brazil, Diretoria de Ciências Exatas (DCX), Centro Universitário do Leste de Minas Gerais, UniLeste-MG, Campus I, Coronel Fabriciano, MG, 35170-056, Brazil, and Núcleo de Estudos em Química Computacional (NEQC), Departamento de Química, ICE, Universidade Federal de Juiz de Fora (UFJF), Campus
| | - Dalva E. C. Ferreira
- Laboratório de Química Computacional e Modelagem Molecular (LQC-MM), Departamento de Química, ICEx, Universidade Federal de Minas Gerais (UFMG), Campus Universitário, Pampulha, Belo Horizonte, MG, 31270-901, Brazil, Diretoria de Ciências Exatas (DCX), Centro Universitário do Leste de Minas Gerais, UniLeste-MG, Campus I, Coronel Fabriciano, MG, 35170-056, Brazil, and Núcleo de Estudos em Química Computacional (NEQC), Departamento de Química, ICE, Universidade Federal de Juiz de Fora (UFJF), Campus
| | - Hélio F. Dos Santos
- Laboratório de Química Computacional e Modelagem Molecular (LQC-MM), Departamento de Química, ICEx, Universidade Federal de Minas Gerais (UFMG), Campus Universitário, Pampulha, Belo Horizonte, MG, 31270-901, Brazil, Diretoria de Ciências Exatas (DCX), Centro Universitário do Leste de Minas Gerais, UniLeste-MG, Campus I, Coronel Fabriciano, MG, 35170-056, Brazil, and Núcleo de Estudos em Química Computacional (NEQC), Departamento de Química, ICE, Universidade Federal de Juiz de Fora (UFJF), Campus
| | - Wagner B. De Almeida
- Laboratório de Química Computacional e Modelagem Molecular (LQC-MM), Departamento de Química, ICEx, Universidade Federal de Minas Gerais (UFMG), Campus Universitário, Pampulha, Belo Horizonte, MG, 31270-901, Brazil, Diretoria de Ciências Exatas (DCX), Centro Universitário do Leste de Minas Gerais, UniLeste-MG, Campus I, Coronel Fabriciano, MG, 35170-056, Brazil, and Núcleo de Estudos em Química Computacional (NEQC), Departamento de Química, ICE, Universidade Federal de Juiz de Fora (UFJF), Campus
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332
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Wilhelm MJ, McNavage W, Groller R, Dai HL. The ν1 CH stretching mode of the ketenyl (HCCO) radical. J Chem Phys 2008; 128:064313. [DOI: 10.1063/1.2829400] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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333
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Gasser M, Bach A, Chen P. Photodissociation dynamics of the 2-methylallyl radical. Phys Chem Chem Phys 2008; 10:1133-8. [DOI: 10.1039/b715252c] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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334
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Beste A, Buchanan AC, Britt PF, Hathorn BC, Harrison RJ. Kinetic Analysis of the Pyrolysis of Phenethyl Phenyl Ether: Computational Prediction of α/β-Selectivities. J Phys Chem A 2007; 111:12118-26. [DOI: 10.1021/jp075861+] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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335
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Harding ME, Gauss J, Pflüger K, Werner HJ. High-Accuracy Extrapolated Ab Initio Thermochemistry of Vinyl Chloride. J Phys Chem A 2007; 111:13623-8. [DOI: 10.1021/jp0756348] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Michael E. Harding
- Institut für Physikalische Chemie, Universität Mainz, Jakob-Welder-Weg 11, D-55099 Mainz, Germany, and Institut für Theoretische Chemie, Universität Stuttgart, Pfaffenwaldring 55, D-70569 Stuttgart, Germany
| | - Jürgen Gauss
- Institut für Physikalische Chemie, Universität Mainz, Jakob-Welder-Weg 11, D-55099 Mainz, Germany, and Institut für Theoretische Chemie, Universität Stuttgart, Pfaffenwaldring 55, D-70569 Stuttgart, Germany
| | - Klaus Pflüger
- Institut für Physikalische Chemie, Universität Mainz, Jakob-Welder-Weg 11, D-55099 Mainz, Germany, and Institut für Theoretische Chemie, Universität Stuttgart, Pfaffenwaldring 55, D-70569 Stuttgart, Germany
| | - Hans-Joachim Werner
- Institut für Physikalische Chemie, Universität Mainz, Jakob-Welder-Weg 11, D-55099 Mainz, Germany, and Institut für Theoretische Chemie, Universität Stuttgart, Pfaffenwaldring 55, D-70569 Stuttgart, Germany
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336
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Scribano Y, Benoit DM. Calculation of vibrational frequencies through a variational reduced-coupling approach. J Chem Phys 2007; 127:164118. [DOI: 10.1063/1.2798104] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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337
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Lau KC, Zheng W, Wong NB, Li WK. Theoretical prediction of the ionization energies of the C4H7 radicals: 1-Methylallyl, 2-methylallyl, cyclopropylmethyl, and cyclobutyl radicals. J Chem Phys 2007; 127:154302. [DOI: 10.1063/1.2774972] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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338
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Waller MP, Braun H, Hojdis N, Bühl M. Geometries of Second-Row Transition-Metal Complexes from Density-Functional Theory. J Chem Theory Comput 2007; 3:2234-42. [DOI: 10.1021/ct700178y] [Citation(s) in RCA: 139] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Mark P. Waller
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470 Mülheim an der Ruhr, Germany, and Bergische Universität Wuppertal, Fachbereich Mathematik und Naturwissenschaften, D-42097 Wuppertal, Germany
| | - Heiko Braun
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470 Mülheim an der Ruhr, Germany, and Bergische Universität Wuppertal, Fachbereich Mathematik und Naturwissenschaften, D-42097 Wuppertal, Germany
| | - Nils Hojdis
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470 Mülheim an der Ruhr, Germany, and Bergische Universität Wuppertal, Fachbereich Mathematik und Naturwissenschaften, D-42097 Wuppertal, Germany
| | - Michael Bühl
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470 Mülheim an der Ruhr, Germany, and Bergische Universität Wuppertal, Fachbereich Mathematik und Naturwissenschaften, D-42097 Wuppertal, Germany
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339
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Lim IS, Botschwina P, Oswald R, Barone V, Stoll H, Schwerdtfeger P. Calculated spectroscopic and electric properties of the alkali metal-ammonia complexes from Kn–NH3 to Frn–NH3 (n=0,+1). J Chem Phys 2007; 127:104313. [PMID: 17867753 DOI: 10.1063/1.2749517] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The newly developed Stuttgart small-core scalar relativistic pseudopotentials for the alkali metals are used to study spectroscopic and electric properties of the heavier alkali metal-ammonia complexes from K(n)-NH(3) to Fr(n)-NH(3) (n=0,+1) at the second-order Moller-Plesset (MP2) and coupled cluster [CCSD(T)] levels of theory. Equilibrium geometries and dissociation energies computed at the MP2 level are in reasonable agreement with their CCSD(T) counterparts, whereas for the dipole polarizabilities MP2 is not performing well overestimating significantly electron correlation effects. The bond distances increase monotonically with increasing mass of the metal atom as relativistic effects are small in these systems. However, the dipole polarizabilities are more sensitive to such effects and we find a decrease in this property from Cs-NH(3) to Fr-NH(3). Combination of CCSD(T) harmonic frequencies and MP2 anharmonic corrections obtained from a perturbative vibrational treatment leads to fundamental frequencies in good agreement with experimental results obtained by Suzer and Andrews [J. Am. Chem. Soc. 109, 300 (1986)]. We also present the results of variational calculations with a three-dimensional vibrational Hamiltonian, making use of CCSD(T) potential energy and electric dipole moment surfaces. Complexation of NH(3) to the metal causes a strong infrared intensification of the symmetric NH(3) stretching mode in the neutral complexes, which is absent in the charged species.
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Affiliation(s)
- Ivan S Lim
- Department of Chemistry, School of Molecular Science (BK21), Korea Advanced Institute of Science and Technology, 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701, Korea
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340
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Matanović I, Došlić N. Theoretical modeling of the formic acid dimer infrared spectrum: Shaping the O–H stretch band. Chem Phys 2007. [DOI: 10.1016/j.chemphys.2007.04.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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341
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Doslić N, Kovacević G, Ljubić I. Signature of the Conformational Preferences of Small Peptides: a Theoretical Investigation. J Phys Chem A 2007; 111:8650-8. [PMID: 17691755 DOI: 10.1021/jp072565o] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
An extensive computational study of the conformational preferences of N-acetylphenylalaninylamide (NAPA) is reported, including conformational and anharmonic frequency analyses, as well as calculations of excitation energies of the four NAPA conformers lowest in energy. Particular attention is paid to the influence of hydrogen-bonding interactions on the relative stability of the conformers, which was found to be very sensitive to both the level of quantum chemical computations and the anharmonic treatment of molecular vibrations. The assignments of the UV spectral peaks are well supported by the multireference CASSCF/MS-CASPT2 calculations. Upon consideration of the second-order Möller-Plesset (MP2) and density functional theory (DFT) structures, overall energetics, and harmonic and anharmonic corrections, we found no conclusive theoretical evidence for the assumed conformational propensity of small model peptides toward extended beta-strand structures.
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Affiliation(s)
- Nada Doslić
- Department of Physical Chemistry, Ruder Bosković Institute, Bijenicka cesta 54, Post Office Box 180, HR-10002, Zagreb, Republic of Croatia.
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342
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Slipchenko MN, Sartakov BG, Vilesov AF, Xantheas SS. Study of NH Stretching Vibrations in Small Ammonia Clusters by Infrared Spectroscopy in He Droplets and ab Initio Calculations†. J Phys Chem A 2007; 111:7460-71. [PMID: 17530831 DOI: 10.1021/jp071279+] [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
Infrared spectra of the NH stretching vibrations of (NH3)n clusters (n = 2-4) have been obtained using the helium droplet isolation technique and first principles electronic structure anharmonic calculations. The measured spectra exhibit well-resolved bands, which have been assigned to the nu1, nu3, and 2nu4 modes of the ammonia fragments in the clusters. The formation of a hydrogen bond in ammonia dimers leads to an increase of the infrared intensity by about a factor of 4. In the larger clusters the infrared intensity per hydrogen bond is close to that found in dimers and approaches the value in the NH3 crystal. The intensity of the 2nu4 overtone band in the trimer and tetramer increases by a factor of 10 relative to that in the monomer and dimer, and is comparable to the intensity of the nu1 and nu3 fundamental bands in larger clusters. This indicates the onset of the strong anharmonic coupling of the 2nu4 and nu1 modes in larger clusters. The experimental assignments are compared to the ones obtained from first principles electronic structure anharmonic calculations for the dimer and trimer clusters. The anharmonic calculations were performed at the Møller-Plesset (MP2) level of electronic structure theory and were based on a second-order perturbative evaluation of rovibrational parameters and their effects on the vibrational spectra and average structures. In general, there is excellent (<20 cm(-1)) agreement between the experimentally measured band origins for the N-H stretching frequencies and the calculated anharmonic vibrational frequencies. However, the calculations were found to overestimate the infrared intensities in clusters by about a factor of 4.
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Affiliation(s)
- Mikhail N Slipchenko
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
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343
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345
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Pavone M, Cimino P, Crescenzi O, Sillanpää A, Barone V. Interplay of Intrinsic, Environmental, and Dynamic Effects in Tuning the EPR Parameters of Nitroxides: Further Insights from an Integrated Computational Approach. J Phys Chem B 2007; 111:8928-39. [PMID: 17608525 DOI: 10.1021/jp0727805] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The role of stereoelectronic, environmental, and short-time dynamic effects in tuning the hyperfine and gyromagnetic tensors of a prototypical nitroxide spin probe has been investigated by an integrated computational approach based on extended Lagrangian molecular dynamics and discrete-continuum solvent models. Trajectories were generated in two protic solvents as well as in the gas phase for reference; structural analysis of the dynamics, and comparison with optimized solute-solvent clusters, allowed for the identification of the prevailing solute-solvent hydrogen-bonding patterns and helped to define the strategy for the computation of magnetic parameters. This was performed in a separate step, on a large number of frames, by a high-level DFT approach coupling the PBE0 hybrid functional with a tailored basis set and with proper account of specific and bulk solvent effects. Remarkable changes in solvation networks are found on going from aqueous to methanol solution, thus providing a rationalization of indirect experimentally available evidence. The computed magnetic parameters are in satisfactory agreement with the available measured values and allow for an unbiased evaluation of the role of different effects in tuning the overall EPR observables. Apart from their intrinsic interest, our results pave the route toward the development of tunable detection protocols based on specific spectroscopic signatures.
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Affiliation(s)
- Michele Pavone
- Dipartimento di Chimica and INSTM, Università di Napoli Federico II Complesso Universitario di Monte S. Angelo, Via Cintia, I-80126 Napoli, Italy
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346
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Chan WT, Weng C, Goddard JD. Concerted and Stepwise Reaction Mechanisms for the Addition of Ozone to Acetylene: A Computational Study. J Phys Chem A 2007; 111:4792-803. [PMID: 17500541 DOI: 10.1021/jp0633188] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The mechanism of the reaction between acetylene and ozone to form a primary ozonide (POZ) in the gas phase has been studied theoretically. The concerted pathway, HCCH + O3 --> POZ, proceeds via a biradicaloid transition state TS0. The stepwise pathway is a three-step reaction, HCCH + O3 --> M1 --> M2 --> POZ, involving two biradical TSs and two biradical intermediates M1 and M2. The segment of the global potential energy surface (PES) for the concerted pathway is characterized as a R-PES, which is obtained from the restricted (R) density functional theory and Hartree-Fock-based methods. The RDFT and RHF solutions of TS0 and O3 are unstable toward spin-symmetry breaking. The wave function instability for TS0 and O3 results in a discontinuity between the R-PES and the region of the global PES encompassing the biradical TSs and the intermediates of the stepwise pathway, which are characterized with unrestricted (U) methods. The global PES is characterized separately as an U(R)-PES using a combination of the R and U methods. Several different values of barriers for the concerted pathway and the energy of concert (Ec) can be estimated due to complications arising from the discontinuity between the R- and the U(R)-PES and the existence of two different RDFT and UDFT O3 equilibrium geometries. RCCSD(T)//RDFT predicts a barrier of 8.2 kcal/mol. U(R)CCSD(T)/U(R)DFT predicts a barrier of 13.8 kcal/mol for the concerted and 15.3 kcal/mol for the stepwise pathway. Comparison between the R-PES barrier to the concerted pathway and the U(R)-PES barrier to the stepwise pathway suggests the former to be the only significant mechanism. Consideration of the energy difference between TS1, the TS for the first step of the stepwise mechanism, and TS0 within the global PES leads to a significantly smaller Ec. Geometry optimization with CASSCF and energy point calculations with MRMP2 are employed to characterize TS0 and TS1. MRMP2//CASSCF predicts the energy level of TS1 to be higher than that of TS0 by 2 kcal/mol. Analysis of experimental and computational data based on the low estimate of Ec shows that the possibility of the stepwise pathway being a secondary channel at elevated temperatures cannot be ruled out.
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Affiliation(s)
- Wai-To Chan
- Department of Chemistry, University of Guelph, Guelph, Ontario, Canada N1G 2W1
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347
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Li J, Yang J, Mo Y, Lau KC, Qian XM, Song Y, Liu J, Ng CY. Combined vacuum ultraviolet laser and synchrotron pulsed field ionization study of CH2BrCl. J Chem Phys 2007; 126:184304. [PMID: 17508800 DOI: 10.1063/1.2730829] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The pulsed field ionization-photoelectron (PFI-PE) spectrum of bromochloromethane (CH2BrCl) in the region of 85,320-88,200 cm-1 has been measured using vacuum ultraviolet laser. The vibrational structure resolved in the PFI-PE spectrum was assigned based on ab initio quantum chemical calculations and Franck-Condon factor predictions. At energies 0-1400 cm-1 above the adiabatic ionization energy (IE) of CH2BrCl, the Br-C-Cl bending vibration progression (nu1+=0-8) of CH2BrCl+ is well resolved and constitutes the major structure in the PFI-PE spectrum, whereas the spectrum at energies 1400-2600 cm-1 above the IE(CH2BrCl) is found to exhibit complex vibrational features, suggesting perturbation by the low lying excited CH2BrCl+(A 2A") state. The assignment of the PFI-PE vibrational bands gives the IE(CH2BrCl)=85,612.4+/-2.0 cm-1 (10.6146+/-0.0003 eV) and the bending frequencies nu1+(a1')=209.7+/-2.0 cm-1 for CH2BrCl+(X2A'). We have also examined the dissociative photoionization process, CH2BrCl+hnu-->CH2Cl++Br+e-, in the energy range of 11.36-11.57 eV using the synchrotron based PFI-PE-photoion coincidence method, yielding the 0 K threshold or appearance energy AE(CH2Cl+)=11.509+/-0.002 eV. Combining the 0 K AE(CH2Cl+) and IE(CH2BrCl) values obtained in this study, together with the known IE(CH2Cl), we have determined the 0 K bond dissociation energies (D0) for CH2Cl+-Br (0.894+/-0.002 eV) and CH2Cl-Br (2.76+/-0.01 eV). We have also performed CCSD(T, full)/complete basis set (CBS) calculations with high-level corrections for the predictions of the IE(CH2BrCl), AE(CH2Cl+), IE(CH2Cl), D0(CH2Cl+-Br), and D0(CH2Cl-Br). The comparison between the theoretical predictions and experimental determinations indicates that the CCSD(T, full)/CBS calculations with high-level corrections are highly reliable with estimated error limits of <17 meV.
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Affiliation(s)
- Juan Li
- Key Laboratory for Atomic and Molecular Nanosciences, Department of Physics, Tsinghua University, Beijing 10084, China
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348
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Dobrowolski JC, Jamróz MH, Kołos R, Rode JE, Sadlej J. Theoretical Prediction and the First IR Matrix Observation of SeveralL-Cysteine Molecule Conformers. Chemphyschem 2007; 8:1085-94. [PMID: 17429824 DOI: 10.1002/cphc.200600784] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
For the first time the argon-matrix low-temperature IR spectra of cysteine are recorded. They reveal a quite complicated spectral pattern, which can also be reproduced in the N2 matrix. Assignment of the observed spectra is undertaken on the basis of comparison of the experimental and calculated B3LYP/aug-cc-pVDZ anharmonic IR spectra. The presence of at least three, and possibly even six or more, cysteine conformers with and without intramolecular hydrogen bonding is confirmed. On the basis of the calculated vibrational circular dichroism spectra, we predict this technique to be more distinctive for conformers than IR absorption is.
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Affiliation(s)
- Jan Cz Dobrowolski
- National Medicines Institute, 30/34 Chełmska Street, 00-725 Warsaw, Poland.
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349
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350
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Clarkson JR, Herbert JM, Zwier TS. Infrared photodissociation of a water molecule from a flexible molecule-H2O complex: Rates and conformational product yields following XH stretch excitation. J Chem Phys 2007; 126:134306. [PMID: 17430031 DOI: 10.1063/1.2713109] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Infrared-ultraviolet hole-burning and hole-filling spectroscopies have been used to study IR-induced dissociation of the tryptamine.H2O and tryptamine.D2O complexes. Upon complexation of a single water molecule, the seven conformational isomers of tryptamine collapse to a single structure that retains the same ethylamine side chain conformation present in the most highly populated conformer of tryptamine monomer. Infrared excitation of the tryptamine.H2O complex was carried out using a series of infrared absorptions spanning the range of 2470-3715 cm-1. The authors have determined the conformational product yield over this range and the dissociation rate near threshold, where it is slow enough to be measured by our methods. The observed threshold for dissociation occurred at 2872 cm-1 in tryptamine.H2O and at 2869 cm-1 in tryptamine.D2O, with no dissociation occurring on the time scale of the experiment (approximately 2 micros) at 2745 cm-1. The dissociation time constants varied from approximately 200 ns for the 2869 cm-1 band of tryptamine.D2O to approximately 25 ns for the 2872 cm-1 band of tryptamine.H2O. This large isotope dependence is associated with a zero-point energy effect that increases the binding energy of the deuterated complex by approximately 190 cm-1, thereby reducing the excess energy available at the same excitation energy. At all higher energies, the dissociation lifetime was shorter than the pulse duration of our lasers (8 ns). At all wavelengths, the observed products in the presence of collisions are dominated by conformers A and B of tryptamine monomer, with small contributions from the other minor conformers. In addition, right at threshold (2869 cm-1), tryptamine.D2O dissociates exclusively to conformer A in the absence of collisions with helium, while both A and B conformational products are observed in the presence of collisions with helium. Using resolution-of-identity approximation to second-order Moller-Plesset binding energies extrapolated to the complete basis set limit and harmonic vibrational frequencies and transition states calculated at the density functional limit B3LYP/6-31+G* level of theory, Rice-Ramsperger-Kassel-Marcus (RRKM) predictions for the dissociation, isomerization, and water shuttling rates as a function of energy are made. At threshold, the experimental dissociation rate is almost 10(3) faster than RRKM predictions. Reasons for this apparent non-RRKM behavior will be discussed.
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Affiliation(s)
- Jasper R Clarkson
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, USA
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