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Stylianakis I, Zervos N, Lii JH, Pantazis DA, Kolocouris A. Conformational energies of reference organic molecules: benchmarking of common efficient computational methods against coupled cluster theory. J Comput Aided Mol Des 2023; 37:607-656. [PMID: 37597063 PMCID: PMC10618395 DOI: 10.1007/s10822-023-00513-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Accepted: 06/03/2023] [Indexed: 08/21/2023]
Abstract
We selected 145 reference organic molecules that include model fragments used in computer-aided drug design. We calculated 158 conformational energies and barriers using force fields, with wide applicability in commercial and free softwares and extensive application on the calculation of conformational energies of organic molecules, e.g. the UFF and DREIDING force fields, the Allinger's force fields MM3-96, MM3-00, MM4-8, the MM2-91 clones MMX and MM+, the MMFF94 force field, MM4, ab initio Hartree-Fock (HF) theory with different basis sets, the standard density functional theory B3LYP, the second-order post-HF MP2 theory and the Domain-based Local Pair Natural Orbital Coupled Cluster DLPNO-CCSD(T) theory, with the latter used for accurate reference values. The data set of the organic molecules includes hydrocarbons, haloalkanes, conjugated compounds, and oxygen-, nitrogen-, phosphorus- and sulphur-containing compounds. We reviewed in detail the conformational aspects of these model organic molecules providing the current understanding of the steric and electronic factors that determine the stability of low energy conformers and the literature including previous experimental observations and calculated findings. While progress on the computer hardware allows the calculations of thousands of conformations for later use in drug design projects, this study is an update from previous classical studies that used, as reference values, experimental ones using a variety of methods and different environments. The lowest mean error against the DLPNO-CCSD(T) reference was calculated for MP2 (0.35 kcal mol-1), followed by B3LYP (0.69 kcal mol-1) and the HF theories (0.81-1.0 kcal mol-1). As regards the force fields, the lowest errors were observed for the Allinger's force fields MM3-00 (1.28 kcal mol-1), ΜΜ3-96 (1.40 kcal mol-1) and the Halgren's MMFF94 force field (1.30 kcal mol-1) and then for the MM2-91 clones MMX (1.77 kcal mol-1) and MM+ (2.01 kcal mol-1) and MM4 (2.05 kcal mol-1). The DREIDING (3.63 kcal mol-1) and UFF (3.77 kcal mol-1) force fields have the lowest performance. These model organic molecules we used are often present as fragments in drug-like molecules. The values calculated using DLPNO-CCSD(T) make up a valuable data set for further comparisons and for improved force field parameterization.
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Affiliation(s)
- Ioannis Stylianakis
- Department of Medicinal Chemistry, Faculty of Pharmacy, National and Kapodistrian University of Athens, Panepistimioupolis Zografou, 15771, Athens, Greece
| | - Nikolaos Zervos
- Department of Medicinal Chemistry, Faculty of Pharmacy, National and Kapodistrian University of Athens, Panepistimioupolis Zografou, 15771, Athens, Greece
| | - Jenn-Huei Lii
- Department of Chemistry, National Changhua University of Education, Changhua City, Taiwan
| | - Dimitrios A Pantazis
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470, Mülheim an der Ruhr, Germany
| | - Antonios Kolocouris
- Department of Medicinal Chemistry, Faculty of Pharmacy, National and Kapodistrian University of Athens, Panepistimioupolis Zografou, 15771, Athens, Greece.
- Laboratory of Medicinal Chemistry, Section of Pharmaceutical Chemistry, Department of Pharmacy, National and Kapodistrian University of Athens, Panepistimiopolis-Zografou, 15771, Athens, Greece.
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Prakash O, Singh RK. Probing self-associated intermolecular H-bonding using low-frequency SERS coupled with mid-IR SERS and DFT study: a case study of 2-MBA adsorbed on ZnO nanoparticles. Phys Chem Chem Phys 2019; 21:21431-21437. [PMID: 31531501 DOI: 10.1039/c9cp03124c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
In the present study, low-frequency SERS is reported for the first time to investigate intermolecular interactions. Low-frequency SERS in the THz region (>50 cm-1) and the mid-IR region is used to probe the H-bonding interaction in 2-mercaptobenzoic acid (2-MBA) molecules adsorbed on the surface of ZnO nanoparticles. The self-association due to H-bonding leads to dimer formation of 2-MBA through carboxylic acid groups. The characteristic Raman bands of the 2-MBA dimer, H-bonded O-H stretching and out-of-plane O-H bending modes, are observed. Subsequently, this dimer formation causes the evolution of two new low-frequency modes at 90 cm-1 (shear dimer in-plane bending) and 110 cm-1 (shear dimer stretching) of intermolecular H-bonding and a blue-shift of the torsional mode of (-COOH) + (-SH). In the THz region (50-200 cm-1) the vibrational modes are blue-shifted, while in the mid-IR region the symmetric out-of-plane O-H bending is red-shifted. The present work shows that SERS can be used to study intermolecular H-bonding of molecules at very low concentrations.
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Affiliation(s)
- Om Prakash
- Department of Physics, Banaras Hindu University, Varanasi-221005, India.
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Takahashi O, Kohno Y, Nishio M. Relevance of weak hydrogen bonds in the conformation of organic compounds and bioconjugates: evidence from recent experimental data and high-level ab initio MO calculations. Chem Rev 2011; 110:6049-76. [PMID: 20550180 DOI: 10.1021/cr100072x] [Citation(s) in RCA: 447] [Impact Index Per Article: 34.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Osamu Takahashi
- Department of Chemistry, Graduate School of Science, Hiroshima University, Kagamiyama, Higashi-Hiroshima, 739-8526, Japan.
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Guirgis GA, Yu Z, Zheng C, Zhou SX, Durig JR. Conformational stability from variable temperature FT-IR spectra of krypton solutions, r0 structural parameters, vibrational assignment, and ab initio calculations of 4-fluoro-1-butene. J Phys Chem A 2008; 112:2268-81. [PMID: 18298100 DOI: 10.1021/jp0748213] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Variable temperature (-115 to -155 degrees C) studies of the infrared spectra (3200-400 cm-1) of 4-fluoro-1-butene, CH2=CHCH2CH2F, dissolved in liquid krypton have been carried out. The infrared spectra of the gas and solid as well as the Raman spectra of the gas, liquid, and solid have also been recorded from 3200 to 100 cm-1. From these data, an enthalpy difference of 72 +/- 5 cm-1 (0.86 +/- 0.06 kJ x mol-1) has been determined between the most stable skew-gauche II conformer (the first designation refers to the position of the CH2F group relative to the double bond, and the second designation refers to the relative positions of the fluorine atom to the C-C(=C) bond) and the second most stable skew-trans form. The third most stable conformer is the skew-gauche I with an enthalpy difference of 100 +/- 7 cm-1 (1.20 +/- 0.08 kJ x mol-1) to the most stable form. Larger enthalpy values of 251 +/- 12 cm-1 (3.00 +/- 0.14 kJ x mol-1) and 268 +/- 17 cm-1 (3.21 +/- 0.20 kJ x mol-1) were obtained for the cis-trans and cis-gauche conformers, respectively. From these data and the relative statistical weights of one for the cis-trans conformer and two for all other forms, the following conformer percentages are calculated at 298 K: 36.4 +/- 0.9% skew-gauche II, 25.7 +/- 0.1% skew-trans, 22.5 +/- 0.2% skew-gauche I, 10.0 +/- 0.6% cis-gauche, and 5.4 +/- 0.2% cis-trans. The potential surface describing the conformational interchange has been analyzed and the corresponding two-dimensional Fourier coefficients were obtained. Nearly complete vibrational assignments for the three most stable conformers are proposed and some fundamentals for the cis-trans and the cis-gauche conformers have been identified. The structural parameters, dipole moments, conformational stability, vibrational frequencies, infrared, and Raman intensities have been predicted from ab initio calculations and compared to the experimental values when applicable. The adjusted r0 structural parameters have been determined by combining the ab initio predicted parameters with previously reported rotational constants from the microwave data. These experimental and theoretical results are compared to the corresponding quantities of some similar molecules.
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Affiliation(s)
- Gamil A Guirgis
- Department of Chemistry & Biochemistry, College of Charleston, Charleston, South Carolina 29424, USA
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Origin of the gauche preference of n-propyl halides and related molecules investigated by ab initio MO calculations: Importance of the CH/n hydrogen bond. Chem Phys Lett 2007. [DOI: 10.1016/j.cplett.2007.04.013] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Thomas TD, Saethre LJ, Børve KJ. Effects of molecular conformation on inner-shell ionization energies. Phys Chem Chem Phys 2007; 9:719-24. [PMID: 17268683 DOI: 10.1039/b616824h] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Experimental evidence for an effect of molecular conformation on inner-shell ionization energies has been observed for the first time. Examples are seen in the carbon 1s spectra of butyronitrile, 1-fluoropropane, and propanal, and other similar molecules. At room temperature these exist in two different conformations, with different distances and, hence, different Coulombic interactions between the negatively charged electronegative group and the methyl carbon. The experimental results are in accord with theoretical predictions with respect to both ionization energies and populations of the different conformers.
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Affiliation(s)
- T D Thomas
- Department of Chemistry, Oregon State University, Corvallis, OR 97331-4003, USA.
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Ferguson JD, Johnson NL, Kekenes-Huskey PM, Everett WC, Heard GL, Setser DW, Holmes BE. Unimolecular Rate Constants for HX or DX Elimination (X = F, Cl) from Chemically Activated CF3CH2CH2Cl, C2H5CH2Cl, and C2D5CH2Cl: Threshold Energies for HF and HCl Elimination. J Phys Chem A 2005; 109:4540-51. [PMID: 16833790 DOI: 10.1021/jp040735g] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Vibrationally activated CF(3)CH(2)CH(2)Cl molecules were prepared with 94 kcal mol(-1) of vibrational energy by the combination of CF(3)CH(2) and CH(2)Cl radicals and with 101 kcal mol(-1) of energy by the combination of CF(3) and CH(2)CH(2)Cl radicals at room temperature. The unimolecular rate constants for elimination of HCl from CF(3)CH(2)CH(2)Cl were 1.2 x 10(7) and 0.24 x 10(7) s(-1) with 101 and 94 kcal mol(-1), respectively. The product branching ratio, k(HCl)/k(HF), was 80 +/- 25. Activated CH(3)CH(2)CH(2)Cl and CD(3)CD(2)CH(2)Cl molecules with 90 kcal mol(-1) of energy were prepared by recombination of C(2)H(5) (or C(2)D(5)) radicals with CH(2)Cl radicals. The unimolecular rate constant for HCl elimination was 8.7 x 10(7) s(-1), and the kinetic isotope effect was 4.0. Unified transition-state models obtained from density-functional theory calculations, with treatment of torsions as hindered internal rotors for the molecules and the transition states, were employed in the calculation of the RRKM rate constants for CF(3)CH(2)CH(2)Cl and CH(3)CH(2)CH(2)Cl. Fitting the calculated rate constants from RRKM theory to the experimental values provided threshold energies, E(0), of 58 and 71 kcal mol(-1) for the elimination of HCl or HF, respectively, from CF(3)CH(2)CH(2)Cl and 54 kcal mol(-1) for HCl elimination from CH(3)CH(2)CH(2)Cl. Using the hindered-rotor model, threshold energies for HF elimination also were reassigned from previously published chemical activation data for CF(3)CH(2)CH(3,) CF(3)CH(2)CF(3), CH(3)CH(2)CH(2)F, CH(3)CHFCH(3), and CH(3)CF(2)CH(3). In an appendix, the method used to assign threshold energies was tested and verified using the combined thermal and chemical activation data for C(2)H(5)Cl, C(2)H(5)F, and CH(3)CF(3).
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Affiliation(s)
- J D Ferguson
- Lyon College, 2300 Highland Road, Batesville, Arkansas 72503-2317, USA
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Helal MR, Yousef YA, Afaneh AT. Ab Initio calculations of the stabilization energies of the conformational and the structural isomers of C(3)H(7)X where X = F, Cl, and Br. J Comput Chem 2002; 23:966-76. [PMID: 12116402 DOI: 10.1002/jcc.10047] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
HF, MP2, and B3LYP calculations with different basis sets have been used in the computation of the stabilization energies of C(3)H(7)X isomers, where X is F, Cl, and Br. The experimental stabilization energies of the structural isomers of C(3)H(7)Cl and C(3)H(7)Br have been reproduced via B3LYP calculations. However, the calculated stabilization energies of fluoropropane isomers from their reported enthalpies of formation have been reproduced in all methods of calculations in present work. The experimental relative stabilities of the gauche conformers of 1-fluoro-, 1-chloro-, and 1-bromopropanes have been also reproduced via some of the used calculations in the present work. The effect of the geminal interactions on X atomic charges and on the C-X and C-C bond lengths in halopropane isomers are also discussed.
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Durig J, Zhu X, Shen S. Conformational and structural studies of 1-chloropropane and 1-bromopropane from temperature-dependant FT-IR spectra of rare gas solutions and ab initio calculations. J Mol Struct 2001. [DOI: 10.1016/s0022-2860(01)00473-2] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Guirgis GA, Zhu X, Bell S, Durig JR. Conformational Analysis, Barriers to Internal Rotation, ab Initio Calculations, and Vibrational Assignment of 4-Fluoro-1-butyne. J Phys Chem A 2000. [DOI: 10.1021/jp0021796] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Gamil A. Guirgis
- Department of Chemistry, University of MissouriKansas City, Kansas City, Missouri 64110-2499
| | - Xiaodong Zhu
- Department of Chemistry, University of MissouriKansas City, Kansas City, Missouri 64110-2499
| | - Stephen Bell
- Department of Chemistry, University of MissouriKansas City, Kansas City, Missouri 64110-2499
| | - James R. Durig
- Department of Chemistry, University of MissouriKansas City, Kansas City, Missouri 64110-2499
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Meléndez-Pagán Y, Taylor BE, Ben-Amotz D. Cavity Formation and Dipolar Contribution to the Gauche−Trans Isomerization of 1-Chloropropane and 1,2-Dichloroethane. J Phys Chem B 2000. [DOI: 10.1021/jp002781w] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
| | - Brian E. Taylor
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907-1393
| | - Dor Ben-Amotz
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907-1393
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Guirgis GA, Zhu X, Yu Z, Durig JR. Raman and Infrared Spectra, Conformational Stability, Normal Coordinate Analysis, Vibrational Assignment, and ab Initio Calculations of 3,3-Difluorobutene. J Phys Chem A 2000. [DOI: 10.1021/jp993430o] [Citation(s) in RCA: 138] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Gamil A. Guirgis
- Department of Chemistry, University of MissouriKansas City, Kansas City, Missouri 64110-2499
| | - Xiaodong Zhu
- Department of Chemistry, University of MissouriKansas City, Kansas City, Missouri 64110-2499
| | - Zhenhong Yu
- Department of Chemistry, University of MissouriKansas City, Kansas City, Missouri 64110-2499
| | - James R. Durig
- Department of Chemistry, University of MissouriKansas City, Kansas City, Missouri 64110-2499
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Raman and infrared spectra, conformational stability, ab initio calculations and vibrational assignments for 2-chloroethyl silane. J Mol Struct 1999. [DOI: 10.1016/s0022-2860(99)00033-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Durig J, Yu Z, Guirgis G. Conformational stability, barriers to internal rotation, vibrational assignment, and ab initio calculations of 2,2-difluorobutane. J Mol Struct 1999. [DOI: 10.1016/s0022-2860(99)00215-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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15
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Infrared and Raman spectra, conformational stability, barrier to internal rotation, and ab initio calculations of 1,1-difluoropropane. J Mol Struct 1999. [DOI: 10.1016/s0022-2860(99)00230-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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16
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Kuramshina G, Pentin Y, Yagola A. New approaches for molecular conformer force field analysis in combination with ab initio results. J Mol Struct 1999. [DOI: 10.1016/s0022-2860(99)00225-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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17
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Guirgis GA, Nashed YE, Robb II JB, Klaeboe P, Zhen P, Durig JR. Conformational stability, vibrational spectra and ab initio calculations for chloromethyl methyl silane and chloromethyl methyl difluorosilane. J Mol Struct 1999. [DOI: 10.1016/s0022-2860(98)00771-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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DFT force fields, vibrational spectra and potential functions for hindered internal rotation of CF3CH2CH2Cl and CCl3CH2CH2Cl. J Mol Struct 1999. [DOI: 10.1016/s0022-2860(98)00629-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Guirgis GA, Nashed YE, Klaeboe P, Durig JR. Conformational stabilities, ab initio calculations and structural parameters for 2-chloroethyl silane and 2-chloroethyl trifluorosilane. J Mol Struct 1999. [DOI: 10.1016/s0022-2860(98)00768-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Hu MHA, de Souza LES, Lee MR, Ben-Amotz D. Pressure and temperature-dependent gauche-trans isomerization of 1-bromopropane: Raman measurement and statistical thermodynamic analysis. J Chem Phys 1999. [DOI: 10.1063/1.477955] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
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Affiliation(s)
- D. Wu
- Department of Chemistry, Sichuan University, Chengdu, Sichuan, People's Republic of China
| | - A. Tian
- Department of Chemistry, Sichuan University, Chengdu, Sichuan, People's Republic of China
| | - H. Sun
- Molecular Simulations, Inc., San Diego, California 92121-3752
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Guirgis GA, Nashed YE, Robb JB, Durig JR. Raman and infrared spectra, conformational stability, ab initio calculations and vibrational assignments for chloromethyl methyl silane. J Mol Struct 1998. [DOI: 10.1016/s0022-2860(97)00346-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Ferguson HA, Ferguson JD, Holmes BE. Threshold Energies and Unimolecular Rate Constants for Elimination of HF from Chemically Activated CF3CH2CH3 and CF3CH2CF3: Effect of CH3 and CF3 Substituents at the β-Carbon and Implications about the Transition State. J Phys Chem A 1998. [DOI: 10.1021/jp972854k] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
| | - John D. Ferguson
- Department of Chemistry, Lyon College, Batesville, Arkansas 72501
| | - Bert E. Holmes
- Department of Chemistry, Lyon College, Batesville, Arkansas 72501
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Shim JY, Allinger NL, Bowen JP. Molecular Mechanics (MM3) Conformational Studies of Cyclic and Acyclic Monochloroalkanes. J Org Chem 1996. [DOI: 10.1021/jo960623o] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Joong-Youn Shim
- Computational Center for Molecular Structure and Design, Department of Chemistry, The University of Georgia, Athens, Georgia, 30602
| | - Norman L. Allinger
- Computational Center for Molecular Structure and Design, Department of Chemistry, The University of Georgia, Athens, Georgia, 30602
| | - J. Phillip Bowen
- Computational Center for Molecular Structure and Design, Department of Chemistry, The University of Georgia, Athens, Georgia, 30602
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Herrebout WA, van der Veken BJ. Solute−Solvent Interactions in Liquid Noble Gases As Probed by the Conformational Equilibrium of Some 1,2-Disubstituted Ethanes. ACTA ACUST UNITED AC 1996. [DOI: 10.1021/jp953713q] [Citation(s) in RCA: 140] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- W. A. Herrebout
- Department of Chemistry, Universitair Centrum Antwerpen, Groenenborgerlaan 171, B2020-Antwerp, Belgium
| | - B. J. van der Veken
- Department of Chemistry, Universitair Centrum Antwerpen, Groenenborgerlaan 171, B2020-Antwerp, Belgium
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Gundertofte K, Liljefors T, Norrby PO, Pettersson I. A comparison of conformational energies calculated by several molecular mechanics methods. J Comput Chem 1996. [DOI: 10.1002/(sici)1096-987x(199603)17:4<429::aid-jcc5>3.0.co;2-w] [Citation(s) in RCA: 125] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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St.-Amant A, Cornell WD, Kollman PA, Halgren TA. Calculation of molecular geometries, relative conformational energies, dipole moments, and molecular electrostatic potential fitted charges of small organic molecules of biochemical interest by density functional theory. J Comput Chem 1995. [DOI: 10.1002/jcc.540161206] [Citation(s) in RCA: 92] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Stølevik R, Hagen K. Ab initio calculations of conformational structures and energies in chlorosubstituted ethanes and propanes. J Mol Struct 1995. [DOI: 10.1016/0022-2860(94)08495-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Durig J, Zhao W, Zhu X, Geyer T, Dakkouri M. Spectra and structure of small ring compounds. LXV. Raman and infrared spectra, conformational stability, and vibrational assignment of cyclopentylsilane. J Mol Struct 1995. [DOI: 10.1016/0022-2860(94)08484-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Hagen K, Stølevik R. Structure and conformation of 1-Bromopropane: A gas-phase electron-diffraction investigation using microwave-spectroscopy data and results from ab initio calculations as constraints. Struct Chem 1995. [DOI: 10.1007/bf02286445] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Hagen K, Stølevik R, Sæbø PC. Molecular structure and conformational composition of 1-iodopropane as determined from gas-phase electron diffraction, microwave spectroscopy data and ab initio calculations. J Mol Struct 1995. [DOI: 10.1016/0022-2860(94)09003-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Durig J, Guirgis G, Mohamed T, Herrebout W, Afifi M. Spectra and structure of silicon-containing compounds. XIX. Raman and infrared spectra, conformational stability, vibrational assignment, barrier to internal rotation, and ab initio calculations of ethyldifluorosilane. J Mol Struct 1994. [DOI: 10.1016/0022-2860(93)07939-t] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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