Abinitio Calculations of the Barriers to Rotation in Some Monosubstituted Benzenes

1986 ◽  
Vol 39 (7) ◽  
pp. 1157 ◽  
Author(s):  
S Marriott ◽  
RD Topsom
Keyword(s):  
Electron Transfer ◽  
Ab Initio ◽  
Benzene Ring ◽  
Theoretical Calculations ◽  
Geometry Optimization ◽  
Basis Set ◽  
Monosubstituted Benzenes ◽  
Split Valence ◽  
Good Agreement ◽  
Abinitio Calculations

Theoretical calculations at the ab initio level have been made of the twofold rotational barriers of some monosubstituted benzenes, and the effects both of basis set and of geometry optimization have been examined. Values at the STO-3G//STO-3G level are in good agreement with experiment. The use of split-valence sets, even with geometry optimization, is much less satisfactory, and this may be related to an overestimation of π-electron transfer between the substituent and the benzene ring.

Ab initio and MNDO Calculations of the 35Cl NQR Parameters of Some Organic and Inorganic Molecules

1996 ◽  
Vol 51 (5-6) ◽  
pp. 549-553 ◽  
Author(s):  
Valentin P. Feshin ◽  
Mikhail Yu. Konshin
Keyword(s):  
Ab Initio ◽  
Basis Set ◽  
Hartree Fock ◽  
Mndo Calculations ◽  
Inorganic Molecules ◽  
Asymmetry Parameters ◽  
Linear Correlations ◽  
Split Valence ◽  
Valence Basis Set ◽  
Good Agreement

Abstract The results of ab initio and MNDO calculations of the Cl2C = CHOCH3 , XCOCl (X = CH3 , OCH3 and COCl), 4-ClC6H4CH2Cl, (CNCl)3 and PCl5 with total optimization of their geometry are presented. The ab initio calculations were executed using Hartree-Fock theory and the split valence basis set 6-31G* (RHF/6-31 G*//RHF/6-31G*). Using the calculated p-orbital populations of the CI atoms in these molecules the 35Cl NQR frequencies and asymmetry parameters of the EFG at the 35Cl nuclei have been determined. When the populations of the less diffuse components of orbitals in the split valence basis set are used the calculated and experimenal ν and η values are in good agreement. Linear correlations between these calculated and corresponding experimental ν and η values are obtained. The causes of the nonconformity of the earlier calculated ν and η values and their experimental ones are analysed.

scholarly journals Geometric and energetic data from quantum chemical calculations of halobenzenes and xylenes

2020 ◽  
Author(s):  
Sopanant Datta ◽  
Taweetham Limpanuparb
Keyword(s):  
Ab Initio ◽  
Quantum Chemical Calculations ◽  
Quantum Chemical Calculation ◽  
Quantum Chemical ◽  
Software Package ◽  
Geometry Optimization ◽  
Theoretical Data ◽  
Basis Set ◽  
Chemical Calculation ◽  
Custom Made

<p>This article presents theoretical data on geometric and energetic features of halobenzenes and xylenes. Data were obtained from <i>ab initio</i> geometry optimization and frequency calculations at HF, B3LYP, MP2 and CCSD levels of theory on 6-311++G(d,p) basis set. In total, 1504 structures of halobenzenes, three structures of xylenes and one structure of benzene were generated and processed by custom-made codes in Mathematica. The quantum chemical calculation was completed in Q-Chem software package. Geometric and energetic data of the compounds are presented in this paper as supplementary tables. Raw output files as well as codes and scripts associated with production and extraction of data are also provided.</p>

Conformational Structure of Chloromethyldichlorophosphines

2002 ◽  
Vol 57 (6-7) ◽  
pp. 333-336
Author(s):  
Evgenii A. Romanenko ◽  
Alexander M. Nesterenko
Keyword(s):  
Experimental Data ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Electron Correlation ◽  
Basis Set ◽  
Conformational Structure ◽  
Gauche Conformation ◽  
Nuclear Quadrupole ◽  
Set Up ◽  
Good Agreement

IThe 35Cl nuclear quadrupole resonances (77 K) and ab initio calculations of trichloromethyldichlorophosphine () show that it exists in the chess conformation form. The barrier to internal rotation about the P-C bond in I at the RHF/6-31++ G(d,p) level equals to 38.1 kJ mol-1. In chloromethyldichlorophosphine (II) the extension of the basis set up to the RHF/6-311++G(df, pd) level does not improve the description of the most preferable gauche-conformation; only if electron correlation (at the MP2 level) is taken into account the results are in a good agreement with experimental data.

Quantum chemical computations on rotational isomers of hydrogen nitrite and nitritomethane

1982 ◽  
Vol 381 (1781) ◽  
pp. 443-455 ◽  
Keyword(s):  
Excited States ◽  
Quantum Chemical ◽  
Dipole Moments ◽  
Basis Set ◽  
Electronic Transitions ◽  
Rotational Isomers ◽  
Transition Structures ◽  
Quantum Chemical Computations ◽  
Split Valence ◽  
Good Agreement

Ab initio molecular-orbital computations with a split-valence 4-31G basis set have been carried out on syn- and antiperiplanar conformers of both HONO and H 3 CONO, and on the transition structures in the unimolecular isomerization process. Calculated values of geometric structural and rotational parameters, dipole moments, wavenumbers of vibrational transitions, energies of vertical electronic transitions to both neutral and ionized excited states, and thermodynamic properties are compared with experimental data; generally good agreement is found. No explanation of the anomalous stability of antiperiplanar HONO has been discovered.

Structures of simple anions from ab initio molecular orbital calculations

1976 ◽  
Vol 29 (8) ◽  
pp. 1635 ◽  
Author(s):  
L Radom
Keyword(s):  
Ab Initio ◽  
Molecular Orbital ◽  
Basis Set ◽  
Basis Sets ◽  
Molecular Orbital Calculations ◽  
Limited Information ◽  
Orbital Theory ◽  
Comparable Quality ◽  
Split Valence ◽  
Theoretical Results

Ab initio molecular orbital theory with the minimal STO-3G and split-valence 4-31G basis sets is used to obtain geometries of 18 anions:OH-, NH2-, HF2-, BH4-, BF4-, C22-, CN-, NCN2-, N3-, NO2-, NO3-, 0CCO2-, CO32-, HCOO-, CH3COO-, C2O42-, C4O42- and C(CN)3-. The theoretical results are compared with experimental results from the literature. The STO-3G basis set performs somewhat worse for anions than for neutral molecules. On the other hand, the 4-31G basis set gives good results and predicts bond lengths to within 0.02� for all the molecules considered. Limited information on bond angle predictions suggests that these are of comparable quality to those for neutral molecules. The tricyanomethanide ion is predicted to be planar.

Resonance Raman and absorption infrared with density functional theory studies of Fe(III)/Fe(II) and Ni(II) complexes of modified 21-oxaporphyrins

2013 ◽  
Vol 17 (04) ◽  
pp. 289-308 ◽  
Author(s):  
Mateusz Fościak ◽  
Edyta Proniewicz ◽  
Krzysztof Zborowski ◽  
Younkyoo Kim ◽  
Leonard M. Proniewicz
Keyword(s):  
Density Functional ◽  
Theoretical Calculations ◽  
Resonance Raman ◽  
Vibrational Analysis ◽  
Basis Set ◽  
Functional Theory ◽  
B3lyp Level ◽  
Ft Ir ◽  
Optimized Geometries ◽  
Good Agreement

This work presents a complete vibrational analysis of iron [ Fe (II) and Fe (III)] and nickel [ Ni (II)] complexes with 5,10,15,20-tetraphenyl-21-oxaporphyrin [OTPPH] and 5,20-bis(p-tolyl)-10,15-diphenyl-21-oxaporphyrin [ODTDPPH]. In these porphyrins, a furan ring replaces one of the pyrrole rings. The six-coordinate (OTPP) FeIIICl2 and (ODTDPP) FeIIICl2 as well as the five-coordinate (OTPP) FeIICl and (OTPP) NiIICl complexes were investigated using experimental and theoretical methods. The experimental part of this work involved Fourier-transform absorption infrared (FT-IR), resonance Raman (RR), and electron absorption (UV-vis) measurements for all of the investigated complexes. In the theoretical section, optimized geometries and vibrational frequencies for model compounds are provided. The theoretical calculations were performed at the B3LYP level with the LANL2DZ basis set. Good agreement was achieved between the experimental and theoretical vibrational spectra. In addition, charge distributions (GAPT) and geometrical aromaticity indices (Bird's I5 and HOMA) were calculated and discussed.

Nonadditive effects of polysubstitution in CH4 and CH3: a test of abinitio and semiempirical MO methods

1983 ◽  
Vol 61 (7) ◽  
pp. 1567-1572 ◽  
Author(s):  
N. Colin Baird
Keyword(s):  
Basis Set ◽  
Semiempirical Methods ◽  
Valence Shell ◽  
Bond Lengths ◽  
Hartree Fock ◽  
Nonadditive Effects ◽  
D Orbitals ◽  
Split Valence ◽  
Abinitio Calculations

The effects to the bond lengths and molecular energy of making multiple substitutions at the same carbon atom in methane and the methyl free radical are studied using various molecular orbital methods. All abinitio calculations were based upon the Hartree–Fock formalism (unrestricted in the case of free radicals) and employed the STO-3G (with d orbitals on chlorine), 3-21G, and 4-31G bases, the last both with and without a set of Gaussian d orbitals on the carbon. The semiempirical methods used were the MINDO/3 and MNDO methods of Dewar and co-workers; computations for polysubstituted ethanes by these two methods also arc reported. The abinito methods which use a split valence shell basis set account very well for the trends in bond lengths and heats of formation, at least when the polysubstituent is fluorine or hydroxyl. In contrast, the semiempirical calculations and the abinitio STO-3G results gave very poor results. Finally, the role of interactions between the AH bonds in a variety of hydrides AHn is illustrated using experimental energetics.

scholarly journals Geometric and Energetic Data from Quantum Chemical Calculations of Halobenzenes and Xylenes

2020 ◽  
Author(s):  
Sopanant Datta ◽  
Taweetham Limpanuparb
Keyword(s):  
Ab Initio ◽  
Quantum Chemical Calculations ◽  
Quantum Chemical Calculation ◽  
Quantum Chemical ◽  
Software Package ◽  
Geometry Optimization ◽  
Theoretical Data ◽  
Basis Set ◽  
Chemical Calculation ◽  
Custom Made

<div>This article presents theoretical data on geometric and energetic features of halobenzenes and xylenes. Data were obtained from ab initio geometry optimization and frequency calculations at HF, B3LYP, MP2 and CCSD levels of theory on 6-311++G(d,p) basis set. In total, 1504 structures of halobenzenes, three structures of xylenes and one structure of benzene were generated and processed by custom-made codes in Mathematica. The quantum chemical calculation was completed in Q-Chem software package. Geometric and energetic data of the compounds are presented in this paper as supplementary tables. Raw output files as well as codes and scripts associated with production and extraction of data are also provided.</div>

scholarly journals Geometric and energetic data from quantum chemical calculations of halobenzenes and xylenes

2020 ◽  
Author(s):  
Sopanant Datta ◽  
Taweetham Limpanuparb
Keyword(s):  
Ab Initio ◽  
Quantum Chemical Calculations ◽  
Quantum Chemical Calculation ◽  
Quantum Chemical ◽  
Software Package ◽  
Geometry Optimization ◽  
Theoretical Data ◽  
Basis Set ◽  
Chemical Calculation ◽  
Custom Made

<p>This article presents theoretical data on geometric and energetic features of halobenzenes and xylenes. Data were obtained from <i>ab initio</i> geometry optimization and frequency calculations at HF, B3LYP, MP2 and CCSD levels of theory on 6-311++G(d,p) basis set. In total, 1504 structures of halobenzenes, three structures of xylenes and one structure of benzene were generated and processed by custom-made codes in Mathematica. The quantum chemical calculation was completed in Q-Chem software package. Geometric and energetic data of the compounds are presented in this paper as supplementary tables. Raw output files as well as codes and scripts associated with production and extraction of data are also provided.</p>

Vibrational analysis of Ni(II) complex with 4,12-ditolyl-16,24-diphenyl-3-thiaporphyrin (SDTDPPNi(II)Cl) and its isotopic labeled (61Ni(II), −d6, and −d10) derivatives

2007 ◽  
Vol 11 (09) ◽  
pp. 652-675 ◽  
Author(s):  
Edyta Podstawka ◽  
Mateusz Fościak ◽  
Piotr Chmielewski ◽  
Leonard M. Proniewicz
Keyword(s):  
Theoretical Calculations ◽  
Geometry Optimization ◽  
Vibrational Analysis ◽  
Chloride Complex ◽  
Basis Set ◽  
B3lyp Level ◽  
Model Molecule ◽  
Polar Tensor ◽  
Ft Ir ◽  
Point Groups

This work presents complete vibrational analysis of a chloride complex of Ni (II) 4,12-ditolyl-16,24-diphenyl-3-thiaporphyrin ( SDTDPPNi (II) Cl ) and its isotopic derivatives (61 Ni (II), − d 6, and −d 10). Five-coordinate SDTDPPNi (II) Cl , SDTDPP 61 Ni (II) Cl , ( SDTDPP - d 6) Ni (II) Cl , and ( SDTDPP - d 10) Ni (II) Cl were investigated by Fourier-Transform infrared (FT-IR), resonance Raman (RR), and electronic absorption (UV-vis) methods. Because the methyl groups of tolyl rings at the para-position have negligible influence on geometry and vibrational spectra of SDTDPPNi (II) Cl , they can be treated as point groups. Thus, geometry optimization and vibrational frequencies were calculated for the 4,12,16,24-tetraphenyl-3-thiaporphyrin ( STPPNi (II) Cl ) model molecule and its isotopically labeled analogs using Gaussian'03. Moreover, charge distributions (General Atomic Polar Tensor – GAPT) and geometrical aromaticity indexes (Bird's I 5 and Harmonic Oscillator Model of Aromaticity – HOMA) were calculated. All theoretical calculations were performed at the B3LYP level with the LANL2DZ basis set. As is shown, the experimental FT-IR and RR spectra for each compound are reproduced well by the corresponding theoretical spectra.

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