Cálculos teóricos de afinidades por próton de n-alquilaminas usando o método ONIOM

Braga, Ataualpa Albert Carmo; Morgon, Nelson H.

doi:10.1590/s0100-40422006000200002

Cited by 2 publications

(3 citation statements)

References 37 publications

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“…However, complex molecular systems containing external and internal transition atoms, proteins, polymers, or compounds with a higher molecular weight overestimate the ability of these methods and basis sets to obtain molecular properties, which can lead to inaccurate results when compared with experimental data. Therefore, an evaluation of these methods and basis sets will be strongly dependent on the system under consideration [3].…”

Section: Introductionmentioning

confidence: 99%

Evaluation of Quantum Chemical Methods and Basis Sets Applied in the Molecular Modeling of Artemisinin

Santos¹,

Lobato²,

Vieira³

et al. 2013

CMB

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In this paper, we evaluate semiempirical methods (AM1, PM3, and ZINDO), HF and DFT (B3LYP) in different basis sets to determine which method best describes the sign and magnitude of the geometrical parameters of artemisinin in the region of the endoperoxide ring compared to crystallographic data. We also classify these methods using statistical analysis. The results of PCA were based on three main components, explaining 98.0539% of the total variance, for the geometrical parameters C3O13, O1O2C3, O13C12C12a, and O2C3O13C12. The DFT method (B3LYP) corresponded well with the experimental data in the hierarchical cluster analysis (HCA). The experimental and theoretical angles were analyzed by simple linear regression, and statistical parameters (correlation coefficients, significance, and predictability) were evaluated to determine the accuracy of the calculations. The statistical analysis exhibited a good correlation and high predictive power for the DFT (B3LYP) method in the 6-31G** basis set.

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Section: Introductionmentioning

confidence: 99%

Evaluation of Quantum Chemical Methods and Basis Sets Applied in the Molecular Modeling of Artemisinin

Santos¹,

Lobato²,

Vieira³

et al. 2013

CMB

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show abstract

“…[1][2][3][4][5][6][7][8][9] However, practical calculations containing many particles become a task that requires a very high computational cost. 10 Some strategies have been successful, making it possible to study large systems, highlighting the composite methods [11][12][13][14][15][16][17][18][19] and the ONIOM (our own n-layered integrated molecular orbital and molecular mechanics) method.…”

Section: Introductionmentioning

confidence: 99%

“…The ONIOM method application in thermochemical studies have been done considering various chemical species. [49][50][51] The link between the ONIOM and the composite methods allows the calculation of systems with many atoms at high level theory. Both methodologies use the extrapolation of their energies to more accurate results.…”

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confidence: 99%

Theoretical study of thermochemical properties using composite methods adapted to ONIOM

Heerdt

Morgon

2012

J. Braz. Chem. Soc.

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Métodos compostos adaptados ao método ONIOM foram utilizados no cálculo teórico de afinidades por próton (PA) e eletrônica (EA) para um grupo de 50 moléculas (álcoois, cetonas, radicais e alcenos). A energia eletrônica foi descrita considerando-se o escalonamento de ZPE (λ) e a correção de alto nível (HLC). O valor ótimo para λ foi obtido através dos dados de PA. Os cálculos de EA foram utilizados na otimização dos termos presentes em HLC. Foram explorados diferentes tipos de funcionais de troca-correlação. A metodologia ONIOM2(QCISD(T)/6-311++G(2dF,p):HF/6-31G(d))//ONIOM2(B3LYP/6-31G(d):HF/6-31G(d)) forneceu os menores desvios absolutos médios para PA e EA, 5,38 kJ mol -1 e 0,11 eV, respectivamente, em comparação com dados experimentais.Composite methods adapted to the ONIOM approach were used in the description of proton (PA) and electron (EA) affinities for a group of 50 molecules (alcohols, ketones, radicals and alkenes). The electronic energy was described considering the scaling ZPE (λ) and higher level (HLC) corrections. The optimal value for λ was obtained from the PA data. The EA calculations were used for optimization of the terms in HLC. Different performances of exchange-correlation functionals were considered. The methodology ONIOM2(QCISD(T)/6-311++G(2dF,p):HF/6-31G(d))//ONIOM2(B3LYP/6-31G(d):HF/6-31G(d)) provided the smallest median absolute deviation (MAD) for PA and EA, 5.38 kJ mol -1 and 0.11 eV, respectively, in comparison to the experimental data.Keywords: proton and electron affinities, composite methods, ONIOM Introduction Molecular modeling calculations using high level (ab initio and DFT methods) and large basis sets have provided determinations of the precise electronic properties of atomic and molecular systems. 1-9 However, practical calculations containing many particles become a task that requires a very high computational cost. 10 Some strategies have been successful, making it possible to study large systems, highlighting the composite methods [11][12][13][14][15][16][17][18][19] and the ONIOM (our own n-layered integrated molecular orbital and molecular mechanics) method. 20 Developed in the 1980s, the composite methods aim to extrapolate the electronic energies from a sequence of calculations, computationally inexpensive, to an electronic energy with a high level of correlation and large basis set. 2 In addition to the energy terms from the energy calculations, some empirical parameters can be added to correct deficiencies of the method, like additional correlation effects, relativistic effect, etc.The Gaussian-n theory, developed by Pople and co-workers, 13-17 exploits this idea to predict thermochemical data of molecules containing elements of the first three periods of the periodic table. The purpose of this theory is to obtain a general procedure that can reproduce experimental data for properties such as proton and electron affinities, ionization energy, enthalpy of formation, etc., being applicable to any molecular system unambiguously. Recently, new approaches of these theo...

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Cálculos teóricos de afinidades por próton de n-alquilaminas usando o método ONIOM

Cited by 2 publications

References 37 publications

Evaluation of Quantum Chemical Methods and Basis Sets Applied in the Molecular Modeling of Artemisinin

Evaluation of Quantum Chemical Methods and Basis Sets Applied in the Molecular Modeling of Artemisinin

Theoretical study of thermochemical properties using composite methods adapted to ONIOM

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