References

Demaison, J.; Vogt, J.; Wlodarczak, G.

doi:10.1007/10048563_41

Cited by 3 publications

(4 citation statements)

References 790 publications

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“…MNDO/d shows the lowest mean absolute error for the investigated compounds. The dipole moment of magnesium oxide was reported to be 5.94 D . We obtained 6.79 D using AM1, while PM3 predicts 5.03 D and MNDO/d 6.08 D .…”

Section: Resultsmentioning

confidence: 64%

Modeling the Bacterial Photosynthetic Reaction Center. 1. Magnesium Parameters for the Semiempirical AM1 Method Developed Using a Genetic Algorithm

1998

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Magnesium parameters for use with the semiempirical AM1 method are developed using a specially designed genetic algorithm. Parametrization priorities included development of a robust parametrization capable of describing a wide range of properties in diverse chemical environments, with emphasis on structural features of biologically relevant systems, e.g., chlorophylls. Specifically, the test data set included a selection of the heats of formation, geometric properties, dipole moment, and ionization energies evaluated for 32 compounds including halides, oxides, hypervalent compounds, organometallics, and porphyrins. In addition, calculated properties for an additional 27 molecules are used as an independent test on the quality of the parametrization obtained. Reference data are taken from eitherexperiment or previous ab initio calculations or evaluated using ab initio or density functional theory. For comparison, analogous results for all 59 molecules are obtained using the semiempirical PM3 and MNDO/d methods. Both AM1 and MNDO/d are found to be robust and widely applicable for magnesium compounds while the applicability of PM3 appears significantly restricted. MNDO/d appears the method of choice for ionization potentials and heats of formation while, reflecting our parametrization priorities, AM1 appears the method of choice for geometrical properties, especially those of magnesium porphyrins.

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Section: Resultsmentioning

confidence: 64%

Modeling the Bacterial Photosynthetic Reaction Center. 1. Magnesium Parameters for the Semiempirical AM1 Method Developed Using a Genetic Algorithm

1998

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“…However, quadrupole splitting was not expected to be large and presumably unresolved because it has been found that the boron quadrupole coupling constants are relatively small. 24 Another factor that might lead to splitting of the rotational lines is tunneling of the BH 3 group. This effect depends strongly on the vibrational state of the torsion about the N-B bond and is much larger in excited states of this mode than that in the ground state.…”

Section: Resultsmentioning

confidence: 99%

“…This effect should lead to a complex quadrupole splitting of the rotational transitions. However, quadrupole splitting was not expected to be large and presumably unresolved because it has been found that the boron quadrupole coupling constants are relatively small . Another factor that might lead to splitting of the rotational lines is tunneling of the BH 3 group.…”

Section: Resultsmentioning

confidence: 99%

Microwave Spectrum, Structure, Barrier to Internal Rotation, and Dipole Moment of the Aziridine−Borane Complex (C₂H₅N−BH₃)

2009

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The microwave spectrum of the aziridine-borane complex (C(2)H(5)N-BH(3)) has been investigated by microwave spectroscopy in the 18-80 GHz spectral region. The spectra of the ground vibrational state and three vibrationally excited states have been assigned, and the vibrational frequencies of these states have been determined. The complex was found to have a symmetry plane (C(s) symmetry) formed by the N-B bond and the bisector of the aziridine ring. The dative N-B bond is found to be as short as 161.5 pm in MP2/aug-cc-pVTZ calculations. The MP2 structure of the aziridine ring of this complex is nearly the same as that in the substitution structure of aziridine. Complex formation therefore appears to have little influence on this moiety. The dipole moment was determined to be mu(a) = 17.72(11), mu(b) = 0.0 (by symmetry), mu(c) = 5.70(8), and mu(tot) = 18.62(11) x 10(-30) C m [5.581(34) D]. The barrier to internal rotation of the borane group was determined to be 12.1(3) kJ/mol using the microwave splitting method. The microwave investigation has been augmented by high-level quantum chemical calculations at the MP2/aug-cc-pVTZ and B3LYP/6-311++G** levels of theory. There is generally good agreement between the experimental results and quantum chemical predictions.

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“…The selection of reliable experimental reference data is often a difficult practical problem that may involve a judgement on the accuracy of published experimental results. To be as unbiased as possible, we have preferentially taken the experimental data from recognized standard compilations for heats of formation, − molecular geometries, − ionization potentials, and dipole moments. − In the case of multiple entries, we have usually adopted the following priorities: refs > 23 > 24 > 25 > 26, refs > 28 > 29 > 30 > 31, and refs > 34 > 35 > 36. In addition, experimental reference data have been taken from specialized reviews for heats of formation − and occasionally also from previous semiempirical evaluations. ,− Generally we have attempted to exclude experimental reference data of low or dubious accuracy.…”

Section: Statistical Evaluationsmentioning

confidence: 99%

Extension of MNDO to d Orbitals: Parameters and Results for the Second-Row Elements and for the Zinc Group

1996

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The extension of the MNDO formalism to d orbitals is outlined. MNDO/d parameters are reported for Na, Mg, Al, Si, P, S, Cl, Br, I, Zn, Cd, and Hg. According to extensive test calculations covering more than 600 molecules and several properties, MNDO/d provides significant improvements over established semiempirical methods, especially for hypervalent compounds. The mean absolute error in MNDO/d heats of formation amounts to 5.4 kcal/mol for the complete validation set of 575 molecules and is identical for the subsets of 508 normal valent and 67 hypervalent compounds. In addition to the statistical evaluations, several specific applications are briefly discussed to illustrate the performance of MNDO/d in selected areas and to comment on problematic cases.

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References

Cited by 3 publications

References 790 publications

Modeling the Bacterial Photosynthetic Reaction Center. 1. Magnesium Parameters for the Semiempirical AM1 Method Developed Using a Genetic Algorithm

Modeling the Bacterial Photosynthetic Reaction Center. 1. Magnesium Parameters for the Semiempirical AM1 Method Developed Using a Genetic Algorithm

Microwave Spectrum, Structure, Barrier to Internal Rotation, and Dipole Moment of the Aziridine−Borane Complex (C₂H₅N−BH₃)

Extension of MNDO to d Orbitals: Parameters and Results for the Second-Row Elements and for the Zinc Group

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Cited by 3 publications

References 790 publications

Modeling the Bacterial Photosynthetic Reaction Center. 1. Magnesium Parameters for the Semiempirical AM1 Method Developed Using a Genetic Algorithm

Modeling the Bacterial Photosynthetic Reaction Center. 1. Magnesium Parameters for the Semiempirical AM1 Method Developed Using a Genetic Algorithm

Microwave Spectrum, Structure, Barrier to Internal Rotation, and Dipole Moment of the Aziridine−Borane Complex (C2H5N−BH3)

Extension of MNDO to d Orbitals: Parameters and Results for the Second-Row Elements and for the Zinc Group

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Microwave Spectrum, Structure, Barrier to Internal Rotation, and Dipole Moment of the Aziridine−Borane Complex (C₂H₅N−BH₃)