An effective atomic charge model for infrared intensities

Decius, J. C.

doi:10.1016/0022-2852(75)90296-9

Cited by 149 publications

(44 citation statements)

References 22 publications

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“…2͑e͒ arises from the charge flux involving the counterpart molecule͑s͒ of the complex. Within the framework based on atomic partial charges, the dipole derivative ‫ץ‬ / ‫ץ‬Q amI is expanded as [41][42][43][44] …”

Section: A Amide Iј Mode Of the O¯x Systems: General Trendmentioning

confidence: 99%

Intermolecular charge flux as the origin of infrared intensity enhancement upon halogen-bond formation of the peptide group

Torii

2010

The Journal of Chemical Physics

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The changes in the vibrational properties of the peptide group upon formation of O...X and N...X halogen bonds are studied theoretically. Calculations are carried out for complexes of N-methylacetamide (NMA), a well known model molecule of the peptide group, with halogen-containing molecules. For comparison, calculations are also carried out for some NMA-water hydrogen-bonding complexes. It is shown that the infrared (IR) intensity of the amide I mode of the peptide group is enhanced significantly (up to about 520 km mol(-1) or 2.6 times) upon C=O...X halogen-bond formation, in spite of rather modest magnitudes of the intermolecular electric field and of the changes in the C=O bond length and in the amide I vibrational frequency as compared with the cases of the C=O...H(D) hydrogen bonding. From the analysis of the changes in the dipole derivative and in the electronic structure, it is shown that this IR intensity enhancement arises from the intermolecular charge flux. For the N...X halogen bonding complexes, some characteristic changes in the vibrational properties are seen, among which the IR intensity enhancement of the ND out-of-plane wagging mode is most notable. The reason why such large IR intensity enhancements are seen for these particular vibrational modes is examined.

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Section: A Amide Iј Mode Of the O¯x Systems: General Trendmentioning

confidence: 99%

Intermolecular charge flux as the origin of infrared intensity enhancement upon halogen-bond formation of the peptide group

Torii

2010

The Journal of Chemical Physics

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“…Similar extensions of the FPC model to include charge redistribution during vibration have been made in the calculation of IR intensities [12] and vibrational circular dichroism [13,14]. In molecular mechanics calculations in which Coulombic terms are included [15,16], it may be important to allow for DPC effects.…”

Section: Introductionmentioning

confidence: 95%

CO stretch mode splitting in the formic acid dimer: Electrostatic models of the intermonomer interaction

Dybal

Cheam

Krimm

1987

Journal of Molecular Structure

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The physical origin of the large (74 cm-1) splitting between the symmetric (Ag) and antisymmetric (B u) components of the C-~-~O stretch mode in the formic acid dimer has previously been attributed to tautomerism effects, transition dipole-dipole coupling, or dynamical charge transfer through the hydrogen bonds. We show that an electrostatic model involving atomic charge-charge interactions can account for a splitting of 56 cm-1, provided the atomic partial charges are allowed to vary in magnitude during vibrational motion. The charges and charge derivatives have been obtained from ab initio Hartree-Fock calculations up to the 6-31G** level. An additional 13 cm-1 of the remaining discrepancy in the splitting is shown to be due to a difference in diagonal cubic anharmonicity between the Ag and B u modes. The charge-charge model plus anharmonicity thus lead to a predicted splitting of 69 cm-1, compared to the observed value of 74 cm-1.

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“…Many different partition models were developed over the years in order to extract charge information from the infrared spectrum, usually separating infrared intensities into dynamic and static contributions. Sorted by their formulation dates, some of the most successful include Equilibrium Charge-Charge Flux (ECCF), 1 the Charge-Charge Flux-Overlap (CCFO), 2 the Charge-Charge Flux-Overlap Modified (CCFOM) 3 and the Charge-Charge Flux-Dipole Flux (CCFDF) 4 model, developed within the physics of Bader's Quantum Theory of Atoms in Molecules (QTAIM). 5 Recently intensity results were expressed as a squared function of charge, charge flux and dipole flux terms.…”

Section: Introductionmentioning

confidence: 99%

Dynamic atomic contributions to infrared intensities of fundamental bands

Silva

Richter

Bassi

et al. 2015

Phys. Chem. Chem. Phys.

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Dynamic atomic intensity contributions to fundamental infrared intensities are defined as the scalar products of dipole moment derivative vectors for atomic displacements and the total dipole derivative vector of the normal mode. Intensities of functional group vibrations of the fluorochloromethanes can be estimated within 6.5 km mol(-1) by displacing only the functional group atoms rather than all the atoms in the molecules. The asymmetric CF2 stretching intensity, calculated to be 126.5 km mol(-1) higher than the symmetric one, is accounted for by an 81.7 km mol(-1) difference owing to the carbon atom displacement and 40.6 km mol(-1) for both fluorine displacements. Within the Quantum Theory of Atoms in Molecules (QTAIM) model differences in atomic polarizations are found to be the most important for explaining the difference in these carbon dynamic intensity contributions. Carbon atom displacements almost completely account for the differences in the symmetric and asymmetric CCl2 stretching intensities of dichloromethane, 103.9 of the total calculated value of 105.2 km mol(-1). Contrary to that found for the CF2 vibrations intramolecular charge transfer provoked by the carbon atom displacement almost exclusively explains this difference. The very similar intensity values of the symmetric and asymmetric CH2 stretching intensities in CH2F2 arise from nearly equal carbon and hydrogen atom contributions for these vibrations. All atomic contributions to the intensities for these vibrations in CH2Cl2 are very small. Sums of dynamic contributions of the individual intensities for all vibrational modes of the molecule are shown to be equal to mass weighted atomic effective charges that can be determined from atomic polar tensors evaluated from experimental infrared intensities and frequencies. Dynamic contributions for individual intensities can also be determined solely from experimental data.

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An effective atomic charge model for infrared intensities

Cited by 149 publications

References 22 publications

Intermolecular charge flux as the origin of infrared intensity enhancement upon halogen-bond formation of the peptide group

Intermolecular charge flux as the origin of infrared intensity enhancement upon halogen-bond formation of the peptide group

CO stretch mode splitting in the formic acid dimer: Electrostatic models of the intermonomer interaction

Dynamic atomic contributions to infrared intensities of fundamental bands

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