Molecular Vibrations: The Theory of Infrared and Raman Vibrational Spectra

Wilson, Edwin Bidwell; Decius, J. C.; Cross, Paul C.; Sundheim, Benson R.

doi:10.1149/1.2430134

Cited by 1,053 publications

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“…Possible Conformations of 1-Cyanovinyl Acetate. Our DFT calculation results show that there are five possible conformers for 1-cyanovinyl acetate in gas and in CCl 4 . The optimized structures are listed in Figure 1.…”

Section: Resultsmentioning

confidence: 82%

“…The thickness of the spacer was adjusted based on the optical densities of different modes from 2.5 to 250 μm. 1-Cyanovinyl acetate was dissolved into CCl 4 , where its concentration was controlled to maintain an optical density (OD) of ∼0.5 in the measured probe frequency. The experimental optical path and apparatus after the generation of mid-IR pulses was purged with CO 2 -and H 2 O-free clean air.…”

Section: Methodsmentioning

confidence: 99%

“…4 However, most IR methods are linear, only providing information about the frequencies of molecular vibrations. In general, molecular vibrational frequencies in condensed phases are sensitive not only to the molecular bond connectivity but also to the solute/solvent interactions.…”

Section: Introductionmentioning

confidence: 99%

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Mapping Molecular Conformations with Multiple-Mode Two-Dimensional Infrared Spectroscopy

Bian

Wen

et al. 2011

J. Phys. Chem. A

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The multiple-mode two-dimensional infrared (2D-IR) spectrum in a broad frequency range from 1000 to 3200 cm−1 of a 1-cyanovinyl acetate solution in CCl4 is reported. By analyzing its relative orientations of the transition dipole moments of normal modes that cover vibrations of all chemical bonds, the three-dimensional molecular conformations and their population distributions of 1-cyanovinyl acetate are obtained, with the aid of quantum chemistry calculations that translate the experimental transition dipole moment cross angles into the cross angles among chemical bonds.

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Section: Resultsmentioning

confidence: 82%

Section: Methodsmentioning

confidence: 99%

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Mapping Molecular Conformations with Multiple-Mode Two-Dimensional Infrared Spectroscopy

Bian

Wen

et al. 2011

J. Phys. Chem. A

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“…17 The analysis was carried out using the General Vibrational Analysis System program package (QCPE program 576) developed by McIntosh and Peterson. 18 …”

Section: Normal Coordinate Analysismentioning

confidence: 99%

Synthesis, X-Ray Crystallographic Characterization, and Electronic Structure Studies of a Di-Azide Iron(III) Complex: Implications for the Azide Adducts of Iron(III) Superoxide Dismutase

et al. 2008

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We have synthesized and characterized, using X-ray crystallographic, spectroscopic, and computational techniques, a six-coordinate diazide Fe 3+ complex, LFe(N 3 ) 2 (where L is the tetradentate ligand 7-diisopropyl-1,4,7-triazacyclononane-1-acetic acid), that serves as a model of the azide adducts of Fe 3+ superoxide dismutase (Fe 3+ SOD). While previous spectroscopic studies revealed that two distinct azide-bound Fe 3+ SOD species can be obtained at cryogenic temperatures depending on protein and azide concentrations, the number of azide ligands coordinated to the Fe 3+ ion in each species has been the subject of some controversy. In the case of LFe(N 3 ) 2 , the electronic absorption and magnetic circular dichroism spectra are dominated by two broad features centered at 21 500 cm −1 (ε ≈ 4000 M −1 cm −1 ) and ~30 300 cm −1 (ε ≈ 7400 M −1 cm −1 ) attributed to N 3 − → Fe 3+ charge transfer (CT) transitions. A normal coordinate analysis of resonance Raman (RR) data obtained for LFe(N 3 ) 2 indicates that the vibrational features at 363 and 403 cm −1 correspond to the Fe-N 3 stretching modes (ν Fe-N3 ) associated with the two different azide ligands and yields Fe-N 3 force constants of 1.170 and 1.275 mdyne/Å, respectively. RR excitation profile data obtained with laser excitation between 16 000 and 22 000 cm −1 reveal that the ν Fe-N3 modes at 363 and 403 cm −1 are preferentially enhanced upon excitation in resonance with the N 3 − → Fe 3+ CT transitions at lower and higher energies, respectively. Consistent with this result, density functional theory electronic structure calculations predict a larger stabilization of the molecular orbitals of the more strongly bound azide due to increased σ-symmetry orbital overlap with the Fe 3d orbitals, thus yielding higher N 3 − → Fe 3+ CT transition energies. Comparison of our data obtained for LFe(N 3 ) 2 with those reported previously for the two azide adducts of Fe 3+ SOD provides compelling evidence that a single azide is coordinated to the Fe 3+ center in each protein species.© 2008 American Chemical Society * Author to whom correspondence should be addressed. brunold@chem.wisc.edu. Supporting Information Available: Cartesian coordinates of crystal-structure and DFT geometry-optimized LFe(N 3 ) 2 models, INDO/S-CI calculated ZFS parameters for all models of LFe(N 3 ) 2 , DFT predicted MO energies and compositions for LFe(N 3 ) 2 models, TD-DFT calculated electronic excitation energies, Abs and MCD data of LFe(N 3 ) 2 collected at 4.5 K, and analysis of VTVH MCD data collected at 20 661 cm −1 . This material is available free of charge via the Internet at

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“…A melhor descrição do movimento vibracional molecular é obtida pelo uso do sistema de coordenadas normais, cujos métodos de cálculo foram originalmente propostos por Dennison 1 . Porém, a solução completa do problema vibracional foi formulada por Wilson 2 , que utilizou a teoria de grupos para sua simplificação. Atualmente, o uso da teoria de grupo juntamente com as coordenadas normais representa o método mais apropriado para cálculo de amplitudes, bem como a correta atribuição das freqüências vibracionais.…”

Section: Introductionunclassified

Coordenadas cartesianas moleculares a partir da geometria dos modos normais de vibração

Borges¹,

Braga²,

Belchior³

2007

Quím. Nova

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MOLECULAR CARTESIAN COORDINATES FROM VIBRATIONAL NORMAL MODES GEOMETRY. A simple method to obtain molecular Cartesian coordinates as a function of vibrational normal modes is presented in this work. The method does not require the definition of special matrices, like the F and G of Wilson, neither of group theory. The Eckart's conditions together with the diagonalization of kinetic and potential energy are the only required expressions. This makes the present approach appropriate to be used as a preliminary study for more advanced concepts concerning vibrational analysis. Examples are given for diatomic and triatomic molecules.Keywords: normal modes; Cartesian coordinates; vibrational analysis. INTRODUÇÃOMoléculas não rígidas podem ser tratadas pela teoria clássica de pequenas vibrações, que estabelece os princípios da análise vibracional. A melhor descrição do movimento vibracional molecular é obtida pelo uso do sistema de coordenadas normais, cujos métodos de cálculo foram originalmente propostos por Dennison 1 . Porém, a solução completa do problema vibracional foi formulada por Wilson 2 , que utilizou a teoria de grupos para sua simplificação. Atualmente, o uso da teoria de grupo juntamente com as coordenadas normais representa o método mais apropriado para cálculo de amplitudes, bem como a correta atribuição das freqüências vibracionais.Existem, entretanto, alguns processos químicos importantes cujo entendimento requer a separação das diferentes componentes da energia cinética molecular, que são as energias rotacional, vibracional e de acoplamento rotovibracional, conhecido como acoplamento de Coriolis. Exemplos nos quais a partição da energia cinética molecular é importante em química são estudos de relaxação vibracional molecular 3 , flutuação de energia interna (de modos vibracionais para rotacionais) 4 e processos de transferência de energia em colisões moleculares 5 .Para a partição da energia cinética molecular é apropriado definir um sistema de coordenadas normais acopladas às coordenadas Cartesianas, como originalmente proposto por Crawford e Fletcher 6 . Esse método é geral e matricial, requerendo conhecimento das matrizes da teoria de pequenas vibrações 2 . No presente trabalho, é apresentada uma abordagem analítica para transformar coordenadas Cartesianas em normais. Esse método baseia-se em conceitos físicos elementares e possibilita a obtenção de equações de fácil interpretação, em alternativa ao tratamento numérico proposto na ref. 6. Exemplos simples são discutidos para moléculas diatômicas e triatômicas. DESCRIÇÃO DO MÉTODOMoléculas poliatômicas podem ser descritas por um conjunto de osciladores harmônicos com energia total dada por, sendo ν k a freqüência do modo normal de vibração Q k . O primeiro termo, do lado direito da Equação 1, representa a energia cinética e o segundo, a energia potencial. Como não existem termos cruzados nas somas em (1), as energias potencial e cinética são diagonais nessa representação. Quando se representa a figura de um modo normal, assume-se implicitamente que...

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Molecular Vibrations: The Theory of Infrared and Raman Vibrational Spectra

Cited by 1,053 publications

References 0 publications

Mapping Molecular Conformations with Multiple-Mode Two-Dimensional Infrared Spectroscopy

Mapping Molecular Conformations with Multiple-Mode Two-Dimensional Infrared Spectroscopy

Synthesis, X-Ray Crystallographic Characterization, and Electronic Structure Studies of a Di-Azide Iron(III) Complex: Implications for the Azide Adducts of Iron(III) Superoxide Dismutase

Coordenadas cartesianas moleculares a partir da geometria dos modos normais de vibração

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