An ab Initio Investigation of Halocarbenes

Schwartz, M.; Marshall, Paul

doi:10.1021/jp9919213

Cited by 96 publications

(138 citation statements)

References 44 publications

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“…The mean error of the computed frequencies is only +3.0 cm -1 , indicating that the scale factor developed in our earlier work 32 extends well to the current study. The mean absolute deviation is 14.0 cm -1 .…”

Section: Resultssupporting

confidence: 88%

“…Earlier calculations in our laboratories on bromo-and iodomethylidenes, 31 carbenes, 32 and chlorofluoromethyl radicals 33 at the QCISD(T)/6-311+G(3df,2p)//QCISD/6-311G(d,p) level have yielded excellent agreement with experimental data for those species where accurately measured enthalpies are available.…”

Section: Resultssupporting

confidence: 52%

“…In earlier studies on halocarbenes 32 and chlorofluoromethyl radicals, 33 it was found that application of a scale factor of 0.955 to QCISD/6-311G(d,p) frequencies yielded excellent agreement with experiment. We therefore applied the same scale factor to our computed results for the systems studied here.…”

Section: Resultsmentioning

confidence: 81%

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A Computational Study of the Thermochemistry of Bromine- and Iodine-Containing Methanes and Methyl Radicals

2005

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Bromo-and iodomethanes and the corresponding halogenated methyl radicals have been investigated by ab initio methods. Geometries and vibrational frequencies were derived with quadratic configuration interaction methods at the QCISD/6-311G(d,p) level of theory, and energies via QCISD(T)/6-311+G(3df,2p). Core electrons were represented with relativistic effective potentials. Anharmonicity of the out-of-plane bending modes in the methyl radicals was taken into account by numerical integration of the Schrödinger equation with potentials derived from relaxed scans of these modes. The results are in good accord with experimental data where available. Thermochemistry derived via isodesmic reactions referenced to CH 3 , CH 4 , and monohalomethanes yields excellent accord with new experiments on dihalomethanes and provides recommendations for the more poorly characterized tri-and tetrahalomethanes and halomethyl radicals. For the methanes CH 2 Br 2 , CHBr 3 , CBr 4 , CH 2 I 2 , CHI 3 , CI 4 , CH 2 BrI, CHBr 2 I, and CHBrI 2 we compute ∆ f H°2 98 values of 4.3, 51.6, 110.6, 108.1, 208.5, 321.3, 56.8, 104.8, and 157.1 kJ mol -1 , respectively. For the methyl radicals CH 2 Br, CHBr 2 , CBr 3 , CH 2 I, CHI 2 , CI 3 , CHBrI, CBr 2 I, and CBrI 2 we compute ∆ f H°2 98 values of 166.6, 191.7, 224.0, 217.2, 290.4, 369.1, 241.6, 320.8, and 272.3 kJ mol -1 , respectively. Recommended confidence limits are (3 kJ mol -1 per Br or I atom. Trends in these values and the corresponding C-H bond strengths are discussed and compared with prior experiments, empirical estimation schemes, and ab initio calculations.

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Section: Resultssupporting

confidence: 88%

Section: Resultssupporting

confidence: 52%

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A Computational Study of the Thermochemistry of Bromine- and Iodine-Containing Methanes and Methyl Radicals

2005

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“…Harmonic basis functions up to h (10,30) with the restriction of v 1 ϩv 2 Ͻ30 were employed for the ground state calculation. For the Ã 1 B 1 state, harmonic basis functions of up to h (10,15) with the restriction v 1 ϩv 2 Ͻ15 were used. The total numbers of basis functions used in the variational calculations were 286 and 121 for the X 1 A 1 and Ã 1 B 1 states of CF 2 , respectively.…”

Section: Theoretical Considerations and Computational Detailsmentioning

confidence: 99%

Simulation of Ã 1B1→X̃ 1A1 CF2 single vibronic level emissions: Including anharmonic and Duschinsky effects

Chau

Dyke

Lee

et al. 2001

The Journal of Chemical Physics

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CASSCF/MRCI/aug-cc-pVQZ͑no g͒ and RCCSD͑T͒/aug-cc-pVQZ potential energy functions were reported for the Ã 1 B 1 and X 1 A 1 states of CF 2 , respectively. Vibrational wave functions of the symmetric stretching and bending modes of the two states of CF 2 were obtained in variational calculations, employing Watson's Hamiltonian for a nonlinear molecule and anharmonic vibrational wave functions expressed as linear combinations of harmonic basis functions. Franck-Condon factors ͑FCFs͒ were computed for Ã 1 B 1 →X 1 A 1 CF 2 single vibronic level ͑SVL͒ emissions and the SVL emission spectra were simulated with the computed FCFs. When compared with the observed spectra, the simulated spectra obtained in the present investigation, which include allowance for anharmonicity and the Duschinsky effect, were found to be significantly superior to those reported previously, based on the harmonic oscillator model. Using the iterative Franck-Condon analysis procedure, with the geometry of the X 1 A 1 state fixed at the recently determined experimental equilibrium geometry, the geometry of the Ã 1 B 1 state of CF 2 , which gave the best match between simulated and observed spectra, was found to be r e (CF͒ϭ1.317 Å and e (FCF)ϭ121.25°.

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“…However, significantly less attention has been paid to the heavier germanium analogues (for examples, see refs. [1][2][3], and references therein). In relation to chemical reactivity and spectroscopy, the singlet-triplet separations of these Group 14 compounds have in particular received considerable attention.…”

Section: Introductionmentioning

confidence: 99%

Ab Initio Calculations and Franck–Condon Simulation of the Absorption Spectra of GeCl₂ Including Anharmonicity

et al. 2005

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Geometrical parameters, vibrational frequencies and relative electronic energies of the X1A1, ã3B1 and A1B1 states of GeCl2 have been calculated at the CCSD(T) and/or CASSCF/MRCI level with basis sets of up to aug-cc-pV5Z quality. Core electron correlation and relativistic contributions were also investigated. RCCSD(T)/ aug-cc-pVQZ potential energy functions (PEFs) of the X1A1 and ã3B, states, and a CASSCF/MRCl/aug-cc-pVQZ PEF of the A1B1 state of GeCl2 are reported. Anharmonic vibrational wavefunctions of these electronic states of GeCl2, obtained variationally using the computed PEFs, are employed to calculate the Franck-Condon factors (FCFs) of the ã-X and A-X transitions of GeCl2. Simulated absorption spectra of these transitions based on the computed FCFs are compared with the corresponding experimental laser-induced fluorescence (LIF) spectra of Karolczak et al. [J. Chem. Phys. 1993, 98, 60-70]. Excellent agreement is obtained between the simulated absorption spectrum and observed LIF spectrum of the ã-X transition of GeCl2, which confirms the molecular carrier, the electronic states involved and the vibrational assignments of the LIF spectrum. However, comparison between the simulated absorption spectrum and experimental LIF spectrum of the A-X transition of GeCl2 leads to a revision of vibrational assignments of the LIF spectrum and suggests that the X1A1 state of GeCl2 was prepared in the experimental work, with a non-Boltzmann vibrational population distribution. The X(0,0,1) level is populated over 4000 times more than expected from a Boltzmann distribution at 60 K, which is appropriate for the relative population of the other low-lying vibrational levels, such as the X(1,0,0) and X(0,1,0) levels.

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An ab Initio Investigation of Halocarbenes

Cited by 96 publications

References 44 publications

A Computational Study of the Thermochemistry of Bromine- and Iodine-Containing Methanes and Methyl Radicals

A Computational Study of the Thermochemistry of Bromine- and Iodine-Containing Methanes and Methyl Radicals

Simulation of Ã 1B1→X̃ 1A1 CF2 single vibronic level emissions: Including anharmonic and Duschinsky effects

Ab Initio Calculations and Franck–Condon Simulation of the Absorption Spectra of GeCl₂ Including Anharmonicity

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An ab Initio Investigation of Halocarbenes

Cited by 96 publications

References 44 publications

A Computational Study of the Thermochemistry of Bromine- and Iodine-Containing Methanes and Methyl Radicals

A Computational Study of the Thermochemistry of Bromine- and Iodine-Containing Methanes and Methyl Radicals

Simulation of Ã 1B1→X̃ 1A1 CF2 single vibronic level emissions: Including anharmonic and Duschinsky effects

Ab Initio Calculations and Franck–Condon Simulation of the Absorption Spectra of GeCl2 Including Anharmonicity

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Ab Initio Calculations and Franck–Condon Simulation of the Absorption Spectra of GeCl₂ Including Anharmonicity