An Electron Diffraction Investigation of the Molecular Structure of Azulene.

Bastiansen, Otto; Derissen, J. L.; Mooney, R. W.; Kristiansen, L. A.; Brünvoll, J.; Bunnenberg, E.; Djerassi, Carl; Records, Ruth

doi:10.3891/acta.chem.scand.20-1319

Cited by 51 publications

(14 citation statements)

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“…III 1,4,5, 14 . i" Measurement by: X, X-ray diffraction; E, electron diffraction. References: (a) Ammon & Wheeler (1978); (b) Bastiansen & Derissen (1966); (c) Fallon, Ammon, Anderson, Currie & Labar (1974); (d) Ammon, Sherrer & Either (1978); (e) Ammon (1974); (f) Baron, Brown, Burden, Donaille & Kent (1972); (g) Shimanouchi, Ashida, Sasada, Murata & Kitahara (1966); (h) Shimanouchi, Sasada, Kabuto & Kitahara (1974); (i) Thomas & Coppens (1972); (k) Winter & Butters (1981); (l) Ammon, Wheeler & Agrant (1973). ing CN groups and the electron-releasing odd ring, the HOSE value drops from 17.7 to 11.8 kJ mol -t. This reason does not apply, however, to the case of unsubstituted non-alternant systems, e.g.…”

Section: Non-alternant Hydrocarbonsmentioning

confidence: 99%

Crystallographic studies and physicochemical properties of π-electron compounds. III. Stabilization energy and the Kekulé structure contributions derived from experimental bond lengths

Krygowski¹,

Anulewicz²,

Kruszewski³

1983

Acta Crystallogr Sect B

113

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Simple-harmonic-oscillator calculations of the deformation energy necessary to transform molecules with n-electron systems into their Kekul6 structures are presented. They enable estimation of (i) relative stabilization energies and (ii) Kekul6-structure contributions; both are calculated directly from experimental molecular geometries. Correlation between HOSE (Harmonic Oscillator Stabilization Energy) values and the Hess & Schaad resonance energies for alternant unsaturated hydrocarbons is very good (r = 0.991, n = 22); for non-alternant species the correlation is worse (r = 0.937, n = 12) but still acceptable. A very good correlation exists too between percentage contributions of the Kekul6 structures calculated by use of the HOSE model and those calculated by use of the quantumchemical method of Randi6 (r = 0.985, n = 65). Analysis of errors shows that only the geometries of molecules estimated with e.s.d.'s for bond lengths <0.004A are sufficiently precise for successful application of the HOSE model. The HOSE model enabled the percentage contributions of the quinoid structure to be estimated for EDA complexes of N,N,N',N'-tetramethyl-p-phenylenediamine and 7,7,8,8-tetracyano-p-quinodimethane (TCNQ); in both cases the percentage quinoid form obtained was in line with chemical expectations. For TCNQ salts a good correlation was found between the Flandrois-Chasseau• charge at TCNQ species and percentage contribution of the quinoid form calculated by use of the HOSE model (r = 0.992, n = 11). The HOSE model may serve as a convenient method of prediction and summarization of some chemical properties of molecules of n-electron compounds, directly from experimental geometry. AbstractLattice-energy calculations in the atom-atom potential approach have been performed for observed and isostructurally derived hypothetical forms of pheno-0108-7681/83/060739-04501.50 thiazine and phenoselenazine compounds. Energy minimizations with respect to cell constants and molecular rigid-body coordinates lead to absolute minima of energy surfaces in all cases. The experimental values of cell constants for the three

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Section: Non-alternant Hydrocarbonsmentioning

confidence: 99%

Crystallographic studies and physicochemical properties of π-electron compounds. III. Stabilization energy and the Kekulé structure contributions derived from experimental bond lengths

Krygowski¹,

Anulewicz²,

Kruszewski³

1983

Acta Crystallogr Sect B

113

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“…For the molecular structure in the gas phase Bastiansen & Derissen (1966) assumed C 2v symmetry in their interpretation of electron diffraction data. Huber et al (2005), showed by Fourier transform microwave spectroscopy that the isolated molecule has C 2v symmetry.…”

Section: Introductionmentioning

confidence: 99%

Azulene revisited: solid-state structure, invariom modeling and lattice-energy minimization of a classical example of disorder

Dittrich

Fabbiani

Henn³

et al. 2018

Acta Crystallogr B Struct Sci Cryst Eng Mater

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The molecular and solid-state structure of azulene both raise fundamental questions. Therefore, the disordered crystal structure of azulene was re-refined with invariom non-spherical atomic scattering factors from new single-crystal X-ray diffraction data with a resolution of d = 0.45 Å . An unconstrained refinement results in a molecular geometry with C s symmetry. Refinements constrained to fulfill C 2v symmetry, as observed in the gas phase and in highlevel ab initio calculations, lead to similar figures of merit and residual densities as unconstrained ones. Such models are consistent with the structures from microwave spectroscopy and electron diffraction, albeit they are not the same. It is shown that for the disorder present in azulene, the invariom model describes valence electron density as successfully as it does for non-disordered structures, although the disorder still leads to high correlations mainly between positional parameters. Lattice-energy minimizations on a variety of ordered model structures using dispersion-corrected DFT calculations reveal that the local deviations from the average structure are small. Despite the molecular dipole moment there is no significant molecular ordering in any spatial direction. A superposition of all ordered model structures leads to a calculated average structure, which explains not only the experimental determined atomic coordinates, but also the apparently unusual experimental anisotropic displacement parameters.

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“…To test roughly the obtained theoretical So structure data with regard to their spectroscopic suitability, the vertical S, + So transition energies, and oscillator strengths were calculated through the conventional QCFF-PI method [ 16,171. As can be seen in [33] and completely optimized molecular geometries of azulene: C-C bond distances R, (in pm) and bond angles &ijk (in 7.…”

Section: Resultsmentioning

confidence: 99%

Vibronic spectral behavior of molecules. XIII. Theoretical contribution to the vibronic coupling and the dushinsky effect on the S₁ ← S₀ absorption and the S₁ → S₀, S₂ → S₁, and S₂ → S₀ fluorescences of azulene

Gustav

Storch

1990

Int J of Quantum Chemistry

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Based on the completely optimized So, S,, and S2 molecular geometries of azulene, the vibronic structure of the S, + So absorption as well as of the S, + So, S2 + S,, and S, + So fluorescences is investigated theoretically within the adiabatic approximation. By means of theory-experiment comparisons, the influence of non-Condon terms and of the Dushinsky effect on the vibronic structure of azulene spectral behavior is discussed. Typical for the S1 + So absorption and the SI --* So fluorescence are vibronic transition moment contributions of Condon type, whereas the interpretation of azulene S2 + SI and Sz + So fluorescences is successful only within the scope of the Herzberg-Teller approach by taking into account vibronic coupling terms and, additionally, the Dushinsky effect in the latter case. An analysis of the relevant vibrational modes'is given.

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An Electron Diffraction Investigation of the Molecular Structure of Azulene.

Cited by 51 publications

References 0 publications

Crystallographic studies and physicochemical properties of π-electron compounds. III. Stabilization energy and the Kekulé structure contributions derived from experimental bond lengths

Crystallographic studies and physicochemical properties of π-electron compounds. III. Stabilization energy and the Kekulé structure contributions derived from experimental bond lengths

Azulene revisited: solid-state structure, invariom modeling and lattice-energy minimization of a classical example of disorder

Vibronic spectral behavior of molecules. XIII. Theoretical contribution to the vibronic coupling and the dushinsky effect on the S₁ ← S₀ absorption and the S₁ → S₀, S₂ → S₁, and S₂ → S₀ fluorescences of azulene

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An Electron Diffraction Investigation of the Molecular Structure of Azulene.

Cited by 51 publications

References 0 publications

Crystallographic studies and physicochemical properties of π-electron compounds. III. Stabilization energy and the Kekulé structure contributions derived from experimental bond lengths

Crystallographic studies and physicochemical properties of π-electron compounds. III. Stabilization energy and the Kekulé structure contributions derived from experimental bond lengths

Azulene revisited: solid-state structure, invariom modeling and lattice-energy minimization of a classical example of disorder

Vibronic spectral behavior of molecules. XIII. Theoretical contribution to the vibronic coupling and the dushinsky effect on the S1 ← S0 absorption and the S1 → S0, S2 → S1, and S2 → S0 fluorescences of azulene

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Vibronic spectral behavior of molecules. XIII. Theoretical contribution to the vibronic coupling and the dushinsky effect on the S₁ ← S₀ absorption and the S₁ → S₀, S₂ → S₁, and S₂ → S₀ fluorescences of azulene