Molecular Structure and Torsional Potential of trans-Azobenzene. A Gas Electron Diffraction Study
| Autor: | Shigehiro Konaka, Hiroshi Takeuchi, Hiroyuki Takashima, Takemasa Tsuji, Toru Egawa |
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| Rok vydání: | 2001 |
| Předmět: | |
| Zdroj: | The Journal of Physical Chemistry A. 105:9347-9353 |
| ISSN: | 1520-5215 1089-5639 |
| DOI: | 10.1021/jp004418v |
| Popis: | The molecular structure of trans-azobenzene (Ph−NN−Ph) has been determined by gas electron diffraction. Diffraction patterns were taken at 407 K and data analysis was made using the structural constraints obtained from MP2/6-31+G* calculations. Vibrational mean amplitudes and shrinkage corrections were calculated from the harmonic force constants given by a normal coordinate analysis. Vibrational mean amplitudes were refined as groups. The torsion of each phenyl ring was treated as a large amplitude vibration. The potential function for torsion was assumed to be V(φ1,φ2) = Σi=1,2{V2(1 − cos 2φi)/2 + V4(1 − cos 4φi)/2}, where φi denotes the torsional angle around each N−C bond. Quantum mechanical calculations were performed by taking account of two torsional motions to derive a probability distribution function, P(φ1,φ2). Because P(φ1,φ2) = N exp(−V(φ1,φ2)/kT) was found to be a good approximation at 407 K where N is a constant, it was adopted in the data analysis. The determined potential constants (V2 and... |
| Databáze: | OpenAIRE |
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