Lopes, S. ; Gómez-Zavaglia, A. ; Lapinski, L. ; Chattopadhyay, N. ; Fausto, R. (2004) Matrix-isolation FTIR spectroscopy of benzil: probing the flexibility of the CC torsional coordinate Journal of Physical Chemistry A, 108 (40). pp. 8256-8263. ISSN 1089-5639
Full text not available from this repository.
Official URL: http://pubs.acs.org/doi/abs/10.1021/jp047116s
Related URL: http://dx.doi.org/10.1021/jp047116s
Abstract
The infrared spectrum and conformational flexibility of benzil, (C6H5CO)2, are studied by matrix-isolation FTIR spectroscopy, supported by DFT calculations. It is shown that the low-frequency (ca. 25 cm-1), large-amplitude torsion around the C-C central bond strongly affects the structural and spectroscopic properties exhibited by the compound. The equilibrium conformational distribution of molecules with different O=C-C=O dihedral angles, existing at room temperature in the gas phase, and trapped in a low-temperature (T = 9 K) inert matrix can be changed either by in situ irradiation with UV light (λ > 235 nm) or by annealing the matrix to higher temperatures (T ≈ 34 K). In the first case, the increase of the average O=C-C=O angle results from conformational relaxation in the excited electronic states (S1 and T1), whose lowest-energy conformations correspond, for both S1 and T1 states, to a nearly planar configuration with the O=C-C=O dihedral angle equal to 180°. In the second case, the decrease of the average value of the O=C-C=O dihedral angle is a consequence of the change in the So C-C torsional potential, resulting from interactions with the matrix media, which favors the stability of the more polar structures with smaller O=C-C=O dihedral angles.
Item Type: | Article |
---|---|
Source: | Copyright of this article belongs to American Chemical Society. |
ID Code: | 74774 |
Deposited On: | 19 Dec 2011 04:18 |
Last Modified: | 19 Dec 2011 04:18 |
Repository Staff Only: item control page