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Title: | Matrix-Isolation FTIR Spectroscopy of Benzil: Probing the Flexibility of the C−C Torsional Coordinate | Authors: | Lopes, S. Gómez-Zavaglia, A. Lapinski, L. Chattopadhyay, N. Fausto, R. |
Issue Date: | Sep-2004 | Publisher: | American Chemical Society | Serial title, monograph or event: | J. Phys. Chem. A | Volume: | 108 | 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 OC−CO 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 OC−CO 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 OC−CO dihedral angle equal to 180°. In the second case, the decrease of the average value of the OC−CO 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 OC−CO dihedral angles. | URI: | https://hdl.handle.net/10316/17883 | DOI: | 10.1021/jp047116s | Rights: | openAccess |
Appears in Collections: | FCTUC Química - Artigos em Revistas Internacionais |
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File | Description | Size | Format | |
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J.Physical Chemistry A, 108 (2004) 8256.pdf | 353.95 kB | Adobe PDF | View/Open |
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