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Photodissociation of C6H5I, C6F5I, and related iodides in the ultraviolet

Kavita, K and Das, Puspendu K (2002) Photodissociation of C6H5I, C6F5I, and related iodides in the ultraviolet. In: Journal of Chemical Physics, 117 (5). pp. 2038-2044.


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The quantum yields of I*(2P1/2) production from iodobenzene and pentafluoroiodobenzene at five different dissociation wavelengths of 222, 236, 266, 280, and ~305 nm are presented and compared with those obtained from nonaromatic cyclic iodides (i.e., cyclohexyl iodide and adamantyl iodide). The I(2P3/2) and I*(2P1/2) atoms generated in the photolysis of the above iodides were monitored using a two-photon laser-induced fluorescence technique. From the measured I* quantum yields, two general observations are made for aryl iodides. They are that (i) the I* yield is influenced by the \sigma* \leftarrow n as well as \pi * \leftarrow \pi transitions at all photolysis wavelengths within the A band and (ii) there is a clear indication of a fluorine substitution effect on the dynamics of I* production. The contribution from the benzene type \pi * \leftarrow \pi transition varies with excitation wavelength. Fluorine substitution in aryl iodides is found to increase the I* quantum yield similar to what is reported in alkyl iodides. The effect of fluorine substitution is more pronounced at the red edge of the A-band excitation than at any other wavelengths. This is explained by invoking the presence of a charge-transfer band arising due to the transition of a 5p\pi nonbonding iodine electron to the \pi* molecular orbital near the red edge of the A band. This charge-transfer state is coupled more strongly to the 3Q1 state of the \sigma* \leftarrow n transition in pentafluoroiodobenzene than in iodobenzene. The dynamics of I* formation is found to be unaltered by ring strain in cyclic iodides except at the blue wing excitation. At the blue wing, B-band transitions affect the dynamics of I* production in cyclic iodides, leading to the formation of more I* from adamantyl iodide.

Item Type: Journal Article
Publication: Journal of Chemical Physics
Publisher: American Institute of Physics
Additional Information: Copyright for this article belongs to American Institute of Physics (AIP).
Department/Centre: Division of Chemical Sciences > Inorganic & Physical Chemistry
Date Deposited: 30 Dec 2004
Last Modified: 19 Sep 2010 04:17
URI: http://eprints.iisc.ac.in/id/eprint/2537

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