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

Kavita, K. ; Das, Puspendu K. (2002) Photodissociation of C6H5I, C6F5I, and related iodides in the ultraviolet Journal of Chemical Physics, 117 (5). pp. 2038-2044. ISSN 0021-9606

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The quantum yields of I(2P½) 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(2P½) 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 σ←n as well as π←π 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 π←π 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 5pπ nonbonding iodine electron to the π molecular orbital near the red edge of the A band. This charge-transfer state is coupled more strongly to the 3Q1 state of the σ←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:Article
Source:Copyright of this article belongs to American Institute of Physics.
Keywords:Organic Compounds; Photodissociation; Two-photon Spectra; Fluorescence; Charge Transfer States
ID Code:86342
Deposited On:09 Mar 2012 10:41
Last Modified:09 Mar 2012 10:41

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