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Spectroscopic Signatures of Halogens in Clathrate Hydrate Cages. 2. Iodine Galina Kerenskaya,* Ilya U. Goldschleger, V. Ara Apkarian, Everly Fleischer, and
 

Summary: Spectroscopic Signatures of Halogens in Clathrate Hydrate Cages. 2. Iodine
Galina Kerenskaya,* Ilya U. Goldschleger, V. Ara Apkarian, Everly Fleischer, and
Kenneth C. Janda
Department of Chemistry, UniVersity of California-IrVine, IrVine, California 92697
ReceiVed: June 18, 2007; In Final Form: August 14, 2007
UV-vis and Raman spectroscopy were used to study iodine molecules trapped in sII clathrate hydrate structures
stabilized by THF, CH2Cl2, or CHCl3. The spectra show that the environment for iodine inside the water cage
is significantly less perturbed than either in aqueous solution or in amorphous water-ice. The resonance
Raman progression of I2 in THF clathrate hydrate can be observed up to V ) 6 when excited at 532 nm. The
extracted vibrational frequency e ) 214 ( 1 cm-1 is the same as that of the free molecule to within
experimental error. At the same time, the UV-vis absorption spectrum of I2 in the sII hydrate exhibits a
relatively large, 1440 cm-1, blue-shift. This is mainly ascribed to the differential solvation of the I2 electronic
states. We conclude that iodine in sII hydrate resides in a 512
64
cavity, in which the ground-state I2 potential
is not significantly perturbed by the hydrate lattice. In contrast, in water and in ice, the valence absorption
band of I2 is dramatically broadened and blue-shifted by 3000 cm-1
, and the resonance Raman scattering is
effectively quenched. These observations are shown to be consistent with a strong interaction between water
molecule and iodine through the lone pair of electrons on water as in the case of bromine in the same media.

  

Source: Apkarian, V. Ara - Department of Chemistry, University of California, Irvine

 

Collections: Chemistry