Absorption spectra of iodine molecule in water confirm the formation of H2O-I2 C-T complex with a shifted iodine visible band at 461 nm and a charge transfer (C-T) band at 202 nm. Iodine oxidizes water leading to the formation of I-3 ion. Absorption bands of I-3 the ion at 351 nm and 284 nm are observed in Iodine solution in water. The concentration of I-3 is about 1% of H2O-I2 C-T complex when iodine is dissolved in water with e value of 16771M-1cm-1 at 351 nm. DFT calculation shows that two I2 molecules can bind to two lone pairs of O in H2O nearly in tetrahedral geometry with stabilization energy - 8.3 kcal/M.But, one I2 bonded to one of the lone pairs on oxygen and one H2O molecule is hydrogen-bonded to the second lone pair on oxygen in nearly tetrahedral geometry is more stable with energy -8.5 kcal/M. By plotting experimental ionization energies of H2O and I2 from photoelectron spectroscopy, MOs of H2O-I2 C-T complex is constructed. C-T band at 202 nm (6.14 eV) is the excitation from the stabilized sp3 hybridized oxygen lone pair in H2O to destabilized σ* orbital of I2 in the H2O-I2 C-T complex.
Volume 134, 2022
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