Polyiodine and Polyiodide Species in an Aqueous Solution of Iodine + KI: Theoretical and Experimental Studies

摘要

In the presence of KI, iodine crystals dissolve rapidly in an aqueous solution forming triiodide ions(I_3~-) and other neutral species. The experimental evidence does not support the formation of polyiodide ions such as I_5~-, I_7~-, etc. in the solution. However, there is a strong evidence suggesting the formation of polyiodine species, I_(2x), where X-2,3,etc., stabilized by H~+ ions in the solution. Ab initio results are presented for structures and energies of some of these species than an x value of up to 4. Each geometry optimization was done at the HF/LANL2DZ level followed by a single-point energy calculation at the MP2/LANL2DZ level. These calculations suggest the the isolated polyiodine species are not stable and, among the complexed species, the protonated clusters are most stable.