Abstract
The nature and strength of the complexation of polyvinylpyrrolidone (PVP) with iodine were investigated by spectroscopic method. The complex included combined triiodide anion in the structure, and was considered to be an "inner complex" reported by Mulliken. This was supported from the fact that triethylamine, a strong electron-donor, exhibited spectroscopically same behavior as PVP and 2-pyrrolidone toward tetracyanoethylene as well as iodine in a polar medium. The apparent complexation constant was evaluated by utilizing the Langmuir isotherm equation at 30° in ethanol. The complexation constant appeared generally dependent on the size of PVP and 2-pyrrolidone molecules, and therefore the complexation between PVP and iodine may be attributed to van der Waals-type forces or the like as well as charge-transfer forces.
