Polyiodine units in starch–iodine complex: INDO CI study of spectra and comparison with experiments

Mark Minick, Kristen Fotta, Arshad Khan

Research output: Contribution to journalArticle

23 Scopus citations

Abstract

The starch–iodine blue complex formation does not involve negatively charged iodine species like I 3−, I 5−, or I 7−; rather, neutral iodine units are involved. The heat of reaction is determined to be about −110 kJ for every mole of I‐I unit in the amylose helix, which suggests that the dissociation of I2 (binding energy 149 kJ/mol) does not take place during the complex formation. Quantum mechanical (INDO CI) calculations indicate that the linear as well as nonlinear polyiodine units, I6, with interiodine distance of 3.0 Å are responsible for characteristic absorbance bands of the starch–iodine complex. Based on our previous article [(1989) J. Polym. Sci. A 27, 4161] and the present studies we identify (C6H10O5)16.5I6 to be the polymeric unit responsible for the characteristic blue color of the complex.

Original languageEnglish (US)
Pages (from-to)57-63
Number of pages7
JournalBiopolymers
Volume31
Issue number1
DOIs
StatePublished - Jan 1991

All Science Journal Classification (ASJC) codes

  • Biophysics
  • Biochemistry
  • Biomaterials
  • Organic Chemistry

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