On the blue color of triiodide ions in starch and starch fractions. I. Characterization and assignment of absorption and circular dichroism spectra of triiodide ions in amylose

Four fundamental Raman lines were observed at 159, 111, 55 and 27 cm ‐1 corresponding to the I bound (I ) in amyloses with DP from 20 to 100, regardless of the degree of polymerization of I and the excitation wavelength. The spectral resolution was based on the molar extinction coefficient and molar ellipticity spectra of I . Eight bands, named, S 1 , S 2 , ⃛, S 8 from long to short wavelength, were isolated. These were found regardless of the DP . By a resonance excitation Raman study, the characteristics of S 3 and S 4 , comprising the shoulder around 480 nm, were found to be different from those of S 1 and S 2 , comprising the blue band. The assignment of the spectra was based on the electronic states of the monomeric I in the exciton‐coupled dimeric unit. It was concluded that the blue band (S 1 ,S 2 ) belonged to the long‐axis transitions and the shoulder band (S 3 ,S 4 ) to the short‐axis ones on the monmeric coordinate system.