Normal modes and structure of iodine in the starch–iodine complex

Abstract

Normal modes of a linear array of iodine atoms with various repeat units, (I 3−), (I 3−I 3−), (I 3−I 2−), and (I 5−), have been calculated. The four resonance Raman bands (158, 107, 57, and 27 cm−1) observed with the starch–iodine complex can be assigned to the symmetric modes of either the (I 3−I 3−)n or (I 5−)n linear chain. However, the nature of the valence force fields of these two structures is very different: the former consists of a weakly coupled linear chain of (I 3−) structure, while the latter, (I 5−)n, is a tightly bound chain approaching equidistant iodine spacings. The nearly equivalent I‐I stretching force constants obtained in the present normal mode analysis of the (I 5−)n structure is supported by the results of previous x‐ray and I‐129 Mössbauer effect measurements. A numerical method of calculating the frequency dispersions of one‐ and two‐dimensional molecular arrays is given.

Color Formation and Gelation of Xyloglucan Upon Addition of Iodine Solutions

“…The amylose-iodine complex also shows an I 5 À component. [12][13][14] These results suggest that I 5 À is the component primarily responsible for the color and formation of the complex of xyloglucan and iodine. Circular dichroism was conducted under the same conditions as the Raman spectroscopy, but the complex of xyloglucan and iodine exhibited no CD characteristics.…”

Synthesis, Structure, and Bonding in Polyiodide and Metal Iodide−Iodine Systems

“…Gabes et al have performed numerous UV/vis investigations of polyiodides, and they report that the triiodide ion has two absorption bands at 290 and 367 nm (in the solid state and in CCl 4 ) , The absorption band for pentaiodides has also been reported as occurring at about 700 nm . Higher polyiodides, such as I 7 - and I 9 - , have been reported to show the same spectral features as the triiodide and pentaiodide ions 19e.…”

Molecular iodine/polymer complexes

“…Kim [73] attributed these bands to the symmetric modes of either the (I 3¯· I 3¯)n or (I 5¯)n linear chain; the former consists of a weakly coupled linear chain of (I 3¯)n structure, while the latter, (I 5¯)n , is a tightly bound chain. Handa and Yajima [74] found that the color variation of the triiodide species in amylose was dependent on the degree of polymerization of amylose.…”