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Normal modes and structure of iodine in the starch–iodine complex
Author(s) -
Kim Hyunyong
Publication year - 1982
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.360211102
Subject(s) - chemistry , iodine , equidistant , normal mode , raman spectroscopy , chain (unit) , valence (chemistry) , crystallography , computational chemistry , molecular physics , vibration , geometry , physics , organic chemistry , optics , quantum mechanics , mathematics
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.