Mössbauer Effect in CsI3 and Tri-iodide Complexes of Benzamide and Amylose

Mössbauer resonance experiments have been carried out at 4.2°K on CsI3 and the tri-iodide complexes of benzamide and amylose. The data unambiguously demonstrate the existence of inequivalent iodine atoms in the tri-iodide ions of each species. For all three compounds, the quadrupole couplings of the central iodines are similar and indicate a small positive charge on the atom. The terminal iodine atoms are negatively charged, and in CsI3 are significantly different from those in the benzamide and amylose complexes. The close relationship between the Mössbauer spectra of benzamide–HI3 and amylose–I3 supports a similar configuration of the tri-iodide ions in these helical complexes, as predicted by a previous model of the blue starch–iodine complex.