Tri-iodide charge-transfer complexes synthesized upon the chemical interaction between iodine and tryptophan or tyrosine
were characterized using different spectroscopic techniques (e.g., infrared, Raman, electronic, X-ray powder diffraction (XRD) and
scanning electron microscopy (SEM). The triiodide charge-transfer complexes were prepared by dry grinding of potassium iodide,
iodine and amino acid with 1:1:1 molar ratio in presence of few drops of methylene chloride solvent. The electronic spectra exhibit two
absorption bands around 360 and 280 nm due to the formation of the triiodide ion (I3
). The Raman spectra show the characteristic
bands for the triiodide ion at 160, 126 and 100 cm-1, which are assigned to  as (I-I),  s (I-I) and  (I3
), respectively. The iodine
complexes were shown to contain the triiodide species based on the electronic absorptions as well as on the Raman absorption bands
characteristic for the non-linear triiodide species, I3
, with C2v symmetry. The proposed structures of these complexes are further
supported by thermal analyses measurements. The DC electrical properties as a function of temperature of these charge transfer
complexes have been studied.