SPECTROSCOPIC STUDIES OF THE REACTION OF IODINE WITH THE MIXED OXYGEN-NITROGEN CYCLIC BASE 1,4,10,13-TETRAOXA-7,16-DIAZACYCLOOCTADECANE

The reaction of iodine with the interesting mixed oxygen-nitrogen cyclic base 1,4,10,13-tetraoxa-7,16-diazacyclooctadecane (TODACOD) has been investigated spectrophotometrically in the solvent 1,2-dichloroethane. The spectra indicate the formation of the pentaiodide ion, I5-, judging from its two strong absorptions around 360 and 290 nm. Elemental analysis for the solid iodine-(TODACOD) complex indicate that the (TODACOD) base-iodine ratio is 1:3 in agreement with the ratio concluded from the photometric titration plots based on the absorptions of the formed polyiodide ion. Therefore, the formed iodine complex is formulated as [(TODACOD)I]+.I5-. The formation of the I5- species was also confirmed by the resonance Raman spectrum of the solid product. The Raman spectrum can be explained entirely by the presence of the bent I5- ion with C2-nu structure. The vibrations of I5- ion are nu-s(I-I); outer, nu-s(I-I); inner, nu-as(I-I); outer, and nu-as(I-I); inner and are assigned as expected at 164, 110, 137 and 87 cm-1, respectively.