129I Mössbauer Effect in Several Charge-Transfer Complexes of Iodine

The Mössbauer effect of the 27.8‐keV transition in ¹²⁹I has been studied in the iodine complexes I₂·phenazine, I₂·acridine, and I₂·hexamethylenetetramine. The Mössbauer spectrum of the I₂·phenazine complex has shown only one chemical species of iodine, whereas those of the other complexes have shown the existence of two species of bridging and terminal iodine. From the Mössbauer parameters such as the isomer shift, quadrupole coupling constant, and asymmetry parameter, the electron distribution on the iodine atoms in the complexes was calculated. In the I₂·phenazine complex, ${\text{0.09e}}^{-}$ is transferred to the iodine atom from the phenazine molecule. In the I₂·acridine and I₂·hexamethylenetetramine complexes, the charges on the bridging iodine atoms are decreased and those on the terminal atoms are increased. In the later complex, a net charge of ${\text{0.08e}}^{-}$ is transferred to the iodine molecule through the nitrogen atom from the hexamethylenetetramine molecule.