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

Abstract The 129I Mössbauer spectra at 16 K have been measured for the π-σ charge transfer complexes of iodine with benzene, coronene, perylene, and poly(p-phenylene). It is suggested that the benzene-iodine complex in benzene prepared by slow cooling consists of alternate benzene and iodine molecules with the six-fold axial symmetry. The Mössbauer spectrum for the coronene-iodine complex (1:1) shows only one chemical state of iodine. The acceptor orbital is described by only the σu-antibonding molecular orbital of iodine. The extent of charge transfer in the complex is estimated to be 0.06e− in the electronic ground state. In the poly(p-phenylene)-iodine complex the iodine exists as almost a free molecule, indicating that the interaction between the phenylene ring and iodine is very weak.