I62- anion composed of two asymmetric triiodide moieties: A competition between halogen and hydrogen bond

Abstract

The reaction of 1,8-diaminooctane with hydroiodic acid in the presence of iodine gave a new polyiodide-containing salt: 1,8-diaminiumoctane bis(triiodide), (H3N- (CH2)8-NH3)[I3]2. The title compound has been characterized by crystallographic and spectroscopic methods. The polyiodide ion is the first example of a hydrogen bonded I62- dianion consisting of two very asymmetric triiodide components with I-I distances of 2.7739(4) and 3.1778(4) Å interacting by a weak halogen bond (I···I: 3.5017(2) Å). The structural parameters of the triiodide anions, derived from X-ray crystallographic data, are in good agreement with the Raman and Far-IR spectroscopic results.