I5 – polymers with a layered arrangement: synthesis, spectroscopy, and structure of a new polyiodide salt in the nicotine/HI/I2 system

Abstract

Abstract The reaction of S-nicotine with hydroiodic acid in the presence of iodine gave the new polyiodide-containing salt nicotine-1,1′-diium bis(triiodide)-diiodine (1/1) (C10H16N2) [I3]2·I2 (1). The title compound has been characterised by spectroscopic methods (Raman and IR) and single-crystal X-ray diffraction. The asymmetric unit of the title structure consists of one dication, two triiodide anions, and one iodine molecule, all located in general positions in the non-centrosymmetric space group P1. One of the two crystallographically independent triiodide anions and the doubly protonated nicotinium dication form hydrogen-bonded chains along b, which are arranged parallel to each other in the ½bc plane. The second crystallographically independent triiodide anion and the iodine molecule form an I5 – moiety, which is end-on connected to two symmetry-related anions resulting in polyiode zig–zag chains along the [0 1 1̅] direction. These polyiodide chains are stacked parallel to each other in the 0bc plane. The Raman spectrum of the title compound shows characteristic lines in the 50–200 cm–1 range, which are in excellent agreement with the findings derived from the crystal structure.