Crystal Engineering of a New Layered Polyiodide Using 1,9-Diammoniononane as a Flexible Template Cation

The reaction of 1,9-diaminononane with hydroiodic acid in the presence of iodine gave a compound best described as 1,9-diammoniononane bis-triiodide iodine, (H3N-(CH2)9-NH3)[I3]2· I2. The structure is built from two crystallographically independent I3-anions, which are connected via secondary I···I interactions to the iodine molecules, and the 1,9-diammonioalkane cations are connected via weak hydrogen bonds to neighbouring iodine atoms. By a cooperative phenomenon, the shape and the functionality of the cation lead to a solid state structure that includes a polyiodide substructure with the formula 28[I8]2-or 28[I3· I2· I3]2-, is best described as a brick-shaped layered array. Its rectangular pores fit excellently with the hydrogen bonding functionality as well as with the conformational needs of the 1,9-diammoniononane template. The Raman spectrum shows typical bands of coordinated triiodide anions and iodine molecules. The thermal analysis (DSC/TG) of the title compound indicates decomposition at temperatures above 210°C.