Hydrogen bonded 1,10-diammoniodecane – an example of an organo-template for the crystal engineering of polymeric polyiodides

Abstract

Using the rod-like 1,10-diammoniodecane (dadH₂) as a template it is possible to synthesize and crystallize the two polyiodide compounds (dadH₂)₂I₂[I₃]₂ (1) and dadH₂[I₃]₂·I₂·2H₂O (2). Compound 1 crystallizes in the polar monoclinic space group P2₁ with eight iodine atoms and two all-trans conformated 1,10-diammoniodecanes in the asymmetric unit. The structure is built by the dications and the two iodide anions forming a hydrogen bonded framework in which channels contain the two crystallographically independent I₃⁻ anions. These I₃⁻ anions are interconnected via extremely weak I⋯I interactions to a one-dimensional polymer with the I₃⁻ units linked to each other. They do not form hydrogen bonds of reasonable strength to the host framework. Compound 2 crystallizes in the centrosymmetric space group P2₁/n. The 1,10-diammonioalkane cations are lying on centres of symmetry and are showing an all-trans conformation. These cations form a sub-structure that is built by hydrogen bonded ribbons of 1,10-diammoniodecanes and water molecules in the ratio 1∶2. These ribbons act as polymeric templates for the formation of a iodine–iodide framework. This anionic sub-structure is best described as a three-dimensional framework built by I₂ molecules and I₃⁻ anions showing the habit of a herring-bone motif. Neglecting the weak I⋯I interactions of ca. 4 Å the polyiodide framework can be separated into outstretched, Z-shaped [I₃⋯I₂⋯I₃]²⁻ sub-units lying on centres of symmetry. In the structures of the compounds 1 and 2 the 1,10-diammoniodecane cations form hydrogen bonded ring motifs that may be classified to Etter's rules as R²₄(30) with the iodide anions in 1 and water molecules in 2 acting as hydrogen bond acceptors. The crystal structure of the 1,10-diaminodecane (3) has been determined. This ‘soft as butter’ material crystallizes in the centrosymmetric space group Pbca with the molecules lying on a centre of symmetry and shows nearly ideal all-trans conformation. Only weak N–H⋯N hydrogen bonds occur between neighbouring molecules to form a layered structure. The molecules are arranged in the ac plane to form a herring-bone motif with the building ring motifs classified according Etter's rules with the symbol R⁴₄(30).