Structure Direction, Solvent Effects, and Anion Influences in Halogen-Bonded Adducts of 2,6-Bis(iodoethynyl)pyridine

Abstract

A new divergent and self-complementary halogen bond donor–acceptor molecule 2,6-bis(iodoethynyl)pyridine L has been prepared and structurally characterized, and used to generate a series of extended halogen-bonded adducts with tetrabutylammonium halide salts. The reaction between L and anions such as either bromide or chloride gives the one-dimensional polymeric species {L·TBABr} or {L·TBACl}, respectively, which contains helical strands linked by C–I···X– halogen bonds which partially encapsulate the associated organic cations. Varying the reaction solvent from ethyl acetate to 5:95 methanol/ethyl acetate gives rise to another polymeric phase on combining L with tetrabutylammonium chloride, the one-dimensional looped chain structure {L2·TBACl} in which each chloride ion acts as a four-connected square planar node for halogen bonding interactions originating from L. Similar solvent effects are observed in the discrete macrocyclic species {L·TBAI}-α and {L·TBAI}-β, both consisting of cyclic (L2I2)2– specie...