Role of halogen bonding in clathrate formation of tetra- and hexasalicylides derived from halogenated salicylic acids

A series of oligomeric lactones, namely tetra- and hexasalicylides 1 and 2, was synthesized from various halogenated salicylic acids by a cyclocondensation reaction using POCl3. The clathrate inclusion properties of the macrocycles for some organic solvents were investigated. X-ray structures of several representative clathrates in this series were determined and the results were used to explain various features of their thermal desolvation. Halogen bonding (in particular C–I⋯Odouble bond; length as m-dashC) was found to play a significant role in the thermal stabilization of these crystalline clathrates.