Synthesis and characterization of azathiaethers macrocyclic rings decorated with one or two 2-pyridylmethyl fragments

Monoaza-dithia- (1a ? 3a) and diaza-tetrathia- (1b and 3b) macrocycles with a pendant 2-pyridylmethyl fragment have been prepared by the reaction between 2-(aminomethyl)pyridine with dibromide-dithioether derivatives. Four of the macrocycles have been characterized by X-ray crystallography, revealing the formation of two 14- and 15-membered monoaza-dithiaethers, and two 26- and 30-membered diaza-tetrathiaether macrocycles featuring one or two exo-2-pyridylmethyl fragments, respectively. The monoaza-dithiaethers macrorings adopt a twisted conformation while the diaza-tetrathiaethers macrorings display a rectangular conformation. Intramolecular interactions of macrorings 2a, 3a, 1b and 3b were studied by non-covalent interaction analysis. It was found that smaller macrorings are less stable than larger ones due to larger strain energies and that intramolecular dispersive interactions and hydrogen bonding play an important role in the macrocycle conformation adopted.