Molecular rectangles from metallomacrocycles: development of dibenzofuran ligands

Two new ligands 4,6-bis(4'-pyridylsulfide)dibenzofuran L-1 and 4,6-bis(methylsulfanylmethyl) dibenzofuran L-2, based on dibenzofuran with exodentate thio-pyridine arms were prepared. The crystal structures of three metallomacro-cycles were determined. Reaction of L-1 with AgClO4 in a 1:1 metal-to-ligand ratio gave a ClO4- clamped metallomacrocycle, 1. The analogous reaction with CuCl2 gave a metallomacrocycle, 2, in which bridging chloride ions bisected the macrocycle. Both metallomacrocycles were rectangular in shape but their cavities were occluded by bridging interactions. Reaction of L-2 with CuI in a 1:2 metal-to-ligand ratio gave a metallomacrocycle, 3, in which Cu2I2 moieties were incorporated into the edge of the macrocycle. This allowed for clearly defined cavities, which formed channels containing MeCN molecules in the overall three-dimensional honeycomb array.