Supramolecular chemistry. Supramolecular rectangles and their guests

Two molecular spacers which cofacially dispose terpyridyl-palladium(II)-acetonitrile units separated by similar to7 Angstrom are described. The spacers are polyaromatic molecules, one spacer is fully aromatic whereas the other has two symmetrically disposed reduced aromatic rings. Addition of the linker, 4,4'-dipyridyl, to solutions of these spacer-chelator complexes leads to the rapid and quantitative formation of supramolecular rectangles. It is found that the reduced rectangle forms a 4:1 adduct with 9-methylanthracene whereas the oxidized rectangle forms a 5:1 adduct with 9-methylanthracene. The possible reasons for this high level of agglomeration and the difference in adduct formation for the two systems are discussed.