18-membered tetraimino macrocyclic complexes containing furan groups: Stacking of two macrocycles and characterization of organic derivatives

The structures of the Na⁺ and Pb²⁺ complexes of a 18-membered macrocycle L¹ which are prepared by the reactions of 2,5-furandicarboxaldehyde and o-phenylenediamine in the presence of metal ions were studied by X-ray diffraction. The Na⁺ complex has a methanol ligand and shows a stacking structure of the two complex cations in the crystal. The sandwich-type structure was found for the Pb²⁺ complex. Two organic products obtained in the preparations of the macrocycles containing other metal ions were also characterized by X-ray analyses. One (L^1a) is a derivative of the macrocycle in which addition of two methanol residues were found. The other product (L²) has a ring-contracted structure containing two benzimidazole residues. Structures of the macrocycles and sizes of the metal ions are discussed.