Design of molecular rectangles by using compartmental and exo-bidentate ligands

Molecular rectangles with different sizes can be obtained by reacting a binuclear copper(II) complex, [L(μ-OH)Cu2](ClO4)2 (L=the compartmental end-off ligand, 2,6-bis[N-(2-pyridylethyl)formimidoyl]-phenolato), with bis-(4-pyridyl) derivatives (4,4′-bipyridine, 1,2-bis(4-pyridyl)ethylene). Two tetranuclear complexes have been obtained and characterized by single-crystal X-ray diffraction: [{L(μ-OH)Cu2}-(μ-4,4′-bipy)2-{Cu2(μ-OH)L}](ClO4)4·3H2O (1), and [{L(μ-OH)Cu2}-(μ-bpe)2-{Cu2(μ-OH)L}](ClO4)4·4H2O (2). Compounds 1 and 2 have been obtained also through a multicomponent self-assembly process, namely by mixing together the stoichiometric amounts of compartmental Schiff base, exo-bidentate ligand and lithium hydroxide, followed by the addition of copper(II) perchlorate.