MONONUCLEAR AND BINUCLEAR COPPER(II) COMPLEXES OF AZAPARACYCLOPHANES WITH A SINGLE AROMATIC SPACER - CRYSTAL-STRUCTURE OF [CU(2)L(2)CL(4)]CENTER-DOT-1.5H(2)O (L(2)=2,5,8,11-TETRAAZA[12]PARACYCLOPHANE)

The protonation behaviour of-the azaparacyclophanes 2,6,9,13-tetraaza[14]paracyclophane (L(1)), 2,5,8,11-tetraaza[12] paracyclophane (L(2)) and 2,5,8,11,14-pentaaza[15] paracyclophane (L(3)) has been studied at 298.1 K in 0.15 mol dm(-3) NaClO4 by potentiometry, direct microcalorimetry, and H-1 and C-13 NMR spectroscopy. The data obtained by the different techniques suggest that first protonation of L(1) and L(2) occurs mainly on the benzylic nitrogens. All three ligands form mononuclear copper(II) complexes in aqueous solution characterized by an incomplete participation of the nitrogen donors in the co-ordination to the metal ion. The ligands L(2) and L(3) also form the binuclear species [Cu(2)L(2)(OH)(2)](2+) and [Cu(2)L(3)](4+), f [Cu(2)L(3)(OH)](3+) and [Cu(2)L(3)(OH)(2)](2+) in solution. The crystal structure of the complex [Cu(2)L(2)Cl(4)].1.5H(2)O has been solved by X-ray crystal diffraction analysis [space group P2(1)/n, a = 10.625(3), b = 14.014(3). c = 14.952(7) Angstrom, beta = 109.55(3)degrees, Z = 4, R = 0.066 and R' = 0.066]. Both metal ions show a distorted square-pyramidal co-ordination geometry. The basal plane is defined for each metal centre by a benzylic nitrogen atom, the adjacent nitrogen atom in the chain and two chloride ions. The apical position is occupied by another chloride from a symmetry-related molecule:with a much weaker bond than those in the plane. The presence of the para-phenylene subunit imposes enough strain to divide the macrocyclic cavity of L(2) into two separate ethylenediamine subunits.