Three heptadentate Zn(II) macrocyclic bis(pendant donor) Schiff-base complexes, [Zn Ln](ClO4)2 (n = 5, 6, 7) have been prepared via the Zn(II) templated [1+1] condensation of 2,6-diacetylpyridine with branched hexaamines, and characterised by X-ray diffraction, IR, 1H and 13C NMR spectroscopy. The ligands are 15-, 16- and 17-membered pentaaza macrocycles with two pendant 2-aminoethyl groups [L5 = 2,13-dimethyl-6,9-bis(2-aminoethyl)-3,6,9,12,18-pentaazabicyclo[12.3.1]octadeca-1(18), 2, 12, 14, 16-pentaene, L6 = 2,14-dimethyl-6,10-bis(2-aminoethyl)-3,6,10,13,19-pentaazabicyclo[13.3.1]nonadeca-1(19), 2, 13, 15, 17-pentaene and L7 = 2,15-dimethyl-6,11-bis(2-aminoethyl)-3,6,11,14,20-pentaazabicyclo[14.3.1]eicosa-1(20),2,14,16,18-pentaene]. The crystal structure of [Zn L5](ClO4)2, was determined by X-ray diffraction and showed that the complex cation that had formed consisted of a pentagonal bipyramidally coordinated Zn(II) ion, centrally located in a pentaaza macrocycle, with two pendant amines coordinating on opposite sides of a plane defined by the macrocycle and the metal ion. The spectroscopic characterisation of the three complexes is consistent with them all having this basic structure.
