The interactions of O2N2- and O2N3-donor macrocycles with Ni(II) and Pd(II) have been investigated and four new complexes (L(1)a, L-2 L(2)c) , L(2)b and L(2)c were synthesized. In rigid 15-membered macrocyclic complex (L(1)a), the etheric oxygens are coordinated to the metal ion, while in the more flexible 17-membered macrocyclic complexes (L(2)a, L(2)b and L(2)c) the etheric oxygens are not bonded to the metal ions. Comparative FTIR, FAB, TGA, DSC, H-1- and C-13-NMR, elemental analyses, magnetic measurements as well as X-ray structure analysis (on two complexes, L(2)a and L(2)b) have been used to elucidate the nature of the species formed. The Ni(II) complexes (L(1)a and L(2)a) were found to be octahedral geometry while the Pd(II) complexes (L(2)b and L(2)c) were square planar structure. The 1,4,7-triazaheptane macrocyclic fragment in L(2)a was co-ordinated to Ni(II) ion in a facial manner as supported by the X-ray structural analysis. Two types of Pdjl) complexes have been isolated with acetate ligand, the more insoluble form contains three water molecules without bonding to Pd(II) ion, the other one has not contained any water molecule as proven by TGA and DSC data. L(2)a crystallizes in the monoclinic space group P2(1)/n with a = 15.820(1) b = 8.237(2). c = 17.529(1) Angstrom, beta = 93.17(1)degrees, V = 2280.7(5) Angstrom(3), Z = 4 and D-x = 1.527 g cm(-3). The complex has a distorted octahedral structure, incorporating the three nitrogen donors of the macrocyclic ring, two oxygen atoms of the bidentate and one oxygen atom of the monodentate nitrate ions. L(2)b crystallizes in the orthorhombic space group P cab with a = 13.791(2), b = 14.620(1), c = 29.295(2) Angstrom. V = 5705.0(9) Angstrom(3), Z = 8 and D-x = 1.444 g cm(-3). The complex contains a mononuclear Pd(II) ion in which there are three water molecules. together with one acetate ion and one acetate ligand bonded to Pd(II). The hydrogen bonds are highly effective between the water molecules, acetate ions and the macroring for stabilizing the molecule as a whole. The coordination around Pd(II) is a distorted square planar. But the close contact of the second O atom of the acetate ligand may cause to a distorted square pyramidal coordination geometry around Pd(II). (C) 2003 Elsevier B.V. All rights reserved.