Different nuclearities of M(II) nitrate complexes (M = Co, Ni, Cu and Cd) with a tetrapyridyl pendant-armed hexaazamacrocyclic ligand

A new series of nitrate M(II) (M = Co, Ni, Cu and Cd) complexes with a tetrapyridyl pendant-armed hexaazamacrocyclic ligand (L) has been synthesized. The complexes have been characterized by microanalysis, FAB-MS, conductivity measurements, IR, UV-Vis, H-1 NMR spectroscopy and magnetic measurements at room temperature. In all cases, complexes with 1: 1 and 2:1 metal:ligand molar ratios were obtained depending on the stoichiometry. Crystal structures of [Co2L(NO3)(4)] center dot 2H(2)O, [Cu2L(H2O)(2)](NO3)(4), [Cd2L(NO3)(2)](NO3)(2) center dot 5H(2)O center dot CH3CN and [CdL](NO3)(2) center dot 6H(2)O have been determined. The X-ray studies show that in [Co2L(NO3)(4)] center dot 2H(2)O and [Cu2L(H2O)(4)](NO3)(4), the metal atoms are exocyclically coordinated to the pyridine pendant arms and the tertiary amine nitrogen atoms in a distorted square pyramid [N4O] and distorted octahedral geometry [N4O2], respectively. In both cases, the pyridine rings of the macrocyclic backbone (bridgehead) are not coordinated. In contrast, in [Cd2L(NO3)(2)](NO3)(2) center dot 5H(2)O center dot CH3CN the metal atoms are coordinated by both types of pyridine group (bridgehead and pendant arm) and the tertiary amine with an [N5O2] core in a distorted capped octahedral geometry. Finally, the structure of the 1: 1 cadmium complex [CdL](NO3)(2) center dot 6H(2)O was also resolved and this showed the metal centre in a distorted octahedral geometry [N6] with the metal coordinated by both types of pyridine group and the tertiary amine. (c) 2005 Elsevier Ltd. All rights reserved.