Abstract: | Three bis-macrocyclic ligands consisting of two N3-, N2S-, or NS2-cyclononane rings, i.e., of two octahydro-1H-1,4,7-triazonine, octahydro-1,4,7-thiadiazonine, or hexahydro-5H-1,4-7-dithiazonine rings, connected by a 1H-pyrazolediyl unit were prepared. They form dinuclear CuII and NiII complexes which are able to bind one additional exogenous bridging molecule such as Cl?, Br?, N, SO, and 1H-pyrazol-1-ide. The structures determined by X-ray diffraction show that each Cu2+ is coordinated by the three donor atoms of the macrocyclic ring, by a pyrazolidodiyl N-atom, by an atom of the exogenous bridging ligand, and sometimes by a solvent molecule. In the majority of the Cu2+ cases, the metal ion exhibits square-pyramidal or trigonal-bipyramidal coordination geometry, except in the sulfato-bridged complex, in which one Cu2+ is hexacoordinated with the participation of a water molecule. The X-ray structure of the azide-bridged dinuclear Ni2+ complex was also solved and shows that both Ni2+ centres have octahedral coordination geometries. In all complexes, the 1H-pyrazolediyl group connecting the macrocycles is deprotonated and bridges the two metal centres, which, depending on the exogenous ligand, have distances between 3.6 and 4.5 Å. In the dinuclear Cu2+ complexes, antiferromagnetic coupling is present. The azido-bridged complex shows a very strong interaction with ?2J ≥ 1040 cm?1; in contrast, the H-pyrazol-1-ide and chloride bridged species have ?2J values of 300 and 272cm?1, respectively. Cyclic voltammetry of the Cu2+ complexes in MeCN reveals a strong dependence of the potentials CuII/Cu-II → CuII/CuI → CuI/CuI on the nature of the donor atoms of the macrocycle as well as on the type of bridging molecule. The more S-donors are present in the macrocycle, the higher is the potential, indicating a stabilization of the Cu1 oxidation state. |