The dinickel(II) complex of the face-to-face bicyclam ligand alpha,alpha'-bis(5,7-dimethyl-1,4,8,11-tetraazacydotetradecan-6-yl)-o-xylene (L boolean AND L) in a dimethyl sulfoxide solution exists as a mixture of high- and low-spin forms and uptakes up to three halide and pseudohalide ions (X-), according to stepwise equilibria, whose constants were determined through spectrophotometric titration experiments. In the case of halides, the first anion goes into the intermetallic cavity, whereas pseudohalides first coordinate the metal center from outside. Comparison with equilibrium data for the complex with the macrocycle 5,7-dimethy1-6-benzyl-1,4,8,11-tetraazacyclotetradecane (L) shows that the dinuclear complex [Ni-2(II)(L boolean AND L)](4+) displays an affinity for the first halide distinctly higher than the mononuclear complex [Ni-II(L)](2+), thus disclosing the existence of a bimacrocyclic effect for anion binding. Differential pulse voltammetry studies typically showed a three -peak profile: the most anodic pertaining to the [Ni-2(II)(L boolean AND L)](4+) -> Ni-2(III)(L boolean AND L)](6+) two-electron process, then one originating from the [Ni-2(II)(L boolean AND L)X](3+) -> Ni-2(III)(L boolean AND L)X](5+) two-electron process, and one deriving from the two two -electron half reactions [Ni-2(II)(L boolean AND L)X-2](2+) -> Ni-2(III)(L boolean AND L)X-2](4+) and [Ni-2(II)(L boolean AND L)X-3](+) -> Ni-2(III)(L boolean AND L)X-3](3+), taking place at nearly the same potential. The crystal structure of the Ni-2(II)(L boolean AND L) (mu-NCO) (NCO)(2)]ClO4 center dot 2.5H(2)O complex salt showed a caterpillar arrangement of the three metal -bound cyanate ions.