The dinucleating ligand "susan" [4,7-dimethyl-1,1,10,10-tetra(2-pyridylmethyl)-1,4,7,10-tetraazadecane] has been used for the synthesis of a series of dinuclear Cu II complexes with varying exogenous ligands: [(susan){Cu(MeCN)} 2 ]-(ClO 4 ) 4 , [(susan){CuCl} 2 ]Cl 2 , [(susan){CuBr} 2 ]Br 2 , [(susan){Cu(μ-OH)Cu}](ClO 4 ) 3 , and [(susan){Cu(μ-OH)Cu}](PF 6 ) 3 . In the solid state, the Cu II ions are trigonal-bipyramidally coordinated in [(susan){Cu(μ-OH)Cu}] 3+ , whereas they are in a square-pyramidal environment in the other complexes although mononuclear Cu II complexes are trigonal-bipyramidal. In solution, all complexes are trigonal-bipyramidal; only [(susan){Cu(MeCN)} 2 ] 4+ is distorted even in solution. The UV/Vis spectra exhibit unique charge-transfer (CT) transitions, which make them easy to iden-[a] 3571 [a] X = N5, Cl1, Br1, or O3. [b] Y = N45, Cl2, Br2, or O3. [c] As there are two half molecules in the asymmetric unit, there are two different Cu···Cu distances: Cu1···Cu1′, Cu2···Cu2′.