The reaction of a tripodal ligand (H2L = N, N-bis(2-hydroxybenzyl)-N', N'-dimethylethylenediamine) with Cu(NO3)(2).3H(2)O and Cu(ClO4)(2).6H(2)O in methanol yielded [Cu-2 (HL)(2)](NO3)(2).H2O (1) and [Cu-2 (HL)(2)](ClO4)(2) (1'), respectively. When H2L was allowed to react with CuSO4.5H(2)O in the presence of triethylamine (1 : 1 : 2) in methanol, the neutral dicopper(II,II) complex [Cu-2 (L)(2)] (2) was obtained. The monopositive species [Cu-2 (L)(HL)] ClO4. CH3OH.H2O (3) crystallized on mixing 1' and 2 (1 : 1) in methanol-dichloromethane. The crystal structures of 1, 2, and 3 were determined by X-ray crystallography. All of the complexes consist of a discrete dinuclear molecule with bis(mu-phenoxide)-bridges. The tripodal ligand functions as a tetradentate ligand and one of the phenolic oxygen atoms serves as a bridging ligand. Protonation/deprotonation takes place at the terminal phenol moiety and as the phenol group is deprotonated the coordination geometry changes from a distorted square pyramid to a distorted trigonal bipyramid. The two copper ions in 1-3 are antiferromagnetically coupled with 2J = -714 (1), -19.9 (2), and -277 cm(-1) (3). The results clearly demonstrate that protonation/deprotonation causes a change in coordination geometry, which in turn drastically affects magnetic exchange interactions.