The crystal structure of the title compound has been determined. The normal four-coordinate geometry of [Cu(NN) 2] + cations (where NN denotes an α,α′-diimine chelate) is highly distorted, with a wide spread of bond lengths and angles, due to the presence of one strong intramolecular π-stacking interaction between a phenyl ring of one ligand and the coordinated bipyridyl fragment of the other.