Five pentacoordinate copper(II) complexes with 2-acetylpyridine or di(2-pyridyl) ketone 1-adamantoyl hydrazone ligands (Adpy and Addpy, respectively) of the formulae [CuCl2(Adpy)] (1), [Cu2(μ-Cl)2(Adpy-H)2] (2), [Cu(NCS)2(Adpy)] (3), [Cu2(μ-Cl)2(Addpy-H)2] (4), and [Cu2(NCS)2(μ-Addpy-H)2] (5) were synthesized and characterized by spectral, electrochemical, and X-ray structural analysis. Flow cytometry and morphological analysis confirmed that the copper(II) complexes 2 and 5 induced accumulation of a sub-G1 phase population, and fluorescence microscopy indicated the presence of large cells in apoptosis. The interaction of the copper(II) complexes with calf thymus DNA (CT-DNA) was monitored by changes in their UV/Vis spectra. The observed intrinsic binding constants for 2 and 5 (Kb = 1.77 × 106 and 3.58 × 106M–1, respectively) together with ethidium displacement fluorescence experiments indicate intercalative binding. Complexes 2 and 5 showed nuclease activity against pUC19 plasmid DNA.