The reaction of cyclohexylphosphonic acid (C6H 11PO3H2), anhydrous CuCl2 and 2,2′-bipyridine (bpy) in the presence of triethylamine followed by a metathesis reaction with KNO3 afforded [Cu4(μ-Cl) 2(μ3-C6H11PO3) 2(bpy)4](NO3)2 (1). In an analogous reaction involving Cu(OAc)2•H2O, the complex [Cu 4(μ-CH3COO)2(μ3-C 6H11PO3)2(2,2′-bpy) 4](CH3COO)2 (2) has been isolated. The three-component reaction involving Cu(NO3)2•3H 2O, cyclohexylphosphonic acid and 2,2′-bipyridine in the presence of triethylamine afforded the tetranuclear assembly [Cu 4(μ-OH)(μ3-C6H11PO 3)2(2,2′-bpy)4 (H2O) 2](NO3)3 (3). Replacing 2,2′-bipyridine with 1,10-phenanthroline (phen) in the above reaction resulted in [Cu 4(μ-OH)(μ3-C6H11PO 3)2(phen)4(H2O)2](NO 3)3 (4). In all the copper(ii) phosphonates (1-4) the two phosphonate ions bridge the four copper(ii) ions in a capping coordination action. Each phosphonate ion bridges four copper(ii) ions in a μ4, η3 coordination mode or 4.211 of the Harris notation. Variable-temperature magnetic studies on 1-4 reveal that all four complexes exhibit moderately strong intramolecular antiferromagnetic coupling. The DNA cleavage activity of complexes 1-4 is also described. Compounds 1 and 3 were able to completely convert the supercoiled pBR322 DNA form I to nick form II without any co-oxidant. In contrast, 50% conversion occurred with 2 and 40% with 4. In the presence of magnesium monoperoxyphthalate all four compounds achieved rapid conversion of form I to form II. © The Royal Society of Chemistry.