Reaction of the ligand 1,1,7,7-tetrakis(imidazol-2-yl)-2,6-diazaheptane (H 4L) with CuCl 2 in MeCN results in the formation of an interesting 1D polynuclear copper(II) complex with formula [Cu 4(H 3L)(H 2L)Cl 3(H 2O) 2]Cl 2 · 5H 2O. The complex contains tetranuclear building blocks, and very interestingly, three of the four imidazole rings coordinated to Cu1 and Cu2 are dehydronated. Nevertheless, all the imidazolate rings are coordinated to Cu in a monodentate mode, although each dehydronated N is strongly hydrogen bonded to a lattice water molecule. The Cu–Cu distances between the copper(II) atoms in the tetranuclear units vary from 5.843 to 6.013 Å. The polynuclear complex, based on chloro-bridged Cu(II) pairs, is further stabilized by stacking interaction between imidazolate moieties and by a network of intermolecular hydrogen bonds. The differences between the ligand-field spectrum and the UV–Vis spectrum of the complex in MeOH indicate that the complex may partially dissociate in MeOH, as also evidenced by ESI-MS. The X-band EPR spectrum of the polycrystalline powder of the complex shows fairly broad isotropic signal centered at a g = 2.11, and EPR study in the MeOH solution at 77 K shows two group of signals due to [Cu(MeOH) 6] 2+ cation and the mononuclear species from the dissociated polynuclear compound. A weak antiferromagnetic interaction in dichloro-bridged Cu(II) pair dominates the magnetic behaviour of the compound.