catena-Poly[diaquabis(5-chloropyridinium-2-olato-kappaO)copper(II)]-mu-pyrazine-kappa2N:N'] diperchlorate].

In the title compound, [Cu(C(5)H(4)ClNO)(2)(C(4)H(4)N(2))(H(2)O)(2)](ClO(4))(2), the Cu atom, which lies on an inversion centre, has an octahedral environment. The pyrazine ligand also lies about an inversion centre and links adjacent Cu atoms into a chain running along the b axis; perchlorate anions occupy the space between the chains, and the chains use the coordinated water molecules to link to the anions, resulting in a hydrogen-bonded ribbon structure. The donor 5-chloro-2-hydroxypyridine ligand exists in the zwitterionic form, i.e. 5-chloropyridinium-2-olate.