cyclo-Tetra­kis{μ-N′-[(8-oxidoquinolin-7-yl)methyl­idene]isonicotino­hydrazidato}tetra­zinc tetra­hydrate

In the title compound, [Zn(4)(C(16)H(10)N(4)O(2))(4)]·4H(2)O, the N′-[(8-oxidoquinolin-7-yl)methyl­idene]isonicotinohydrazidate (L (2−)) ligand binds to the metal ions, forming stable five- and six-membered chelate rings, leaving the pyridyl groups free. The compound is a tetra­nuclear Zn(II) complex centered about a fourfold roto-inversion axis, with the ligand coordinating in the doubly deprotonated form. The Zn(II) atom has a distorted square-pyramidal geometry being coordinated by one N and two O-atom donors from the doubly deprotonated L (2−) ligand, and by one N atom and one O-atom donor from a symmetry-related L (2−) ligand. In the crystal, four symmetry-related lattice water mol­ecules, centred about a fourfold roto-inversion axis, form a cyclic tetra­mer through O—H⋯O hydrogen bonds. These tetra­mers connect to the complex mol­ecules through O—H⋯N hydrogen bonds, forming a chain propagating along [100]. Neighbouring mol­ecules are linked by π–π inter­actions [centroid–centroid distance = 3.660 (2) Å] involving the quinolidine rings.