(E)-2,4-Dihydroxy­benzaldehyde 4-ethyl­thio­semicarbazone–4,4′-bipyridine–water (4/7/2)

The asymmetric unit of the title compound, 7C(10)H(8)N(2)·4C(10)H(13)N(3)O(2)S·2H(2)O, contains two independent 2,4-hydroxy­benzaldehyde 4-ethyl­thio­semicarbazone mol­ecules, three and a half 4,4′-bipyridine mol­ecules and one water mol­ecule. Two of the 4,4′-bipyridine mol­ecules lie on general positions and the other three on centers of inversion. The two 4,4′-bipyridine mol­ecules on general positions and one of the three on special positions are disordered over two positions each with an occupancy of 0.50. The –NH—C(=S)—NH—NC fragment is close to planar in the two 2,4-hydroxy­benzaldehyde 4-ethyl­thio­semicarbazone mol­ecules (r.m.s. deviations = 0.04 and 0.05 Å). In the crystal, the Schiff base, N-heterocycle and water mol­ecules engage in O—H⋯O, O—H⋯N and N—H⋯O hydrogen-bonding inter­actions, generating a layer structure.