The first square-planar copper(II) 1:2 complex with differently coordinated 2-hydroxybenzaldehyde 4-allylthiosemicarbazone ligands.

The title compound, [(Z)-4-allyl-2-(2-hydroxybenzylidene)thiosemicarbazide-κS][(E)-4-allyl-1-(2-oxidobenzylidene)thiosemicarbazidato-κ(3)O,N(1),S]copper(II) monohydrate, [Cu(C(11)H(11)N(3)OS)(C(11)H(13)N(3)OS)]·H(2)O, crystallized as a rotational twin in the monoclinic crystal system (space group Cc) with two formula unit (Z' = 2) in the asymmetric unit, one of which contains an allyl substituent disordered over two positions. The Cu(II) atom exhibits a distorted square-planar geometry involving two differently coordinated thiosemicarbazone ligands. One ligand is bonded to the Cu(II) atom in a tridentate manner via the phenolate O, azomethine N and thioamide S atoms, while the other coordinates in a monodentate manner via the S atom only. The complex is stabilized by an intramolecular hydrogen bond, which creates a six-membered pseudo-chelate metalla-ring. The structure analysis indicates the presence of the E isomer for the tridentate ligand and the Z isomer for the monodentate ligand. The crystal structure contains a three-dimensional network built from intermolecular O-H...O, N-H...O, O-H...N and N-H...S hydrogen bonds.