The coordination chemistry towards the M(II) metal centre (M = Mn, Ni, Cu or Zn) of the hydrazone ligand (E)-2-amino-N'-[1-(pyridin-2-yl)ethylidene]benzohydrazide (H3L) has been explored and complexes having formulae [Mn(H2L)2] (1), {[Ni(H2L)2]. DMF. 0.4H2O} (2), {[Cu2(H2L)2(µ-Cl)2]. DMF} (3) and [Zn(H2L)2] (4) have been isolated and characterized by IR, UV-Visible spectroscopy, elemental analysis and Xray crystal diffraction. Structural studies reveal that the mononuclear complexes (1), (2) and (4) adopt highly distorted octahedral geometries while the dinuclear complex (3) adopts a square pyramidal geometry around each copper(II) ion.

In the title compound, C21H17N3O3, the dihydro­quinazoline ring adopts a screw-boat conformation and its stereogenic C atom has an S configuration. The dihedral angle between the mean planes of the two hy­droxy­phenyl rings is 86.61 (12)°. The amino H atom forms an intra­molecular hydrogen bond with a phenol O atom, while the hydrazine N atom acts as an acceptor for the H atom of the other phenol group. In the crystal, O—H⋯N and O—H⋯O hydrogen bonds and weak C—H⋯centroid(π-ring) inter­molecular inter­actions are observed, forming chains along [1-10] and [110].

Key indicators: single-crystal X-ray study; T = 293 K; mean (C-C) = 0.006 Å; R factor = 0.037; wR factor = 0.103; data-to-parameter ratio = 12.4.The title complex, [Cu(SO 4 ) (C 13

In the title complex, [MnCl2(C13H13N3)]·H2O, the MnII atom is in a distorted square-pyramidal environment, with an Addison τ parameter of 0.037. The coordination geometry is defined by three N-atom donors from the tridentate 2-(pyridin-2-yl)-N-(pyridin-2-yl­methyl­idene)ethanamine ligand and two terminal Cl atoms. Although the H atoms of the lattice water molecule were not located, O⋯O distances of 3.103 (7) Å and O⋯Cl distances of 3.240 (3) and 3.482 (4) Å suggest that hydrogen bonding is responsible for the stabilization of the crystal packing.