3-{[(E)-(2-Hydroxynaphthalen-1-yl)methylidene]amino}pyridinium per-chlorate.

In the title Schiff base salt, C16H13N2O(+)·ClO4 (-), the pyridine ring and the naphthalene ring system are approximately co-planar [making a dihedral angle of 6.05 (12)°] and an intra-molecular O-H⋯N hydrogen bond occurs between the hydroxyl and imino groups. In the crystal, the cations and anions are linked by N-H⋯O and weak C-H⋯O hydrogen bonds, forming the supra-molecular layers parallel to (100).

8-Hy-droxy-quinolin-1-ium hydrogen sulfate monohydrate.

In the crystal structure of the title salt hydrate, C9H8NO(+)·HSO4 (-)·H2O, the quinoline N-H atoms are hydrogen bonded to the bis-ulfate anions. The bis-ulfate anions and water mol-ecules are linked together by O-H⋯O hydrogen-bonding inter-actions. The cations and anions form separate layers alternating along the c axis, which are linked by N-H⋯O and O-H⋯O hydrogen bonds into a two-dimensional network parallel to (100).

Di-μ-chlorido-bis-[(2-amino-benzamide-κ(2) N (2),O)chlorido-copper(II)].

The title compound, [Cu2Cl4(C7H8N2O)2], crystallizes as discrete [CuLCl2]2 (L = 2-amino-benzamide) dimers with inversion symmetry. Each Cu(II) ion is five-coordinated and is bound to two bridging chloride ligands, a terminal chloride ligand and a bidentate 2-amino-benzamide ligand. The crystal structure exhibits alternating layers parallel to (010) along the b-axis direction.

Zwitterionic (E)-1-[(4-nitro-phen-yl)iminio-meth-yl]naphthalen-2-olate.

The title compound, C(17)H(12)N(2)O(3), was synthesized by the reaction of 2-hy-droxy-1-naphthaldehyde with 4-nitro-benzenamine. These condense to form the Schiff base, which crystallizes in the zwitterionic form. In the structure, the keto-amino tautomer has a fairly short intra-molecular N-H⋯O hydrogen bond between the 2-naphthalenone and amino groups, with electron delocalization.

Diaqua-(2,2'-bipyridine-κN,N')bis-(perchlorato-κO)copper(II).

The central CuN(2)O(4) motif of the title compound, [Cu(ClO(4))(2)(C(10)H(8)N(2))(H(2)O)(2)], exhibits a Jahn-Teller-distorted octa-hedral geometry around the metal atom, showing a considerably long Cu-O bond distance of 2.5058 (12) Å towards the second perchlorate group, giving a (4 + 1+1)-type coordination mode. In the crystal, the components are linked via inter-molecular O-H⋯O hydrogen bonds, forming layers parallel to (001).