Intramolecular hydrogen bonding and tautomerism in Schiff bases. Part II. Structures of 1-[N-(2-pyridyl)aminomethylidene}-2(1H)-naphtalenone (1) and bis[2-hydroxy-kappa O-N-(2-pyridyl)-1-naphthaldiminato-kappa N]zinc(II) (2)

Hokelek T., KILIC Z., ISIKLAN M., TOY M.

JOURNAL OF MOLECULAR STRUCTURE, vol.523, pp.61-69, 2000 (SCI-Expanded) identifier identifier


The Schiff base ligand (1) and its Zn(II) complex (2) have been synthesized and their crystal structures have been determined. Compound (1) crystallizes in the monoclinic space group C2/c with a = 26.993(2), b = 5.891(1), c = 16.000(2) W, P = 103.29(1)degrees, V = 2476.0(6) Angstrom(3), Z = 8 and D-x = 1.332 g cm(-3) Compound (2) crystallizes in the orthorhombic space group Pbca with a = 19.580(3), b = 9.416(2), c = 27.801(2) Angstrom, V = 5125.5(6) Angstrom(3), Z = 8 and D-x = 1.451g cm(-3) In the crystal structure of the free Schiff base ligand (1), the existence of a strong intramolecular N-H...O hydrogen bond INO = 2.572(4), N-H = 0.90(4), H...O = 1.759(4) Angstrom, N-H...O = 149.6(3)degrees] is observed. The C-N amine bond and C-N-C bond angle are 1.345(4)Angstrom and 124.4(3)degrees, respectively. The C3 = O1 and C4 = C5 bond lengths [1.274(4) and 1.351(5) Angstrom] are shortened by the pronounced quinoidal effect. In solution, compound (1) is in tautomeric equilibria (phenol-imine, O-H ... N keto-amine, O ... H-N forms), as supported by H-1 NMR and UV-visible data. In the crystal structure of the Zn(II) complex (2), zinc atom has a distorted tetrahedral coordination. One of the pyridine N atom of the ligands is in close contact with the Zn(II) atom [Zn1 ... N4 = 2.864(5) Angstrom].It is interesting that the C-N amine bond [1.345(4) Angstrom] in compound (1) changes to the imine bond [1.27(5) Angstrom] in the Zn(TI) complex (2). (C) 2000 Elsevier Science B.V. All rights reserved.