Nickel(II) and tridentate 8-hydroxyquinoline-2-carbaldehyde-N-methylnitrone (HL):: enantioselective association of octahedral [M(HL)(L)]+ moieties driven by strong hydrogen bonding

The novel organic tridentate ligand, 8-hydroxyquinoline-2-carbaldehyde-N-methylnitrone (HL), has been synthesized and used for the design of a metal-organic system capable of self-association. Interaction of the nitrone HL with nickel nitrate afforded the hydrogen nitronate complex [Ni(HL)(L)](2)(NO3). 7H(2)O, which was characterized by means of X-ray diffraction. The coordination environment of the metal atoms consists of four oxygen and two nitrogen atoms from neutral and-anionic forms of the ligand. [Ni(HL)(L)](+) cations possess a set of self-complementary H-bond donor/acceptor sites and dimerize via strong hydrogen bonding (O . . .O 2.43, 2.45 -Angstrom) forming supramolecular dications [Ni(HL)(L)](2) (2+). Dimerization occurs enantioselectively between [Ni(HL)(L)](+) moieties of the same chirality and the resulting dimeric ensemble is inherently chiral. The stability of the dimer is essentially influenced by stacking interactions between two pairs of aromatic frames. (C) 2001 Elsevier Science B.V. All rights reserved.