Dinuclear complexes of M^II Thiocyanate (M = Ni and Cu) containing a tridentate Schiff-base ligand: synthesis, structural diversity and magnetic properties

Abstract

A dinuclear Ni^II complex, [Ni₂(L) ₂(H₂O)(NCS) ₂]•3H₂O (1) in which the metal atoms are bridged by one water molecule and two μ ₂-phenolate ions and a thiocyanato-bridged dimeric Cu^II complex, [Cu(L)NCS] ₂ (2) [L = tridentate Schiff-base ligand, N-(3-aminopropyl)salicylaldimine, derived from 1:1 condensation of salicylaldehyde and 1,3-diaminopropane], have been synthesized and characterized by IR and UV/vis spectroscopy, cyclic voltammetry and single-crystal X-ray diffraction studies. The structure of 1 consists of dinuclear units with crystallographic C₂ symmetry in which each Ni^II atom is in a distorted octahedral environment. The Ni–O distance and the Ni–O–Ni angle, through the bridged water molecule, are 2.240(11) Å and 82.5(5)°, respectively. The structure of 2 consists of dinuclear units bridged asymmetrically by di-μ_1,3-NCS ions; each Cu^II ion is in a square-pyramidal environment with τ = 0.25. Variable-temperature magnetic susceptibility studies indicate the presence of dominant ferromagnetic exchange coupling in complex 1 with J = 3.1 cm^–1, whereas complex 2 exhibits weak antiferromagnetic coupling between the Cu^II centers with J = –1.7 cm^–1.