Synthesis and characterization of chiral trinuclear cobalt and nickel complexes supported by binaphthol-derived bis(salicylaldimine) ligands

Abstract

Chiral bis(salicylaldimine) ligands derived from binaphthol (LH2) were synthesized by condensation of (R/S) 2,2′-dihydroxy-1,1′-binaphthyl-3,3′-dicarbaldehyde with 2-anisidine. Cobalt and nickel complexes (CoL)2(OAc)2Co (1) and (NiL)2(OAc)2Ni (2) were synthesized via reactions of the ligand with the corresponding metal acetate salt. Both complexes were characterized by elemental analysis, IR, MS, and single-crystal X-ray diffraction analysis. The X-ray analysis reveals linear trinuclear for 1 and 2 and the metal ions in both complexes are octahedral coordination. The two acetates separately bridge the center metal with one of the terminal metals in M–O–C–O–M manner. The magnetic susceptibility of 1 below 150 K suggests the existence of a weak ferromagnetic exchange at low temperatures, while antiferromagnetic interactions among Co(II) cores were observed above 150 K. Complex 2 shows similar magnetic behavior to that of 1.