Dinuclear and 1D iron(iii) Schiff base complexes bridged by 4-salicylideneamino-1,2,4-triazolate: X-ray structures and magnetic properties

Abstract

Four new iron(III) complexes were obtained by the reaction of 4-salicylideneamino-1,2,4-triazole (Hsaltrz) and selected dinuclear μ-oxo-bridged iron(III) Schiff base complexes [{FeL⁴}₂(μ-O)], where L⁴ represents a terminal tetradentate dianionic Schiff-base ligand. X-ray structural analysis revealed a novel bridging mode of κN,κO of the saltrz ligand to form dinuclear complexes [{Fe(salen)(μ-saltrz)}₂]·CH₃OH (1) (H₂salen = N,N′-ethylenebis(salicylimine)) and [{Fe(salpn)(μ-saltrz)}₂] (2) (H₂salpn = N,N′-1,2-propylenbis(salicylimine)), whereas one-dimensional (1D) zig-zag chains were formed in the case of [{Fe(salch)(μ-saltrz)}·0.5CH₃OH]_n (3) (H₂salch = N,N′-cyclohexanebis(salicylimine)) and [Fe(salophen)(μ-saltrz)]_n (4) (H₂salophen = N,N′-o-phenylenebis(salicylimine)). It was also shown that the rigidity of the terminal ligand L⁴ can be considered as the key factor for the molecular dimensionality of the products. The thorough magnetic analysis based on SQUID experiments, including the isotropic exchange and the zero-field splitting of both temperature and field dependent data, was performed for dimeric (1 and 2) and also for polymeric compounds (3 and 4) and revealed weak antiferromagnetic exchange mediated by the saltrz anions with much larger D-parameter (|D| ≫ |J|).