Design, synthesis, structure and magnetic behavior of a high spin binuclear Fe(III) complex of N-(1-ethanol)-N,N-bis(3-tert-butyl-5-methyl-2-hydroxybenxyl) amine

The Mannich reaction of 2-aminoethanol, 2-tert-butyl-4-methylphenol, and formaldehyde at the ratio sets of 1:2:2 provided a new ligand, N-(1-ethanol)-N,N-bis(3-tert-butyl-5-methyl-2-hydroxybenxyl)amine (H3L). In the presence of base, H3L reacted with FeCl3·6H2O to form a dinuclear Fe(III) complex [Fe2L2] 1. The value of μeff at room temperature (5.95 μB), is much less than the expected spin-only value (8.37 μB) of two high spin (hs) Fe3+ (S = 5/2) ions [μ = g[∑ ZS(S + 1)]1/2], indicating there were strong interactions between Fe3+ ions. The effective magnetic moment (μeff) decreased abruptly with cooling to a minimum value of 0.1 μB at 2 K. It was worth noting that Fe3+ ions of 1 exhibited thermally induced quartet ↔ doublet spin transitions, and these transitions were abrupt. The magnetic behaviors of 1 denoted the occurrence of intramolecular anti-ferromagnetic interactions. J (− 13.58 cm− 1) agrees with the result from Gorun–Lippard equation, − J (cm− 1) = Aexp(BP(Å) = 12.9).