Di-, tetra- and hexanuclear iron(III), manganese(II/III) and copper(II) complexes of Schiff-base ligands derived from 6-substituted-2-formylphenols

Abstract

Acyclic Schiff base ligands, derived from the condensation of 2,3-disubstituted benzaldehydes and 1,3-diaminopropan-2-ol, react with iron(II/III), manganese(II/III) and copper(II) salts to give di-, tetra- and hexanuclear complexes [Fe^III₂(L5)₂]·2MeOH (1), [Fe^III₄(μ₃-OMe)₂(HL4)₂Cl₂] (2), [Mn^II₂Mn^III₂(μ-OMe)₂(HL4)₂(DMF)₂]·2DMF (3) and [Cu^II₆(L5)₂(μ₅-SO₄)₂(μ-SO₄)(MeOH)₂]·H₂O·15.5(MeOH)·15.5(MeCN) (4). All compounds have been characterised by X-ray crystallography. Variable-temperature solid-state dc magnetisation studies have been performed in the temperature range 1.8–300 K. Antiferromagnetic interactions are present in all the compounds. The dinuclear compound 1 has a zero total spin ground state with J = −9.66(1) cm⁻¹ and g = 2.07(1). The magnetic data for the tetranuclear compounds 2 and 3 have been interpreted using a tetranuclear butterfly model (b = body, w = wingtip) with the parameters: J_wb = −9.35(4) cm⁻¹, J_bb = −6.02(7) cm⁻¹, zJ′ = −0.21(4) cm⁻¹ and g = 2.03(1) for 2; and J_wb = −3.40(3) cm⁻¹, J_bb = −8.11(7) cm⁻¹, zJ′ = −0.042(2) cm⁻¹ and g = 2.0 (fixed) for 3. The hexanuclear compound 4 contains two {Cu₃(L5)(MeOH)} units linked by three sulfate ligands: antiferromagnetic interactions are present in each trinuclear unit leading to two S = 1/2 motifs which do not or only very weakly interact across the sulfate bridges.