Use of a Reduced Schiff-Base Ligand to Prepare Novel Chloro-Bridged Chains of Rare Cu(II) Trinuclear Complexes with Mixed Azido/Oxo and Chloro/Oxo Bridges

Two mixed bridged one-dimensional (1D) polynuclear complexes, [Cu₃L₂(μ_1,1-N₃)₂(μ-Cl)Cl]_n (1) and {[Cu₃L₂(μ-Cl)₃Cl]·0.46CH₃OH}_n (2), have been synthesized using the tridentate reduced Schiff-base ligand HL (2-[(2-dimethylamino-ethylamino)-methyl]-phenol). The complexes have been characterized by X-ray structural analyses and variable-temperature magnetic susceptibility measurements. In both complexes the basic trinuclear angular units are joined together by weak chloro bridges to form a 1D chain. The trinuclear structure of 1 is composed of two terminal square planar [Cu(L)(μ_1,1-N₃)] units connected by a central Cu(II) atom through bridging nitrogen atoms of end-on azido ligands and the phenoxo oxygen atom of the tridentate ligand. These four coordinating atoms along with a chloride ion form a distorted trigonal bipyramidal geometry around the central Cu(II). The structure of 2 is similar; the only difference being a Cl bridge replacing the μ_1,1-N₃ bridge in the trinuclear unit. The magnetic properties of both trinuclear complexes can be very well reproduced with a simple linear symmetrical trimer model (H = −JS_iS_i+1) with only one intracluster exchange coupling (J) including a weak intertrimer interaction (j) reproduced with the molecular field approximation. This model provides very satisfactory fits for both complexes in the whole temperature range with the following parameters: g = 2.136(3), J = −93.9(3) cm⁻¹ and zj = −0.90(3) cm⁻¹ (z = 2) for 1 and g = 2.073(7), J = −44.9(4) cm⁻¹ and zJ′ = −1.26(6) cm⁻¹ (z = 2) for 2.