Synthesis, structures and magnetic properties of heterobimetallic RuIII–3d (3d = Mn, Ni) compounds based on the chiral RuIII building block

Abstract

Two pairs of chiral cyano-bridged heterobimetallic compounds, [Mn(salen)Ru((R,R)-(5-Br-salcy))(CN)₂]_n (1), [Mn(salen)Ru((S,S)-(5-Br-salcy))(CN)₂]_n (2), [Ni(tren)][Ru((R,R)-(5-Cl-salcy))(CN)₂]₂ (3), and [Ni(tren)][Ru((S,S)-(5-Cl-salcy))(CN)₂]₂ (4) [salcy²⁻ = N,N′-(1,2-cyclohexanediylethylene) bis(salicylideneiminato) dianion, tren = tri(2-aminoethyl)amine], have been synthesized and characterized by elemental analysis, IR spectroscopy, X-ray diffraction analyses, and circular dichroism (CD) and vibrational circular dichroism (VCD) spectra. Single X-ray diffraction analysis reveals that complexes 1 and 2 possess a chiral 1D zigzag chain structure that consists of alternating (R,R/S,S)-trans-[Ru(5-Br-salcy)(CN)₂]⁻ and [Mn^III(salen)]⁺ units. Complexes 3 and 4 are trinuclear complexes in which the central Ni(II) ion is coordinated with two terminal (R,R/S,S)-trans-[Ru(5-Cl-salcy)(CN)₂]⁻ units through cyanide bridges. Investigation of magnetic susceptibilities indicates that antiferromagnetic coupling exists between the cyano-bridged Ru^III and Mn^III ions for complexes 1 and 2. An estimation of the barrier size (E_a) for 1 reveals a value of 19.1 K, with a characteristic time (τ₀) of 1.95 × 10⁻⁸. Moreover, complexes 3 and 4 exhibit ferromagnetic coupling between Ru^III and Ni^II through the cyanide bridges with J = 2.73 cm⁻¹.