Interplay of Anisotropic Exchange Interactions and Single-Ion Anisotropy in Single-Chain Magnets Built from Ru/Os Cyanidometallates(III) and Mn(III) Complex

Two novel 1D heterobimetallic compounds {[Mn(III)(SB(2+))M(III)(CN)(6)]·4H(2)O}(n) (SB(2+) = N,N′-ethylenebis(5-trimethylammoniomethylsalicylideneiminate) based on orbitally degenerate cyanidometallates [Os(III)(CN)(6)](3−) (1) and [Ru(III)(CN)(6)](3−) (2) and Mn(III) Schiff base complex were synthesized and characterized structurally and magnetically. Their crystal structures consist of electrically neutral, well-isolated chains composed of alternating [M(III)(CN)(6)](3−) anions and square planar [Mn(III)(SB(2+))](3+) cations bridged by cyanide groups. These -ion magnetic anisotropy of Mn(III) centers. These results indicate that the presence of compounds exhibit single-chain magnet (SCM) behavior with the energy barriers of Δτ(1)/k(B) = 73 K, Δτ(2)/k(B) = 41.5 K (1) and Δτ(1)/k(B) = 51 K, Δτ(2) = 27 K (2). Blocking temperatures of T(B) = 2.8, 2.1 K and magnetic hysteresis with coercive fields (at 1.8 K) of 8000, 1600 Oe were found for 1 and 2, respectively. Theoretical analysis of the magnetic data reveals that their single-chain magnet behavior is a product of a complicated interplay of extremely anisotropic triaxial exchange interactions in M(III)(4d/5d)–CN–Mn(III) fragments: −J(x)S(M)(x)S(Mn)(x)−J(y)S(M)(y)S(Mn)(y)−J(z)S(M)(z)S(Mn)(z), with opposite sign of exchange parameters J(x) = −22, J(y) = +28, J(z) = −26 cm(−1) and J(x) = −18, J(y) = +20, J(z) = −18 cm(−1) in 1 and 2, respectively) and single orbitally degenerate [Os(III)(CN)(6)](3−) and [Ru(III)(CN)(6)](3−) spin units with unquenched orbital angular momentum in the chain compounds 1 and 2 leads to a peculiar regime of slow magnetic relaxation, which is beyond the scope of the conventional Glaubers’s 1D Ising model and anisotropic Heisenberg model.