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 heterobimetallic compounds {[Mn(SB)M(CN)]·4HO} (SB = N,N'-ethylenebis(5-trimethylammoniomethylsalicylideneiminate) based on orbitally degenerate cyanidometallates [Os(CN)] () and [Ru(CN)] () and Mn Schiff base complex were synthesized and characterized structurally and magnetically. Their crystal structures consist of electrically neutral, well-isolated chains composed of alternating [M(CN)] anions and square planar [Mn(SB)] cations bridged by cyanide groups. These -ion magnetic anisotropy of Mn centers. These results indicate that the presence of compounds exhibit single-chain magnet (SCM) behavior with the energy barriers of Δ/ = 73 K, Δ/ = 41.5 K () and Δ/ = 51 K, Δ = 27 K (). Blocking temperatures of = 2.8, 2.1 K and magnetic hysteresis with coercive fields (at 1.8 K) of 8000, 1600 Oe were found for and , 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(4d/5d)-CN-Mn fragments: ---, with opposite sign of exchange parameters = -22, = +28, = -26 cm and = -18, = +20, = -18 cm in and , respectively) and single orbitally degenerate [Os(CN)] and [Ru(CN)] spin units with unquenched orbital angular momentum in the chain compounds and leads to a peculiar regime of slow magnetic relaxation, which is beyond the scope of the conventional Glaubers's Ising model and anisotropic Heisenberg model.