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 Δ τ 1 / k B = 73 K, Δ τ 2 / k B = 41.5 K ( 1 ) and Δ τ 1 / k B = 51 K, Δ τ 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.