One-dimensional end-to-end azide-bridged Mn^III complexes incorporating alkali metal ions: Slow magnetic relaxations and metamagnetism

Three azide-bridged Mn^III chains [Mn(3-MeOsalpn)(N ₃)]-0.5AClO₄ (A=Na (1), K (2), Rb (3); 3-MeOsalpn=N,Ń-propylenebis(3-methoxysalicylideneiminato) dianion) incorporating alkali metal ions and perchlorate anions were systematically synthesized. The overall structure can be described as a one-dimensional chain bridged by end-to-end azide ligands, although spatial arrangements of Jahn-Teller axes of Mn in 1 and 2 are different from that in 3. Relying on the alkali metal ions, magnetic properties are varied from a two-step phase transition (1) to metamagnetic transitions (2 and 3). In this system, spin canting definitely plays a central role in giving rise to the apparent slow magnetic relaxations in 1 and 2 because application of a high external magnetic field tends to destroy single-chain magnet (SCM) properties. Despite the existence of a long-range antiferromagnetic order at T_N, slow magnetic relaxation is notably observed in 2, which likely emanates from the operative spin canting below T_N.