End-to-end azide-bridged manganese(III) chain compounds: Field-induced magnetic phase transitions and variation of T _C to 38 K depending on the side groups of the schiff bases

Three one-dimensional coordination polymers [Mn(L)(N₃)] _n [L = L1 (1), L2 (2), L3 (3); L1H₂ = N,N′-bis(5- chlorosalicylideneiminato)-1,3-diaminopentane, L2H₂ = N,N′-bis(5-bromosalicylideneiminato)-1,3-diaminopentane, L3H₂ = N,N′-bis(5-bromosalicylideneiminato)-1,3-diamino-2-dimethylpropane] bridged by end-to-end azides were prepared. The crystal systems differ according to the Schiff bases used. Each Mn atom adopts a typical Jahn-Teller distortion. The helicity of the chains occurs in a racemic manner only for 2. No noncovalent forces are relevant in 2, while π-π contacts are visible in 1 and 3. Magnetic measurements show the presence of apparent spin canting. Complexes 1 and 3 exhibit a field-induced metamagnetic transition from an antiferromagnetic state to a weak ferromagnetic phase, whereas 2 embraces a field-induced two-step magnetic phase transition. The critical temperature is observed at 38 K for 2, which is relatively higher than those for 1 (11 K) and 3 (10 K). The pronounced long-range order may contribute from intrachain exchange couplings and through-space dipolar interactions between adjacent chains.