Polymeric Manganese(II) Acetate Derivatives: Syntheses, Crystal Structures and Magnetic Properties

Three novel polymeric Mn(II) acetate derivatives, identified as {[Mn_2.5(OH)(CH₃COO)₄] ⋅ 0.5CH₃OH ⋅ 0.5CH₃CN}_n (1), {[Mn₃(CH₃CO O)₆] ⋅ 0.5CH₃CN}_n (2) and {Mn_1.5K(CH₃COO)₄}_n (3), have been successfully prepared by systematically adjusting the ratio of reactants and using the 2-mercapto-5-methyl-1,3,4-thiadiazole (Hmmt) as the template agent. These three complexes can be regarded as the different crystalline forms of Mn(CH₃COO)₂ under different reaction conditions. Single-crystal X-ray diffraction analyses revealed that 1 and 2 feature the unique three-dimensional (3D) framework. For 3, it displays a 2D structure, which is further assembled to form a 3D extended network via the weak hydrogen bond interactions. Magnetic studies confirmed that 1 and 2 show antiferromagnetic interactions, and 1 displays a long-range ordering phase below the critical temperature (T_c) of 7.8 K. In addition, magnetisation data collected for 1–2 yield low magnetic entropy changes, which can be attributed to the strong antiferromagnetic interactions among the Mn(II) centres.