A new Cu-Mn heterobinuclear complex exhibiting magnetization relaxation

A new heterometallic complex CuMn(5-Brsap)₂(MeOH)(Ac)] ⋅ CH₃OH (1) (5-Brsap = 5-bromo-2-salicylideneamino-1-propanol) has been synthesized and characterized structurally as well as magnetically. Complex 1 has an alkoxo-bridged Cu(II) and Mn(III) heterobinuclear core, where the Mn(III) and Cu(II) ions have elongated octahedral and square-pyramidal geometries, respectively. In dc magnetic susceptibility measurements reveal that there is strong ferromagnetic interaction between the Mn(III) and Cu(II) ions with an exchange coupling constant J = 67.64 cm⁻¹. The ac magnetic susceptibility measurements, frequency dependence in both the real and imaginary signals is observed, which indicates slow relaxation of magnetization. An Arrhenius plot gave the effective anisotropy barrier Δ/k_B = 11.58 K and the pre-exponential factor ι₀ = 1.28 × 10⁻⁶ s.