Slow magnetic relaxation in a Co(ii) octahedral-tetrahedral system formed of a [CoL3]2+ core with L = bis(diphenylphosphanoxido) methane and tetrahedral [CoBr4]2- counter anions.

A bimetallic Co(ii) compound [Co(dppmO,O)3][CoBr4] consisting of cationic octahedral and anionic tetrahedral units in the crystal lattice shows a sizable magnetic anisotropy and field-supported slow magnetic relaxation with the relaxation time τ = 0.1-0.3 s at T = 1.9 K.