MnIII zero-field splitting parameters and weak exchange interactions in a cyanide-bridged {MnIII–IrIII–MnIII} cluster

Abstract The reaction of [Mn III (5-Brsalen)(MeOH)](ClO 4 ) (5-Brsalen 2 −  =  N , N′ -ethylenebis(5-bromosalicylidene-iminate)) with [Ir III (CN) 6 ] 3 − yields a trinuclear, cyanide-bridged Mn III –Ir III –Mn III cluster which is a member of an isostructural series of Mn III –M III –Mn III clusters. The presence of the large, diamagnetic [Ir III (CN) 6 ] 3 − bridging unit facilitates a precise determination of the Mn III zero-field splitting (zfs) parameters by the combined use of inelastic neutron scattering, high-field, high-frequency EPR spectroscopy and magnetic measurements. The single-ion axial ( D ) and rhombic ( E ) zfs parameters are found to be D  = − 3.72(5) cm − 1 and | E | = 0.21(1) cm − 1 . The experimental data are consistent with a small, antiferromagnetic exchange interaction between the two Mn III ions.