Magnetic theory for MnIII–O–MnIII spin-cluster in oxo-bridged covalent complex Mn2O(5-NO2saldien)2

A theoretical method for describing magnetic-exchange-interactions in covalent molecular systems is established by introducing covalent effect into Girerd–Journaux–Kahnʹs (GJK) magnetic formula and adopting our Double-Slater-Function (DSF) calculation method. The calculations show that the exchange coupling parameter J depends sensitively on the covalent factor N; the stronger the covalent effect the stronger the antiferromagnetic exchange interaction; the direct- and kinetic- exchange interactions are both important. The calculation for MnIII–O–MnIII spin-clusters in Mn2O(5-NO2saldien)2 reveals that about 30% of the antiferromagnetic contribution comes from covalent effect, and that the theoretical values J=−111.02 to −138.85 cm−1 agree well with the experimental findings (J(expt.)=−120 cm−1).