Chemical Tuning of Magnetic Exchange Couplings Using Broken-Symmetry Density Functional Theory

With broken-symmetry Kohn-Sham density functional theory calculations, it is demonstrated that the ferromagnetic or anti-ferromagnetic character of two prototypical binuclear copper complexes can be modified, both in the sign and in magnitude, by means of chemical substitutions operated on the bridges connecting the two magnetic centers. The level of detail provided by the magnetic exchange decomposition in terms of direct exchange, kinetic exchange, and core polarization puts forward the relative importance of the different bridges. At variance with the principal bridge for which chemical substitutions modify both the direct and the kinetic exchange contributions, modifications of the secondary bridge only affect the magnitude of the anti-ferromagnetic kinetic exchange mechanism, ultimately allowing for a direct control of the magnetic character of the modified compound.