Tailoring Magnetic Properties in Transition Metal–Benzene Sandwich Clusters: Ways to Design Molecular Magnets

Abstract

Transition metal–benzene (TM_nBz_n+1, with TM=Sc, Ti, and V, n=1 and 2) multiple-decker sandwich clusters have been studied by first-principles calculations. It was shown in our previous paper that in V₂Bz₃, the antiferromagnetic (AFM) and ferromagnetic (FM) states are nearly degenerate since the energy gain in FM state due to Kanamori–Terakura mechanism is compensated by the energy gain in AFM state due to polarization of edge Bzs. To design new clusters having much more stable FM state, two approaches are suggested. One is reducing the number of d electrons and the other is to weaken the hybridization strength between transition metals and edge Bz. In order to demonstrate the latter aspect, we take a thought experiment of replacing edge Bz with cyclopentadienyl ring C₅H₅. Either of these two methods or combinations of both has been demonstrated to be effective. Thus, magnetic properties of transition metal–aromatic molecule sandwich clusters can be tailored.