Origin of Ferromagnetism in Cyano-Bridged Compounds Containing d1 Octacyanometallates

Abstract

Giant-spin molecular clusters have attracted much attention in recent years in connection to the design of singlemolecule magnets (SMM) based on the phenomenon of blocking of magnetization at low temperatures.[1] One of the requirements for the polynuclear clusters to become a molecular magnet is the high value of the ground-state spin. In this respect, cyano-bridged clusters seem to be promising. Their structural and magnetic properties can easily be tuned by combining [M(CN)n] mononuclear-complex building blocks. As a result, a large variety of cyano-bridged compounds of different dimensionality ranging from clusters to three-dimensional (3D) networks have been synthesized.[2] Among them molecular magnets with high magnetic-ordering temperatures have been obtained on the basis of bimetallic and mixed-valence transition metal cyanides of the Prussian blue family.[3] Recently, two new groups of heterometallic cyano-bridged compounds have been reported.[4±7] The first corresponds to clusters with fully capped cubane structure (Figure 1) and unusually high ground-state spin. Three compounds of this structure are known to date: they are 1 with S 51/2,[4] , 2 with S 39/2,[5] and 3 with S 12.[6]