The exploitation of versatile building blocks for the self-assembly of novel molecular magnets

Using molecular building blocks to self-assemble lattices supporting long-r ange magnetic order is currently an active area of solid-state chemistry. C onsequently, it is the realm of supramolecular chemistry that synthetic che mists are turning to in order to develop techniques for the synthesis of st ructurally well-defined supramolecular materials. In recent years we have i nvestigated the versatility and usefulness of two classes of molecular buil ding blocks, namely, tris-oxalato transition-metal (M. Pilkington and S. De curtins, in "Magnetoscience-From Molecules to Materials," Wiley-VCH, 2000), and octacyanometalate complexes (Pilkington and Decurtins, Chimia 54, 593 (2001)), for applications in the field of molecule-based magnets. Anionic, tris-chelated oxalato building blocks are able to build up two-dimensional honeycomb-layered structural motifs as well as three-dimensional decagon fr ameworks. The discrimination between the crystallization of the two- or thr ee-dimensional structures relies on the choice of the templating counterion s (Decurtins, Chimia 52, 539 (1998); Decurtins pr at. Mel. Cryst. Liq. Crys t. 273, 167 (1995); New J. Chem. 117 (1998)). These structural types displa y a range of ferro, ferri, and antiferromagnetic properties (Pilkington and Decurtins, in "Magnetoscience-From Molecules to Materials"). Octacyanometa late building blocks self-assemble to afford two new classes of cyano-bridg ed compounds namely, molecular clusters and extended three dimensional netw orks (J. Larionova et al., Angew. Chem. Int. Ed. 39, 1605 (2000); Pilkingto n et al., in preparation). The molecular cluster with a (Mn9Mo6V)-Mo-II cor e has the highest ground state spin value, S = 51/2, reported to-date (Lari onova et al., Angew. Chem. Int. Ed. 39, 1605 (2000)). In the high-temperatu re regime, the magnetic properties are characterized by ferromagnetic intra cluster coupling. In the magnetic range below 44 K, the magnetic cluster si gnature is lost as possibly a bulk behavior starts to emerge. The three-dim ensional networks exhibit both paramagnetic and ferromagnetic behavior, sin ce the magnetic properties of these materials directly reflect the electron ic configuration of the metal ion incorporated into the octacyanometalate b uilding blocks (Pilkington et al., in preparation). For both the oxalate- a nd cyanide-bridged materials, we are able to manipulate the magnetic proper ties of the supramolecular assemblies by tuning the electronic configuratio ns of the metal ions incorporated into the appropriate molecular building b locks (Pilkington and Decurtins, in "Magnetoscience-From Molecules to Mater ials," Chimia 54, 593(2000)). (C) 2001 Academic Press.