Keeping the Ball Rolling: Fullerene-like Molecular Clusters

摘要

Tnhe discovery of fullerenes in 1985 opened a new chapter in the chemistry ofnhighly symmetric molecules. Fullerene-like metal clusters, characterized by (multi)-nshell-like structures, are one rapidly developing class of molecules that share thisnshape. In addition to creating aesthetically pleasing molecular structures, the orderednarrangement of metal atoms within such frameworks provides the opportunity tondevelop materials with properties not readily achieved in corresponding mono-nnuclear or lower-nuclearity complexes.nIn this Account, we survey the great variety of fullerene-like metal-containingnclusters with an emphasis on their synthetic and structural chemistry, a first stepnin the discussion of this fascinating field of cluster chemistry. We group the com-npounds of interest into three categories based on the atomic composition of the clus-nter core: those with formal metal metal bonding, those characterized by ligand participation, and those supported bynpolyoxometalate building blocks. The number of clusters in the first group, containing metal metal bonds, is relatively small.nHowever, because of the unique and complex bonding scenarios observed for some of these species, these metalloid clus-nters present a number of research questions with significant ramifications. Because these cores contain molecular clustersnof precious metals at the nanoscale, they offer an opportunity to study chemical properties at size ranges from the molec-nular to nanoscale and to gain insights into the electronic structures and properties of nanomaterials of similar chemicalncompositions.nClusters of the second type, whose core structures are facilitated by ligand participation, could aid in the devel-nopment of functional materials. Of particular interest are the magnetic clusters containing both transition and lan-nthanide elements. A series of such heterometallic clusters that we prepared demonstrates diverse magnetic propertiesnincluding antiferromagnetism, ferrimagnetism, and ferromagnetism. Considering the diversity of their composition, theirndistinct electronic structures, and the disparate coordination behaviors of the different metal elements, these materi-nals suggest abundant opportunities for designing multifunctional materials with varied structures.nThe third type of clusters that we discuss are based on polyoxometalates, in particular those containing pentagonal units.nHowever, unlike in fullerene chemistry, which does not allow the use of discrete pentagonal building blocks, the metal oxide-nbased pentagonal units can be used as fundamental building blocks for constructing various Keplerate structures. These struc-ntures also have a variety of functions, including intriguing magnetic properties in some cases. Coupled with different linkingngroups, such pentagonal units can be used for the assembly of a large number of spherical molecules whose propertiesncan be tuned and optimized.nAlthough this Account focuses on the topological aspects of fullerene-like metal clusters, we hope that this topical reviewnwill stimulate more efforts in the exploratory synthesis of new fullerene-like clusters. More importantly, we hope that fur-nther study of the bonding interactions and properties of these molecules will lead to the development of new functionalnmaterials.