POM-Based Nanocomposites DOI: 10.1002/anie.200901650 Supramolecular Silver Polyoxometalate Architectures Direct the Growth of Composite Semiconducting Nanostructures** Carsten Streb, Ryo Tsunashima, Donald A. MacLaren, Thomas McGlone, Tomoyuki Akutagawa, Takayoshi Nakamura, Antonino Scandurra, Bruno Pignataro, Nikolaj Gadegaard, and Leroy Cronin* The controlled bottom-up assembly of nanostructured mate- rials from molecular precursors has great promise if molec- ular synthetic control can be translated to the nanoscale. [1] This is because the assembly of molecules in the low- nanometer domain (0.5–5 nm) is possible by bottom-up molecular self-assembly [2] yet is not possible for top-down methods owing to the present limitations of lithography (ca. 10 nm). In our own work we have hypothesized [3] that linkable polyoxometalates (POMs) (anionic transition-metal-oxide clusters) have great potential to direct nanomaterial growth, [4] since POMs themselves are molecular, yet can approach 5 nm in size for the largest known cluster. [5] Although POMs have a host of applications, [6] they have not yet been extensively exploited as precursors for the formation of composite metal oxide nanostructures, because they first need to be linked into highly organized arrays. One of the most successful assembly methods to connect POM clusters involves the coordination of secondary transition metal species, thereby giving access to a range of molecular materials with diverse structures and properties. [7] In this respect we have been using silver-based linkers to generate POM-based 0-, 1-, 2-, and 3D frameworks using cation control, in which silver ions are ligated mainly in an oxo-based ligand environment. [8] Herein, we demonstrate that it is possible to embed {Ag 3 } and {Ag 1 } units with [H 2 V 10 O 28 ] 4 clusters into supramolecular architectures, giving compounds 1, a 1D zigzag chain, and 2,a 2D network (see Figure 1). f½Ag 3 ðdmsoÞ 6 ½Ag 1 ðdmsoÞ 3 ½H 2 V 10 O 28  1 DMSOg n 1 f½Ag 3 ðdmsoÞ 6 ½Ag 1 ðdmsoÞ 2 ½H 2 V 10 O 28  2 DMSOg n 2 Furthermore, we show that these crystalline precursors can be utilized in a novel reactive-template route for the gram-scale production of composite semiconducting vana- dium oxide nanowires incorporating discrete silver nano- particles. [9] We also demonstrate that the crystalline long- range ordering of the precursors is an essential prerequisite for the nanostructure formation, as identical amorphous compounds do not yield the composite nanowires. The synthetic route for the nanowire production involves the simultaneous reduction and degradation of the silver poly- oxovanadate precursors 1 or 2 to form a composite Ag@VO x nanowire system (3) in which metallic silver nanoparticles are embedded within a semiconducting vanadium oxide VO x matrix. Compounds 1 and 2 are two structurally closely related crystalline silver polyoxovanadate precursors that were developed to investigate their transformation into nanostruc- tured composite materials. Compounds 1 and 2 were synthe- sized by the reaction of silver(I) nitrate with tetra-n-buty- lammonium decavanadate, (nBu 4 N) 3 [H 3 V 10 O 28 ] in dimethyl sulfoxide (DMSO)/acetonitrile mixtures in 49 % and 34 % yield, respectively. Single-crystal X-ray diffraction analysis, [10] along with chemical analysis, and bond valence sum calcu- lations allowed the formulae to be assigned. The crystallo- graphic analysis of the materials showed that 1 and 2 feature virtually identical structural building blocks (Figure 1). Both contain diprotonated decavanadate clusters [H 2 V 10 O 28 ] 4 (= {V 10 }) as their main backbone, which are linked by linear trimeric silver(I) DMSO units [Ag 3 (dmso) 6 ] 3+ (= {Ag 3 }) bind- ing to the cluster through coordinative Ag O V bonds. In addition, both compounds contain a monomeric silver(I) unit : In compound 1, this {Ag 1 } cap unit, [Ag(dmso) 3 ] + , acts as a capping group, resulting in the formation of 1D supramolec- ular chains. In compound 2 however, the {Ag 1 } link unit, [Ag(dmso) 2 ] + , acts as a secondary linker between neighboring clusters and results in the formation of 2D networks (Figure 2). [*] Dr. C. Streb, Dr. R. Tsunashima, T. McGlone, Prof. L. Cronin WestCHEM, Department of Chemistry The University of Glasgow Glasgow G12 8QQ (UK) Fax: (+ 44) 141-330-4888 http://www.chem.gla.ac.uk/staff/lee/index.html E-mail: l.cronin@chem.gla.ac.uk Dr. D. A. MacLaren Department Physics and Astronomy, The University of Glasgow Dr. N. Gadegaard Department of Electronics and Electrical Engineering, The University of Glasgow Prof. T. Akutagawa, Prof. T. Nakamura Research Institute for Electronic Science, Hokkaido University, Sapporo, 001-0020 (Japan) Dr. A. Scandurra Superlab—Consorzio Catania Ricerche, Catania (Italy) Prof. B. Pignataro Dipartimento di Chimica Fisica “F. Accascina”, Università di Palermo (Italy) [**] This work was supported by the EPSRC, the Leverhulme Trust, WestCHEM, and the University of Glasgow. Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/anie.200901650. Communications 6490  2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Angew. Chem. Int. Ed. 2009, 48, 6490 –6493