Ionic borohydride clusters for the next generation of boron thin-films: Nano-building blocks for electrochemical and ref
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Ionic borohydride clusters for the next generation of boron thin-films: Nano-building blocks for electrochemical and refractory materials Mark F. Rolla) Department of Chemical and Materials Engineering, University of Idaho, MS 1021, Moscow, Idaho 83844-31021, United States (Received 2 March 2016; accepted 20 June 2016)
Boron cluster chemistry roared to life in the 20th century with seminal discoveries outlining the incredibly versatile chemistry of boron, producing a range of neutral and ionic boron compounds that paved the way for a robust suite of hybrid materials that incorporate these electronically delocalized inorganic clusters with the additional organic flexibility. Looking toward further materials research in the 21st century, these stable, inorganic polyhedral borane clusters discovered during previous century will provide a particularly fertile ground for exploration. These stable clusters have already seen significant exploration, but their utility has been obscured by classical synthetic routes using highly toxic neutral borane compounds. This incongruity is quite ironic given the current variety of medical explorations conducted with the essentially nontoxic dodecahedral borane dianion. This article will lay out some essential context and outline key synthetic studies that may dramatically simplify access to these unique compounds to a broader community of materials scientists and engineers. I. INTRODUCTION
The assembly of compact or extended 2- and 3-D structures from molecular or nano-building blocks is of immense current interest due to the potential for unexpected, synergistic, and novel properties.1 Central to the production of such materials is tailored nano-building blocks2–4 and hierarchal mesoscale ordering,5 ultimately providing exquisitely defined, gradient properties.6,7 This concept argues for highly symmetrical nano-building blocks at smallest scale, offering diverse and easily modified functionality. In other words, a properly chosen macromolecular building block of nanometer scale should allow the design of materials on a nm by nm basis, in a “bottom-up” approach.1,8,9 Seminal studies of borane clusters by Professor William Lipscomb10–12 led to his award of the 1976 Nobel Prize.13 The isolation and characterization of the decahedral B10H102 by Lipscomb and Reddy10,14 nearly coincided with the isolation of the dodecahedral B12H122 by Hawthorne and Pitochelli15; and this foundation opened the door to studies of borane clusters by inorganic chemists around the world.16–20 Carboranes (dicarba-closo-dodecaboranes, C2B10H12) and metallacarboranes have been extensively Contributing Editor: Scott P. Beckman a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2016.261
explored and documented by Grimes21–25 and Bregadze,20 while Hosmane26,27 and others have collected and reviewed the state of boron science,28 particularly applications in boron-neutron capture therapy (BNCT),29 polymers,30–34 liquid crystals,35–37 electro-optical,32,38–40 non-linear optics,41–43
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