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Chemoctopus has superlative redox powers

Metallodendrimer’s redox-active arms acting in unison has potential for multiple materials applications

by Stephen K. Ritter
November 28, 2016 | A version of this story appeared in Volume 94, Issue 47

An octasilsesquioxane grafted with redox-active metallacarborane arms—we’ll call it a chemoctopus—could prove to be a versatile material for a host of sensing, catalytic, and biomedical applications (Inorg. Chem. 2016, DOI: 10.1021/acs.inorgchem.6b02394). Octasilsesquioxanes are intriguing Si8O12 cubes that are favorites of materials researchers because they are easy to make. The cagey framework ensures mechanical and thermal stability, and the easily functionalized silicon atoms give rise to tunable properties. Researchers have previously prepared electroactive metallodendrimers by attaching ferrocene units to silsesquioxane cores. But these compounds haven’t always been soluble in common solvents or exhibited uniform redox activity. In the new example, a team led by Rosario Núñez of the Institute of Materials Science of Barcelona grafted metallacarboranes to the silicon atoms of octavinylsilsesquioxane via olefin metathesis. The resulting octopus-like molecules exhibit high solubility in organic solvents, the researchers note, but in addition their electrochemical studies show that the pendant metallacarboranes act as independent, one-electron redox units that can transfer eight electrons at essentially the same potential. Developing such molecules that can uniformly store and transfer many electrons is an ongoing challenge in developing molecule-based electronics.

CORRECTION: On Dec. 5, 2016, this story was updated to correct the silsesquioxane formula. It should be Si8O12 rather than Si8O8 as originally stated.

Structure of an octasilsesquioxane with pendant metallocarborane groups.
Credit: Courtesy of Rosario Núñez


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