The molecular junction is surprisingly insensitive to structural changes

The field of molecular electronics is one sown with expectation. Subtle changes in the structure of molecules could, the proponents argue, have drastic effects on their ability to transport charge. The promise of tailoring the electronic properties of circuitry using the near limitless electronic architecture of molecules is therefore extremely attractive and has enticed scientists the world over.

But amid all this excitement comes a somewhat sobering paper from perennial pie-poker George Whitesides. In a recent publication, Whitesides et al take a systematic, empirical approach to investigating these effects and come up with some results that might be described as a surprising disappointment.

In their experiment, a series of organic molecules are called upon to perform as the junction in an electrical circuit. Each molecule is the same apart from the terminal functional group, which varies in chemical nature or structure over a range of common moieties that might be expected to exert some influence on the junction’s properties. But regardless of the nature of the functional group, the performance of the junction remained effectively unchanged. Instead, the transport properties of the junction appear to depend simply upon its thickness. To borrow the authors’ own colloquialism – ‘it’s all fat’.

However, the interest of this paper lies not just in this seemingly unexpected finding but, more generally, in its significance as a report of research composed entirely of what could be viewed as ‘negative’ results.

It’s tempting to imagine an eager postgraduate, ready to deduce the rules by which molecular devices should be constructed and to pen the manual of molecular electronics by faithfully recording and interpreting the nuances borne of each delicate molecular difference. Then, after doggedly investigating, week after week, experiment after experiment, they fail to find any effect at all. Surely even the best laid plans of George Whitesides must fall foul of the vicissitudes of research? Thankfully, someone wisely advises our dejected researcher that failing to find something is itself a discovery and another Angewandte paper is born.

That is, of course, speculative fancy and may be a rather blunt cut with Occam’s butter knife. But whatever the story behind the paper it deserves a notable mention for its remarkable feat of containing no positive result. In other hands, the tiny variations that were observed might have been dissected and presented as evidence supporting the hypothesis; the results may have found their way into a minor publication or perhaps even under the carpet. Instead, the paper proudly bears its negative results and what might have been regarded as a failure becomes a thought-provoking, if not illuminating, triumph.

It is arguable that great scientists not only conduct excellent science, but also know how to spot it.

Philip Robinson

H J Yoon et al., Angew. Chem., Int. Ed., 2012, 51, 1 (DOI:10.1002/anie.201201448)

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