COVER Voltage pulses from the tip of a scanning probe microscope induce single-molecule chemical reactions with selectivity and reversibility. Different constitutional isomers (distinguished here in shades of red, orange, and yellow) are selected by the polarity and magnitude of the voltage pulse. The findings advance the understanding of tip-induced chemistry and reduction-oxidation reactions in general. See pages 261 and 298.
Illustration: C. Bickel/Science; Structural data: Shadi Fatayer/IBM