Realizing a Four-Step Molecular Switch in Scanning Tunneling Microscope Manipulation of Single Chlorophyll-a Molecules

TL;DR

This study demonstrates controlled four-step conformational switching of single chlorophyll-a molecules on gold using STM manipulation, revealing electron-induced bond rotation mechanisms at cryogenic temperatures.

Contribution

It introduces a novel method for manipulating and switching single chlorophyll-a molecules via electron-induced bond rotation, advancing molecular control techniques.

Findings

Controlled four-step conformational switching achieved

Switching initiated by single-electron energy transfer

Structural analysis confirms bond rotation mechanism

Abstract

Single chlorophyll-a molecules, a vital resource for the sustenance of life on Earth, have been investigated by using scanning-tunneling-microscope manipulation and spectroscopy on a gold substrate at 4.6 K. The chlorophyll-a binds on Au(111) via its porphyrin unit while the phytyl-chain is elevated from the surface by a support of four CH3 groups. By injecting tunneling electrons from the STM-tip, we are able to bend the phytyl-chain, which enable switching of four molecular conformations in a controlled manner. Statistical analyses and structural calculations reveal that all reversible switching mechanisms are initiated by a single tunnelling-electron energy-transfer process, which induces bond rotation within the phytyl-chain.