# Cooperative Rotation and Spin State Switching of Molecules in Artificial Arrays

## TL;DR

Scientists observed how tin phthalocyanine molecules on a surface can rotate and switch spin states together when triggered by an electric current.

## Contribution

The study reveals a cooperative rotation mechanism in molecular arrays triggered by current injection and modeled with intermolecular and molecule–substrate interactions.

## Key findings

- Molecules in artificial arrays adopt two orientations with distinct spin states, forming a checkerboard pattern.
- Current injection changes the central molecule's conformation, causing all molecules to swap orientation cooperatively.
- A model combining potential energies explains the cooperative rotation and spin state switching.

## Abstract

Artificial arrays of tin phthalocyanine molecules have
been studied
on Pb(100) using scanning tunneling microscopy (STM). The molecules
adopt two azimuthal orientations with distinct spin states, which
results in a checkerboard pattern in STM images. Upon converting the
central molecule by current injection from its pristine state with
the Sn ion above the molecular plane to a conformation with Sn between
the macrocycle and the substrate, the orientations of all molecules
are swapped. This cooperative rotation is modeled by combining the
potential energies of the intermolecular and the molecule–substrate
interactions.