Tunneling-induced translation of intact $\pi$-radical clusters on Au(111)

The scanning tunneling microscope (STM) is a powerful tool for investigating and manipulating molecules on surfaces. We demonstrate with a low-temperature STM operated at 6.2 K the controlled manipulation of ternary clusters of persistent molecular $\pi$ radicals as a whole. The ternary clusters $-$ each self-assembled from three $\alpha ,\gamma$-bisdiphenylene-$\beta$-phenylallyl (BDPA) molecules on Au(111) $-$ maintain their natural cluster structure throughout tip-induced translation and rotation relative to the surface. Sustained and repeated dragging of radical clusters is shown to facilitate the construction of artificial assemblies of several clusters. Our results provide new opportunities for the creation and investigation of radical-based spin assemblies on surfaces.