Isolated heterometallic Cr7Ni rings grafted on Au(111) surface

A study of the deposition of heterometallic antiferromagnetically coupled rings onto gold surfaces is reported. Twonew {Cr7Ni} rings, [NH2nPr2][Cr7NiF8(3-tpc)16] (1) (where 3-tpc ) 3-thiophenecarboxylate) and [nBuNH2CH2CH2SH][Cr7NiF8(O2CtBu)16] (2) have been made and structurally characterized. They have been deposited from the liquidphase on Au(111) and the adsorbed molecules compared by means of scanning tunneling microscopy (STM) andX-ray photoemission spectroscopy (XPS). In both cases a two-dimensional distribution of individually accessible{Cr7Ni} heterometallic rings on the gold surface has been obtained, exploiting the direct grafting of sulfur-functionalizedclusters. There is a competition between the chemisorption of the {Cr7Ni} clusters and a thiolic self-assembledmonolayer (SAM) formed by free ligands. In 2, the presence of a single sulfur ligand should force the molecule tograft with the ring axis normal to the surface. The cluster stability in the STM images and the S-2p energy positionsdemonstrate, for both functionalizations, the strength of the grafting with the gold surface.