Successful grafting of isolated molecular Cr7 Ni rings on Au(111) surface

We deeply investigated the properties of submonolayer distributions of isolated molecular Cr7 Ni rings deposited on Au(111) by liquid phase. X-ray absorption spectra measured at the Cr and Ni L2,3 edges show that the grafting of the Cr7 Ni rings onto the gold surface does not affect the oxidation state and the local symmetry of the Cr and Ni sites. The circular dichroism shows a change in sign of the Ni magnetic moment. This is due to a reduction in the exchange coupling constants that, however, preserves the structure of the low-energy levels of the grafted rings, as corroborated by spin-Hamiltonian simulations and comparison with measurements on bulk sample. Density-functional theory calculations show that the Ni-Cr bond gets weaker with slight ring distortion suggesting possible explanation for the observed magnetic behavior. These results show that complex magnetic molecules can be grafted onto surfaces, and that changes in their magnetic behavior must be examined in individual cases. © 2009 The American Physical Society