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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

Structural, electronic, and magnetic properties of [Mn 12O 12(bet) 16(EtOH) 4](PF 6) 14·4CH 3CN·H 2O (in short Mn 12bet, bet = betaine = +N(CH 3) 3-CH 2-COO -) single-molecule magnets (SMMs) deposited on previously functionalized gold surfaces have been investigated. Self-assembled monolayers (SAMs) either of sodium mercaptoethanesulfonate (MES) or mercaptopropionic acid (MPA) are used as functionalization to avoid the direct interaction between the Mn 12bet molecules and the Au surface with the aim of preserving the main functional properties of the molecules. Scanning tunneling microscopy (STM) and X-ray photoemission spectroscopy (XPS) analysis show deposited Mn 12bet SMMs well-isolated from each other and uniformly distributed on both MES and MPA SAMs. X-ray absorption spectroscopy (XAS) studies show that the oxidation state of the mixed-valence Mn 12bet core is largely reduced to Mn 2+ when molecules are deposited on MES-SAM, whereas in the case of MPA-SAM the relative weights of Mn 2+, Mn 3+, and Mn 4+ in the Mn 12bet core are preserved. Despite the substantial retaining of their electronic properties, the magnetization of Mn 12bet molecules deposited on MPA-SAM measured by X-ray magnetic circular dichroism (XMCD) is perturbed with respect to the pristine molecules. © 2012 American Chemical Society., Financial support from the European Union (project ELFOS and ERC Advanced Grant SPINMOL to EC), the Spanish MINECO (Project CONSOLIDER on Molecular Nanoscience CSD2007-00010 and Projects CTQ-2008-06720-C02-01/BQU, MAT2007-61584, MAT2009-13977-C03 and MAT2011-22785) and the Generalitat Valenciana (PROMETEO Program) is gratefully acknowledged.

Bisphthalocyaninato terbium complexes show a long magnetization relaxation time at relatively high temperatures-which makes them very interesting as magnets at single-molecule level. Their technological exploitation, however, requires the addressing of the individual molecules, therefore the deposition of single-molecule magnets on surfaces is a topic of great interest as the interaction with the substrate can play a crucial role in the definition of the molecule properties. In this work we investigate the electronic and magnetic properties of anionic and neutral forms of a bis(phthalocyaninato)terbium derivative deposited on graphite by means of x-ray absorption spectroscopy and x-ray magnetic circular dichroism, performed at low temperature and high magnetic field at the M4,5edge of Tb. We were able to reproduce the experimental spectra by means of multiplet calculations and to validate the applicability of sum rules to the present case. Sum rules were then used for determining the orbital and spin moments of thick (several monolayers) and of thin films (submonolayer range). Calculations of spectra as a function of the molecule orientation with respect to the impinging x-ray beam, allowed us to ascertain the adsorption geometry of molecules. For both compounds, molecules stay essentially flat when adsorbing as thin film on graphite. This result is also confirmed by scanning probe microscopy, which also finds a very interesting ordered arrangement for the molecules of the neutral form. In the thick film of the neutral compound the molecules keep the same orientational order, arranging almost flat as well. On the contrary, in the thick film of the anionic compound their orientation appears to be random. The origin of this different behavior can be related to the hindrance of the counterion moiety and/or to the different solvent used for each compound. Finally, the comparison of the magnetization values and their dependence on the external magnetic field and temperature suggest that the magnetic properties of molecules are preserved when adsorbed onto the graphite surface. © 2010 The American Physical Society