Electronic and Magnetic Properties of Mn-12 Molecular Magnets on Sulfonate and Carboxylic Acid Prefunctionalized Gold Surfaces.

Structural, electronic, and magnetic properties of [Mn12O12(bet)(16)(EtOH)(4)](PF6)(14)center dot 4CH(3)CN center dot H2O (in short Mn(12)bet, bet = betaine = N+(CH3)(3)-CH2-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(12)bet 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(12)bet SMMs well-isolated from each other and uniformly distributed on both MES SAMs. X-ray absorption spectroscopy (XAS) studies show that the oxidation state of the mixed-valence Mn(12)bet core is largely reduced to Mn+ when molecules are deposited on MES-SAM, whereas in the case of MPA-SAM the relative weights of Mn2+, Mn3+, and Mn4+ in the Mn(12)bet core are preserved. Despite the substantial retaining of their electronic properties, the magnetization of Mn(12)bet molecules deposited on MPA-SAM measured by X-ray magnetic circular dichroism (XMCD) is perturbed with respect to the pristine molecules.