title: XAS and XMCD investigation of Mn12 monolayers on gold.
abstract: The deposition of Mn(12) single molecule magnets on gold surfaces was studied for the first time using combined X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD) methods at low temperature. The ability of the proposed approach to probe the electronic structure and magnetism of Mn(12) complexes without significant sample damage was successfully checked on bulk samples. Detailed information on the oxidation state and magnetic polarization of manganese ions in the adsorbates was obtained from XAS and XMCD spectra, respectively. Partial reduction of metal ions to Mn(II) was clearly observed upon deposition on Au(111) of two different Mn(12) derivatives bearing 16-acetylthio-hexadecanoate and 4-(methylthio)benzoate ligands. The average oxidation state, as well as the relative proportions of Mn(II), Mn(III) and Mn(IV) species, are strongly influenced by the deposition protocol. Furthermore, the local magnetic polarizations are significantly decreased as compared with bulk Mn(12) samples. The results highlight an utmost redox instability of Mn(12) complexes at gold surfaces, presumably accompanied by structural rearrangements, which cannot be easily revealed by standard surface analysis based on X-ray photoelectron spectroscopy and scanning tunnelling microscopy.
authors.affiliation: Department of Chemistry and INSTM Research Unit, Università di Firenze, Via della Lastruccia 3, Sesto Fiorentino, Florence, Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Mannini
authors.forename: Philippe
authors.initials: P
authors.lastname: Sainctavit
authors.forename: Roberta
authors.initials: R
authors.lastname: Sessoli
authors.forename: Christophe
authors.initials: C
authors.lastname: Cartier dit Moulin
authors.forename: Francesco
authors.initials: F
authors.lastname: Pineider
authors.forename: Marie-Anne
authors.initials: MA
authors.lastname: Arrio
authors.forename: Andrea
authors.initials: A
authors.lastname: Cornia
authors.forename: Dante
authors.initials: D
authors.lastname: Gatteschi
mesh_terms: D002942:Circular Dichroism / Q000379:methods; D006046:Gold / Q000737:chemistry*; D008280:Magnetics; D008345:Manganese / Q000737:chemistry*; D008567:Membranes, Artificial; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D010316:Particle Size; D013057:Spectrum Analysis / Q000379:methods; D013499:Surface Properties; D013696:Temperature; D014965:X-Rays
chemical_list: D008567:Membranes, Artificial; D009942:Organometallic Compounds; D008345:Manganese; D006046:Gold