Reduction of Mn 19 Coordination Clusters on a Gold Surface

The magnetic properties of a Mn19 coordination cluster equipped with methylmercapto substituents on the organic ligands, (Mn III 12Mn II 7(μ4-O)8(μ3-Cl)7.7(μ3-OMe)0.3 (HL SMe )12(MeOH)6)Cl2·27MeCN (Mn19(SMe)) (H3L SMe = 2,6-bis(hydroxymethyl)-4-mercapto- methylphenol) deposited on Au(111) surfaces from solution, have been investigated by X-ray absorption spectroscopy and X-ray magnetic circular dichroism. The data reveal that in the submonolayer regime the molecules contain only divalent Mn II in contrast to the presence of Mn II and Mn III ions in the powder sample. Brillouin function fits to the field-dependent magnetization suggest that the total spin ground state in the submonolayer is much lower than STOT = 83/2 of the pristine molecules. These findings suggest that significant changes of the electronic structure, molecular geometry, and intramolecular exchange coupling take place upon surface deposition. A sample with coverage of 2−3 monolayers shows the presence of Mn III , suggesting that a decoupling layer could stabilize the Mn19 core on a metallic surface.