Reduction of Mn19 Coordination Clusters on a Gold Surface

The magnetic properties of a Mn-19 coordination cluster equipped with methylmercapto substituents on the organic ligands, [(Mn12Mn7II)-Mn-III(mu(4)-O)(8)(mu(3)-Cl)(7.7)(mu(3)-OMe)(0.3)(HLSMe)(12)(MeOH)(6)]Cl-2 center dot 27MeCN (Mn-19(SMe)) (H3LSMe = 2,6-bis(hydroxymethyl)-4-mercaptomethylphenol) 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 MnII 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 S-TOT = 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 Mn-19 core on a metallic surface.