Grafting derivatives of Mn6 single-molecule magnets with high anisotropy energy barrier on Au(111) surface

We study the magnetic properties of two new functionalized single-molecule magnets belonging to the Mn6family (general formula [MnIII6O2(R-sao)6(O2C-th)2L4-6], where R ) H (1) or Et (2), HO2C-th ) 3-thiophenecarboxylic acid, L ) EtOH, H2O and saoH2 is salicylaldoxime) and their grafting on the Au(111) surface.Complex 1 exhibits spin ground-state S ) 4, as the result of ferromagnetic coupling between the twoantiferromagnetic MnIII3 triangles, while slight structural changes in complex 2, switch the dominant magneticexchange interactions from anti- to ferromagnetic, enhancing the spin ground-state to S ) 12 and, consequently,the effective energy barrier for the relaxation of magnetization. Direct-current and alternating-current magneticsusceptibility measurements show that the functionalized complexes preserve the main magnetic propertiesof the corresponding not-functionalized Mn6 clusters (i.e., total spin value and magnetic behavior as a functionof temperature), though a reduction of the anisotropy barrier is observed in complex 2. For both complexes,the -O2C-th functionalization allows the direct grafting on Au(111) surface by liquid-phase deposition. X-rayphotoemission spectroscopy demonstrates that the stoichiometry of the molecular cores is preserved aftergrafting. Scanning tunneling microscopy (STM) reveals a sub-monolayer distribution of isolated clusters witha slightly higher coverage for complex 1. The cluster stability in the STM images and the S-2p energy positionsdemonstrate, for both derivatives, the strength of the grafting with the gold surface.