The Spin Structure of Surface-Supported Single-Molecule Magnets from Isomorphous Replacement and X-ray Magnetic Circular Dichroism

Surface-supported arrays of Fe4-type Single-Molecule Magnets retain a memory effect and are of current interest in the frame of molecule-based information storage and spintronics. To reveal the spin structure of [Fe4(L)2(dpm)6] (1) on Au, an isomorphous compound [Fe3Cr(L)2(dpm)6 ] was synthesized and structurally and magnetically characterized (H3L is tripodal ligand 11-(acetylthio)-2,2-bis(hydroxymethyl)undecan-1-ol and Hdpm is dipivaloylmethane). The new complex contains a central Cr 3+ ion and has a S = 6 ground state as opposed to S = 5 in 1. Low-temperature X-ray Magnetic Circular Dichroism studies at Fe- and Cr-L2,3 edges revealed that the antiparallel alignment between Fe and Cr spins is preserved on surfaces. Moreover, the different Fe-L2,3 spectral features found in the homo- and heterometallic species disclose the opposing contribution of the central Fe 3+ ion in the former compound, proving that its ferrimagnetic spin structure is retained on surfaces.