New single-molecule magnets by site-specific substitution: Incorporation of "Alligator clips" into Fe-4 complexes

"Alligator clips" suitable for grafting on H-terminated silicon or gold surfaces have been incorporated into single-molecule magnets (SMMs) of the Fe-4 family. Tripodal ligands 2,2-bis(hydroxymethyl)-10-undecen-1-ol (H3L1) and 11-(acetylthio)-2,2-bis(hydroxymethyl)undecan-1-ol (H3L2) have been used to replace the six methoxide bridges in [Fe-4(OMe)(6)(dpm)(6)], affording new Fe-4 derivatives [Fe-4(L-1)(2)(dPm)(6)] (1) and [Fe-4(L-2)(2)(dpm)(6)] (2) in high yield (Hdpm = dipivaloylmethane). The molecular structures have been unambiguously established by XRD combined with ESI-MS and magnetic characterization techniques, including DC and AC magnetometry and high-frequency EPR spectroscopy. The two SMMs have an S = 5 ground state and an easy-axis magnetic anisotropy leading to slow relaxation of the magnetization at low temperature, with effective anisotropy barriers of 15.9(2) K in 1 and 15.1(2) K in 2.