Multiple magnetic relaxation pathways in T-shaped N-heterocyclic carbene-supported Fe(I) single-ion magnets
The magnetic properties of the T-shaped three-coordinate complexes, namely, [(sIMes)2Fe(THF)][BPh4] (1, sIMes: 1,3-bis(2′,4′,6′-trimethylphenyl)-imidazolin-2-ylidene) and [(cyIMes)2Fe(THF)][BPh4] (2, cyIMes: 1,3-bis(2′,4′,6′-diethylphenyl)-4,5-(CH2)4-imidazol-2-ylidene) and quasi-linear two-coordinate complexes [(sIDep)2Fe][BArF4] (3, sIDep: 1,3-bis(2′,6′-diethylphenyl)-imidazolin-2-ylidene; ArF: 3,5-di(trifluoromethyl)phenyl) and [(cyIDep)2Fe][BArF4] (4, cyIDep: 1,3-bis(2′,6′-diethylphenyl)-4,5-(CH2)4-imidazol-2-ylidene) were studied. Magnetic characterization indicated the unquenched first-order angular momentum and large zero-field splitting. AC susceptibility measurements showed that the T-shaped three-coordinate Fe(I) complexes exhibited field-induced relaxation of magnetization. The Direct, resonant quantum tunneling, and Raman processes were observed and contributed to the determination of the overall magnetic relaxations.