Comparison of Two Field-Induced ErIII Single Ion Magnets

We present the synthesis, magnetic and photophysical properties of four mononuclear LnIII complexes in two isostructural lattices containing GdIII and ErIII. A heptadentate Schiff base ligand and acetate versus trifluorocetate were used to synthesise complexes 1 - 4, where both ErIII complexes 2 and 4 exhibit field-induced SIM behaviour with similar Ueff values (31.6 K for 2 and 32.7 K for 4). Ab initio calculations show the structure of the low-lying energy states and highlight that there is significant tunnelling already in the ground doublet state, but the application of a weak magnetic field of 0.05 T is sufficient for the ac magnetic measurements to suppress the tunnelling in the ground state. The calculated main magnetic axes (gZ) in the ground Kramers doublets show small differences between the two ErIII compounds 2 and 4, due to their different ligand field.