New series of mononuclear β-diketonate cerium(III) field induced single-molecule magnets

Five new β-diketonate Ce³⁺ mononuclear complexes, [Ce(Btfa)₃(H₂O)₂] (1), [Ce(Btfa)₃(phen)] (2), [Ce(Btfa)₃(bipy)] (3), [Ce(Btfa)₃(terpy)] (4) and [Ce(Btfa)₃(bathophen)(DMF)] (5), where Btfa^- = 4,4,4-trifluoro-1-phenyl-1,3-butanedionate, phen = 1,10-phenanthroline, bipy = 2,2'-bipyridyl, terpy = 2,2':6',2''-terpyridine and bathophen = 4,7-diphenyl-1,10-phenanthroline, have been synthesized and structurally characterized through X-ray diffraction of single crystals. The central Ce³⁺ atom displays a coordination number of 8 for 1, 2 and 3 and of 9 for 4 and 5. Under a 0 T external magnetic field, none of the given compounds exhibits single molecule magnet (SMM) behaviour. However, a small magnetic field, between 0.02 and 0.1 T, is enough for all the compounds to exhibit slow relaxation of the magnetization. A comprehensive magnetic analysis, with experimental magnetic data and ab initio calculations, was undertaken for all the complexes, and the study highlights the significance of the different spin relaxation mechanisms that must be considered for a Ce³⁺ lanthanide ion.