Insights into the Spin Dynamics of Mononuclear Cerium(III) Single-Molecule Magnets.

Four novel Ce(III) mononuclear complexes of formulas [Ce(ntfa)(3)(MeOH)(2)] (1), [Ce(ntfa)(3)(5,5'-Me(2)bipy)] (2), [Ce(ntfa)(3)(terpy)] (3), and [Ce(ntfa)(3)(bipy)(2)] (4), where ntfa = 4,4,4-trifluoro-1-(naphthalen-2-yl)butane-1,3-dionato, 5,5'-Me(2)bipy = 5,5'-dimethyl-2,2'-dipyridyl, terpy = 2,2':6',2″-terpyridine, and bipy = 2,2'-bipyridine, have been synthesized and structurally characterized with Ce(III) displaying coordination numbers of 8, 8, 9, and 10, respectively. Magnetic measurements indicate that all the complexes show a field-induced single-ion magnet behavior under a small applied dc field. The magnetic analysis shows the relevance of the different spin relaxation mechanisms in the magnetic relaxation of the Ce(III) compounds, with special emphasis on the local-mode process. Multiconfigurational calculations were also performed to get more information on the axiality of the compounds.