Slow relaxation of magnetization in CoIII decorated {Dy2} compounds

ALEJANDRO FUNES; LUCA CARRELLA; EVA RENTSCHLER; PABLO ALBORÉS

Saint Petersburg

Congreso; The 14th International Conference on Molecule-Based Magnets, , July 5th to July 10th 2014.; 2014

Russian Academy of Sciences/Saint-Petersburg State University /The Ministry of Education and Science of Russia

Recent years have witnessed rapid growth and success in the field of Lanthanide-based Single Molecule Magnets (Ln-SMMs)1 after the discovery that lanthanide mononuclear complexes can exhibit slow relaxation of the magnetization at liquid nitrogen temperature2. Within this context we have recently reported the first example within the {CoIII2DyIII2} family of compounds with two evident relaxation pathways in zero DC field not ascribable to different DyIII sites3. This complex of formula [CoIII2DyIII2(OMe)2(teaH)2(Piv)6] (1), (teaH3= triethanolamine, Piv= trimethlyacetate), shows two well resolved thermal activated magnetization relaxation pathways under AC experiments in zero DC field with Ueff of 51K and 127 K. Fitted crystal field parameters suggest that the origin of these two pathways relies on two different excited mJ sub-levels. In order to further test this hypothesis and contribute with new examples to this series of complexes we have now prepared a new CoIII decorated {Dy2} related compound, exhibiting a {CoIII4DyIII2} core (see Figure) with formula [CoIII4DyIII2(OH)2(teaH)2(tea)2(Piv)6] (2). Complex 2 exhibits the classic butterfly arrangement in comparison to compound 1 where a wing alternated butterfly core is observed in the inner {Co2Dy2} unit. This structural modification impacts directly in magnetic properties inverting the local DyIII ions mJ low lying energy levels and hence modifying relaxation pathways. Now only one relaxation process can be observed for complex 2 in AC experiments in zero DC field. In this report we are communicating the structural and the complete magnetic characterization of the new compound 2. We compare relaxation pathways with the observed in 1 and discuss these results in terms of crystal field effects over DyIII sites.