RESUMO
A series of di- and tetranuclear lanthanide complexes with the formulas [Dy2bmzch(tmhd)5 (CH3OH)]·CH3OH (1), [Dy2bmzch(dbm)4 (CH3O)(CH3OH)]·0.5CH3OH·0.5H2O (2), and Dy4bmzch(btfa)10 (3), where tmhd = 2,2,6,6-tetramethyl-3,5-heptanedionate, dbm = dibenzoylmethane, btfa = benzoyltrifluoroacetone, and bmzch = (Z)-N-[(E)-pyrimidin-2-ylmethylene]pyrimidine-2-carbohydrazonate, were structurally and magnetically characterized. More strikingly, although the nitrogen-enriched bridged ligand 3,6-di(pyrimidin-2-yl)-1,2,4,5-tetrazine (bmtz) was initially adopted, the structures of the complexes obtained indicated that bmtz underwent unprecedented asymmetric ring opening and generated a new ligand bmzch. Combined with different ß-diketonates, di- and tetranuclear dysprosium complexes were constructed in which the structural patterns are very sensitive to the selected ß-diketonates. In view of this, the bilateral and unilateral dinuclear Dy2 complexes 1 and 2 and tetranuclear Dy4 complex 3 were obtained by choosing different ß-diketonates. Magnetic test results reveal that both complexes 1 and 3 showcase typical slow magnetic relaxation behavior without an external direct-current field and the effective energy barrier of the latter is almost twice that of the former, while complex 2 only displays in-field single-molecule-magnetic behavior. Also of note is that these are the first tetrazine-type dysprosium-based single-molecule-magnets undergoing in situ asymmetric ring-opening reaction of this ligand that are formed.
RESUMO
Two lanthanide complexes with formulae [DyIII(LN5)(pentafluoro-PhO)3] (1) and [DyIII(LN5)(2,6-difluoro-PhO)2](BPh4) (2) (LN5 = 2,14-dimethyl-3,6,10,13,19-pentaazabicyclo[13.3.1]nonadecal (19),2,13,15,17-pentaene) were structurally and magnetically characterized. DyIII ions lie in the cavity of a five coordinate nitrogen macrocycle, and in combination with the introduction of multi-fluorinated monodentate phenoxyl coligands a high axiality coordination symmetry is built. Using the pentafluorophenol co-ligand, complex 1 with a D2d coordination environment, is obtained and displays moderate single-molecule magnets (SMMs) behavior. When difluorophenol co-ligands were used, a higher local axisymmetric pentagonal bipyramidal coordination geometry was observed in complex 2, which displays apparent slow magnetic relaxation behavior with a hysteresis temperature of up to 5 K. Further magnetic studies of diluted samples combined with ab initio calculations indicate that the high axiality plays a crucial role in suppressing quantum tunneling of magnetization (QTM) and consequently results in good slow magnetic relaxation behavior. Different fluoro-substituted phenoxyl co-ligands have phenoloxy oxygen atoms with different electrostatic potentials as well as a different number of phenoloxy coligands along the magnetic axis, resulting in different ligand field strengths and coordination symmetries.
RESUMO
Lanthanide-based single-molecule magnets (SMMs) have captivated the attention of researchers due to their great potential application in quantum information processing, storage, spintronics etc. Recent years have witnessed continuous breakthroughs in the field of SMMs, which make them very promising to be used in future practical functional applications. However, there remain formidable obstacles involving suppression of the quantum tunneling of magnetization (QTM) to maximize magnetic anisotropy, integrating and applying them in devices etc. Meanwhile, multifunctional 4f-based SMMs, which combine optical and electronic properties, are attracting increasing attention. This will provide a new perspective for future multifunctional device applications and deep insight into understanding the magnetic relaxation behavior as well. In this frontier article, we highlight the research that recently emerged involving 4f-based SMMs in combination with luminescence thermometry and photochromic and ferroelectric properties, respectively.