Regulating Spin Dynamics of Nitronyl Nitroxide Biradical Lanthanide Complexes through Introducing Different Transition Metals |
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| Authors: | Pei Jing Dr Lu Xi Jiao Lu Jing Han Xiaohui Huang Chaoyi Jin Junfang Xie Prof Licun Li |
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| Institution: | Department of Chemistry, Key Laboratory of Advanced Energy Materials Chemistry, College of Chemistry, Nankai University, Tianjin, 300071 P. R China |
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| Abstract: | Four biradical-Ln complexes with different transition metal ions, namely LnM(hfac)5(NITPh-PyPzbis)] (MII=MnII and LnIII=Gd 1 , Dy 2 ; MII=NiII and LnIII=Tb 3 , Dy 4 ), were prepared by the reaction of Ln(hfac)3 ? 2H2O, Mn(hfac)2 ? 2H2O or Ni(hfac)2 ? 2H2O with NITPh-PyPzbis biradical (hfac=hexafluoroacetylacetonate, NITPh-PyPzbis=5-(3-(2-pyridinyl)-1H-pyrazol-1-yl)-1,3-bis(1’-oxyl-3’-oxido- 4’,4’,5’,5’-tetramethyl-4,5-hydro-1H-imidazol-2-yl)benzene). In complexes 1 – 4 , the NITPh-PyPzbis biradical chelates one LnIII ion by means of its aminoxyl moieties and the transition metal ion is introduced through the two N donors from the pyridyl pyrazolyl moiety. Magnetic investigations indicate that complex 4 displays visible maxima in frequency/temperature-dependent χ′′ signals with two-step relaxation processes, but complex 2 exhibits no slow magnetization relaxation. The comparison of structure parameters of both Dy complexes indicates that the symmetries of coordination spheres of two Dy ions are D2d for 2 and C2v for 4 , which thus probably results in different magnetic relaxation behaviors. This work provides new insight for improving properties of Ln-biradical based SMMs. |
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| Keywords: | nitronyl nitroxide biradical transition metals local symmetry two-relaxation processes |
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