Wang Xiufeng, Li Cun, Sun Juan, Li Licun
Department of Chemistry, Key Laboratory of Advanced Energy Materials Chemistry and Tianjin Key Laboratory of Metal and Molecule-based Material Chemistry, Nankai University, Tianjin 300071, China.
Dalton Trans. 2015 Nov 14;44(42):18411-7. doi: 10.1039/c5dt02783g. Epub 2015 Oct 5.
Four new nitronyl nitroxide radical based hetero-tri-spin one-dimensional compounds, namely [{Ln(hfac)3}3{Cu(hfac)2}{NIT-Ph(OMe)2}4]n (Ln = Gd (1), Tb (2), Dy (3), Er (4); hfac = hexafluoroacetylacetonate; NIT-Ph(OMe)2 = 2-(2',4'-dimethoxyphenyl)-4,4,5,5-tetramethyl-imidazolyl-1-oxyl-3-oxide) have been successfully prepared. Single crystal X-ray crystallographic analysis reveals that complexes 1-4 possess a 1D chain structure with a repeating [Cu-Rad-Ln-Rad-Ln-Rad-Ln-Rad] moiety in which Ln(hfac)3 and Cu(hfac)2 units are bridged by nitronyl nitroxide radicals through the NO groups. DC magnetic studies found that ferromagnetic interactions between metals and the coordinated NO groups are active in all four compounds. The Tb derivative displays frequency dependent ac magnetic susceptibilities, indicating slow magnetic relaxation behavior. The Gd complex shows an important cryogenic magnetocaloric effect with the entropy change (-ΔSm) of 13.5 J kg(-1) K(-1) at 2 K and a magnetic field of 7 T, representing the first example of Gd-radical molecular species exhibiting the magnetocaloric effect.
成功制备了四种基于硝酰基氮氧化物自由基的新型杂三自旋一维化合物，即[{Ln(hfac)3}3{Cu(hfac)2}{NIT-Ph(OMe)2}4]n（Ln = Gd (1)、Tb (2)、Dy (3)、Er (4)；hfac = 六氟乙酰丙酮；NIT-Ph(OMe)2 = 2-(2',4'-二甲氧基苯基)-4,4,5,5-四甲基-咪唑基-1-氧基-3-氧化物）。单晶X射线晶体学分析表明，配合物1-4具有一维链状结构，其重复单元为[Cu-Rad-Ln-Rad-Ln-Rad-Ln-Rad]，其中Ln(hfac)3和Cu(hfac)2单元通过硝酰基氮氧化物自由基经NO基团桥连。直流磁性研究发现，金属与配位的NO基团之间的铁磁相互作用在所有四种化合物中均有活性。Tb衍生物表现出频率依赖性的交流磁化率，表明存在慢磁弛豫行为。Gd配合物在2 K和7 T磁场下显示出重要的低温磁热效应，熵变(-ΔSm)为13.5 J kg(-1) K(-1)，这是首例表现出磁热效应的Gd-自由基分子物种。
