Single-ion magnet behaviour in mononuclear and two-dimensional dicyanamide-containing cobalt(ii) complexes.
Single-ion magnet behaviour in mononuclear and two-dimensional dicyanamide-containing cobalt(ii) complexes.
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DOI：
10.1039/c6dt01160h
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发表时间：
2016-06
影响因子：
4
通讯作者：
Anna Świtlicka-Olszewska;J. Palion-Gazda;Tomasz Klemens;B. Machura;J. Vallejo;J. Cano;F. Lloret
中科院分区：
文献类型：
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作者：
Anna Świtlicka-Olszewska;J. Palion-Gazda;Tomasz Klemens;B. Machura;J. Vallejo;J. Cano;F. Lloret
制备了[Co(dca)2(bim)4]（）、[Co(dca)2(bim)2]n（）和[Co(dca)2(bim)2]n () [dca =二氰酰胺，bim = 1-苄基咪唑和bmim = 1-苄基-2-甲基咪唑]3种钴（ii）配合物，并用单晶x射线晶体学对其结构进行了分析。该化合物是一种单核化合物，其中钴（ii）离子是六配位的，四个bim分子位于赤道位置[Co-Ndca = 2.1546（15）和2.1489（15）Å]，两个移位的dca配体[Co-Ndca = 2.1575（18） Å]位于稍微扭曲的八面体周围的轴位。其结构由钴离子的二维网格组成，其中每个金属原子通过单个dca桥连接到其他四个金属中心，表现出μ1,5-dca配位模式[Co-Ndca = 2.190(3)-2.220(3)（）和2.127(3)-2.153(3)Å（）]。两个跨配位的bim ()/bmim（）分子在每个钴离子周围实现了六配位[Co-Nbim = 2.128(3)-2.134(4) Å（）和Co-Nbmim = 2.156(3)-2.163（39） Å（）]。通过单dca桥的钴钴分离值分别为8.927(2)和8.968(2)Å in和8.7110(5)和8.7158(5)Å in。在2.0 ~ 300 K温度范围内的磁化率测量表明，这些化合物表现为磁隔离的高自旋钴离子，轨道对磁矩有显著的贡献。交流（ac）磁化率测量显示，在500-2500 G范围内的静态施加磁场下，异相磁化率与频率相关，这是其中Co（ii）离子的单离子磁铁行为（SIM）的特征。磁弛豫能垒Ea值分别为5.45 ~ 7.74（）、4.53 ~ 9.24（）和11.48 ~ 15.44 cm(-1)（）。它们与先前报道的类似dca桥接的2D化合物[Co(dca)2(atz)2]n()（在施加1000 G的静态场下Ea = 5.1 cm(-1)）的结果相比较，这是先前报告的主题。
Three cobalt(ii) complexes of formulae [Co(dca)2(bim)4] (), [Co(dca)2(bim)2]n () and [Co(dca)2(bmim)2]n () [dca = dicyanamide, bim = 1-benzylimidazole and bmim = 1-benzyl-2-methylimidazole] were prepared and structurally analyzed by single-crystal X-ray crystallography. Compound is a mononuclear species where the cobalt(ii) ion is six-coordinate with four bim molecules in the equatorial positions [Co-Nbim = 2.1546(15) and 2.1489(15) Å] and two trans-positioned dca ligands [Co-Ndca = 2.1575(18) Å] in the axial sites of a somewhat distorted octahedral surrounding. The structures of and consist of two-dimensional grids of cobalt(ii) ions where each metal atom is linked to the other four metal centres by single dca bridges exhibiting the μ1,5-dca coordination mode [Co-Ndca = 2.190(3)-2.220(3) () and 2.127(3)-2.153(3) Å ()]. Two trans-coordinated bim ()/bmim () molecules achieve the six-coordination around each cobalt(ii) ion [Co-Nbim = 2.128(3)-2.134(4) Å () and Co-Nbmim = 2.156(3)-2.163(39) Å ()]. The values of the cobalt-cobalt separation through the single dca bridges are 8.927(2) and 8.968(2) Å in and 8.7110(5) and 8.7158(5) Å in . Magnetic susceptibility measurements for in the temperature range of 2.0-300 K reveal that these compounds behave as magnetically isolated high-spin cobalt(ii) ions with a significant orbital contribution to the magnetic moment. Alternating current (ac) magnetic susceptibility measurements for show a frequency dependence of out-of-phase susceptibility under static applied fields in the range of 500-2500 G, a feature which is characteristic of the single-ion magnet behaviour (SIM) of the Co(ii) ion in them. The values of the energy barrier for the magnetic relaxation (Ea) are 5.45-7.74 (), 4.53-9.24 () and 11.48-15.44 cm(-1) (). They compare well with those previously reported for the analogous dca-bridged 2D compound [Co(dca)2(atz)2]n () (Ea = 5.1 cm(-1) under an applied static field of 1000 G), which was the subject of a previous report.