Huang Xing-Cai, Zhao Xin-Hua, Shao Dong, Wang Xin-Yi
State Key Laboratory of Coordination Chemistry, Collaborative Innovation Centre of Advanced Microstructures, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210093, China.
Dalton Trans. 2017 Jun 6;46(22):7232-7241. doi: 10.1039/c7dt01167a.
The reaction of Cu(valdmpn) (Hvaldmpn = N,N'-bis-(3-methoxysalicylidene)-1,3-diamino-2,2-dimethylpropane), LnCl·nHO (Ln = La(1), Ce (2), Pr(3), Nd(4), Sm(5), Eu(6), Gd(7), Tb(8), Dy(9), Ho(10), Er(11), Tm(12), Yb(13), Lu(14)) and NaN in methanol led to a whole series of heterometallic Cu-Ln complexes. The basic structural components of these complexes are the [Cu(valdmpn)Ln] units with a compartmental Schiff-base ligand. These [CuLn] units were then further connected by the end-on (EO) azides between the Ln centers to form tetranuclear {CuLn[LnCu]} motifs, where n is 3 for the complexes of larger radii lanthanides (1 to 5) and 2 for the complexes of smaller radii lanthanides (6 to 14). While compounds 6 to 14 remain isolated tetranuclear clusters, compounds 1 to 5 are one-dimensional chains where tetranuclear motifs are further connected by end-to-end (EE) azides between Cu and Ln centers. Direct current (dc) magnetic susceptibilities have been measured in the range of 1.8-300 K for all complexes, revealing the different nature of magnetic interactions between the spin centers. Among them, dominant ferromagnetic interactions were found in compounds 7, 8 and 9. Alternating current (ac) magnetic measurements performed on 8, 9, and 10 demonstrated the presence of slow magnetic relaxation under zero applied dc field. The spin relaxation barrier U was determined to be 19.54 cm (28.12 K) and 10.34 cm (14.87 K) for compounds 8 and 9. The SMM behavior of 8 was further confirmed by the presence of magnetic hysteresis loops; while no hysteresis loop was observed for 9 and 10. These results demonstrated that azido-bridged copper(ii)-lanthanide(iii) complexes could be synthesized successfully despite the generally weak azido-lanthanide interaction.
在甲醇中，Cu(valdmpn)（Hvaldmpn = N,N'-双-(3-甲氧基水杨醛)-1,3-二氨基-2,2-二甲基丙烷）、LnCl₃·nH₂O（Ln = La(1)、Ce (2)、Pr(3)、Nd(4)、Sm(5)、Eu(6)、Gd(7)、Tb(8)、Dy(9)、Ho(10)、Er(11)、Tm(12)、Yb(13)、Lu(14)）与NaN反应生成了一系列异金属Cu-Ln配合物。这些配合物的基本结构单元是带有分隔席夫碱配体的[Cu(valdmpn)Ln]单元。然后，这些[CuLn]单元通过Ln中心之间的端基（EO）叠氮化物进一步连接，形成四核{CuLn[LnCu]}结构单元，其中对于较大半径镧系元素（1至5）的配合物，n为3；对于较小半径镧系元素（6至14）的配合物，n为2。虽然化合物6至14保持为孤立的四核簇，但化合物1至5是一维链，其中四核结构单元通过Cu和Ln中心之间的端对端（EE）叠氮化物进一步连接。对所有配合物在1.8 - 300 K范围内测量了直流（dc）磁化率，揭示了自旋中心之间磁相互作用的不同性质。其中，在化合物7、8和9中发现了占主导的铁磁相互作用。对8、9和10进行的交流（ac）磁性测量表明，在零外加直流场下存在缓慢的磁弛豫。化合物8和化合物9的自旋弛豫势垒U分别确定为19.54 cm⁻¹（28.12 K）和10.34 cm⁻¹（14.87 K）。8的单分子磁体行为通过磁滞回线的存在得到进一步证实；而9和10未观察到磁滞回线。这些结果表明，尽管叠氮化物与镧系元素之间的相互作用通常较弱，但仍能成功合成叠氮桥联的铜（II）-镧系（III）配合物。
