Dipartimento di Scienze Chimiche, Università di Padova, via Marzolo 1, I-35131, Italy.
Dalton Trans. 2018 Jun 25;47(25):8337-8345. doi: 10.1039/c8dt00880a.
Heterotopic divergent ligand N-oxide-4,4'-bipyridine (bipyMO) has been herein exploited for the preparation of hetero-bimetallic coordination polymers where Ln(hfac)3 and M(hfac)2 nodes regularly alternate (Hhfac = 1,1,1,5,5,5-hexafluoro-2,4-pentanedione), bipyMO being able to selectively use its two potential coordination sites to discriminate the metal ions. The synthesis of three coordination polymers, [Ln(hfac)3M(hfac)2(bipyMO)2]n (Ln = Eu, M = Zn, 1; Ln = Eu, M = Cu, 2, Ln = Dy, M = Co, 3), was carried out by reacting the appropriate [M(hfac)2(bipyMO)]n and [Ln(hfac)3] precursors in toluene in the presence of a given stoichiometric amount of bipyMO. The products were characterized by elemental analysis, X-ray powder diffraction, and FTIR spectroscopy. Single crystal X-ray diffraction studies carried out on 2 showed that it was formed by chains containing the hexa-coordinated 3d metal (Cu(hfac)2[N]2) and the octa-coordinated lanthanide (Eu(hfac)3[O]2) nodes, where [N] and [O] stand for the donor atom of the bridging divergent ligand. The X-ray powder diffraction patterns of the three compounds and the comparison of their cell constant values allowed establishing that the derivatives were isotypic. Photoluminescence (PL) studies on microcrystalline sample powders evidenced a bright red emission for 1 with an absolute PL quantum yield of 0.24. The sensitized emission of Eu3+ can be excited in a wide wavelength range, from UV to visible, up to ≈450 nm. Conversely, europium emissions are not detectable in 2 due to the presence of Cu(hfac)2(bipyMO) moieties whose strong absorption overlaps Eu3+ transitions. Magnetic measurements conducted on 3 revealed the presence of a weak ferromagnetic interaction below 2.1 K. An ac susceptibility study highlighted a slow relaxation of the magnetization of 3 with an applied static magnetic field of 0.1 T, which could be equally fitted with a Orbach-direct or a Raman-direct mechanism. No relaxation dynamics was detected without the application of a static magnetic field.
杂化发散配体 N-氧化物-4,4'-联吡啶（bipyMO）已被用于制备异双金属配位聚合物，其中 Ln(hfac)3 和 M(hfac)2 节点规则交替（Hhfac = 1,1,1,5,5,5-六氟-2,4-戊二酮），bipyMO 能够选择性地使用其两个潜在的配位位点来区分金属离子。通过在甲苯中反应适当的[M(hfac)2(bipyMO)]n 和 [Ln(hfac)3]前体，并在给定的化学计量比下加入 bipyMO，合成了三种配位聚合物[Ln(hfac)3M(hfac)2(bipyMO)2]n（Ln = Eu，M = Zn，1；Ln = Eu，M = Cu，2，Ln = Dy，M = Co，3）。通过元素分析、X 射线粉末衍射和 FTIR 光谱对产物进行了表征。对 2 进行的单晶 X 射线衍射研究表明，它由包含六配位 3d 金属（Cu(hfac)2[N]2）和八配位镧系元素（Eu(hfac)3[O]2）节点的链组成，其中[N]和[O]分别代表桥接发散配体的供体原子。三种化合物的 X 射线粉末衍射图谱及其晶胞常数值的比较表明，这些衍生物是同型的。对微晶体粉末的光致发光（PL）研究表明，1 具有明亮的红色发射，绝对 PL 量子产率为 0.24。Eu3+的敏化发射可以在从 UV 到可见的宽波长范围内激发，直至约 450nm。相反，由于存在 Cu(hfac)2(bipyMO)部分，其强吸收与 Eu3+跃迁重叠，因此在 2 中无法检测到铕的发射。对 3 进行的磁测量表明，在 2.1K 以下存在弱铁磁相互作用。交流磁化率研究强调了在施加 0.1T 静态磁场时，3 的磁化缓慢弛豫，这可以通过 Orbach 直接或 Raman 直接机制进行相同拟合。在没有施加静态磁场的情况下，没有检测到弛豫动力学。
