Lehrstuhl für Anorganische Chemie I, Fakultät für Chemie, Universität Bielefeld, Universitätsstr. 25, 33615, Bielefeld, Germany.
Fakultät für Physik, Universität Bielefeld, Universitätsstr. 25, 33615, Bielefeld, Germany.
Chemistry. 2019 Apr 1;25(19):4992-5004. doi: 10.1002/chem.201805543. Epub 2019 Mar 12.
The anisotropy barrier of polynuclear single-molecule magnets is expected to be higher with less tunneling the better stabilized the spin ground state is so that less M mixing in the ground state and with excited spin states occur. We have realized this experimentally in two structurally related heptanuclear SMMs: the triplesalen-based [Mn Cr ] and the triplesalalen-based [Mn Cr ] . The ligand system triplesalen was developed to enforce ferromagnetic interactions by the spin-polarization mechanism. However, we found weak antiferromagnetic couplings, that we assigned to an inefficient spin-polarization by a heteroradialene formation. To prevent this heteroradialene formation, the triplesalalen ligand H talalen was designed. Here, we present the building block [(talalen )Mn ] and its application for the assembly of [{(talalen )Mn } {Cr (CN) }] (=[Mn Cr ] ). Both the trinuclear and heptanuclear complexes are SMMs. The comparison to the related triplesalen complex [(feld )Mn ] proves the absence of heteroradialene character and the enforcement of ferromagnetic Mn -Mn interactions in the (talalen ) complexes. This results in an increase of the barrier for spin reversal U from 25 K in the triplesalen-based [Mn Cr ] SMMs to 37 K in the triplesalalen-based *[Mn Cr ] SMM proving the success of our concept. Based on this study, the next step in the rational improvement of our SMMs is discussed.
多核单分子磁体的各向异性势垒预计会更高，隧穿越小，自旋基态越稳定，基态和激发态中的 M 混合越少。我们在两个结构相关的七核 SMM 中实验上实现了这一点：基于三齿配体的[MnCr]和基于三齿配体的*[MnCr]。三齿配体三齿配体被开发出来是为了通过自旋极化机制来增强铁磁相互作用。然而，我们发现了较弱的反铁磁耦合，我们将其归因于杂并苯烯形成导致的自旋极化效率低下。为了防止这种杂并苯烯的形成，设计了三齿配体 Htalalen。在这里，我们提出了构建块[(talalen)Mn]及其在组装[{(talalen)Mn}{Cr(CN)}]（=[MnCr]）中的应用。这两个三核和七核配合物都是 SMM。与相关的三齿配体配合物[(feld)Mn]的比较证明了杂并苯烯特征的不存在，以及（talalen）配合物中 Mn-Mn 相互作用的铁磁性增强。这导致自旋反转 U 的势垒从基于三齿配体的[MnCr]SMM 中的 25 K 增加到基于三齿配体的[MnCr]SMM 中的 37 K，证明了我们概念的成功。基于这项研究，讨论了下一步如何合理改进我们的 SMM。
