Lanthanide-mediated tuning of electronic and magnetic properties in heterotrimetallic cyclooctatetraenyl multidecker self-assemblies |
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| Authors: | Zheng Zhou James McNeely Joshua Greenough Zheng Wei Haixiang Han Mathieu Rouzires Andrey Yu Rogachev Rodolphe Clrac Marina A Petrukhina |
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| Institution: | Department of Chemistry, University at Albany, State University of New York, Albany NY 12222 USA.; Department of Chemistry, Boston University, Boston MA USA ; Department of Materials Science and Engineering, Cornell University, Ithaca New York 14853 USA ; Univ. of Bordeaux, CNRS, Centre de Recherche Paul Pascal, UMR 5031, F-33600 Pessac France.; Department of Chemistry, Illinois Institute of Technology, Chicago IL 60616 USA, |
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| Abstract: | The synthesis of a novel family of homoleptic COT-based heterotrimetallic self-assemblies bearing the formula LnKCa(COT)3(THF)3] (Ln(iii) = Gd, Tb, Dy, Ho, Er, Tm, and Yb) is reported followed by their X-ray crystallographic and magnetic characterization. All crystals conform to the monoclinic P21/c space group with a slight compression of the unit cell from 3396.4(2) Å3 to 3373.2(4) Å3 along the series. All complexes exhibit a triple-decker structure having the Ln(iii) and K(i) ions sandwiched by three COT2− ligands with an end-bound {Ca2+(THF)3} moiety to form a non-linear (153.5°) arrangement of three different metals. The COT2− ligands act in a η8-mode with respect to all metal centers. A detailed structural comparison of this unique set of heterotrimetallic complexes has revealed consistent trends along the series. From Gd to Yb, the Ln to ring-centroid distance decreases from 1.961(3) Å to 1.827(2) Å. In contrast, the separation of K(i) and Ca(ii) ions from the COT-centroid (2.443(3) and 1.914(3) Å, respectively) is not affected by the change of Ln(iii) ions. The magnetic property investigation of the LnKCa(COT)3(THF)3] series (Ln(iii) = Gd, Tb, Dy, Ho, Er, and Tm) reveals that the Dy, Er, and Tm complexes display slow relaxation of their magnetization, in other words, single-molecule magnet (SMM) properties. This behaviour is dominated by thermally activated (Orbach-like) and quantum tunneling processes for DyKCa(COT)3(THF)3] in contrast to ErKCa(COT)3(THF)3], in which the thermally activated and Raman processes appear to be relevant. Details of the electronic structures and magnetic properties of these complexes are further clarified with the help of DFT and ab initio theoretical calculations.A new class of heterotrimetallic COT-based self-assemblies accommodates metals from groups I–III in three different oxidation states and enables tuning of electronic and magnetic properties. |
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