Dehydration–Hydration Switching of Single-Molecule Magnet Behavior and Visible Photoluminescence in a Cyanido-Bridged DyIIICoIII Framework

• Published in: Journal of the American Chemical Society Vol. 141; no. 45; pp. 18211 - 18220
• Main Authors: Xin, Yue, Wang, Junhao, Zychowicz, Mikolaj, Zakrzewski, Jakub J, Nakabayashi, Koji, Sieklucka, Barbara, Chorazy, Szymon, Ohkoshi, Shin-ichi
• Format: Journal Article
• Language: English; Japanese
• Published: American Chemical Society 13.11.2019
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.9b09103

Microporous magnets compose a class of multifunctional molecule-based materials where desolvation-driven structural transformation leads to the switching of magnetic properties. Herein, we present a special type of microporous magnet where a dehydration–hydration process within a bimetal coordination framework results in the switching of emissive DyIII single-molecule magnets (SMMs). We report a three-dimensional (3-D) cyanido-bridged coordination polymer, {[DyIII(H2O)2]­[CoIII(CN)6]}·2.2H2O (1), and its dehydrated form of {DyIII[CoIII(CN)6]} (2), which was obtained through a reversible single-crystal-to-single-crystal transformation. Both phases are composed of paramagnetic DyIII centers alternately arranged with diamagnetic hexacyanidocobaltates­(III). The hydrated phase contains eight-coordinated [DyIII(μ-NC)6(H2O)2]3– complexes of a square antiprism geometry, while the dehydrated form contains six-coordinated [DyIII(μ-NC)6]3– moieties of a trigonal prism geometry. This change in coordination geometry results in the generation of DyIII single-molecule magnets in 2, whereas slow magnetic relaxation effect is not observed for DyIII sites in 1. The D 4d-to-D 3h symmetry change of DyIII complexes produces also the shift of photoluminescent color from nearly white to deep yellow thanks to the modulation of emission bands of f–f electronic transitions. A combined approach utilizing dc magnetic data and low-temperature emission spectra confirmed an axial crystal field of trigonal prismatic DyIII complexes in 2, which produces an Orbach type of slow magnetic relaxation. Therefore, we present a unique route to the efficient switching of SMM behavior and photoluminescence of DyIII complexes embedded in a 3-D cyanido-bridged framework.