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Magnetic Sponge Behavior via Electronic State Modulations.

Authors :: Zhang J
Kosaka W
Sugimoto K
Miyasaka H
Source :: Journal of the American Chemical Society [J Am Chem Soc] 2018 Apr 25; Vol. 140 (16), pp. 5644-5652. Date of Electronic Publication: 2018 Apr 11.
Publication Year :: 2018
Abstract: A reversible magnetic change in response to external stimuli is a desired function of molecular magnetic materials. The magnetic change induced by a change in the intrinsic spin is significant because the magnetic change is inevitable and could become drastic. In this study, we demonstrate a reversible magnetic change closely associated with electronic state modulations, as well as structural modifications realized by solvation/desolvation cycles of a magnetic sponge. The compound was a D <subscript>2</subscript> A-type layered magnet, [{Ru <subscript>2</subscript> (O <subscript>2</subscript> CPh-2,3,5-Cl <subscript>3</subscript> ) <subscript>4</subscript> } <subscript>2</subscript> (TCNQMe <subscript>2</subscript> )]·4DCM (1; 2,3,5-Cl <subscript>3</subscript> PhCO <subscript>2</subscript> <superscript>-</superscript> = 2,3,5-trichlorobenzoate; TCNQMe <subscript>2</subscript> = 2,5-dimethyl-7,7,8,8-tetracyanoquinodimethane; DCM = dichloromethane), where [Ru <subscript>2</subscript> (O <subscript>2</subscript> CPh-2,3,5-Cl <subscript>3</subscript> ) <subscript>4</subscript> ] ([Ru <subscript>2</subscript> <superscript>II,II</superscript> ]) is an electron donor (D) and TCNQMe <subscript>2</subscript> is an electron acceptor (A). Compound 1 had a one-electron-transferred, charge-ordered state with a [{Ru <subscript>2</subscript> <superscript>II,II</superscript> }-TCNQMe <subscript>2</subscript> <superscript>•-</superscript> -{Ru <subscript>2</subscript> <superscript>II,III</superscript> } <superscript>+</superscript> ] (1e-I) formula. Strong intralayer antiferromagnetic couplings between [Ru <subscript>2</subscript> <superscript>II,II</superscript> ] with S = 1 or [Ru <subscript>2</subscript> <superscript>II,III</superscript> ] <superscript>+</superscript> with S = 3/2 and TCNQMe <subscript>2</subscript> <superscript>•-</superscript> with S = 1/2, as well as ferromagnetic interlayer interactions, induced long-range ferrimagnetic ordering at T <subscript>c</subscript> = 101 K. Interstitial DCM molecules were located between layers, and these were gradually eliminated under vacuum at 80 °C to form a solvent-free compound (1-dry) without loss of crystallinity. The electronic state of 1-dry thermally fluctuated and eventually provided a charge-disproportionate disordered state, with a [{Ru <subscript>2</subscript> } <superscript>0.5+</superscript> -TCNQMe <subscript>2</subscript> <superscript>1.5-</superscript> -{Ru <subscript>2</subscript> <superscript>II,III</superscript> } <superscript>+</superscript> ] (1.5e-I) formula as the ground state. The T <subscript>c</subscript> in 1-dry was 34 K because of the presence of diamagnetic TCNQMe <subscript>2</subscript> <superscript>2-</superscript> in some parts of the framework. A large T <subscript>c</subscript> variation with Δ T <subscript>c</subscript> ≈ 70 K was switchable; switching was achieved by charge-state modulations accompanied by subtle structural modifications in solvation/desolvation treatments.