Reversible magnetism between an antiferromagnet and a ferromagnet related to solvation/desolvation in a robust layered [Ru2]2TCNQ charge-transfer system

Natsuko Motokawa, Satoshi Matsunaga, Shinya Takaishi, Hitoshi Miyasaka, Masahiro Yamashita, Kim R. Dunbar

Research output: Contribution to journalArticlepeer-review

110 Citations (Scopus)

Abstract

The charge-transfer compound [{Ru2(O2CPh-o-Cl) 4}2TCNQ(MeO)2]·CH2Cl 2 (1; o-ClPhCO2- = o-chlorobenzoate; TCNQ(MeO)2 = 2,5-dimethoxy-7,7,8,8-tetracyanoquinodimethane) was synthesized from the reaction of the neutral precursors [Ru2 II,II(O2CPh-o-Cl)4] (abbreviated as [Ru 2II,II] or [Ru24+]) and TCNQ(MeO)2 in a CH2Cl2/nitrobenzene solution. The structure consists of two-dimensional layers consisting of an infinite array in which [Ru2II,II] units are involved in charge transfer to TCNQ(MeO)2 to give a formal charge of [{Ru2 4.5+}-TCNQ(MeO)2̇ --{Ru2 4.5+}]. Interstitial CH2Cl2 molecules are located in the void spaces between the layers. Strong intralayer magnetic coupling between the units [Ru2II,II] with S = 1 or [Ru2II,III] with S = 3/2 and TCNQ(MeO)2 ̇ - with S = 1/2, as well as long-range ordering due to antiferromagnetic interlayer interactions, was observed. An antiferromagnetic ground state exists below TN = 75 K, which undergoes a metamagnetic transition under applied fields less than 2 T to a field-induced canted antiferromagnetic state with large coercivities up to Hc = 1.6 T at 1.8 K. Compound 1 gradually loses the interstitial CH2Cl2 molecule at room temperature to form a dried sample (1-dry) without loss of crystallinity and converts nearly reversibly back to 1 after being exposed to CH2Cl2 vapor for 72 h (distinguished as 1′). Interestingly, during this process there is no significant change in lattice dimensions and bond distances or angles with a volume change of only 1.2 vol %. The only discernible difference is ordering/disordering of a pendant ligand orientation, but the magnetism is dramatically altered to a ferromagnetic state with Tc ≈ 56 K for 1-dry. The magnetic property changes are gradual and depend on the degree of interstitial CH2Cl2 molecule loss with reversibility in the process of going between 1 and 1-dry. In addition, in the case of partially desolvated crystals that have mixed domains of ferromagnetically and antiferromagnetically ordered domains for desolvated and solvated segments, respectively, the complete change to ferromagnet can also be triggered by magnetic fields even if the desolvated segments are comparatively minor compared to the solvated segments in a crystal. Surprisingly, the information of the existence of ferromagnetically ordered domains is dynamically recorded in the entire crystal after applying significant magnetic fields as if the majority of the antiferromagnetically ordered domains for solvated segments were never present.

Original languageEnglish
Pages (from-to)11943-11951
Number of pages9
JournalJournal of the American Chemical Society
Volume132
Issue number34
DOIs
Publication statusPublished - 2010 Sep 1

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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