Single-chain magnet behavior in an alternated one-dimensional assembly of a MnIII schiff-base complex and a TCNQ radical

Hitoshi Miyasaka, Tomokura Madanbashi, Kunihisa Sugimoto, Yasuhiro Nakazawa, Wolfgang Wernsdorfer, Ken Ichi Sugiura, Masahiro Yamashita, Claude Coulon, Rodolphe Clérac

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156 Citations (Scopus)

Abstract

An alternated 1:1 chain compound of a MnIII salen derivative and the TCNQ monoradical was synthesized: [Mn(5-TMAMsaltmen)-(TCNQ)](ClO 4)2 (1) (TCNQ = tetracyano-p-quinodimethane; 5-TMAM-saltmen = N,N′-(1,1,2,2-tetramethylethylene) bis(5-trimethylammoniomethylsalicylideneiminato)). Compound 1 has a zigzag chain structure packed with adjacent chains with an interchain Mn⋯Mn distance of over 8 Å. As compound 1 contains no crystallization solvent, the void spaces between chains are occupied only by ClO4- counter ions. Compound 1 has a structure reminiscent of what has been observed in the family, of MnIII(porphyrin)-TCNE or -TCNQ compounds reported previously by Miller and co-workers and we demonstrate herein its unique single-chain magnet behavior among this family of compounds. The direct current (dc) magnetic measurements established the one-dimensional nature of compound 1 with an antiferromagnetic exchange coupling, J/kB≈-96K, between the MnIII ion and TCNQ radical and with an activated correlation length (Δξ = 26.5K) at low temperatures (50-15 K). The slow relaxation of the magnetization was shown in compound 1 by the field hysteresis of the magnetization observed below 3.5 K (with a coercive field up to 14 kOe at 1.8 K). Single-crystal magnetization measurements demonstrated the uniaxial symmetry of this compound and allowed an estimation of the anisotropy field, Ha≈97 kOe. The absence of magnetic ordered phase or spin-glass behavior was established by heat-capacity calorimetry measurements that exhibit no abnormality of Cp between 0.5 K and 10 K. The study of the magnetization relaxation by combined ac (alternating current) and dc techniques showed that compound 1 possesses a single relaxation time (r). As the consequence of the finite size of the chain, the temperature dependence of r presents two activated regimes above and below 4.5 K with τ01 =2.1 × 10-10 s, Δτ1 = 94.1 K and τ02 = 6.8× 10-8s and Δ τ2 = 67.7 K, respectively. The detailed analysis of these dynamics properties together with the correlation length, allows an unambiguous demonstration of the single-chain magnet behavior in 1.

Original languageEnglish
Pages (from-to)7028-7040
Number of pages13
JournalChemistry - A European Journal
Volume12
Issue number27
DOIs
Publication statusPublished - 2006 Sep 18

Keywords

  • Magnetic properties
  • Manganese
  • Salen-type ligand
  • Single-chain magnet
  • TCNQ

ASJC Scopus subject areas

  • Catalysis
  • Organic Chemistry

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