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      Pentagonal Bipyramid FeII Complexes: Robust Ising-Spin Units towards Heteropolynuclear Nanomagnets.

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          Abstract

          Pentagonal bipyramid FeII complexes have been investigated to evaluate their potential as Ising-spin building units for the preparation of heteropolynuclear complexes that are likely to behave as single-molecule magnets (SMMs). The considered monometallic complexes were prepared from the association of a divalent metal ion with pentadentate ligands that have a 2,6-diacetylpyridine bis(hydrazone) core (H2 LN3O2R ). Their magnetic anisotropy was established by magnetometry to reveal their zero-field splitting (ZFS) parameter D, which ranged between -4 and -13 cm-1 and was found to be modulated by the apical ligands (ROH versus Cl). The alteration of the D value by N-bound axial CN ligands, upon association with cyanometallates, was also assessed for heptacoordinated FeII as well as for related NiII and CoII derivatives. In all cases, N-coordinated cyanide ligands led to large magnetic anisotropy (i.e., -8 to -18 cm-1 for Fe and Ni, +33 cm-1 for Co). Ab initio calculations were performed on three FeII complexes, which enabled one to rationalize the role of the ligand on the nature and magnitude of the magnetic anisotropy. Starting from the pre-existing heptacoordinated complexes, a series of pentanuclear compounds were obtained by reactions with paramagnetic [W(CN)8 ]3- . Magnetic studies revealed the occurrence of ferromagnetic interactions between the spin carriers in all the heterometallic systems. Field-induced slow magnetic relaxation was observed for mononuclear FeII complexes (Ueff /kB up to 53 K (37 cm-1 ), τ0 =5×10-9  s), and SMM behavior was evidenced for a heteronuclear [Fe3 W2 ] derivative (Ueff /kB =35 K and τ0 =4.6 10-10  s), which confirmed that the parent complexes were robust Ising-type building units. High-field EPR spectroscopic investigation of the ZFS parameters for a Ni derivative is also reported.

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          Author and article information

          Journal
          Chemistry
          Chemistry (Weinheim an der Bergstrasse, Germany)
          Wiley
          1521-3765
          0947-6539
          Mar 28 2017
          : 23
          : 18
          Affiliations
          [1 ] CNRS, LCC (Laboratoire de Chimie de Coordination), 205, route de Narbonne, 31077, Toulouse, France.
          [2 ] Université de Toulouse, UPS, INPT, LCC, 31077, Toulouse, France.
          [3 ] Indian Institute of Science, Bangalore, 560012, India.
          [4 ] Ulsan National Institute of Science and Technology (UNIST), 50, UNIST-gil, Ulsan, 44919, Republic of Korea.
          [5 ] Laboratoire de Chimie et Physique Quantiques, UMR5626, IRSAMC, Université de Toulouse 3, Paul Sabatier, 118 route de Narbonne, 31062, Toulouse Cedex 9, France.
          [6 ] Laboratoire National des Champs Magnétiques Intenses, UPR CNRS 3228, Université Grenoble Alpes, 25, Avenue des Martyrs, B.P. 166, 38042, Grenoble Cedex 9, France.
          Article
          10.1002/chem.201605549
          28118518
          6f4e9abb-245e-4217-808c-4f14d4c8563d
          © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
          History

          ab initio calculations,bipyramid pentagonal,coordination chemistry,iron,magnetic properties

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