title: Pentagonal Bipyramid FeIIComplexes: Robust Ising-Spin Units towards Heteropolynuclear Nanomagnets.
abstract: Pentagonal bipyramid FeIIcomplexes 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 (H2LN3O2R). Their magnetic anisotropy was established by magnetometry to reveal their zero-field splitting (ZFS) parameter D, which ranged between -4 and -13 cm-1and 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 FeIIas well as for related NiIIand CoIIderivatives. In all cases, N-coordinated cyanide ligands led to large magnetic anisotropy (i.e., -8 to -18 cm-1for Fe and Ni, +33 cm-1for Co). Ab initio calculations were performed on three FeIIcomplexes, 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 FeIIcomplexes (Ueff/kBup to 53 K (37 cm-1), τ0=5×10-9s), and SMM behavior was evidenced for a heteronuclear [Fe3W2] derivative (Ueff/kB=35 K and τ0=4.6 10-10s), 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.
authors.affiliation: CNRS, LCC (Laboratoire de Chimie de Coordination), 205, route de Narbonne, 31077, Toulouse, France.|Université de Toulouse, UPS, INPT, LCC, 31077, Toulouse, France.
authors.forename: Arun Kumar
authors.initials: AK
authors.lastname: Bar
authors.affiliation: CNRS, LCC (Laboratoire de Chimie de Coordination), 205, route de Narbonne, 31077, Toulouse, France.|Université de Toulouse, UPS, INPT, LCC, 31077, Toulouse, France.
authors.forename: Nayanmoni
authors.initials: N
authors.lastname: Gogoi
authors.affiliation: CNRS, LCC (Laboratoire de Chimie de Coordination), 205, route de Narbonne, 31077, Toulouse, France.|Université de Toulouse, UPS, INPT, LCC, 31077, Toulouse, France.
authors.forename: Céline
authors.identifier: http://orcid.org/0000-0002-5429-1224
authors.initials: C
authors.lastname: Pichon
authors.affiliation: Indian Institute of Science, Bangalore, 560012, India.|Ulsan National Institute of Science and Technology (UNIST), 50, UNIST-gil, Ulsan, 44919, Republic of Korea.
authors.forename: V M L Durga Prasad
authors.initials: VM
authors.lastname: Goli
authors.affiliation: CNRS, LCC (Laboratoire de Chimie de Coordination), 205, route de Narbonne, 31077, Toulouse, France.|Université de Toulouse, UPS, INPT, LCC, 31077, Toulouse, France.
authors.forename: Mehrez
authors.initials: M
authors.lastname: Thlijeni
authors.affiliation: CNRS, LCC (Laboratoire de Chimie de Coordination), 205, route de Narbonne, 31077, Toulouse, France.|Université de Toulouse, UPS, INPT, LCC, 31077, Toulouse, France.
authors.forename: Carine
authors.initials: C
authors.lastname: Duhayon
authors.affiliation: Laboratoire de Chimie et Physique Quantiques, UMR5626, IRSAMC, Université de Toulouse 3, Paul Sabatier, 118 route de Narbonne, 31062, Toulouse Cedex 9, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Suaud
authors.affiliation: Laboratoire de Chimie et Physique Quantiques, UMR5626, IRSAMC, Université de Toulouse 3, Paul Sabatier, 118 route de Narbonne, 31062, Toulouse Cedex 9, France.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Guihéry
authors.affiliation: Laboratoire National des Champs Magnétiques Intenses, UPR CNRS 3228, Université Grenoble Alpes, 25, Avenue des Martyrs, B.P. 166, 38042, Grenoble Cedex 9, France.
authors.forename: Anne-Laure
authors.initials: AL
authors.lastname: Barra
authors.affiliation: Indian Institute of Science, Bangalore, 560012, India.
authors.forename: S
authors.initials: S
authors.lastname: Ramasesha
authors.affiliation: CNRS, LCC (Laboratoire de Chimie de Coordination), 205, route de Narbonne, 31077, Toulouse, France.|Université de Toulouse, UPS, INPT, LCC, 31077, Toulouse, France.
authors.forename: Jean-Pascal
authors.identifier: http://orcid.org/0000-0003-4960-0579
authors.initials: JP
authors.lastname: Sutter
keywords: ab initio calculations; bipyramid pentagonal; coordination chemistry; iron; magnetic properties