Field-Induced Dysprosium Single-Molecule Magnet Based on a Redox-Active Fused 1,10-Phenanthroline-Tetrathiafulvalene-1,10-Phenanthroline Bridging Triad.

Bertrand Lefeuvre,Vincent Dorcet,Boris Le Guennic,Olivier Galangau,Jessica Flores Gonzalez,Fabrice Pointillart,Vincent Montigaud,Lahcène Ouahab,Olivier Cador

doi:10.3389/fchem.2018.00552

Abstract

Tetrathiafulvalene and 1,10-phenanthroline moieties present, respectively remarkable redox-active and complexation activities. In this work, we investigated the coordination reaction between the bis(1,10-phenanthro[5,6-b])tetrathiafulvalene triad (L) and the Dy(hfac)3·2H2O metallo precursor. The resulting {[Dy2(hfac)6(L)]·CH2Cl2·C6H14}3 (1) dinuclear complex showed a crystal structure in which the triad L bridged two terminal Dy(hfac)3 units and the supramolecular co-planar arrangement of the triads is driven by donor-acceptor interactions. The frequency dependence of the out-of-phase component of the magnetic susceptibility highlights three distinct maxima under a 2000 Oe static applied magnetic field, a sign that 1 displays a Single-Molecule Magnet (SMM) behavior with multiple magnetic relaxations. Ab initio calculations rationalized the Ising character of the magnetic anisotropy of the DyIII ions and showed that the main anisotropy axes are perpendicular to the co-planar arrangement of the triads. Single-crystal rotating magnetometry confirms the orientation of the main magnetic axis. Finally combining structural analysis and probability of magnetic relaxation pathways through Quantum Tunneling of the Magnetization (QTM) vs. excited states (Orbach), each DyIII center has been attributed to one of the three observed magnetic relaxation times. Such coordination compound can be considered as an ideal candidate to perform redox-magnetic switching.

Highlights

Single-Molecule Magnets (SMMs) are intensively studied for more than 25 years due to their potential applications in high density data storage, quantum computing, and spintronics (Leuenberger and Loss, 2001; Gatteschi et al, 2006; Lehmann et al, 2007; Bogani and Wernsdorfer, 2008; Mannini et al, 2009; Ganzhorn et al, 2013)
TTF-Based Single-Molecule Magnet quickly grown during the last decade due to their high magnetic moment and strong magnetic anisotropy making them potential candidates for the elaboration of SMMs (Benelli and Gatteschi, 2002; Sessoli and Powell, 2009; Rinehart and Long, 2011; Woodruff et al, 2013; Liddle and van Slageren, 2015; Goodwin et al, 2017; Guo et al, 2017; Pointillart et al, 2017; Gupta and Murugavel, 2018)
All the DyIII centers are linked to three hfac− anions and one L ligand giving an N2O6 surrounding with a D4d symmetry for Dy1, D2d symmetry for Dy2-Dy5 and an intermediate symmetry between D2d and C2v for Dy6

Summary

Introduction

Single-Molecule Magnets (SMMs) are intensively studied for more than 25 years due to their potential applications in high density data storage, quantum computing, and spintronics (Leuenberger and Loss, 2001; Gatteschi et al, 2006; Lehmann et al, 2007; Bogani and Wernsdorfer, 2008; Mannini et al, 2009; Ganzhorn et al, 2013). Among the plethora of possible decorations of the TTF fragment, the 1,10-phenanthroline (phen) is an excellent choice to construct donor-acceptor (D-A) systems (Jia et al, 2007; Keniley et al, 2010, 2013; Qin et al, 2011). Their association with metallic precursors as led already to the observation of auspicious optical (Dupont et al, 2013; Lapadula et al, 2015) and magnetic (Pointillart et al, 2015b, 2016) properties. Few triads involving the phen moiety are already available in the literature such as the bis-(dipyrido[3,2-a:2′,3′-c]phenazine)-TTF (Jia et al, 2014) and Bis(1,10-phenanthro[5,6-b])tetrathiafulvalene (Chen et al, 2016)

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Conclusion