Bar Arun Kumar, Gogoi Nayanmoni, Pichon Céline, Goli V M L Durga Prasad, Thlijeni Mehrez, Duhayon Carine, Suaud Nicolas, Guihéry Nathalie, Barra Anne-Laure, Ramasesha S, Sutter Jean-Pascal
CNRS, LCC (Laboratoire de Chimie de Coordination), 205, route de Narbonne, 31077, Toulouse, France.
Université de Toulouse, UPS, INPT, LCC, 31077, Toulouse, France.
Chemistry. 2017 Mar 28;23(18):4380-4396. doi: 10.1002/chem.201605549. Epub 2017 Mar 6.
Pentagonal bipyramid Fe 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 (H L ). Their magnetic anisotropy was established by magnetometry to reveal their zero-field splitting (ZFS) parameter D, which ranged between -4 and -13 cm 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 Fe as well as for related Ni and Co derivatives. In all cases, N-coordinated cyanide ligands led to large magnetic anisotropy (i.e., -8 to -18 cm for Fe and Ni, +33 cm for Co). Ab initio calculations were performed on three Fe 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) ] . 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 Fe complexes (U /k up to 53 K (37 cm ), τ =5×10 s), and SMM behavior was evidenced for a heteronuclear [Fe W ] derivative (U /k =35 K and τ =4.6 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.
已对五角双锥铁配合物进行了研究，以评估其作为伊辛自旋构建单元的潜力，用于制备可能表现为单分子磁体（SMM）的异多核配合物。所考虑的单金属配合物是由二价金属离子与具有2,6 - 二乙酰基吡啶双（腙）核心（H₂L）的五齿配体结合制备而成。通过磁测量确定了它们的磁各向异性，以揭示其零场分裂（ZFS）参数D，其范围在-4至-13 cm⁻¹之间，并且发现其受顶端配体（ROH对Cl）的调节。还评估了七配位铁以及相关镍和钴衍生物与氰基金属酸盐结合时，通过N键合轴向CN配体对D值的改变。在所有情况下，N配位的氰化物配体导致大的磁各向异性（即，铁和镍为-8至-18 cm⁻¹，钴为+33 cm⁻¹）。对三种铁配合物进行了从头算计算，这使得人们能够合理化配体对磁各向异性的性质和大小的作用。从预先存在的七配位配合物开始，通过与顺磁性的[W(CN)₈]²⁻反应获得了一系列五核化合物。磁性研究表明，在所有异金属体系中自旋载体之间存在铁磁相互作用。对于单核铁配合物观察到了场诱导的慢磁弛豫（Ueff/kB高达53 K（37 cm⁻¹），τ = 5×10⁻⁶ s），并且对于异核[Fe₄W]衍生物证明了SMM行为（Ueff/kB = 35 K且τ = 4.6×10⁻⁶ s），这证实了母体配合物是稳健的伊辛型构建单元。还报道了对一种镍衍生物的ZFS参数的高场EPR光谱研究。
