Chiral Supramolecular Nanotubes of Single‐Chain Magnets

Abstract

We report a single‐chain magnet (SCM) made of a terbium(III) building block and a nitronyl‐nitroxide radical (NIT) functionalized with an aliphatic chain. This substitution is targeted to induce a long‐range distortion of the polymeric chain and accordingly it gives rise to chains that are curled with almost 20 nm helical pitch. They self‐organize as a chiral tubular superstructure made of 11 chains wound around each other. The supramolecular tubes have a 4.5 nm internal diameter. Overall, this forms a porous chiral network with almost 44 % porosity. Ab initio calculations highlight that each TbIII ion possesses high magnetic anisotropy. Indeed, notwithstanding the supramolecular arrangement each chain behaves as a SCM. Magnetic relaxation with both finite and infinite‐size regimes is observed and confirms the validity of the Ising approximation. This is associated with quite strong coercive field and magnetic remanence (Hc=2400 Oe MR=2.09 μB at 0.5 K) for this class of compounds.

Enhanced Single‐Chain Magnet Behavior via Anisotropic Exchange in a Cyano‐Bridged MoIII–MnII Chain

“…[4] Therefore, it should be easier, in principle, to increase D t of the SCMs by enhancing both the local magnetic anisotropy and the intrachain magnetic coupling. [5] This strategy has led to a number of high performance SCMs prepared by connecting highly anisotropic magnetic units, such as those containing Co II , Mn III and Ln III ions or polynuclear molecules behaving as SMM themselves (for example, Mn 2 Fe, [6] Mn 3 , [7] and Mn 4 SMMs [8] ), with bridges such as nitronyl nitroxides [9] and organonitrile [10] radicals, azides, [11] and cyanides as well as others. [12][13][14][15] Among the reported SCMs, the 4d and 5d cyanometallate complexes are of special interest.…”

Single-chain magnet behavior in a finite linear hexanuclear molecule

“…It is worth comparing the finite hexanuclear molecules obtained here with the previously reported chains. 49 At a first glance, one could think that the chains form first and that water molecules cut it in special points to form the finite molecule. However, no obvious “cutting point” can be found on the chains using either the symmetry operation of the space group, the number of repeating asymmetric unit, the Tb coordination polyhedron or the calculated easy-magnetic axes orientation ( Fig.…”

“…The chemical integrity of the compound can be conrmed using luminescence measurements. Such measurements provide a very sensitive estimation of the stability of NIT-Tb III based compounds 49 because both uncoordinated reactants emit in the visible: a line-shaped green emission for the uncoordinated Tb(hfac) 3 unit (because of the efficient antenna effect of the b-diketonate ligand) 55 and a broad red emission for the NIT radical. 56,57 When the two molecules are coordinated, Tb III emission is quenched while the NIT radical emission is blue-shied by metal-ligand charge transfer (MLCT).…”

“…We showed that the chains of formula [(Tb(hfac) 3 ) 6 (NITPhOHexyl) 5 (H 2 O) 2 ] n (with hfac − = hexafluoroacetylacetonate and NIT-Ph- O -Hexyl = 2-(4′-(hexyloxy)phenyl)-4,4,5,5-tetramethylimidazolin-1-oxyl-3-oxide) can be organized in the crystal packing to form chiral supramolecular nanotubes of single-chain magnets. 49 In this paper, we report how chains can be converted into finite hexanuclear species (latter called hexanuclears ) with an enhanced SCM behavior.…”

Enhanced Single‐Chain Magnet Behavior via Anisotropic Exchange in a Cyano‐Bridged MoIII–MnII Chain

“…[4] Therefore, it should be easier, in principle, to increase D t of the SCMs by enhancing both the local magnetic anisotropy and the intrachain magnetic coupling. [5] This strategy has led to a number of high performance SCMs prepared by connecting highly anisotropic magnetic units, such as those containing Co II , Mn III and Ln III ions or polynuclear molecules behaving as SMM themselves (for example, Mn 2 Fe, [6] Mn 3 , [7] and Mn 4 SMMs [8] ), with bridges such as nitronyl nitroxides [9] and organonitrile [10] radicals, azides, [11] and cyanides as well as others. [12][13][14][15] Among the reported SCMs, the 4d and 5d cyanometallate complexes are of special interest.…”