Magnetic Archimedean Tessellations in Metal–Organic Frameworks

Abstract

The self-assembly of lanthanide ions with ditopic organic spacers results in the formation of complex tiling patterns that mimic the structural motifs of quasi-periodic 2D materials. The linking of trans-{LnI 2 } + nodes (Ln = Gd, Dy) by both closedshell and anion radicals of 4,4′-bipyridine affords rare examples of Archimedean tessellations in a metal−organic framework. We furthermore demonstrate the occurrence of sizable magnetic exchange interactions and slow relaxation of magnetization behavior in a complex tessellation pattern. The implementation of Archimedean tessellations in lanthanide(III) coordination solids couriers a strategy to design elusive quasi-periodic metal−organic frameworks with inimitable magnetic properties.T he design of complex and aperiodic two-dimensional tessellations in molecule-based materials constitutes a novel route to harvest physical properties, for instance, photonic, electronic, magnetic, and phononic characteristics, which are expected to be unparalleled compared to their periodic counterparts. 1−3 However, applications are elusive due to the severe scarcity of materials exhibiting the desired structural motifs. The two-dimensional dodecagonal quasicrystalline phase (Figure 1a, ddQC) is well-known in both hard and soft materials as well as in supramolecular networks. 4−6 In these system, the tessellation of triangles and squares, at a ratio of 4/√3 ≈ 2.3, leads to the disappearance of periodicity and the formation of local 12-fold rotational symmetry. Generally, quasicrystals are found in the vicinity of structurally related, periodic structures, and the ddQCs often co-occur with the periodic Archimedean tessellations (ATs, Figure 1b,c), which are termed quasicrystal approximants. 7 The sole example of a quasicrystal phase found in a metal−organic network structure

Towards Frustration in Eu(II) Archimedean Tessellations

“…[24] The tessellation of EuI2(pyz)5/2 can be described as a distorted elongated triangular pattern with an acute rhombohedral angle, j, of 72.5°. The departure of a from 90° is significantly larger than those found in both of the previously obtained coordination solids with distorted elongated triangular tessellations (LnI2(bipy)5/2, Ln = Gd (j = 78.7°), [22] Yb (j =89.9°) [21] ) and the ligand geometry at the Eu may, alternatively, be described as approaching a defect hexagonal bipyramid. Importantly, the triangular motifs are close to perfect equilateral triangles with Eu×××Eu distances (8.1924(9), 8.273(1), 8.226(1) Å) and Eu×××Eu×××Eu angles (60.51(1)°, 59.54(1)°, 59.95(1)°) departing by less than 1% from ideality.…”

“…It is structurally similar, but not isomorphous, to the previously reported triclinic phases of (LnI2(bipy)5/2, Ln = Gd, Yb). [21,22] The local coordination geometry metrics are strikingly similar to that of EuI2(pyz Recently, some of us reported the coordination solid CrCl2(pyz)2, which incorporates Cr(III) and a partially reduced pyz scaffold, owing to the significant reducing power of Cr(II) as used as a starting material (E°Cr(III)/Cr(II) = -0.42 V). [25,26] For the lanthanide series, the reduction potential of Eu(III) compares well to that of Cr(III) (E°Eu(III)/Eu(II) = -0.35 V).…”

“…[21] Similarly, the reaction of LnI3 (Ln = Gd, Dy) with bipy and elemental Na led to related LnI2(bipy)5/2 coordination solids, which, however, contain Ln(III) nodes and a "redox non-innocent", mixed-valency bipy •-/bipy 0 ligand scaffold. [22] This electrochemical handle and the apparent structure-directing {trans-LnI2} +/0 nodes provides a unique possibility for designing geometrical frustration in 2D coordination solids. Herein, we report two isoreticular {trans-Eu II I2}-based coordination solids, differing in the ditopic linker units, but with conserved pentagonal bipyramidal coordination around the constituent Eu(II) ions, which fulfill the requirements S1; Supporting Information).…”

Structural cutting and recombining in layered sodium dysprosium phosphonate: key roles of flexible pyrazinyl hydrazone molecular tools

“…22 In doing so, the possible intra-/inter-molecular antiferromagnetic interactions between the Dy III ions should not be ignored in this recombination at 2D dysprosium phosphonates. 23…”

Towards frustration in Eu(ii) Archimedean tessellations

“…21 Similarly, the reaction of LnI 3 (Ln = Gd, Dy) with bipy and elemental Na led to related LnI 2 (bipy) 5/2 coordination solids, which, however, contain Ln( iii ) nodes and a “redox non-innocent”, mixed-valency bipy˙ − /bipy 0 ligand scaffold. 22 This electrochemical handle and the apparent structure-directing { trans -LnI 2 } +/0 nodes provides a unique possibility for designing frustration in 2D coordination solids. Herein, we report two isoreticular { trans -Eu II I 2 }-based coordination solids, differing in the ditopic linker units, but with conserved pentagonal bipyramidal coordination around the constituent Eu( ii ) ions, which fulfill the requirements for the observation of frustration in a non-kagome AT.…”