Terbium and Europium Chlorocyananilate-Based 2D Coordination Polymers

Abstract

Two-dimensional layered coordination polymers based on the hetero-substituted 3-chloro-6-cyano-2,5-dihydroxybenzoquinone ligands, hereafter ClCNAn2− anilate, and LnIII ions (Tb and Eu) are reported. Compounds 1 and 2, formulated as Ln2(ClCNAn)3(DMSO)6 (LnIII = Tb, 1; Eu, 2), and their related intermediates 1′ and 2′, formulated as Ln2(ClCNAn)3(H2O)x·yH2O (x + y likely = 12, Ln = Tb, 1′; and Eu, 2′), were prepared by a conventional one-pot reaction (the latter) and recrystallized from DMSO solvent (the former). Polyhydrated intermediates 1′ and 2′ show very similar XRPD patterns, while, despite their common stoichiometry, 1 and 2 are not isostructural. Compound 1 consists of a 2D coordination framework of 3,6 topology, where [Tb(DMSO)3]III moieties are bridged by three bis-chelating ClCNAn2− ligands, forming distorted hexagons. Ultrathin nanosheets of 1 were obtained by exfoliation via the liquid-assisted sonication method and characterized by atomic force microscopy, confirming the 2D nature of 1. The crystal structure of 2, still showing the presence of 2D sheets with a “hexagonal” mesh and a common (3,6) connectivity, is based onto flat, non-corrugated slabs. Indeed, at a larger scale, the different “rectangular tiles” show clear roofing in 1, which is totally absent in 2. The magnetic behavior of 1 very likely indicates depopulation of the highest crystal-field levels, as expected for TbIII compounds.

Tuning the slow magnetic relaxation with the substituents in anilate bridged bis(dysprosium) complexes

“…Indeed, the Cl/CN substituents are equally distributed in the structure due to the 0.5 partial occupancy in the asymmetric unit, this feature being common for compounds involving the ClCNAn 2− ligand. 16 The octacoordinated Dy III has the same coordination sphere {N 6 O 2 } but with a different geometry suggested by CShM. It adopts indeed a D 2d triangular dodecahedron geometry (Fig.…”

“…10–13 Among quinone ligands, those based on 2,5-dihydroxy-1,4-benzoquinone (or anilic acid), referred to as anilates, can efficiently coordinate lanthanide and d-metal ions and, thanks to their non-innocent redox behaviour, allow a wide range of redox states 14,15 with fine tuning of the magnetic interactions. 16–21 Indeed, the anilate ligands can accommodate two subsequent mono-electronic redox processes, in the first one a semiquinone radical system being formed, that is generally stabilized by coordination, which can promote strong magnetic exchange interaction thanks to the open shell character. 22,23 Dinuclear lanthanide complexes based on the hydrotris(pyrazol-1-yl)borate (HBpz 3 − ) scorpionate capping ligand and anilate (An) bridging linkers were first reported in 2004.…”

Anilato‐Based Coordination Polymers with Slow Relaxation of the Magnetization: Role of the Synthetic Method and Anilato Ligand

“…From the magnetic point of view, these ligands can connect magnetic centres with a tuneable weak antiferromagnetic coupling (when connecting transition metals) [17] or with a negligible one when connecting lanthanoid(III) ions. [7,[17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] This good magnetic isolation of the lanthanoid(III) ions is due to the absence of overlap between the internal 4 f orbitals on the Ln III and the 2p orbitals of the coordinated O atoms of the anilato ligand. A consequence of this isolation is the presence of slow relaxation of the magnetization of the Ln III ions at low temperatures in these CPs and MOF.…”