Pentanuclear Lanthanide Mono-organophosphates: Synthesis, Structure, and Magnetism

Abstract

Research on rare-earth phosphates has recently received substantial interest because of their unique physical and chemical properties. In recent years, because of their low solubility, research interest has been built on developing methodologies to prepare nanostructures and grow single crystals of inorganic rare-earth phosphates. The chemistry of rare-earth organophosphates, however, is still at a latent stage. Contrary to the traditional hydrothermal route, we report rare examples of discrete pentanuclear lanthanide(III) organophosphate clusters assembled from a sterically encumbered monoester of phosphoric acid under mild reaction conditions. Single-crystal X-ray analysis revealed that all of the compounds possess a similar core structure, [Ln(μ-OH)(dipp)(NO)(CHOH)(HO)] [Ln = Nd (1), Sm (2), Eu (3), Gd (4), Tb (5), Dy (6), Ho (7), Er (8), Tm (9); dipp = 2,6-diisopropylphenylphosphate], where the anionic charge balance is maintained by the presence of chelating nitrate anions (in the case of 9, x = 0), protonated tmeda, or dipp ligands. The vacant coordination sites on the metal ions are satisfied by coordinated methanol or water molecules. The core structure of these clusters is built on a [Ln(μ-OH)(dipp)] triangle where the phosphate ligands bridge to two further Ln(III) ions. The complexes display lanthanide contraction along the series, with Ln(III) ions displaying different coordination environments/geometries as we move along the series. All of the compounds have been characterized by both analytical and spectroscopic techniques. Magnetic studies revealed the presence of weak antiferromagnetic exchange through the bridging μ-hydroxo moiety and organophosphate groups for the {Gd} analogue, with a significant magnetic entropy change (25.8 J kg K, ΔH = 7 T). The anisotropic complexes reveal an absence of slow relaxation of magnetization, except for Nd (1), Dy (6), and Er (8), which show slow relaxation in an applied DC field.

Coordination Polymers based on the Neutral Ditopic Ligand (C6H4PO(OCH3)2)2 Involving some f‐Block Elements

“…The most frequently used binding sites in metal‐organic frameworks or coordination polymers are carboxylates or nitrogen bases , . In recent times phosphonates are being explored due to the possibility of accessing new metal phosphate morphologies . In contrast, neutral phosphonate esters have not been so widely explored as ligands , .…”

Isomorphous rare-earth tris[bis(2,6-diisopropylphenyl) phosphate] complexes and their catalytic properties in 1,3-diene polymerization and in the inhibited oxidation of polydimethylsiloxane

“…It should be noted that related rare-earth complexes with a related monosubstituted [O 3 P(O-2,6-i Pr 2 C 6 H 3 )] 2À ligand have been described recently. However, due to the lower steric hindrance and various possible coordination modes of the phosphate ligand, these complexes are mainly represented by pentanuclear (Gupta et al, 2015(Gupta et al, , 2017b and one-dimensional coordination polymeric structures (Gupta et al, 2017a). Introduction of a second bulky substituent, i.e.…”

Facile access to efficiently luminescent Ln3+ phosphonic ester coordination polymers (Ln = Eu, Tb, Dy)

“…[4][5][6] While the most frequently employed binding sites in coordination polymers or metal-organic frameworks are carboxylates or nitrogen bases, 7,8 phosphonates 9, 10 and organophosphates have been used as ligands as well. 11 By contrast, the use of phosphonic esters for this purpose is less explored and just started to emerge. 12,13 The special benefit of the P (V) QO units as ligands towards lanthanide ions is their property to increase quantum yields of complexes compared to their carboxylic acid counterparts.…”