title: 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, [Ln5(μ3-OH)(dipp)6(NO3)x(CH3OH)y(H2O)z]2+[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 dipp2-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 [Ln3(μ3-OH)(dipp)6] 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 μ3-hydroxo moiety and organophosphate groups for the {GdIII5} analogue, with a significant magnetic entropy change (25.8 J kg-1K-1, 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.
authors.affiliation: Department of Chemistry, Indian Institute of Technology Bombay , Powai, Mumbai 400 076, India.
authors.forename: Sandeep K
authors.initials: SK
authors.lastname: Gupta
authors.affiliation: School of Science and the Environment, Division of Chemistry, Manchester Metropolitan University , Manchester M15 6BH, U.K.
authors.forename: Stuart K
authors.initials: SK
authors.lastname: Langley
authors.affiliation: Department of Chemistry, Indian Institute of Technology Bombay , Powai, Mumbai 400 076, India.
authors.forename: Kamna
authors.initials: K
authors.lastname: Sharma
authors.affiliation: School of Chemistry, Monash University , Clayton, Victoria 3800, Australia.
authors.forename: Keith S
authors.initials: KS
authors.lastname: Murray
authors.affiliation: Department of Chemistry, Indian Institute of Technology Bombay , Powai, Mumbai 400 076, India.
authors.forename: Ramaswamy
authors.identifier: http://orcid.org/0000-0002-1816-3225
authors.initials: R
authors.lastname: Murugavel