Adiabatic demagnetisation experiments on a C3h symmetric molecular {Gd7} cluster reveal effects of intramolecular dipolar interactions and geometric spin frustration.

Two {Ln10} cages are reported (Ln = Dy or Gd) which feature a nine-metal ring surrounding a central metal site. Magnetic studies show weak anti-ferromagnetic exchange around the nine-metal ring, which should create spin frustration.

Reaction of (aminomethyl)phosphonic acid (ampH2) with a mixture of gadolinium and cobalt pivalates under solvothermal conditions, led to a pseudo-icosahedral cage {Gd12}, which shows a large magnetocaloric effect (MCE).

Reaction of oxo-centered Cr(iii) triangles with a lanthanide salt and t-butylphosphonate leads to {Cr6Ln2} compounds. Magnetic and EPR studies show the ground state of the individual Cr triangles is S = 3/2 with little communication between them.

Three octanuclear phosphonate clusters, formulated as [Ln8(O3P(t)Bu)6(μ3-OH)2(H2O)2(HO(i)Bu)(O2C(t)Bu)12](NH3(i)Pr)2 (Ln = Gd, Dy and Tb), were synthesised by refluxing a mixture of pivalic acid (HO2C(t)Bu), Ln(NO3)3·6H2O, tert-Butyl phosphonic acid (H2O3P(t)Bu) and isopropylamine ((i)PrNH2) in isobutyl alcohol (i)BuOH.

Two new tetrametallic lanthanide-phosphonate complexes have been structurally and magnetically characterised. The {Dy4} complex is a single molecule magnet.

The synthesis, structures and magnetic properties of a family of lanthanide complexes containing phosphonate ligands are reported. Reaction of hydrated lanthanide nitrate and (t)butylphosphonic acid under reflux conditions in iso-butanol, in the presence of pivalic acid as a co-ligand produced five new lanthanide complexes; pyridine (py) was present as a base. The compounds formed are tetrametallic, with the general formula [pyH]4[Ln4(μ3-OH)(O3P(t)Bu)3(HO3P(t)Bu)(O2C(t)Bu)2(NO3)6] where Ln = Gd(III), 1; Tb(III), 2; Dy(III), 3; Ho(III), 4 and Er(III), 5. The metal sites within the complexes lie on the vertices of a triangle-based pyramid, with phosphonate ligands on the triangular faces linking the apical Ln site to the Ln sites in the base. Each lanthanide(III) site is eight-coordinate. Magnetic studies of the compounds show a decline in the product χ(M)T with T; modelling the behaviour of 1 shows anti-ferromagnetic exchange between Gd(III) centres within the triangle with a negligible interaction to the fourth Gd(III) centre at the apex of the trigonal pyramid.

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