Observation of the influence of dipolar and spin frustration effects on the magnetocaloric properties of a trigonal prismatic {Gd} molecular nanomagnet.

We report the synthesis and structure of a molecular {Gd} cage of the formula (PrNH)[Gd(μ-OH)(CO)(OC Bu)] which has crystallographic symmetry. Low temperature specific heat and adiabatic demagnetization experiments (the latter achieving temperatures below 100 mK), lead to the observation of the effects of both intramolecular dipolar interactions and geometric spin frustration. The dipolar interaction leads to a massive rearrangement of energy levels such that specific heat and entropy below 2 K are strongly modified while magnetic susceptibility and magnetization above 2 K are not affected.

A pseudo-icosahedral cage {Gd12} based on aminomethylphosphonate.

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).

Single molecule magnet behaviour in a {Dy4P2} octahedron.

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

Crystal structure of diethyl 2,2'-[((1E,1'E)-{[(1R,4R)-cyclo-hexane-1,4-di-yl]bis-(aza-nylyl-idene)}bis-(methanylyl-idene))bis-(1H-pyrrole-2,1-di-yl)]di-acetate.

The whole mol-ecule of the title compound, C24H32N4O4, is generated by inversion symmetry. The cyclo-hexane ring adopts a chair conformation and the conformation about the C=N bonds is E. The pyrrole rings have an anti confirmation with respect to the cyclo-hexane moiety and the ethyl acetate groups have extended conformations.

Tetrametallic lanthanide(III) phosphonate cages: synthetic, structural and magnetic studies.

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.

Linking Cr₃ triangles through phosphonates and lanthanides: synthetic, structural, magnetic and EPR studies.

The preparation and structural characterisation of five 3d-4f mixed metal phosphonate cages with general formula [Cr(III)6Ln(III)2(μ3-O)2(H2O)2(O3P(t)Bu)4(O2C(t)Bu)12(HO(i)Bu)2((i)PrNH2)2] where Ln(III) = La, 1; Tb, 3; Dy, 4; Ho, 5 and [Cr(III)6Gd(III)2(μ3-O)2(H2O)2(O3P(t)Bu)4(O2C(t)Bu)12(HO(i)Bu)4] (2) are reported. The structure contains two oxo-centred {Cr3} triangles, bridged by phosphonates and lanthanides. The magnetic behaviour of 1 has been modelled as two non-interacting isosceles triangles, involving two antiferromagnetic interactions (J1 = -8.

Centred nine-metal rings of lanthanides.

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.

Octametallic 4f-phosphonate horseshoes.

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.