Andrews, Philip C., Deacon, Glen B., Frank, René, Fraser, Benjamin H., Junk, Peter C., Maclellan, Jonathan G., Massi, Massimiliano, Moubaraki, Boujemaa, Murray, Keith S., and Silberstein, Morry (2009) Formation of Ho-III trinuclear clusters and Gd-III monodimensional polymers induced by ortho and para regioisomers of pyridyl-functionalised beta-diketones: synthesis, structure, and magnetic properties. European Journal of Inorganic Chemistry, 2009 (6). pp. 744-751.

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Abstract

Reaction of GdCl3(H2O)6 and 1,3-bis(pyridin-4-yl)propane-1,3-dione in methanol with an excess of triethylamine produced a monodimensional polymeric chain [Gd(p-dppd)3(H2O)]∞, whereas treatment of HoCl3(H2O)6 with 1,3-bis(pyridin-2-yl)propane-1,3-dione yielded a trinuclear cluster [Ho3(o-dppd)3(μ3-OH)2(H2O)4Cl2]Cl2. The compounds were characterised by elemental analysis, IR spectroscopy and magnetism, and their structures were investigated by X-ray crystallography. The 8.20-μB magnetic-moment value of the polymeric [Gd(p-dppd)3(H2O)]∞, between 300 and 20 K, and the magnetisation isotherms (2–20 K; fields 0–5 T), are in agreement with essentially uncoupled single-ion Gd3+ f7 centres, a small decrease in μeff below 20 K being indicative of zero-field splitting. A temperature-dependent dc-susceptibility and magnetisation investigation of the trinuclear (triangular) [Ho3(o-dppd)3(μ3-OH)2(H2O)4Cl2]Cl2 revealed that spin-orbit and ligand-field effects on the Ho3+ centres, leading to thermal depopulation of Zeeman levels and consequent decreases in μeff values with decreasing temperature, are occurring rather than weak intra-cluster antiferromagnetic coupling. Frequency- and temperature-dependent ac-susceptibility studies on this homometallic Ho3+ cluster did not show clear evidence for slow magnetisation reversal, characteristic of single-molecule magnetism (SMM), and this contrasts with such behaviour recently reported, elsewhere, for a Dy3+ triangle having the same core structure but with different chelating {O,O} ligands.

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