Spectroscopy and magnetism of polymeric Ln(CCl3COO)3•2 H2O and their heteronuclear Ln2Cu(CCl3COO)8•6 H2O analogues (Ln = Sm, Gd)

In order to study the exchange interactions between f- and d-electron ions two series of compounds, heteronuclear Ln(2)Cu(CCl3COO)(8) . 6H(2)O (1, Sm; 2 Gd) and polymeric Ln(CCl3COO)(3) . 2H(2)O (3, Sm; 4, Gd) trichloroacetates, were synthesised. Polymeric trichloroacetates 3 and 4 are isomorphous with erbium chloroacetate, whose structure contains dimeric units linked by carboxyl bridges and water molecules into endless chains. Heteronuclear 1 and 2 are isomorphous with Nd2Cu(CCl3COO)(8) . 6H(2)O reported by us previously. Absorption spectra of single crystals of 1-4 for two orientations of the crystals down to 4 K were investigated. Magnetic susceptibility measurements in the range 300-1.8 K were carried out. Optical and magnetic properties are related to the X-ray data. Electron transition probabilities were calculated and the effect of coupled ion pairs in the polymeric structure on the optical and magnetic properties was analysed. Changes in magnetic properties in relation to the mononuclear systems are discussed.