COMPARATIVE SPECTROSCOPIC AND MAGNETIC STUDIES OF 2 TYPES OF LN AND LN-CU TRICHLOROACETATES

Heteronuclear copper-lanthanide complexes have attracted much attentio n as models for the theoretical investigation of magnetic exchange inv olving d and f electrons and because of their potential application in superconducting ceramics. Synthesis, structural, spectroscopic and ma gnetic characterization of one-dimensional polymeric Ln(Cl3CCOO)(3). 2 H(2)O (Ln=Nd, Eu, Dy) (I) and heteronuclear CuNd2(Cl3CCOO)(8). 6H(2)O (II) single crystals was undertaken. The structure of (II) is construc ted from dimers of two crystallographically independent types of NdO8( 9) polyhedra linked by carboxyl bridges. These dimers are separated by square planar coordinated copper ions which are bridged to the lantha nide by four carboxyl groups and two water molecules. The chains are f urther connected via a hydrogen bonding system to layers. The optical and magnetic properties were investigated in the 4.2-293 K temperature range and are discussed on the basis of X-ray data. Electronic spectr a reveal marked differences in the structures of these two types of co mpounds. The spectra allow the determination of the splitting pattern of the ground state multiplet of the Nd3+ ion. Vibronic components wer e detected in the europium excitation spectra and their assignments we re made on the basis of Raman data. The temperature dependence of chi( M) and mu(eff) shows a decrease of the magnetic moment with temperatur e and the reverse relation for magnetic susceptibility in mixed Nd:Cu crystals. The cooperative interaction of ion-pairs coupled in polymeri c chains could be considered based both on spectroscopic and magnetic investigations. (C) 1998 Elsevier Science S.A.