LnIIICuII Schiff base compounds (Ln=Ce, Gd, Tb, Dy, Ho, Er): structural and magnetic properties

The crystal structures of two compounds have been determined, namely [Ce(NO 3 ) 3 {Cu(salen)} 2 ] ( 1 ) and [Gd(NO 3 ) 3 Cu(salen)] ( 2 ), salen being N,N′-ethylenebis(salicylideneaminato). The compounds [Ln(NO 3 ) 3 Cu(salen)] with Ln=Tb ( 3 ), Dy ( 4 ), Ho ( 5 ) and Er ( 6 ), which are isomorphous with 2 , have also been synthesized. 1 crystallizes in the monoclinic system, space group C 2/ c , with a =10.925(2) A, b =20.406(5) A, c =15.618(5) A, α =90°, β =94.73(2)°, γ =90°, Z =8. 2 crystallizes in the monoclinic system, space group P 2 1 / c , with a =12.123(3) A, b =10.321(3) A, c =18.248(2) A, α =90.04°, β =102.93(2)°, γ =90.04°, Z =4. The structure of 1 consists of neutral trinuclear units in which the Ce atom is linked to the two Cu atoms via the oxygen atoms of the salen ligand. The structure of 2 consists of neutral binuclear units in which the metal atoms are linked by the oxygen atoms of the salen ligand. In 1 and 2 the bridging network LnO 2 Cu has a butterfly shape. The magnetic properties of compounds 1 – 6 have been investigated. As expected, the Gd III Cu II magnetic interaction for 2 has been found to be ferromagnetic. The energy gap between ground S =4 and excited S =3 states has been determined as 4 J =+17.32 cm –1 . This value has been compared to what has been reported for other Gd III Cu II binuclear compounds. The magnetic properties for 1 , 3 , 4 , 5 and 6 are dominated by the crystal field effect on the Ln III site, masking the magnetic interaction between the paramagnetic centers. © 2000 Academie des sciences / Editions scientifiques et medicales Elsevier SAS copper/ crystal structure/ heterobinuclear complexes/ lanthanide/ magnetic properties