Synthesis and characterization of di-, tri- and tetranuclear carboxylate complexes containing both lanthanide(III) and zinc(II) ions

Treatment of Ln(NO3)3·6H2O, Zn(NO3)2·6H2O and carboxylic acids with quinoline in stoichiometric molar ratios in ethanol produces four structural types of carboxylate-bridged lanthanide(III)zinc(II) complexes [C9H7N·H][LnZn(O2CC2H5)3(C9H7N)(NO3)3]·H2O (Ln=Er 1 or Y 2), [DyZn2(O2CCMe3)6(C9H7N)2(NO3)] (3), [DyZn2(μ-O2CC2H5)5(O2CC2H5)(C9H7N)2(NO3)(H2O)] (4) and [Gd2Zn2(O2CC2H5)8(C9H7N)2(NO3)2(H2O)2] (5), all of which have been characterized by single-crystal X-ray diffraction. Complexes 1 and 2 are isostructural and comprise quinolinium cations, triply propionate-bridged dimeric LnZn anions and lattice water molecules. In 3 the central Dy ion and two terminal Zn ions are bridged by two sets of three equivalent bismonodentate pivalate ligands to form a symmetrical trinuclear DyZn2 structure. While the Dy ion in 4 is connected to one Zn ion via three bismonodentate propionate ligands and connected to another Zn via only two bismonodentate propionate ligands generating a novel unsymmetrical trinuclear DyZn2 structure. Complex 5 consists of two triply propionate-bridged dinuclear [GdZn(O2CC2H5)3(C9H7N)(NO3)(H2O)] subunits, being linked together by two tridentate propionate groups via two Gd ions. The magnetic properties of complex 5 containing a pair of Gd3+ ions bridged by two carboxylate groups have been investigated. A quantitative analysis of the magnetic data shows the interaction is of antiferromagnetic type with a J constant of −0.042 cm−1.