Multi-modal bridging ligands to engineer molecular magnets

ECHEVERRÍA, G.; PUNTE, G.; SIVES, F.; BRUSAU, E. V.; E. V.; PEDREGOSA; J. C.; NARDA; G. E.; ELLENA

Buenos Aires

Congreso; At the Frontiers of Condensed Matter; 2004

Comisión Nacional de Energía Atómica

Dicarboxylates are versatile tools useful  in the design of polynuclear complexes with interesting magnetic properties. The ability of the carboxylate bridge to mediate significant ferro- or anti-ferromagnetic interaction accounts for their use. Depending on the length of the dicarboxylate chain [O2C(CH2)nCO2] a large variation in coordination behaviors, which can coexist, can be obtained. Coordination ways include chelating, bidentate-bridging or chelating-bridging modes, which allows for the formation of polymeric arrangements of different dimensionalities. Rare earth metals are attractive as metal centers for their high coordination number, which help construction of magnetically interesting coordination polymers that also exhibit other attractive and advantageous properties, such as optical activity, and thermal stability. In this study, we report two Nd adipates, [Nd2(O2C(CH2)4CO2)3(H2O)4]. 6H2O (I) and Nd2(O2C(CH2)4CO2)3 (H2O)4].2H2O (II). The x-ray analysis of I shows infinite chains, form by Nd-O-Nd bridges alternating with Nd-O-C-O-Nd bridges while in the structure of II two different  Nd-O-Nd  bridges build the chain. The influence of the coordination sphere, bridging units and coordination and hydration water on the AC magnetic susceptibility of both compounds is discussed.