Cobalt-Lanthanide Coordination Polymers Constructed with Metalloligands: A Ferromagnetic Coupled Quasi-1D Dy3+ Chain Showing Slow Relaxation

Four types of cobalt-lanthanide heterometallic compounds based on metalloligand Co(2,5-pydC)(3)(3-) (2,5-H(2)pydc=pyridine-2,5-dicarboxylate acid), [Ln(2)Co(2)(2,5-pydc)(6)(H2O)(4)](n)center dot 2n H2O (1) (Ln=Tb, Dy for 1a, 1b respectively), [Tb2Co2(2,5-pydc)(6)(H2O)(4)](n)center dot 3n H2O (2), [Tb2Co2(2,5-pydc)(6)(H2O)(9)](n)center dot 4nH(2)O (3), and [LaCo-(2,5-pydc)(3)(H2O)(2)](n)center dot 2n H2O (4) have been synthesized. Compound I has a layer structure with well-isolated carboxylate-bridged Ln(3+) chains, compound 2 is a three-dimensional (3D) porous network with Tb3+ chains that are also well isolated and carboxylate bridged, 3 is a layer structure based on dinuclear units, and 4 is a 3D network with boron nitride (BN) topology. DC magnetic studies reveal ferromagnetic coupling in all the carboxylate-bridged Ln(3+) chains in 1a, 1b, and 2. Compared to the silence of the out-of-phase ac susceptibility of 2, above 1.9 K the magnetic relaxation behavior of both I a and 1b is slow like that of a single-chain magnet.