Embedding 1D or 2D cobalt-carboxylate substrates in 3D coordination polymers exhibiting slow magnetic relaxation behaviors: crystal structures, high-field EPR, and magnetic studies.

By utilizing well-designed bifunctional ligands derived from 1H-imidazole-4,5-dicarboxylic acid, magnetic coordination polymers (CPs) that exhibit slow magnetic relaxation at the low temperature regions were constructed and further structurally characterized. In 1, 1D cobalt-carboxyl chains were stabilized in the final structure. In contrast, by adjusting the length of the substituted arms on imidazole-4,5-dicarboxylic acid, a novel 3D CP, 2 containing 2D 63 cobalt-carboxyl layer was obtained. A combination of Quantum Monte Carlo (QMC) simulations and the first-principles Density functional theory (DFT) calculations showed that compound 2 features weak ferro- and antiferro-magnetic coupling mechanisms with two different super-exchange paths of -/+/- for syn-anti carboxylate bridges and -/-/- for syn-syn carboxylate bridges. Through HF-EPR measurements performed on polycrystalline samples over the frequency range of 60-260 GHz and field range of 0-12 T, the effective g-values of 1 and 2 were all larger than 2.00, and the signs of their D values were probably positive.