Field-Induced Slow Magnetic Relaxation and Gas Adsorption Properties of a Bifunctional Cobalt(II) Compound

A new compound, {[Co­(bmzbc)2]·2DMF}n (JXNU-1, JXNU denotes Jiangxi Normal University), based on the 4-(benzimidazole-1-yl)­benzoate (bmzbc–) ligand has been synthesized and structurally characterized. The Co­(II) ions are bridged by the rod-like bmzbc– ligands to give a two-dimensional (2D) sheet wherein the Co­(II) ions are spatially separated from each other by the long bmzbc– rods. The 2D sheets are further stacked into a 3D framework with 1D channels occluding the guest DMF molecules. Detailed magnetic studies show that the individual octahedral Co­(II) ions in JXNU-1 exhibit field-induced slow magnetic relaxation, which is characteristic behavior of single-ion magnets (SIMs). The rarely observed positive value of zero-field splitting (ZFS) parameter D for the Co­(II) ion in JXNU-1 demonstrates that JXNU-1 is a unique example of Co­(II)-based SIMs with easy-plane anisotropy, which is also confirmed by the calculations. The microporous nature of JXNU-1 was established by measuring CO2 sorption isotherms. The abrupt changes observed in the C3H8 and C2H6 adsorption isotherms indicate that a structural transformation occurred in the gas-loading process. The long connection between the magnetic metal centers in JXNU-1 meets the requirements for construction of porosity and SIM in a well-defined network, harmoniously providing a good candidate of functional molecular materials exhibiting SIM and porosity.