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.