Weak Ferromagnetism and Dynamic Magnetic Behavior of Two 2D Compounds with Hydroxy/Carboxylate-Bridged Co(II) Chains

Two isomorphous compounds [ACo(pa)(OH)] n ( 1·K, A = K, and 1·Cs, A = Cs; H 2 pa = phthalic acid) have been synthesized by solvothermal reaction of cobalt acetate, H 2 pa, KOH solution, or Cs 2 CO 3 in MeOH. Single-crystal X-ray diffraction shows that they both crystallize in the monoclinic space group C 2/ c with small differences in the lattice parameters. Their structures are built up from Co II zigzag chains, which are connected and separated by alkali metal ions and pa ligands to form two-dimensional layers. These layers are packed in ABAB fashion into a three-dimensional network by the π−π interactions. Both of them show spin canting behaviors, for the antisymmetric exchange between adjacent Co II atoms in the chain, with the critical temperature T c = 7 K for 1·K and 6 K for 1·Cs . The magnetic coupling between Co II atoms in them are estimated based on the model developed by Fisher for a uniform chain of classical spins with the best fit gives J = −5.99 cm −1 for 1·K and J = −7.26 cm −1 for 1·Cs . At the same time, the noncritical-scaling theory is also used to reveal the ferrimagnetic-like behaviors of these two compounds. Moreover, dynamic magnetic relaxations are observed for these compounds, which are scarce for simple chains with uniform antiferromagnetic interactions.