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; H2pa = phthalic acid) have been synthesized by solvothermal reaction of cobalt acetate, H2pa, KOH solution, or Cs2CO3 in MeOH. Single-crystal X-ray diffraction shows that they both crystallize in the monoclinic space group C2/c with small differences in the lattice parameters. Their structures are built up from CoII 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 CoII atoms in the chain, with the critical temperature Tc = 7 K for 1·K and 6 K for 1·Cs. The magnetic coupling between CoII 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, ...