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 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 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 pi-pi 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 Coll 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.