A Two-Dimensional Manganese(II) Carboxylato Polymer. Structure, Magnetism, and EPR Study

The synthesis, crystal structure, and properties of [Mn^II(MCPA)₂(H₂O)₂]_n (MCPA = 2-methyl-4-chlorophenoxyacetic acid), 1, a 2-D manganese carboxylato polymer is reported. The synthesis of 1 has been achieved via the reaction of MCPA with MnCl₂·2H₂O and NaHCO₃ in methanol. Crystal structure data:  [C₁₈H₂₀Cl₂O₈Mn]; orthorhombic; space group Pbca; a = 7.811(6) Å; b = 34.67(3) Å; c = 7.481(6) Å; Z = 4. The compound has a two-dimensional structure with Mn²⁺ atoms in an octahedral environment and mixed water/carboxylate coordination. The metal atoms are segregated in planes which are perpendicular to the b axis and are spaced 17.73 Å apart. Variable-temperature magnetic susceptibility measurements indicate the presence of antiferromagnetic behavior. The EPR spectra of polycrystalline samples at 4 K show that the intensity of the signal decreases significantly with decreasing temperature and below ∼4 K becomes EPR silent.