Synthesis and Characterization of the New Manganese Hydroxide Chloride γ-Mn(OH)Cl.

A new modification of Mn(OH)Cl was obtained under high-pressure/high-temperature conditions in a Walker-type multianvil device. The pale pink, hygroscopic compound crystallizes in the orthorhombic space group (no. 62) with = 602.90(4), = 350.98(2), = 1077.69(7) pm, and = 228 × 10 pm. The layered centrosymmetric structure consists of edge-sharing Mn(OH)Cl octahedra arranged in sheets parallel to the (001) plane. The comparatively long HCl distance of 275 pm suggests only weak hydrogen bonds between neighboring layers. Spin-polarized scalar-relativistic DFT+ calculations predict a non-conducting magnetically ordered ground state with a band gap of at least 3.2 eV and an effective magnetic moment of 4.65 µ/f. u. The experimentally determined magnetic response of Mn(OH)Cl is paramagnetic in the range of 10-300 K. The estimated moment of 5.6 µ/f. u. indicates the high-spin configuration of manganese(II). We find hints for a long-range magnetic ordering below 10 K.