Salt-inclusion synthesis of Ba2MnSi2O7Cl. A fresnoite-type polar framework containing the acentric [Si2O7]6 - polyanion in the anti-ReO3 type [(Ba2Mn)Cl]6+) cage

A novel non-centrosymmetric (NCS) solid, Ba(2)Mn(Si(2)O(7))Cl (CU-13), was isolated via high-temperature, salt-inclusion reactions. This manganese(III) silicate chloride adopts the fresnoite structure exhibiting pseudo-one-dimensional channels in which the Ba(2+) cations reside. The framework can be viewed alternatively as made of a fascinating anti-ReO(3) type (Ba(2)Mn)Cl lattice centered on the acentric Si(2)O(7) unit. This new compound crystallizes in one of the 10 NCS polar crystal classes, 4mm (C(4)(v)()), which is cooperatively attributed to the MnO(4)Cl(2) tetragonal distortion and the oriented Si(2)O(7) polyhedral unit. This discovery once again demonstrates the utility of salt inclusion with the formation of NCS frameworks.