MgMn3CuO8 is beta indium sulfide-derived structured and crystallizes in the trigonal R-3m space group. Mg(1) is bonded to six equivalent O(2) atoms to form MgO6 octahedra that share corners with six equivalent Cu(1)O6 octahedra and edges with six equivalent Mn(1)O6 octahedra. The corner-sharing octahedral tilt angles are 13°. Mn(1) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form MnO6 octahedra that share edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Cu(1)O6 octahedra, and edges with four equivalent Mn(1)O6 octahedra. Cu(1) is bonded to six equivalent O(2) atoms to form CuO6 octahedra that share corners with six equivalent Mg(1)O6 octahedra and edges with six equivalent Mn(1)O6 octahedra. The corner-sharing octahedral tilt angles are 13°. There are two inequivalent O sites. In the first O site, O(1) is bonded in a distorted T-shaped geometry to three equivalent Mn(1) atoms. In the second O site, O(2) is bonded in a see-saw-like geometry to one Mg(1), two equivalent Mn(1), and one Cu(1) atom.
MgMn3CuO8 is beta indium sulfide-derived structured and crystallizes in the trigonal R-3m space group. Mg(1) is bonded to six equivalent O(2) atoms to form MgO6 octahedra that share corners with six equivalent Cu(1)O6 octahedra and edges with six equivalent Mn(1)O6 octahedra. The corner-sharing octahedral tilt angles are 13°. All Mg(1)-O(2) bond lengths are 2.09 Å. Mn(1) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form MnO6 octahedra that share edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Cu(1)O6 octahedra, and edges with four equivalent Mn(1)O6 octahedra. Both Mn(1)-O(1) bond lengths are 1.97 Å. All Mn(1)-O(2) bond lengths are 1.93 Å. Cu(1) is bonded to six equivalent O(2) atoms to form CuO6 octahedra that share corners with six equivalent Mg(1)O6 octahedra and edges with six equivalent Mn(1)O6 octahedra. The corner-sharing octahedral tilt angles are 13°. All Cu(1)-O(2) bond lengths are 2.14 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded in a distorted T-shaped geometry to three equivalent Mn(1) atoms. In the second O site, O(2) is bonded in a see-saw-like geometry to one Mg(1), two equivalent Mn(1), and one Cu(1) atom.