MgMn4(CuO4)2 crystallizes in the orthorhombic Imm2 space group. Mg(1) is bonded to two equivalent O(1) and two equivalent O(3) atoms to form distorted MgO4 tetrahedra that share corners with six equivalent Mn(3)O6 octahedra and  an edgeedge with one Mn(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 28-65°. There are three inequivalent Mn sites. In the first Mn site, Mn(1) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms. In the second Mn site, Mn(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form MnO6 octahedra that share corners with four equivalent Mn(3)O6 octahedra,  an edgeedge with one Mg(1)O4 tetrahedra, and faces with two equivalent Mn(3)O6 octahedra. The corner-sharing octahedral tilt angles are 52°. In the third Mn site, Mn(3) is bonded to one O(2), one O(3), two equivalent O(1), and two equivalent O(4) atoms to form MnO6 octahedra that share corners with two equivalent Mn(2)O6 octahedra, corners with three equivalent Mg(1)O4 tetrahedra, edges with two equivalent Mn(3)O6 octahedra, and  a faceface with one Mn(2)O6 octahedra. The corner-sharing octahedral tilt angles are 52°. Cu(1) is bonded in a 5-coordinate geometry to one O(4), two equivalent O(2), and two equivalent O(3) atoms. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 5-coordinate geometry to one Mg(1), one Mn(1), one Mn(2), and two equivalent Mn(3) atoms. In the second O site, O(2) is bonded to one Mn(2), one Mn(3), and two equivalent Cu(1) atoms to form distorted OMn2Cu2 tetrahedra that share  a cornercorner with one O(2)Mn2Cu2 tetrahedra, corners with two equivalent O(4)Mn4Cu trigonal bipyramids, corners with five equivalent O(3)MgMn2Cu2 trigonal bipyramids,  an edgeedge with one O(2)Mn2Cu2 tetrahedra, and edges with two equivalent O(4)Mn4Cu trigonal bipyramids. In the third O site, O(3) is bonded to one Mg(1), one Mn(1), one Mn(3), and two equivalent Cu(1) atoms to form distorted OMgMn2Cu2 trigonal bipyramids that share corners with five equivalent O(2)Mn2Cu2 tetrahedra,  a cornercorner with one O(3)MgMn2Cu2 trigonal bipyramid, corners with two equivalent O(4)Mn4Cu trigonal bipyramids, edges with two equivalent O(4)Mn4Cu trigonal bipyramids, and  a faceface with one O(3)MgMn2Cu2 trigonal bipyramid. In the fourth O site, O(4) is bonded to one Mn(1), one Mn(2), two equivalent Mn(3), and one Cu(1) atom to form distorted OMn4Cu trigonal bipyramids that share corners with two equivalent O(2)Mn2Cu2 tetrahedra,  a cornercorner with one O(4)Mn4Cu trigonal bipyramid, corners with two equivalent O(3)MgMn2Cu2 trigonal bipyramids, edges with two equivalent O(2)Mn2Cu2 tetrahedra, edges with two equivalent O(3)MgMn2Cu2 trigonal bipyramids, and  a faceface with one O(4)Mn4Cu trigonal bipyramid.
MgMn4(CuO4)2 crystallizes in the orthorhombic Imm2 space group. Mg(1) is bonded to two equivalent O(1) and two equivalent O(3) atoms to form distorted MgO4 tetrahedra that share corners with six equivalent Mn(3)O6 octahedra and  an edgeedge with one Mn(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 28-65°. Both Mg(1)-O(1) bond lengths are 1.97 Å. Both Mg(1)-O(3) bond lengths are 2.04 Å. There are three inequivalent Mn sites. In the first Mn site, Mn(1) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms. Both Mn(1)-O(1) bond lengths are 2.60 Å. Both Mn(1)-O(3) bond lengths are 2.08 Å. Both Mn(1)-O(4) bond lengths are 2.08 Å. In the second Mn site, Mn(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form MnO6 octahedra that share corners with four equivalent Mn(3)O6 octahedra,  an edgeedge with one Mg(1)O4 tetrahedra, and faces with two equivalent Mn(3)O6 octahedra. The corner-sharing octahedral tilt angles are 52°. Both Mn(2)-O(1) bond lengths are 2.23 Å. Both Mn(2)-O(2) bond lengths are 2.00 Å. Both Mn(2)-O(4) bond lengths are 2.21 Å. In the third Mn site, Mn(3) is bonded to one O(2), one O(3), two equivalent O(1), and two equivalent O(4) atoms to form MnO6 octahedra that share corners with two equivalent Mn(2)O6 octahedra, corners with three equivalent Mg(1)O4 tetrahedra, edges with two equivalent Mn(3)O6 octahedra, and  a faceface with one Mn(2)O6 octahedra. The corner-sharing octahedral tilt angles are 52°. The Mn(3)-O(2) bond length is 1.98 Å. The Mn(3)-O(3) bond length is 1.98 Å. Both Mn(3)-O(1) bond lengths are 2.18 Å. Both Mn(3)-O(4) bond lengths are 2.22 Å. Cu(1) is bonded in a 5-coordinate geometry to one O(4), two equivalent O(2), and two equivalent O(3) atoms. The Cu(1)-O(4) bond length is 2.09 Å. Both Cu(1)-O(2) bond lengths are 1.99 Å. Both Cu(1)-O(3) bond lengths are 2.17 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 5-coordinate geometry to one Mg(1), one Mn(1), one Mn(2), and two equivalent Mn(3) atoms. In the second O site, O(2) is bonded to one Mn(2), one Mn(3), and two equivalent Cu(1) atoms to form distorted OMn2Cu2 tetrahedra that share  a cornercorner with one O(2)Mn2Cu2 tetrahedra, corners with two equivalent O(4)Mn4Cu trigonal bipyramids, corners with five equivalent O(3)MgMn2Cu2 trigonal bipyramids,  an edgeedge with one O(2)Mn2Cu2 tetrahedra, and edges with two equivalent O(4)Mn4Cu trigonal bipyramids. In the third O site, O(3) is bonded to one Mg(1), one Mn(1), one Mn(3), and two equivalent Cu(1) atoms to form distorted OMgMn2Cu2 trigonal bipyramids that share corners with five equivalent O(2)Mn2Cu2 tetrahedra,  a cornercorner with one O(3)MgMn2Cu2 trigonal bipyramid, corners with two equivalent O(4)Mn4Cu trigonal bipyramids, edges with two equivalent O(4)Mn4Cu trigonal bipyramids, and  a faceface with one O(3)MgMn2Cu2 trigonal bipyramid. In the fourth O site, O(4) is bonded to one Mn(1), one Mn(2), two equivalent Mn(3), and one Cu(1) atom to form distorted OMn4Cu trigonal bipyramids that share corners with two equivalent O(2)Mn2Cu2 tetrahedra,  a cornercorner with one O(4)Mn4Cu trigonal bipyramid, corners with two equivalent O(3)MgMn2Cu2 trigonal bipyramids, edges with two equivalent O(2)Mn2Cu2 tetrahedra, edges with two equivalent O(3)MgMn2Cu2 trigonal bipyramids, and  a faceface with one O(4)Mn4Cu trigonal bipyramid.