MgAl2(CuO2)4 crystallizes in the trigonal R3m space group. Mg(1) is bonded to one Cu(2), three equivalent Cu(1), one O(3), and three equivalent O(2) atoms to form distorted MgCu4O4 tetrahedra that share corners with four equivalent Al(2)O4 tetrahedra. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a 7-coordinate geometry to one Mg(1), one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms. In the second Cu site, Cu(2) is bonded in a 7-coordinate geometry to one Mg(1), three equivalent O(1), and three equivalent O(2) atoms. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded in a tetrahedral geometry to one O(4) and three equivalent O(1) atoms. In the second Al site, Al(2) is bonded to one O(3) and three equivalent O(2) atoms to form AlO4 tetrahedra that share corners with four equivalent Mg(1)Cu4O4 tetrahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Cu(2), two equivalent Cu(1), and one Al(1) atom. In the second O site, O(2) is bonded in a distorted linear geometry to one Mg(1), one Cu(2), two equivalent Cu(1), and one Al(2) atom. In the third O site, O(3) is bonded in a distorted linear geometry to one Mg(1), three equivalent Cu(1), and one Al(2) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to three equivalent Cu(1) and one Al(1) atom.
MgAl2(CuO2)4 crystallizes in the trigonal R3m space group. Mg(1) is bonded to one Cu(2), three equivalent Cu(1), one O(3), and three equivalent O(2) atoms to form distorted MgCu4O4 tetrahedra that share corners with four equivalent Al(2)O4 tetrahedra. The Mg(1)-Cu(2) bond length is 2.23 Å. All Mg(1)-Cu(1) bond lengths are 2.22 Å. The Mg(1)-O(3) bond length is 1.93 Å. All Mg(1)-O(2) bond lengths are 1.93 Å. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a 7-coordinate geometry to one Mg(1), one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms. The Cu(1)-O(3) bond length is 2.42 Å. The Cu(1)-O(4) bond length is 2.04 Å. Both Cu(1)-O(1) bond lengths are 2.04 Å. Both Cu(1)-O(2) bond lengths are 2.40 Å. In the second Cu site, Cu(2) is bonded in a 7-coordinate geometry to one Mg(1), three equivalent O(1), and three equivalent O(2) atoms. All Cu(2)-O(1) bond lengths are 2.04 Å. All Cu(2)-O(2) bond lengths are 2.41 Å. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded in a tetrahedral geometry to one O(4) and three equivalent O(1) atoms. The Al(1)-O(4) bond length is 1.82 Å. All Al(1)-O(1) bond lengths are 1.82 Å. In the second Al site, Al(2) is bonded to one O(3) and three equivalent O(2) atoms to form AlO4 tetrahedra that share corners with four equivalent Mg(1)Cu4O4 tetrahedra. The Al(2)-O(3) bond length is 1.84 Å. All Al(2)-O(2) bond lengths are 1.84 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Cu(2), two equivalent Cu(1), and one Al(1) atom. In the second O site, O(2) is bonded in a distorted linear geometry to one Mg(1), one Cu(2), two equivalent Cu(1), and one Al(2) atom. In the third O site, O(3) is bonded in a distorted linear geometry to one Mg(1), three equivalent Cu(1), and one Al(2) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to three equivalent Cu(1) and one Al(1) atom.