MgTi2Nb2(CuO4)3 crystallizes in the triclinic P1 space group. Mg(1) is bonded in a 7-coordinate geometry to one Cu(1), one O(1), one O(10), one O(5), one O(6), one O(8), and one O(9) atom. There are two inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to one O(1), one O(11), one O(12), one O(2), one O(5), and one O(8) atom to form distorted TiO6 octahedra that share corners with two equivalent Nb(1)O6 octahedra and corners with two equivalent Nb(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 40-47°. In the second Ti site, Ti(2) is bonded in a 6-coordinate geometry to one O(1), one O(10), one O(12), one O(3), one O(4), and one O(9) atom. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(10), one O(3), one O(5), one O(6), one O(7), and one O(8) atom to form distorted NbO6 octahedra that share corners with two equivalent Ti(1)O6 octahedra and corners with two equivalent Nb(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 34-47°. In the second Nb site, Nb(2) is bonded to one O(11), one O(2), one O(4), one O(6), one O(7), and one O(9) atom to form NbO6 octahedra that share corners with two equivalent Ti(1)O6 octahedra and corners with two equivalent Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 34-41°. There are three inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a 5-coordinate geometry to one Mg(1), one O(12), one O(4), one O(5), one O(7), and one O(8) atom. In the second Cu site, Cu(2) is bonded in a distorted rectangular see-saw-like geometry to one O(10), one O(11), one O(2), and one O(3) atom. In the third Cu site, Cu(3) is bonded in a distorted rectangular see-saw-like geometry to one O(1), one O(12), one O(6), and one O(7) atom. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Mg(1), one Ti(1), one Ti(2), and one Cu(3) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Ti(1), one Nb(2), and one Cu(2) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Ti(2), one Nb(1), and one Cu(2) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Ti(2), one Nb(2), and one Cu(1) atom. In the fifth O site, O(5) is bonded in a 4-coordinate geometry to one Mg(1), one Ti(1), one Nb(1), and one Cu(1) atom. In the sixth O site, O(6) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Nb(1), one Nb(2), and one Cu(3) atom. In the seventh O site, O(7) is bonded to one Nb(1), one Nb(2), one Cu(1), and one Cu(3) atom to form distorted edge-sharing ONb2Cu2 trigonal pyramids. In the eighth O site, O(8) is bonded in a 4-coordinate geometry to one Mg(1), one Ti(1), one Nb(1), and one Cu(1) atom. In the ninth O site, O(9) is bonded in a 3-coordinate geometry to one Mg(1), one Ti(2), and one Nb(2) atom. In the tenth O site, O(10) is bonded in a 4-coordinate geometry to one Mg(1), one Ti(2), one Nb(1), and one Cu(2) atom. In the eleventh O site, O(11) is bonded in a distorted trigonal planar geometry to one Ti(1), one Nb(2), and one Cu(2) atom. In the twelfth O site, O(12) is bonded to one Ti(1), one Ti(2), one Cu(1), and one Cu(3) atom to form edge-sharing OTi2Cu2 trigonal pyramids.
MgTi2Nb2(CuO4)3 crystallizes in the triclinic P1 space group. Mg(1) is bonded in a 7-coordinate geometry to one Cu(1), one O(1), one O(10), one O(5), one O(6), one O(8), and one O(9) atom. The Mg(1)-Cu(1) bond length is 2.32 Å. The Mg(1)-O(1) bond length is 1.97 Å. The Mg(1)-O(10) bond length is 2.21 Å. The Mg(1)-O(5) bond length is 2.09 Å. The Mg(1)-O(6) bond length is 2.05 Å. The Mg(1)-O(8) bond length is 2.37 Å. The Mg(1)-O(9) bond length is 2.02 Å. There are two inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to one O(1), one O(11), one O(12), one O(2), one O(5), and one O(8) atom to form distorted TiO6 octahedra that share corners with two equivalent Nb(1)O6 octahedra and corners with two equivalent Nb(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 40-47°. The Ti(1)-O(1) bond length is 1.86 Å. The Ti(1)-O(11) bond length is 1.86 Å. The Ti(1)-O(12) bond length is 2.22 Å. The Ti(1)-O(2) bond length is 2.24 Å. The Ti(1)-O(5) bond length is 1.86 Å. The Ti(1)-O(8) bond length is 2.22 Å. In the second Ti site, Ti(2) is bonded in a 6-coordinate geometry to one O(1), one O(10), one O(12), one O(3), one O(4), and one O(9) atom. The Ti(2)-O(1) bond length is 2.38 Å. The Ti(2)-O(10) bond length is 1.99 Å. The Ti(2)-O(12) bond length is 1.86 Å. The Ti(2)-O(3) bond length is 2.06 Å. The Ti(2)-O(4) bond length is 2.08 Å. The Ti(2)-O(9) bond length is 1.90 Å. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(10), one O(3), one O(5), one O(6), one O(7), and one O(8) atom to form distorted NbO6 octahedra that share corners with two equivalent Ti(1)O6 octahedra and corners with two equivalent Nb(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 34-47°. The Nb(1)-O(10) bond length is 2.10 Å. The Nb(1)-O(3) bond length is 1.97 Å. The Nb(1)-O(5) bond length is 2.37 Å. The Nb(1)-O(6) bond length is 2.07 Å. The Nb(1)-O(7) bond length is 2.04 Å. The Nb(1)-O(8) bond length is 1.89 Å. In the second Nb site, Nb(2) is bonded to one O(11), one O(2), one O(4), one O(6), one O(7), and one O(9) atom to form NbO6 octahedra that share corners with two equivalent Ti(1)O6 octahedra and corners with two equivalent Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 34-41°. The Nb(2)-O(11) bond length is 2.21 Å. The Nb(2)-O(2) bond length is 1.91 Å. The Nb(2)-O(4) bond length is 1.94 Å. The Nb(2)-O(6) bond length is 2.09 Å. The Nb(2)-O(7) bond length is 2.06 Å. The Nb(2)-O(9) bond length is 2.10 Å. There are three inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a 5-coordinate geometry to one Mg(1), one O(12), one O(4), one O(5), one O(7), and one O(8) atom. The Cu(1)-O(12) bond length is 2.00 Å. The Cu(1)-O(4) bond length is 2.09 Å. The Cu(1)-O(5) bond length is 2.13 Å. The Cu(1)-O(7) bond length is 2.15 Å. The Cu(1)-O(8) bond length is 2.27 Å. In the second Cu site, Cu(2) is bonded in a distorted rectangular see-saw-like geometry to one O(10), one O(11), one O(2), and one O(3) atom. The Cu(2)-O(10) bond length is 2.34 Å. The Cu(2)-O(11) bond length is 1.98 Å. The Cu(2)-O(2) bond length is 2.00 Å. The Cu(2)-O(3) bond length is 2.12 Å. In the third Cu site, Cu(3) is bonded in a distorted rectangular see-saw-like geometry to one O(1), one O(12), one O(6), and one O(7) atom. The Cu(3)-O(1) bond length is 1.96 Å. The Cu(3)-O(12) bond length is 1.98 Å. The Cu(3)-O(6) bond length is 2.16 Å. The Cu(3)-O(7) bond length is 2.13 Å. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Mg(1), one Ti(1), one Ti(2), and one Cu(3) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Ti(1), one Nb(2), and one Cu(2) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Ti(2), one Nb(1), and one Cu(2) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Ti(2), one Nb(2), and one Cu(1) atom. In the fifth O site, O(5) is bonded in a 4-coordinate geometry to one Mg(1), one Ti(1), one Nb(1), and one Cu(1) atom. In the sixth O site, O(6) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Nb(1), one Nb(2), and one Cu(3) atom. In the seventh O site, O(7) is bonded to one Nb(1), one Nb(2), one Cu(1), and one Cu(3) atom to form distorted edge-sharing ONb2Cu2 trigonal pyramids. In the eighth O site, O(8) is bonded in a 4-coordinate geometry to one Mg(1), one Ti(1), one Nb(1), and one Cu(1) atom. In the ninth O site, O(9) is bonded in a 3-coordinate geometry to one Mg(1), one Ti(2), and one Nb(2) atom. In the tenth O site, O(10) is bonded in a 4-coordinate geometry to one Mg(1), one Ti(2), one Nb(1), and one Cu(2) atom. In the eleventh O site, O(11) is bonded in a distorted trigonal planar geometry to one Ti(1), one Nb(2), and one Cu(2) atom. In the twelfth O site, O(12) is bonded to one Ti(1), one Ti(2), one Cu(1), and one Cu(3) atom to form edge-sharing OTi2Cu2 trigonal pyramids.