Sr2YTi2TlO7 crystallizes in the tetragonal P4/mmm space group. Sr(1) is bonded in a 5-coordinate geometry to one O(3) and four equivalent O(2) atoms. Y(1) is bonded in a body-centered cubic geometry to eight equivalent O(1) atoms. Ti(1) is bonded to one O(2) and four equivalent O(1) atoms to form TiO5 square pyramids that share  a cornercorner with one Tl(1)O6 octahedra and corners with four equivalent Ti(1)O5 square pyramids. The corner-sharing octahedra are not tilted. Tl(1) is bonded to two equivalent O(2) and four equivalent O(3) atoms to form TlO6 octahedra that share corners with four equivalent Tl(1)O6 octahedra, corners with two equivalent Ti(1)O5 square pyramids, and edges with four equivalent Tl(1)O6 octahedra. The corner-sharing octahedra are not tilted. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to two equivalent Y(1) and two equivalent Ti(1) atoms. In the second O site, O(2) is bonded in a distorted single-bond geometry to four equivalent Sr(1), one Ti(1), and one Tl(1) atom. In the third O site, O(3) is bonded to two equivalent Sr(1) and four equivalent Tl(1) atoms to form a mixture of edge and corner-sharing OSr2Tl4 octahedra. The corner-sharing octahedra are not tilted.
Sr2YTi2TlO7 crystallizes in the tetragonal P4/mmm space group. Sr(1) is bonded in a 5-coordinate geometry to one O(3) and four equivalent O(2) atoms. The Sr(1)-O(3) bond length is 2.38 Å. All Sr(1)-O(2) bond lengths are 2.79 Å. Y(1) is bonded in a body-centered cubic geometry to eight equivalent O(1) atoms. All Y(1)-O(1) bond lengths are 2.45 Å. Ti(1) is bonded to one O(2) and four equivalent O(1) atoms to form TiO5 square pyramids that share  a cornercorner with one Tl(1)O6 octahedra and corners with four equivalent Ti(1)O5 square pyramids. The corner-sharing octahedra are not tilted. The Ti(1)-O(2) bond length is 1.90 Å. All Ti(1)-O(1) bond lengths are 1.98 Å. Tl(1) is bonded to two equivalent O(2) and four equivalent O(3) atoms to form TlO6 octahedra that share corners with four equivalent Tl(1)O6 octahedra, corners with two equivalent Ti(1)O5 square pyramids, and edges with four equivalent Tl(1)O6 octahedra. The corner-sharing octahedra are not tilted. Both Tl(1)-O(2) bond lengths are 2.74 Å. All Tl(1)-O(3) bond lengths are 2.77 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to two equivalent Y(1) and two equivalent Ti(1) atoms. In the second O site, O(2) is bonded in a distorted single-bond geometry to four equivalent Sr(1), one Ti(1), and one Tl(1) atom. In the third O site, O(3) is bonded to two equivalent Sr(1) and four equivalent Tl(1) atoms to form a mixture of edge and corner-sharing OSr2Tl4 octahedra. The corner-sharing octahedra are not tilted.