Sr2CrCu2AlO7 crystallizes in the monoclinic Cm space group. There are two inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 5-coordinate geometry to one O(1), one O(3), one O(5), one O(8), and two equivalent O(7) atoms. In the second Sr site, Sr(2) is bonded in a 6-coordinate geometry to one O(2), one O(4), one O(6), one O(8), and two equivalent O(7) atoms. There are two inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one O(1), one O(2), and two equivalent O(7) atoms to form corner-sharing CrO4 tetrahedra. In the second Cr site, Cr(2) is bonded to one O(1), one O(2), and two equivalent O(8) atoms to form corner-sharing CrO4 tetrahedra. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a rectangular see-saw-like geometry to one O(3), one O(4), one O(5), and one O(6) atom. In the second Cu site, Cu(2) is bonded in a rectangular see-saw-like geometry to one O(3), one O(4), one O(5), one O(6), and one O(7) atom. Al(1) is bonded in a distorted tetrahedral geometry to one O(3), one O(4), one O(5), and one O(6) atom. There are eight inequivalent O sites. In the first O site, O(7) is bonded in a 6-coordinate geometry to two equivalent Sr(1), two equivalent Sr(2), one Cr(1), and one Cu(2) atom. In the second O site, O(8) is bonded in a 1-coordinate geometry to one Sr(1), one Sr(2), and one Cr(2) atom. In the third O site, O(1) is bonded to two equivalent Sr(1), one Cr(1), and one Cr(2) atom to form distorted corner-sharing OSr2Cr2 tetrahedra. In the fourth O site, O(2) is bonded to two equivalent Sr(2), one Cr(1), and one Cr(2) atom to form distorted corner-sharing OSr2Cr2 tetrahedra. In the fifth O site, O(3) is bonded in a 4-coordinate geometry to one Sr(1), one Cu(1), one Cu(2), and one Al(1) atom. In the sixth O site, O(4) is bonded in a 4-coordinate geometry to one Sr(2), one Cu(1), one Cu(2), and one Al(1) atom. In the seventh O site, O(5) is bonded in a 4-coordinate geometry to one Sr(1), one Cu(1), one Cu(2), and one Al(1) atom. In the eighth O site, O(6) is bonded in a 4-coordinate geometry to one Sr(2), one Cu(1), one Cu(2), and one Al(1) atom.
Sr2CrCu2AlO7 crystallizes in the monoclinic Cm space group. There are two inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 5-coordinate geometry to one O(1), one O(3), one O(5), one O(8), and two equivalent O(7) atoms. The Sr(1)-O(1) bond length is 2.60 Å. The Sr(1)-O(3) bond length is 2.48 Å. The Sr(1)-O(5) bond length is 2.48 Å. The Sr(1)-O(8) bond length is 2.66 Å. There is one shorter (2.52 Å) and one longer (3.15 Å) Sr(1)-O(7) bond length. In the second Sr site, Sr(2) is bonded in a 6-coordinate geometry to one O(2), one O(4), one O(6), one O(8), and two equivalent O(7) atoms. The Sr(2)-O(2) bond length is 2.56 Å. The Sr(2)-O(4) bond length is 2.48 Å. The Sr(2)-O(6) bond length is 2.47 Å. The Sr(2)-O(8) bond length is 2.53 Å. There is one shorter (2.68 Å) and one longer (2.88 Å) Sr(2)-O(7) bond length. There are two inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one O(1), one O(2), and two equivalent O(7) atoms to form corner-sharing CrO4 tetrahedra. The Cr(1)-O(1) bond length is 2.00 Å. The Cr(1)-O(2) bond length is 2.05 Å. Both Cr(1)-O(7) bond lengths are 1.85 Å. In the second Cr site, Cr(2) is bonded to one O(1), one O(2), and two equivalent O(8) atoms to form corner-sharing CrO4 tetrahedra. The Cr(2)-O(1) bond length is 1.84 Å. The Cr(2)-O(2) bond length is 1.84 Å. Both Cr(2)-O(8) bond lengths are 1.79 Å. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a rectangular see-saw-like geometry to one O(3), one O(4), one O(5), and one O(6) atom. The Cu(1)-O(3) bond length is 1.98 Å. The Cu(1)-O(4) bond length is 2.04 Å. The Cu(1)-O(5) bond length is 1.98 Å. The Cu(1)-O(6) bond length is 2.02 Å. In the second Cu site, Cu(2) is bonded in a rectangular see-saw-like geometry to one O(3), one O(4), one O(5), one O(6), and one O(7) atom. The Cu(2)-O(3) bond length is 2.03 Å. The Cu(2)-O(4) bond length is 2.00 Å. The Cu(2)-O(5) bond length is 2.01 Å. The Cu(2)-O(6) bond length is 2.00 Å. The Cu(2)-O(7) bond length is 2.70 Å. Al(1) is bonded in a distorted tetrahedral geometry to one O(3), one O(4), one O(5), and one O(6) atom. The Al(1)-O(3) bond length is 1.84 Å. The Al(1)-O(4) bond length is 1.86 Å. The Al(1)-O(5) bond length is 1.84 Å. The Al(1)-O(6) bond length is 1.85 Å. There are eight inequivalent O sites. In the first O site, O(7) is bonded in a 6-coordinate geometry to two equivalent Sr(1), two equivalent Sr(2), one Cr(1), and one Cu(2) atom. In the second O site, O(8) is bonded in a 1-coordinate geometry to one Sr(1), one Sr(2), and one Cr(2) atom. In the third O site, O(1) is bonded to two equivalent Sr(1), one Cr(1), and one Cr(2) atom to form distorted corner-sharing OSr2Cr2 tetrahedra. In the fourth O site, O(2) is bonded to two equivalent Sr(2), one Cr(1), and one Cr(2) atom to form distorted corner-sharing OSr2Cr2 tetrahedra. In the fifth O site, O(3) is bonded in a 4-coordinate geometry to one Sr(1), one Cu(1), one Cu(2), and one Al(1) atom. In the sixth O site, O(4) is bonded in a 4-coordinate geometry to one Sr(2), one Cu(1), one Cu(2), and one Al(1) atom. In the seventh O site, O(5) is bonded in a 4-coordinate geometry to one Sr(1), one Cu(1), one Cu(2), and one Al(1) atom. In the eighth O site, O(6) is bonded in a 4-coordinate geometry to one Sr(2), one Cu(1), one Cu(2), and one Al(1) atom.