Cu2H2Se2O7 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to one O(1), one O(3), one O(6), one O(7), and two equivalent O(2) atoms to form distorted edge-sharing CuO6 octahedra. In the second Cu site, Cu(2) is bonded in a distorted rectangular see-saw-like geometry to one O(1), one O(4), one O(5), and one O(6) atom. There are two inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one O(5) and one O(7) atom. In the second H site, H(2) is bonded in a single-bond geometry to one O(7) atom. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded in a distorted trigonal non-coplanar geometry to one O(1), one O(2), and one O(3) atom. In the second Se site, Se(2) is bonded in a trigonal non-coplanar geometry to one O(4), one O(5), and one O(6) atom. There are seven inequivalent O sites. In the first O site, O(3) is bonded in a distorted water-like geometry to one Cu(1) and one Se(1) atom. In the second O site, O(4) is bonded in a bent 120 degrees geometry to one Cu(2) and one Se(2) atom. In the third O site, O(5) is bonded in a trigonal planar geometry to one Cu(2), one H(1), and one Se(2) atom. In the fourth O site, O(6) is bonded in a trigonal planar geometry to one Cu(1), one Cu(2), and one Se(2) atom. In the fifth O site, O(7) is bonded in a distorted trigonal planar geometry to one Cu(1), one H(1), and one H(2) atom. In the sixth O site, O(1) is bonded in a 3-coordinate geometry to one Cu(1), one Cu(2), and one Se(1) atom. In the seventh O site, O(2) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Cu(1) and one Se(1) atom.
Cu2H2Se2O7 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to one O(1), one O(3), one O(6), one O(7), and two equivalent O(2) atoms to form distorted edge-sharing CuO6 octahedra. The Cu(1)-O(1) bond length is 2.42 Å. The Cu(1)-O(3) bond length is 2.01 Å. The Cu(1)-O(6) bond length is 2.00 Å. The Cu(1)-O(7) bond length is 2.07 Å. There is one shorter (2.01 Å) and one longer (2.28 Å) Cu(1)-O(2) bond length. In the second Cu site, Cu(2) is bonded in a distorted rectangular see-saw-like geometry to one O(1), one O(4), one O(5), and one O(6) atom. The Cu(2)-O(1) bond length is 1.95 Å. The Cu(2)-O(4) bond length is 1.95 Å. The Cu(2)-O(5) bond length is 1.97 Å. The Cu(2)-O(6) bond length is 1.98 Å. There are two inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one O(5) and one O(7) atom. The H(1)-O(5) bond length is 1.70 Å. The H(1)-O(7) bond length is 1.00 Å. In the second H site, H(2) is bonded in a single-bond geometry to one O(7) atom. The H(2)-O(7) bond length is 0.98 Å. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded in a distorted trigonal non-coplanar geometry to one O(1), one O(2), and one O(3) atom. The Se(1)-O(1) bond length is 1.75 Å. The Se(1)-O(2) bond length is 1.75 Å. The Se(1)-O(3) bond length is 1.77 Å. In the second Se site, Se(2) is bonded in a trigonal non-coplanar geometry to one O(4), one O(5), and one O(6) atom. The Se(2)-O(4) bond length is 1.71 Å. The Se(2)-O(5) bond length is 1.75 Å. The Se(2)-O(6) bond length is 1.76 Å. There are seven inequivalent O sites. In the first O site, O(3) is bonded in a distorted water-like geometry to one Cu(1) and one Se(1) atom. In the second O site, O(4) is bonded in a bent 120 degrees geometry to one Cu(2) and one Se(2) atom. In the third O site, O(5) is bonded in a trigonal planar geometry to one Cu(2), one H(1), and one Se(2) atom. In the fourth O site, O(6) is bonded in a trigonal planar geometry to one Cu(1), one Cu(2), and one Se(2) atom. In the fifth O site, O(7) is bonded in a distorted trigonal planar geometry to one Cu(1), one H(1), and one H(2) atom. In the sixth O site, O(1) is bonded in a 3-coordinate geometry to one Cu(1), one Cu(2), and one Se(1) atom. In the seventh O site, O(2) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Cu(1) and one Se(1) atom.