Mn2CPH2O7 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to one O(2), one O(4), one O(5), one O(6), and two equivalent O(1) atoms to form MnO6 octahedra that share corners with four equivalent P(1)O4 tetrahedra,  an edgeedge with one Mn(1)O6 octahedra, and edges with two equivalent Mn(2)O6 pentagonal pyramids. In the second Mn site, Mn(2) is bonded to one O(2), one O(3), one O(4), one O(5), one O(6), and one O(7) atom to form distorted MnO6 pentagonal pyramids that share corners with three equivalent P(1)O4 tetrahedra and edges with two equivalent Mn(1)O6 octahedra. C(1) is bonded in a distorted bent 120 degrees geometry to one O(4) and one O(7) atom. P(1) is bonded to one O(1), one O(2), one O(3), and one O(5) atom to form PO4 tetrahedra that share corners with four equivalent Mn(1)O6 octahedra and corners with three equivalent Mn(2)O6 pentagonal pyramids. The corner-sharing octahedral tilt angles range from 47-56°. There are two inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one O(6) atom. In the second H site, H(2) is bonded in a single-bond geometry to one O(6) atom. There are seven inequivalent O sites. In the first O site, O(7) is bonded in a distorted bent 120 degrees geometry to one Mn(2) and one C(1) atom. In the second O site, O(1) is bonded in a distorted trigonal planar geometry to two equivalent Mn(1) and one P(1) atom. In the third O site, O(2) is bonded in a distorted trigonal planar geometry to one Mn(1), one Mn(2), and one P(1) atom. In the fourth O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Mn(2) and one P(1) atom. In the fifth O site, O(4) is bonded in a 3-coordinate geometry to one Mn(1), one Mn(2), and one C(1) atom. In the sixth O site, O(5) is bonded in a distorted trigonal planar geometry to one Mn(1), one Mn(2), and one P(1) atom. In the seventh O site, O(6) is bonded in a distorted water-like geometry to one Mn(1), one Mn(2), one H(1), and one H(2) atom.
Mn2CPH2O7 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to one O(2), one O(4), one O(5), one O(6), and two equivalent O(1) atoms to form MnO6 octahedra that share corners with four equivalent P(1)O4 tetrahedra,  an edgeedge with one Mn(1)O6 octahedra, and edges with two equivalent Mn(2)O6 pentagonal pyramids. The Mn(1)-O(2) bond length is 2.19 Å. The Mn(1)-O(4) bond length is 2.27 Å. The Mn(1)-O(5) bond length is 2.15 Å. The Mn(1)-O(6) bond length is 2.30 Å. There is one shorter (2.16 Å) and one longer (2.23 Å) Mn(1)-O(1) bond length. In the second Mn site, Mn(2) is bonded to one O(2), one O(3), one O(4), one O(5), one O(6), and one O(7) atom to form distorted MnO6 pentagonal pyramids that share corners with three equivalent P(1)O4 tetrahedra and edges with two equivalent Mn(1)O6 octahedra. The Mn(2)-O(2) bond length is 2.15 Å. The Mn(2)-O(3) bond length is 2.15 Å. The Mn(2)-O(4) bond length is 2.24 Å. The Mn(2)-O(5) bond length is 2.15 Å. The Mn(2)-O(6) bond length is 2.54 Å. The Mn(2)-O(7) bond length is 2.22 Å. C(1) is bonded in a distorted bent 120 degrees geometry to one O(4) and one O(7) atom. The C(1)-O(4) bond length is 1.27 Å. The C(1)-O(7) bond length is 1.27 Å. P(1) is bonded to one O(1), one O(2), one O(3), and one O(5) atom to form PO4 tetrahedra that share corners with four equivalent Mn(1)O6 octahedra and corners with three equivalent Mn(2)O6 pentagonal pyramids. The corner-sharing octahedral tilt angles range from 47-56°. The P(1)-O(1) bond length is 1.57 Å. The P(1)-O(2) bond length is 1.56 Å. The P(1)-O(3) bond length is 1.54 Å. The P(1)-O(5) bond length is 1.57 Å. There are two inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one O(6) atom. The H(1)-O(6) bond length is 1.00 Å. In the second H site, H(2) is bonded in a single-bond geometry to one O(6) atom. The H(2)-O(6) bond length is 0.99 Å. There are seven inequivalent O sites. In the first O site, O(7) is bonded in a distorted bent 120 degrees geometry to one Mn(2) and one C(1) atom. In the second O site, O(1) is bonded in a distorted trigonal planar geometry to two equivalent Mn(1) and one P(1) atom. In the third O site, O(2) is bonded in a distorted trigonal planar geometry to one Mn(1), one Mn(2), and one P(1) atom. In the fourth O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Mn(2) and one P(1) atom. In the fifth O site, O(4) is bonded in a 3-coordinate geometry to one Mn(1), one Mn(2), and one C(1) atom. In the sixth O site, O(5) is bonded in a distorted trigonal planar geometry to one Mn(1), one Mn(2), and one P(1) atom. In the seventh O site, O(6) is bonded in a distorted water-like geometry to one Mn(1), one Mn(2), one H(1), and one H(2) atom.