Eu8C4N7I9 crystallizes in the trigonal P3m1 space group. There are four inequivalent Eu sites. In the first Eu site, Eu(1) is bonded in a 3-coordinate geometry to one N(2), two equivalent N(3), one I(1), two equivalent I(2), and two equivalent I(3) atoms. In the second Eu site, Eu(2) is bonded in a 7-coordinate geometry to two equivalent N(1), one I(3), two equivalent I(1), and two equivalent I(2) atoms. In the third Eu site, Eu(3) is bonded in a 4-coordinate geometry to one C(1), three equivalent N(3), and three equivalent I(1) atoms. In the fourth Eu site, Eu(4) is bonded in a 3-coordinate geometry to three equivalent N(1), three equivalent I(2), and three equivalent I(3) atoms. There are two inequivalent C sites. In the first C site, C(1) is bonded in a distorted linear geometry to one Eu(3) and one N(2) atom. In the second C site, C(2) is bonded in a linear geometry to one N(1) and one N(3) atom. There are three inequivalent N sites. In the first N site, N(1) is bonded to one Eu(4), two equivalent Eu(2), and one C(2) atom to form distorted NEu3C tetrahedra that share  a cornercorner with one N(3)Eu3C tetrahedra, corners with four equivalent I(1)Eu4 trigonal pyramids, and edges with two equivalent N(1)Eu3C tetrahedra. In the second N site, N(2) is bonded to three equivalent Eu(1) and one C(1) atom to form distorted NEu3C tetrahedra that share corners with three equivalent I(1)Eu4 trigonal pyramids and edges with three equivalent N(3)Eu3C tetrahedra. In the third N site, N(3) is bonded to one Eu(3), two equivalent Eu(1), and one C(2) atom to form distorted NEu3C tetrahedra that share  a cornercorner with one N(1)Eu3C tetrahedra, corners with five equivalent I(1)Eu4 trigonal pyramids,  an edgeedge with one N(2)Eu3C tetrahedra, and edges with two equivalent N(3)Eu3C tetrahedra. There are three inequivalent I sites. In the first I site, I(1) is bonded to one Eu(1), one Eu(3), and two equivalent Eu(2) atoms to form distorted IEu4 trigonal pyramids that share  a cornercorner with one N(2)Eu3C tetrahedra, corners with four equivalent N(1)Eu3C tetrahedra, corners with five equivalent N(3)Eu3C tetrahedra, and corners with four equivalent I(1)Eu4 trigonal pyramids. In the second I site, I(2) is bonded in a 5-coordinate geometry to one Eu(4), two equivalent Eu(1), and two equivalent Eu(2) atoms. In the third I site, I(3) is bonded in a 4-coordinate geometry to one Eu(2), one Eu(4), and two equivalent Eu(1) atoms.
Eu8C4N7I9 crystallizes in the trigonal P3m1 space group. There are four inequivalent Eu sites. In the first Eu site, Eu(1) is bonded in a 3-coordinate geometry to one N(2), two equivalent N(3), one I(1), two equivalent I(2), and two equivalent I(3) atoms. The Eu(1)-N(2) bond length is 2.62 Å. Both Eu(1)-N(3) bond lengths are 2.65 Å. The Eu(1)-I(1) bond length is 3.77 Å. Both Eu(1)-I(2) bond lengths are 3.74 Å. Both Eu(1)-I(3) bond lengths are 3.30 Å. In the second Eu site, Eu(2) is bonded in a 7-coordinate geometry to two equivalent N(1), one I(3), two equivalent I(1), and two equivalent I(2) atoms. Both Eu(2)-N(1) bond lengths are 2.61 Å. The Eu(2)-I(3) bond length is 3.32 Å. Both Eu(2)-I(1) bond lengths are 3.31 Å. Both Eu(2)-I(2) bond lengths are 3.39 Å. In the third Eu site, Eu(3) is bonded in a 4-coordinate geometry to one C(1), three equivalent N(3), and three equivalent I(1) atoms. The Eu(3)-C(1) bond length is 2.55 Å. All Eu(3)-N(3) bond lengths are 2.53 Å. All Eu(3)-I(1) bond lengths are 3.56 Å. In the fourth Eu site, Eu(4) is bonded in a 3-coordinate geometry to three equivalent N(1), three equivalent I(2), and three equivalent I(3) atoms. All Eu(4)-N(1) bond lengths are 2.62 Å. All Eu(4)-I(2) bond lengths are 3.36 Å. All Eu(4)-I(3) bond lengths are 3.74 Å. There are two inequivalent C sites. In the first C site, C(1) is bonded in a distorted linear geometry to one Eu(3) and one N(2) atom. The C(1)-N(2) bond length is 1.19 Å. In the second C site, C(2) is bonded in a linear geometry to one N(1) and one N(3) atom. The C(2)-N(1) bond length is 1.24 Å. The C(2)-N(3) bond length is 1.24 Å. There are three inequivalent N sites. In the first N site, N(1) is bonded to one Eu(4), two equivalent Eu(2), and one C(2) atom to form distorted NEu3C tetrahedra that share  a cornercorner with one N(3)Eu3C tetrahedra, corners with four equivalent I(1)Eu4 trigonal pyramids, and edges with two equivalent N(1)Eu3C tetrahedra. In the second N site, N(2) is bonded to three equivalent Eu(1) and one C(1) atom to form distorted NEu3C tetrahedra that share corners with three equivalent I(1)Eu4 trigonal pyramids and edges with three equivalent N(3)Eu3C tetrahedra. In the third N site, N(3) is bonded to one Eu(3), two equivalent Eu(1), and one C(2) atom to form distorted NEu3C tetrahedra that share  a cornercorner with one N(1)Eu3C tetrahedra, corners with five equivalent I(1)Eu4 trigonal pyramids,  an edgeedge with one N(2)Eu3C tetrahedra, and edges with two equivalent N(3)Eu3C tetrahedra. There are three inequivalent I sites. In the first I site, I(1) is bonded to one Eu(1), one Eu(3), and two equivalent Eu(2) atoms to form distorted IEu4 trigonal pyramids that share  a cornercorner with one N(2)Eu3C tetrahedra, corners with four equivalent N(1)Eu3C tetrahedra, corners with five equivalent N(3)Eu3C tetrahedra, and corners with four equivalent I(1)Eu4 trigonal pyramids. In the second I site, I(2) is bonded in a 5-coordinate geometry to one Eu(4), two equivalent Eu(1), and two equivalent Eu(2) atoms. In the third I site, I(3) is bonded in a 4-coordinate geometry to one Eu(2), one Eu(4), and two equivalent Eu(1) atoms.