Tb7MnBr12 is trigonal omega-derived structured and crystallizes in the trigonal R-3 space group. There are two inequivalent Tb sites. In the first Tb site, Tb(1) is bonded to six equivalent Br(2) atoms to form edge-sharing TbBr6 octahedra. In the second Tb site, Tb(2) is bonded to one Mn(1), two equivalent Br(2), and three equivalent Br(1) atoms to form TbMnBr5 octahedra that share corners with three equivalent Tb(2)MnBr5 octahedra,  an edgeedge with one Tb(1)Br6 octahedra, and edges with five equivalent Tb(2)MnBr5 octahedra. The corner-sharing octahedral tilt angles range from 0-7°. Mn(1) is bonded in an octahedral geometry to six equivalent Tb(2) atoms. There are two inequivalent Br sites. In the first Br site, Br(1) is bonded in a T-shaped geometry to three equivalent Tb(2) atoms. In the second Br site, Br(2) is bonded in a distorted T-shaped geometry to one Tb(1) and two equivalent Tb(2) atoms.
Tb7MnBr12 is trigonal omega-derived structured and crystallizes in the trigonal R-3 space group. There are two inequivalent Tb sites. In the first Tb site, Tb(1) is bonded to six equivalent Br(2) atoms to form edge-sharing TbBr6 octahedra. All Tb(1)-Br(2) bond lengths are 2.82 Å. In the second Tb site, Tb(2) is bonded to one Mn(1), two equivalent Br(2), and three equivalent Br(1) atoms to form TbMnBr5 octahedra that share corners with three equivalent Tb(2)MnBr5 octahedra,  an edgeedge with one Tb(1)Br6 octahedra, and edges with five equivalent Tb(2)MnBr5 octahedra. The corner-sharing octahedral tilt angles range from 0-7°. The Tb(2)-Mn(1) bond length is 2.59 Å. There is one shorter (2.99 Å) and one longer (3.01 Å) Tb(2)-Br(2) bond length. There are a spread of Tb(2)-Br(1) bond distances ranging from 2.88-3.12 Å. Mn(1) is bonded in an octahedral geometry to six equivalent Tb(2) atoms. There are two inequivalent Br sites. In the first Br site, Br(1) is bonded in a T-shaped geometry to three equivalent Tb(2) atoms. In the second Br site, Br(2) is bonded in a distorted T-shaped geometry to one Tb(1) and two equivalent Tb(2) atoms.