Syntheses and Characterizations of Three-Dimensional Channel-like Polymeric Lanthanide Complexes Constructed by 1,2,4,5-Benzenetetracarboxylic Acid

The hydrothermal reaction of YbCl3·6H2O with 1,2,4,5-benzenetetracarboxylic dianhydride resulted in
[{Yb(bbtec)1/4(dbtec)3/6(H2O)2}4·6H2O]n (1) (H4btec = 1,2,4,5-benzenetetracarboxylic acid), and the solvothermal
reaction of Er(NO3)3·6H2O or TbCl3·6H2O with 1,2,4,5-benzenetetracarboxylic dianhydride in H2O/acetic acid gave
rise to [{Er2(cbtec)2/4(ebtec)2/4(fbtec)2/4(H2O)4}·4H2O]n (2) and [{Tb(H2btec)2/4(fbtec)3/6(H2O)}·2H2O]n (3), respectively.
Complex 1 crystallizes in monoclinic space group C2/m with a = 20.8119(5) Å, b = 17.6174(1) Å, c = 5.7252(2)
Å, β = 92.324(1)°, and Z = 1. 1 possesses a three-dimensional framework consisting of eight-coordinate ytterbium
centers and two kinds of channels along the c axis. Complex 2 crystallizes in triclinic space group P1̄ with a =
9.6739(5) Å, b = 11.0039(5) Å, c = 11.5523 Å, α = 104.8330(10)°, β = 91.0000(10)°, γ = 114.2570(10)°, and
Z = 2. 2 has a three-dimensional framework comprising both eight- and nine-coordinate erbium centers and channels
along the a axis. Complex 3 crystallizes in monoclinic space group P21/n with a = 10.7246(12) Å, b = 7.1693(9)
Å, c = 17.158(2) Å, β = 97.109(2)°, and Z = 4. 3 shows a three-dimensional framework containing nine-coordinate
terbium centers and channels along the b axis. Uncoordinated water molecules occupy the channels in the three
complexes. TGA and XRPD were determined for the three complexes, and the results illustrate that the framework
of 1 is retained upon removal of uncoordinated and coordinated water molecules.