New open-framework three-dimensional lanthanide oxalates containing as a template the diprotonated 1,2- or 1,3-diaminopropane

Single crystals of three new open-framework lanthanide oxalates have been synthesized hydrothermally, in the presence of 1,2-diaminopropane, (C3N2H12)[Nd(H2O)(C2O4)2]2·3H2O I and (C3N2H12)[Yb(C2O4)2]2·5H2O II, or 1,3-diaminopropane (C3N2H12)2[La2(C2O4)5]·5H2O III. Their structures have been determined by X-ray diffraction data: I and III crystallize in the triclinic system, space group P  -1, with a=7.8130(5)Å, b=11.8800(6)Å, c=12.9940(8)Å, α=93.092(5)°α=93.092(5)°, β=93.930(6)°β=93.930(6)°, γ=108.359(5)°γ=108.359(5)° and a=11.6650(9)Å, b=11.9240(6)Å, c=13.2230(7)Å, α=104.585(4)°α=104.585(4)°, β=108.268(5)°β=108.268(5)°, γ=111.132(5)°γ=111.132(5)°, respectively while II crystallizes in the orthorhombic system, space group F2ddF2dd, with a=8.7970(4)Å, b=16.1550(8)Å, c=32.170(2)Å. The three-dimensional (3D) framework of these compounds is built up by the linkages of lanthanide atoms and the oxygen atoms of the bischelating oxalate ligands. Instead of four chelating oxalate units surrounding a lanthanide atom (I and II), both lanthanum atoms, in III, are surrounded by five chelating oxalate groups and that is new. In all the cases within the frame, are observed 8- and 12-membered channels where are localized the guest species, 1,2- or 1,3-diaminopropane cations and free water molecules. The ratio of the guest number (especially the diaminopropane) per 12-membered ring could tune the shape and the size of 12-membered channels: thus, the 12-membered channels, observed for I and II, have elliptical cross-section (5.5 Å×11.4 Å and 5.2 Å×9.5 Å) while those, observed for III, have nearly circular cross-section (9.1 Å×9.5 Å). The lanthanide atoms are 8, 9 and 10-fold coordinated for Yb (II), Nd (I) and La (III), respectively.

View of the 12-membered channel of (C3N2H12)2[La2(C2O4)5]·5H2O.Figure optionsDownload as PowerPoint slide