Three-dimensional open-framework neodymium oxalates with organic functional groups protruding in 12-member channels

Abstract

Two open-framework neodymium oxalates, [NH₃CH₂CH(NH₃)CH₃][Nd(C₂O₄)₂(HCOO)]·H₂O (I) and [OC(CH₃)NCH₂CH(CH₃)NH₃][Nd(C₂O₄)₂]·H₂O (II), have been synthesized hydrothermally in the presence of 1,2-diaminopropane (1,2-DAP) and formic (I) and acetic (II) acids. The Nd atoms in both these oxalates have 9-fold coordination with respect to the oxygens, with the Nd atom in a distorted monocapped square antiprism coordination in I and in an idealized D_3h triply capped trigonal prism coordination in II. The three-dimensional framework structures of I and II are built up by in-plane linkages between the Nd and the oxalate moieties, forming layers with 12-membered honeycomb-like apertures, pillared by an out-of-plane oxalate unit. The 12-memberd channel in I contains a dangling formate group in addition to the disordered amine molecule, while in II, the channel has N-(2-aminopropyl acetimide) molecules formed by the in situ reaction of 1,2-DAP and acetic acid. The accessibility of the formate and N-(2-aminopropyl acetimide) functional groups in I and II, respectively, uniformly distributed within the channels enables chemical manipulation. Crystal data: I, monoclinic, space group P2₁/c (no. 14), M=459.5, a=9.0279(4) Å, b=18.1362(8) Å, c=8.5631(4) Å, β=102.735(10)°, V=1367.56(11) ų, Z=4, R₁=0.0229, wR₂=0.0599 [1782 observed reflections with I>2σ(I)]; II, triclinic, space group P_↑ (no. 2), M=454.5, a=8.6222(9) Å, b=9.5683(10) Å, c=9.5712(10) Å, α=109.388(2)°, β=98.508(10)°, γ=102.361(12)°, V=706.73(13) ų, Z=2, R₁=0.0446, wR₂=0.115 [1730 observed reflections with I>2σ(I)].