Structural Determination of a New La(III) Coordination Polymer with Pseudo-merohedral Twinning Structure

Hydrothermal reaction of benzene-1,2,4,5-tetracarboxylic (Btec) dianhydride with La₂O₃ lead to a new organometallic compound, [La₂(betc)(Hbtec)(H₂O)₃][HCONH(CH₃)₂] (I). Single-crystal X-ray diffraction analysis reveals that it crystallizes in monoclinic space group P2₁/n that mimics orthorhombic space group Pnma (viz. pseudo-merohedral twinning structure) with a=7.6002(16), b=18.954(4), c=18.213(4) Å, β=90.121(3)°, V=2623.5(9) ų, Z=4, M_r=907.21, D c=2.297 g/cm³, F(000)=1752, μ(MoKα)=3.32 mm^-1, R=0.0575 and wR=0.0956. The structure of I features a 3-D framework constructed by La(III) cations, btec^4- ligands, Hbtec^3- ligands and coordinated water molecule. All of the La(III) cations are 10-coordinated by O atoms into 1-D infinite chains, which are further interconnected by C atoms of btec ligands to form a 3-D framework.