Isolation and characterization of a polymeric lanthanum citrate

The first lanthanide citrate coordination polymer with the formula [La(Hcit)(H2O)](n) (Hcit(3-) = C(OH)(COO-)(CH2COO-)(2)) was prepared from La2O3 and citric acid at pH = 2.2-2.5 under hydrothermal conditions at 120 degreesC. The compound was characterized by elemental analysis, IR, TG-DTA, and X-ray crystallography. It is thermally stable up to 158 degreesC and insoluble in common solvents. The compound crystallizes in the monoclinic space group C2/c with a = 16.765(3) Angstrom, b = 8.822(2) Angstrom, c = 14.048(3) Angstrom, beta = 120.64(3)degrees, and Z = 8. The structure consists of chains of La(III) cations bridged by O-C-O groups with pendant Hcit anions forming a pillar structure. The Hcit ligand is involved in six La-O bonds to five different La centers in a very compact 3D structure.