Complex of trivalent lanthanum ion with galactitol in the solid state: the crystal structure and an FT-IR study of LaCl3·galactitol·6H2O

The crystal structure of LaCl₃·galactitol·6H₂O has been determined. It is monoclinic. The space group is P2₁/n with unit cell dimensions a=10.5091(7), b=12.5366(7), c=14.4420(10) Å, β=90.974(2)°, V=1902.4(2) ų and Z=4. Each La³⁺ ion in the unit cell is coordinated to 10 oxygen atoms, three from O1, O2 and O3 of one alditol, three from O4, O5 and O6 of another alditol and four from water molecules, with La–O distances from 2.5099 to 2.6916 Å. The other two water molecules are hydrogen-bonded. FT-IR spectrum of LaCl₃·galactitol·6H₂O is apparently different from that of other lanthanide–galactitol complexes. It is consistent with the differences between their crystal structures. Both the IR result and the crystal structure of LaCl₃·galactitol·6H₂O complex show that it has the different coordination mode compared with other lanthanide complexes.