Crystal structure of new lanthanide diphosphates KLnP2O7 2H2O (Ln = Gd, Tb, Yb)

Crystals of lanthanide diphosphates KLnP2O7·2H2O [Ln=Gd, Tb, Yb] have been synthesized and investigated by single-crystal X-ray diffractometry. The three structures resulted to be isostructural within monoclinic space group P21/c, with unit cell parameters of a = 7.7522(2) Å, b = 10.6732(8) Å, c = 10.1375(7) Å, ² = 93.308(5)°, V = 837.39(9) Å3 (KGdP2O7 · 2 H2O = (1)), a = 7.7380(6) Å, b = 10.6360(8) Å, c = 10.1060(7) Å, ² = 93.283(6), V = 830.37(11) Å3 (KTbP2O7 · 2 H2O = (2)), a = 7.6791(3) Å, b = 10.4992(7) Å, c = 9.9554(9) Å, ² = 93.214(6)°, V = 801.39(10) Å3 (KYbP2O7 · 2 H2O = (3)). The three-dimensional frameworks are made by zig-zag chains of KO9 irregular polyhedra down c, sharing vertices with LnO7 polyhedra and P2O7 units; intricate hydrogen bonding networks complete the arrays.