X-ray crystal structure analysis of lanthanide trihydrogeno hydroxy-1-ethanebis(phosphonate)-1,1,dihydrogeno hydroxy-1ethanebis(phosphonate)-1,1 hemiundecahydrate, Ln{[C(CH3)(OH)(P2O6H3)][C(CH3)(OH)(P2O6H2)]}⋅5.5H2O with Ln = Y, Ho, Er; and energy parametrization of the absorption spectrum of the Er compound

The crystal structures of Ln{[C(CH3)⋅(OH)(P2O6H3)][C(CH3)(OH)(P2O6H2)]}⋅5.5H2O, with Ln = Y (compound 1), Ln = Ho (compound 2) and Ln = Er (compound 3), have been determined by single crystal X-ray diffraction. The three compounds are isomorphous and crystallize in the monoclinic space group P21/n (n°14). The cell parameters of 1 are a = 10.451(2) Å, b = 11.395(3) Å, c = 17.173(3) Å, β = 94.28(1)°, those of 2 are a = 10.447(2) Å, b = 11.382(2) Å, c = 17.129(4) Å, β = 94.32(3)°, and those of 3 are a = 10.432(1) Å, b = 11.398(2) Å, c = 17.134(2) Å, β = 94.35(2)°.The coordination polyhedron around the lanthanide cations is a distorted monocapped trigonal prism with a slightly distorted C 2 v symmetry. The UV and visible light absorption spectrum was recorded for 3. A detailed theoretical simulation of the energy level scheme of the 4f11 configuration of Er3+ was carried out. The angular parts were accurately calculated by group-theoretical and tensorial methods and the radial integrals were left as parameters to be determined semi-empirically. The C 2 v symmetry was described by free ion and crystal field parameters after refinement of these parameters on the absorption spectroscopic data of 3.