Crystal structures and spectroscopy studies of lanthanide complexes with l-proline [Ln( l-proH) 2(H 2O) 5]Cl 3 (Ln = Ho, Dy)

Abstract

The isomorphic crystals of dysprosium(III) and holmium(III) complexes with proline of formula [Ln(C 5H 9NO 2) 2(H 2O) 5]Cl 3 (compound I holmium; compound II, dysprosium) were synthesized and characterized by crystal structures and spectroscopic properties. The space group is P2 1 with lattice parameters: I a = 11.968(2), b = 11.030(2), c = 8.309(2) Å, β = 106.97(3)°; II a = 11.968(4), b = 11.038(4), c = 8.302(2) Å, β = 107.00(3)°. The structures of the title compounds differ significantly from that of [Nd(proH) 3(H 2O) 2](ClO 4) 3, with different bonding modes for the proline ligands. The holmium and dysprosium structure contains one-dimensional polymers with the chains lying along the y-axis. Absorption spectra of the holmium monocrystal were measured along the a-axis at room temperature. Intensities of f- f transitions were analysed on the basis of Judd theory. The influence of the bonding mode of the carboxyl group on the intensity of the 5 I 8 → 5 G 6 hypersensitive transition of the Ho 3+ ion was considered and confronted for all spectroscopy data available for holmium carboxylate monocrystals.