Luminescence and crystal structure of neodymium and europium squarate hydrates

Abstract

Compounds of the composition [Nd2(C4O4)3(H2O)11]-2H2O and Eu2(C4O4)3(H2O)8 have been studied. The crystal structure of the neodymium compound was solved as space groups Pc and P2/c. The unit cell dimensions are a=9.673(3) Å, b=7.598(2) Å, c=16.400(4) Å and β=90.05(3)°. There are two non-equivalent Nd3+ ions, both nine coordinated. The former is coordinated by four oxygen atoms of squarate anions and five oxygen atoms of water, the latter by three oxygen atoms of squarate anions and six oxygen atoms of water. Two squarate anions act as bridging bidendate ligands, the third as a bridging tridendate ligand. This leads to the formation of a one-dimensional polymer. In the europium compound two non-equivalent atoms are coordinated by four oxygen atoms of squarate anions and four oxygen atoms of water. Coordination polyhedra of Eu3+ ions were fitted by the Drew method. The compounds are characterized by luminescence spectroscopy and the results are discussed in relation to their crystal structures.