Synthesis and optical study of Ln(III)(tetramethylurea)(AsF 6) 3 (Ln = LaLu, Y) and crystal structure for Ln = Eu [Eu(TMU) 6(AsF 6) 3

Abstract

The fluorescence spectrum of Eu 3+ recorded at a temperature of 12 K between 14.000 and 20.000 cm −1 shows transitions from the excited stare 5D o to the Stark components of the lowest 7F j. The optical analysis suggests an octahedral site symmetry for the rare earth ion which is confirmed by the three-dimensional crystal determination. The highly disordered crystal structure refined in space group F23 to an R-factor of 13.2%. Both the europium and the arsenic ions are located in special positions of point symmetry 23(T). The EuO bond distance is 2.28 Å. The value of the B q k parameters was determined.