Photophysical studies of uranyl complexes 5. Luminescence spectrum of K 4UO 2(CO 3) 3

Abstract

The photoluminescence of K4UO2(CO3)3 has been studied under conditions of high resolution at cryogenic temperatures. The origin corresponding to the pure electronic transition was located at 4774 A (20945 cm−1), and it was found that the totally symmetric uranyl stretching mode was coupled to this transition. A progression of four band systems thus resulted, and from an examination of the energies of corresponding peaks in each system, a value of 813 cm−1 for the U-O stretching mode was determined. Two lattice modes (34 and 80 cm−1) and two molecular vibrational modes (205 and 276 cm−1) were also found to couple with the pure electronic transition, thus yielding approximately 15 major peaks in each band system. The 205 cm−1 vibration corresponded to a CO32− vibration, while the 276 cm−1 vibration was a UO22+ deformation. The low values obtained for the force constant and totally symmetric stretching frequency of the U-O bond suggested that in UO2(CO)34−, the uranium atom is bound in a complex species that may be considered as an intermediate between that of a uranyl (UO22+) and a uranate (UO810−) ion.