Luminescence and vibrational spectra of some polynuclear uranyl fluoride complexes

Abstract

The luminescence and vibrational spectra of M₃(UO₂)₂F₇·xH₂O (M = K, x= 2 and M = Na, x= 6), M₂(UO₂)₃F₈(OH₂)·3H₂O (M = K, Rb, NH₄), (Et₄N)(UO₂)₂F₅(OH₂)·H₂O and K₃(UO₂)₃F₉(OH₂)·2H₂O have been recorded at temperatures down to 10 K. In luminescence, the intense electronic origins are assigned to the lower-symmetry components of the E^″₁→A^′₁(D_5h) transition at non-equivalent uranyl sites. No electronic Davydov effects are detected. Changes in the vibrational spectra of K₃(UO₂)₂F₇·2H₂O occur below ca. 230 K and the luminescence spectra indicate that these are due to the creation of two non-equivalent uranyl sites. Discrepancies between the infrared and vibronic frequencies for the v_as(O—U—O) mode are interpreted.