A theoretical model is developed for simulating optical spectra of uranyl in complexes. The spectral profiles of electronic and vibronic transitions of UO22+ bonded to equatorial ligands are evaluated based on the Huang-Rhys theory of vibronic coupling in solids. This model assumes that only the symmetric O=U=O stretching mode exhibits multi-phonon progression, whereas all other local modes are not Franck-Condon allowed and treated as false origins of the progressing mode. A simulation of vibronic transitions in the UO2(NO3)(2)(TBP)(2) complex is compared with absorption spectrum to determine the excited state energy levels, frequencies of local vibration modes and vibronic coupling strength. (C) 2010 Published by Elsevier B.V.