In this paper, we illustrate the contribution of the quantum chemical calculations to the simulation of two types of spectra. In a first part, the calculations of theoretical resonance Raman spectra of transient species are presented. The comparison of the theoretical and experimental spectra allows validating the methodology. From calculation results, the molecular structure and the spectra assignment of radicals have been deduced. In a second part, the TD-DFT methodology is applied to the determination of the preferential chelating site involved in the metal fixation by a ligand possessing several complexing functions in competition. We show that the use of UV-visible spectroscopy combined with quantum chemical calculations is well adapted to resolve the molecular structure of a complex. The reaction pathway calculations allow a better understanding of the regioselectivity of the complexation mechanism.
['Christine Lapouge', 'Jean-Paul Cornard']
Application of quantum chemical calculations to two non-trivial cases in the field of molecular spectroscopy