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A theoretical study of the lowest electronic states of azobenzene: the role of torsion coordinate in the cis-trans photoisomerization
|Published in||Theoretical Chemistry Accounts. 2004, vol. 111, no. 2-6, p. 363-372|
|Abstract||In the present paper we report the results of a multiconfigurational computational study on potentialenergy curves of azobenzene along the NN twisting to clarify the role of this coordinate in the decay of the S2(ππ*) and S1(nπ*) states. We have found that there is a singlet state, S3 at the trans geometry, on the basis of the doubly excited configuration n2π*2, that has a deep minimum at about 90°of twisting, where it is the lowest excited singlet state. The existence of this state provides an explanation for the short lifetime of S2(ππ*) and for the wavelength-dependence of azobenzene photochemistry. We have characterized the S1(nπ*) state by calculating its vibrational frequencies, which are found to correspond to the recently observed transient Raman spectrum. We have also computed the potential-energy curve for the triplet T1(nπ*) at the density functional theory B3LYP level, which indicates that in this state the isomerization occurs along the twisting coordinate.|
|Keywords||Azobenzene — Excited electronic states — Photoisomerization — Multiconfigurational wave function methods|
|Research group||Groupe Gagliardi|
|GAGLIARDI, Laura et al. A theoretical study of the lowest electronic states of azobenzene: the role of torsion coordinate in the cis-trans photoisomerization. In: Theoretical Chemistry Accounts, 2004, vol. 111, n° 2-6, p. 363-372. https://archive-ouverte.unige.ch/unige:3319|