6533b7d1fe1ef96bd125d8b3
RESEARCH PRODUCT
A theoretical study of the lowest electronic states of azobenzene: the role of torsion coordinate in the cis-trans photoisomerization
Alessandro CembranFernando BernardiGiorgio OrlandiLaura GagliardiMarco Garavellisubject
PhotoisomerizationAzobenzeneMulticonfigurational wave function methodschemistry.chemical_compoundsymbols.namesakeAzobenzenechemistryExcited statePhotoisomerizationddc:540symbolsDensity functional theoryExcited electronic statesSinglet statePhysical and Theoretical ChemistryAtomic physicsRaman spectroscopyIsomerizationCis–trans isomerismdescription
In the present paper we report the results of a multiconigurational computational study on potential- energy curves of azobenzene along the NN twisting to clarify the role of this coordinate in the decay of the S2(pp*) and S1(np*) states. We have found that there is a singlet state, S3 at the trans geometry, on the basis of the doubly excited coniguration n 2 p* 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(pp*) and for the wavelength-dependence of azobenzene photochem- istry. We have characterized the S1(np*) state by calcu- lating 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(np*) at the density functional theory B3LYP level, which indicates that in this state the isomerization occurs along the twisting coordinate.
| year | journal | country | edition | language |
|---|---|---|---|---|
| 2003-12-08 |