The experimental results on the rotameric equilibrium and electronic spectra of aza-derivatives of trans-stilbene and 1,4-diphenylbutadiene, have been rationalized by a theoretical study which combines simple ab initio calculations of molecular energies for the ground state with a theoretical analysis of the splitting of the conjugation band developed at CS INDO Cl level. All results indicate that the stable conformer of each ortho aza-derivative is that corresponding to A species. As suggested by the H-1-NMR experiments, the ab initio geometry of ZE-2-pyridylphenylbutadiene is consistent with the presence of the N.H intramolecular hydrogen bond. As regards the Franck-Condon excited states of aza-derivatives, our theoretical results show that the first singlet excited state has (pi(H), pi(L)(*)) character in all compounds except for E-4,4'-dipyridylethene, where S-1 has (n, pi*) character in non-polar solvent. In this last compound, the theoretical study of solvatochromism indicates a crossing between the (1)(n, pi(L)(*)) and (1)(pi(H), pi(L)(*)) states which occurs in solvents of high polarity. The inclusion of the most important. doubly- and triply-excited configurations in the CI calculations shows that the (1)A(g)(-) excited state is above the spectral region analyzed. (C) 2002 Elsevier Science B.V. All rights reserved.
Anno di pubblicazione: | 2003 |
Titolo: | Rotamerism and electronic spectra of aza-derivatives of stilbene and diphenylbutadiene. A combined experimental and theoretical study |
Autore/i: | I. Baraldi; A. Spalletti; D. Vanossi |
Autore/i UNIMORE: | |
Rivista: | |
Volume: | 59 |
Pagina iniziale: | 75 |
Pagina finale: | 86 |
Codice identificativo ISI: | WOS:000179625800009 |
Codice identificativo Scopus: | 2-s2.0-0037210186 |
Tipologia | Articolo su rivista |
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