In this work we analyzed the infrared and visible transient absorption spectra of all-trans-β-apo-8′-carotenal in several solvents, differing in both polarity and polarizability at different excitation wavelengths. We correlate the solvent dependence of the kinetics and the band shape changes in the infrared with that of the excited state absorption bands in the visible, and we show that the information obtained in the two spectral regions is complementary. All the collected time-resolved data can be interpreted in the frame of a recently proposed relaxation scheme, according to which the major contributor to the intramolecular charge transfer (ICT) state is the bright 1Bu+ state, which, in polar solvents, is dynamically stabilized through molecular distortions and solvent relaxation. A careful investigation of the solvent effects on the visible and infrared excited state bands demonstrates that both solvent polarity and polarizability have to be considered in order to rationalize the excited state relaxation of trans-8′-apo-β-carotenal and clarify the role and the nature of the ICT state in this molecule. The experimental observations reported in this work can be interpreted by considering that at the Franck–Condon geometry the wave functions of the S1 and S2 excited states have a mixed ionic/covalent character. The degree of mixing depends on solvent polarity, but it can be dynamically modified by the effect of polarizability. Finally, the effect of different excitation wavelengths on the kinetics and spectral dynamics can be interpreted in terms of photoselection of a subpopulation of partially distorted molecules.

Mechanism of the intramolecular charge transfer state formation in all-trans-b-apo-8'-carotenal: influence of solvent polarity and polarizability / Elena Ragnoni; Mariangela Di Donato; Alessandro Iagatti; Andrea Lapini; Roberto Righini. - In: JOURNAL OF PHYSICAL CHEMISTRY. B, CONDENSED MATTER, MATERIALS, SURFACES, INTERFACES & BIOPHYSICAL. - ISSN 1520-6106. - STAMPA. - 119:(2015), pp. 420-432. [10.1021/jp5093288]

Mechanism of the intramolecular charge transfer state formation in all-trans-b-apo-8'-carotenal: influence of solvent polarity and polarizability

RAGNONI, ELENA;DI DONATO, MARIANGELA;LAPINI, ANDREA;RIGHINI, ROBERTO
2015

Abstract

In this work we analyzed the infrared and visible transient absorption spectra of all-trans-β-apo-8′-carotenal in several solvents, differing in both polarity and polarizability at different excitation wavelengths. We correlate the solvent dependence of the kinetics and the band shape changes in the infrared with that of the excited state absorption bands in the visible, and we show that the information obtained in the two spectral regions is complementary. All the collected time-resolved data can be interpreted in the frame of a recently proposed relaxation scheme, according to which the major contributor to the intramolecular charge transfer (ICT) state is the bright 1Bu+ state, which, in polar solvents, is dynamically stabilized through molecular distortions and solvent relaxation. A careful investigation of the solvent effects on the visible and infrared excited state bands demonstrates that both solvent polarity and polarizability have to be considered in order to rationalize the excited state relaxation of trans-8′-apo-β-carotenal and clarify the role and the nature of the ICT state in this molecule. The experimental observations reported in this work can be interpreted by considering that at the Franck–Condon geometry the wave functions of the S1 and S2 excited states have a mixed ionic/covalent character. The degree of mixing depends on solvent polarity, but it can be dynamically modified by the effect of polarizability. Finally, the effect of different excitation wavelengths on the kinetics and spectral dynamics can be interpreted in terms of photoselection of a subpopulation of partially distorted molecules.
2015
119
420
432
Elena Ragnoni; Mariangela Di Donato; Alessandro Iagatti; Andrea Lapini; Roberto Righini
File in questo prodotto:
File Dimensione Formato  
apo2rev.pdf

Accesso chiuso

Descrizione: articolo principale
Tipologia: Versione finale referata (Postprint, Accepted manuscript)
Licenza: Tutti i diritti riservati
Dimensione 1.2 MB
Formato Adobe PDF
1.2 MB Adobe PDF   Richiedi una copia

I documenti in FLORE sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificatore per citare o creare un link a questa risorsa: https://hdl.handle.net/2158/957759
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 23
  • ???jsp.display-item.citation.isi??? 23
social impact