Résumé
The molecular orientation of adsorbed molecules forming selfassembled monolayers can be determined by combining vibrational sumfrequency generation (SFG) measurements with quantum chemical calculations. Herein, we present a theoretical methodology used to simulate the SFG spectra for different combinations of polarizations. These simulations are based on calculations of the IR vectors and Raman tensors, which are obtained from density functional theory computations. The dependency of the SFG vibrational signature with respect to the molecular orientation is presented for the molecules pnitrothiophenol and 2,4dinitroaniline. It is found that a suitable choice of basis set as well as of exchangecorrelation (XC) functional is mandatory to correctly simulate the SFG intensities and consequently provide an accurate estimation of the adsor bed molecule orientation. Comparison with experimental data shows that calculations performed at the B3LYP/6311 + + G(d,p) level of approximation provide good agreement with experimental frequencies, and with IR and Raman intensities. In particular, it is demonstrated that polarization and diffuse functions are compulsory for reproducing the IR and Raman spectra, and consequently vibrational SFG spectra, of systems such as pnitrothiophenol. Moreover, the investigated XC functional reveal their influence on the relative intensities, which show rather systematic variations with the amount of HartreeFock exchange. Finally, further aspects of the modeling are revealed by considering the frequency dependence of the Raman tensors.
langue originale  Anglais 

Pages (de  à)  21322142 
Nombre de pages  11 
journal  ChemPhysChem 
Volume  10 
Numéro de publication  12 
Les DOIs  
Etat de la publication  Publié  24 août 2009 
Empreinte digitale Examiner les sujets de recherche de « Theoretical simulation of vibrational sumfrequency generation spectra from density functional theory: Application to pnitrothiophenol and 2,4dinitroaniline ». Ensemble, ils forment une empreinte digitale unique.
Équipement

Optique, Lasers et spectroscopies
Muriel Lepere (!!Manager)
Plateforme technologique Lasers, optiques et spectroscopiesEquipement/installations: Plateforme technolgique