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Detailed analysis of the charge transfer complex N , N ‐dimethylaniline–SO 2 by Raman spectroscopy and density functional theory calculations
Author(s) -
Ando Rômulo A.,
Matazo Deborah R. C.,
Santos Paulo S.
Publication year - 2010
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.2514
Subject(s) - raman spectroscopy , time dependent density functional theory , dimethylaniline , chemistry , density functional theory , intermolecular force , resonance (particle physics) , resonance raman spectroscopy , amine gas treating , computational chemistry , photochemistry , molecule , atomic physics , organic chemistry , physics , optics
Although the amine sulfur dioxide chemistry was well characterized in the past both experimentally and theoretically, no systematic Raman spectroscopic study describes the interaction between N , N ‐dimethylaniline (DMA) and sulfur dioxide (SO 2 ). The formation of a deep red oil by the reaction of SO 2 with DMA is an evidence of the charge transfer (CT) nature of the DMA–SO 2 interaction. The DMA–SO 2 normal Raman spectrum shows the appearance of two intense bands at 1110 and 1151 cm −1 , which are enhanced when resonance is approached. These bands are assigned to ν s (SO 2 ) and ν(ϕN) vibrational modes, respectively, confirming the interaction between SO 2 and the amine via the nitrogen atom. The dimethyl group steric effect favors the interaction of SO 2 with the ring π electrons, which gives rise to a π–π* low‐energy CT electronic transition, as confirmed by time‐dependent density functional theory (TDDFT) calculations. In addition, the calculated Raman DMA–SO 2 spectrum at the B3LYP/6‐311 + + g(3df,3pd) level shows good agreement with the experimental results (vibrational wavenumbers and relative intensities), allowing a complete assignment of the vibrational modes. A better understanding of the intermolecular interactions in this model system can be extremely useful in designing new materials to absorb, detect, or even quantify SO 2 . Copyright © 2009 John Wiley & Sons, Ltd.