The intramolecular charge transfer in a donor-p-acceptor dianion probed by resonance Raman spectroscopy and quantum chemical calculations

The dideprotonation of 4-(4-nitrophenylazo)resorcinol generates an anionic species with substantial electronic delocalization. As compared to the parent neutral species, the anionic first excited electronic transition, characterized as an intramolecular charge transfer (ICT) from the CO- groups to t...

Full description

Saved in:
Bibliographic Details
Published in:Journal of Raman spectroscopy 2009-09, Vol.40 (9), p.1158-1161
Main Authors: Ando, Romulo A, Borin, Antonio C, Santos, Paulo S
Format: Article
Language:English
Subjects:
Charge transfer
Doppler effect
Electronics
Mathematical analysis
Neural networks
Nitrogen dioxide
Quantum chemistry
Raman spectroscopy
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:The dideprotonation of 4-(4-nitrophenylazo)resorcinol generates an anionic species with substantial electronic delocalization. As compared to the parent neutral species, the anionic first excited electronic transition, characterized as an intramolecular charge transfer (ICT) from the CO- groups to the NO2 moiety, shows a drastic red shift of ca. 200 nm in the max in the UV-vis spectrum, leading to one of the lowest ICT energies observed (max = 630 nm in dimethyl sulfoxide (DMSO)) in this class of push-pull molecular systems. Concomitantly, a threefold increase in the molar absorptivity (max) in comparison to the neutral species is observed. The resonance Raman enhancement profiles reveal that in the neutral species the chromophore involves several modes, as (CN), (NN), (CC) and s(NO2), whereas in the dianion, there is a selective enhancement of the NO2 vibrational modes. The quantum chemical calculations of the electronic transitions and vibrational wavenumbers led to a consistent analysis of the enhancement patterns observed in the resonance Raman spectra.
ISSN:0377-0486
DOI:10.1002/jrs.2250