Related Experiment Video
Updated: Jul 19, 2026

High Resolution Phonon-assisted Quasi-resonance Fluorescence Spectroscopy
Published on: June 28, 2016
Optical spectra of delocalized dinitroaromatic radical anions revisited
Stephen F Nelsen1, Michael N Weaver, Jeffrey I Zink
1Department of Chemistry, University of Wisconsin, 1101 University Avenue, Madison, Wisconsin 53706-1396, USA. nelsen@chem.wisc.edu
Abstract:
The optical spectra of nine dinitroaromatic radical anions (1,2- and 1,4-dinitrobenzene, 1,5- and 2,6-dinitro naphthalene, 4,4'-dinitrobiphenyl, 2,7-dinitro-9,9-dimethylfluorene, 2,6-dinitroanthracene, and 2,7- and 1,8-dinitrobiphenylene) in dimethylformamide are reported and analyzed. All have delocalized charge distribution, as demonstrated by the vibrational fine structure that is observed in their optical spectra: All show lowest energy absorption bands that correspond to an alpha-homo (highest occupied molecular orbital) to alpha-lumo (lowest unoccupied) transition, as shown by Koopmans-based UB3LYP calculation of the orbital separation of the neutral at the geometry of the radical anion. These single-point calculations are shown to be significantly more accurate for five of these compounds than the much more complex and expensive TD-DFT method. The two-state model should not be used to estimate the electronic coupling in delocalized intervalence compounds such as these. Neighboring orbital estimation of the electronic couplings show that using the two-state model greatly underestimates electronic coupling here.
More Related Videos
Related Concept Videos
¹³C NMR: Distortionless Enhancement by Polarization Transfer (DEPT)
Molecular Spectroscopy: Absorption and Emission
UV–Vis Spectroscopy: Molecular Electronic Transitions
IR Absorption Frequency: Hybridization
Among the sp, sp2, and sp3 hybridized orbitals, sp orbitals have the maximum s character (50%). Consequently, the electrons are held more closely to the nucleus, resulting in stronger and shorter C–H bonds that stretch at a...
IR Absorption Frequency: Delocalization
In IR spectroscopy,...
IR Frequency Region: Fingerprint Region
The...

