Assignment of the π → π* and n → π* Transitions to the Spectral Bands of Azobenzene and Dimethylaminoazobenzene
- Authors: Mikheev Y.A.1, Ershov Y.A.2
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Affiliations:
- Emanuel Institute of Biochemical Physics, Russian Academy of Sciences
- Bauman Moscow State Technical University
- Issue: Vol 92, No 8 (2018)
- Pages: 1499-1507
- Section: Structure of Matter and Quantum Chemistry
- URL: https://journals.rcsi.science/0036-0244/article/view/170086
- DOI: https://doi.org/10.1134/S0036024418080174
- ID: 170086
Cite item
Abstract
A critical analysis of the UV–Vis absorption spectra of azobenzene (AB) and dimethylaminoazobenzene (DAB) used as an optical probe was performed based on the key empirical regularities of the n → π* transitions of nitrogen- and carbonyl-containing compounds. The spectrum of DAB has an n → π* band located in the same range ν = 28 000–33 000 cm–1 (λ = 350–300 nm) as the n → π* band of protonated azobenzene AB+H, but differs in the presence of a vibronic structure. It was also shown that the low-frequency n → π* band belonging to AB lies in the range where the π → π* band of AB is located with a maximum at a wavelength λmax ≈ 320–340 nm (νmax = 30 300–29 400 cm–1), in contrast to the conventional assignment of this band to the Vis band at 440 nm. This n → π * band is not found in the spectra of AB solutions in polar media, but appears in the nonpolar medium due to the presence of a vibronic structure.
About the authors
Yu. A. Mikheev
Emanuel Institute of Biochemical Physics, Russian Academy of Sciences
Author for correspondence.
Email: mik@sky.chph.ras.ru
Russian Federation, Moscow, 119334
Yu. A. Ershov
Bauman Moscow State Technical University
Email: mik@sky.chph.ras.ru
Russian Federation, Moscow, 105005