Substituent Effects upon Protonation-Induced Red Shift of Phenyl−Pyridine Copolymers
Document Type
Article
Journal/Book Title
Journal of Physical Chemistry B
Publication Date
2002
Publisher
American Chemical Society
Volume
106
Issue
3
First Page
534
Last Page
539
Abstract
Ab initio methods are used to probe the underlying source of the red shift that arises in the absorption band of polymers that contain alternating phenyl and pyridine rings when the N atom of the latter is protonated. It is found that electronic charge transfers from the phenyl to the pyridine as an electron is excited from the HOMO to the LUMO in the protonated system but that no such transfer occurs if the N is unprotonated. Replacement of H atoms by cyano groups reinforces the idea that such an electron-withdrawing substituent facilitates the electron transfer when it is located on the pyridine ring, thereby stabilizing the excited state and thus enhancing the associated red shift; the opposite occurs when cyano is located on the phenyl ring. Unlike cyano and Cl, substitution by F and nitro groups leads to a less consistent pattern of absorption frequencies, suggesting that the effects of these substituents are not simply electrostatic in nature.
Recommended Citation
Substituent Effects upon Protonation-Induced Red Shift of Phenyl−Pyridine Copolymers. Steve Scheiner and, Tapas Kar. The Journal of Physical Chemistry B 2002 106 (3), 534-539.
Comments
Originally published by American Chemical Society in the Journal of Physical Chemistry.
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