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The electronic delocalization in para ‐substituted β‐nitrostyrenes probed by resonance Raman spectroscopy and quantum‐chemical calculations
Author(s) -
Ando Rômulo A.,
Cunha Rodrigo L. O. R.,
Juliano Luiz,
Borin Antonio C.,
Santos Paulo S.
Publication year - 2008
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.1855
Subject(s) - raman spectroscopy , chemistry , delocalized electron , resonance (particle physics) , substituent , excited state , resonance raman spectroscopy , molecule , chromophore , polar effect , quantum chemistry , photochemistry , crystallography , stereochemistry , atomic physics , organic chemistry , physics , quantum mechanics , supramolecular chemistry
The electronic (UV‐vis) and resonance Raman (RR) spectra of a series of para ‐substituted trans ‐β‐nitrostyrenes were investigated to determine the influence of the electron donating properties of the substituent (X = H, NO 2 , COOH, Cl, OCH 3 , OH, N(CH 3 ) 2 , and O − ) on the extent of the charge transfer to the electron‐withdrawing NO 2 group directly linked to the ethylenic (C = C) unit. The Raman spectra and quantum chemical calculations show clearly the correlation of the electron donating power of the X group with the wavenumbers of the ν s (NO 2 ) and ν (C = C) sty normal modes. In conditions of resonance with the lowest excited electronic state, one observes for X = OH and N(CH 3 ) 2 that the symmetric stretching of the NO 2 , ν s (NO 2 ), is the most substantially enhanced mode, whereas for X = O − , the chromophore is extended over the whole molecule, with substantial enhancement of several carbon backbone modes. Copyright © 2008 John Wiley & Sons, Ltd.