The spectra of carbonium ions, cyanine dyes, and protonated Schiff base polyenes

Klaus Schulten, Uri Dinur, Barry Honig

Research output: Contribution to journalArticle

Abstract

The origin of the strong bathochromic shift of the visual pigment supposedly lies in the carbonium ion character of the protonated Schiff base retinal. Following this conjecture, we have carried out a comparative study of the spectra of the carbonium ions, cyanine dyes, and protonated Schiff base polyenes. In our calculation, we have employed PPP (for the carbonium ions) and CNDO/S parametrized Hamiltonians. For a correct description of the electronic excitations in these linear π-systems, we have included all single, double, and in some cases also all triple and quadruple excited configurations in the CI expansion. Our study revealed a close resemblance of the spectral behavior of these three compounds. In particular, we found that higher excitations, accounting for the effect of electron correlation, induce a strong red shift of the main (S1←S0) absorption band. This behavior is due to the mainly covalent character of the S1 state which is poorly described by single excited configurations. As in the polyenes, there exists also a weakly absorbing state of double excited character which in contrast to the polyene case lies above the allowed state.

Original languageEnglish (US)
Pages (from-to)3927-3935
Number of pages9
JournalThe Journal of chemical physics
Volume73
Issue number8
DOIs
StatePublished - Jan 1 1980

Fingerprint

Polyenes
Schiff Bases
imines
Coloring Agents
dyes
Ions
visual pigments
Hamiltonians
Electron correlations
ions
Retinal Pigments
linear systems
configurations
red shift
excitation
Linear systems
Absorption spectra
absorption spectra
expansion
shift

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

Cite this

The spectra of carbonium ions, cyanine dyes, and protonated Schiff base polyenes. / Schulten, Klaus; Dinur, Uri; Honig, Barry.

In: The Journal of chemical physics, Vol. 73, No. 8, 01.01.1980, p. 3927-3935.

Research output: Contribution to journalArticle

Schulten, Klaus ; Dinur, Uri ; Honig, Barry. / The spectra of carbonium ions, cyanine dyes, and protonated Schiff base polyenes. In: The Journal of chemical physics. 1980 ; Vol. 73, No. 8. pp. 3927-3935.
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