Cyanine-like dyes with large bond-length alternation

Karl J. Thorley, Joel M. Hales, Hyeongeu Kim, Shino Ohira, Jean Luc Brédas, Joseph W. Perry, Harry L. Anderson*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


Herein, the synthesis and properties of alkyne-bridged carbocations, which are analogous in structure to cyanine dyes, are reported. An alkene-bridged dye, linked at the third position of the indole, was also synthesized as a reference compound. These new carbocations are stable under ambient conditions, allowing characterization by UV/Vis and NMR (1H and 13C) spectroscopies. These techniques revealed a large degree of delocalization of the positive charge, similar to a previously reported porphyrin carbocation. The linear and nonlinear optical properties are compared with cyanine dyes and triarylmethyl cations, to investigate the effects of the bond-length alternation and the overall molecular geometry. The value of Re(γ), the real part of the third-order microscopic polarizability, of -1.3×10-33 esu for the alkyne-linked cation is comparable to that of a cyanine dye of similar length. Nondegenerate two-photon absorption spectra showed that the alkene-bridged dye exhibited characteristics of cyanines, whereas the alkyne-bridged dye is reminiscent of octupolar chromophores, such as the triarylmethyl carbocation brilliant green. Such attributes were confirmed and rationalized by quantum chemical calculations.

Original languageEnglish (US)
Pages (from-to)10370-10377
Number of pages8
JournalChemistry - A European Journal
Issue number31
StatePublished - Jul 29 2013
Externally publishedYes


  • alkynes
  • carbocations
  • cyanines
  • nonlinear optics

ASJC Scopus subject areas

  • Catalysis
  • Organic Chemistry


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