Bis(1,3-dithiole) Polymethine Dyes for Third-Order Nonlinear Optics - Synthesis, Electronic Structure, Nonlinear Optical Properties, and Structure-Property Relations

Klaus Bæk Simonsen, Tommy Geisler, Jan Conrad Petersen, Jesper Arentoft, Peter Sommer-Larsen, Daniel Rodriguez Greve, Christian Jakobsen, Jan Becher, Massimo Malagoli, Jean Luc Brédas, Thomas Bjørnholm*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

18 Scopus citations

Abstract

The synthesis of a series of new sulfur-containing polymethine dyes is reported. The linear optical properties of these bis(1,3-dithiole) (mono-, tri-, penta-, and hepta-)-methine dyes show intense and narrow optical absorptions typical of cyanine dyes. The absorption maximum is increasingly red-shifted from 489 nm for the monomethine dye to 911 nm for the heptamethine compound. Based on third-harmonic generation measurements at fundamental wavelength between 1064 nm and 1907 nm, γ values were evaluated to lie in the range between 1·10-33 e.s.u. and 14·10-33 e.s.u. showing that the nonlinear response of the bis(1,3-dithiole) polymethine dyes compare well with other organic π-electron systems of similar size. Comparisons of the experimental values of γ to calculated static values obtained by ab initio and semiempirical calculations (AM1, PM3) have been made as well as comparisons to dynamic values estimated from a free-electron model. The computed dynamic values can be described by a power law; γ ≈ L5 where L denotes the length of the molecules. Our studies confirm the stabilizing effect of a carbocyclic ring in the cyanine backbone making the heptamethine dye an unusually stable and highly nonlinear polymethine chromophore possessing a strong NIR optical transition and very good transparency in the visible region.

Original languageEnglish (US)
Pages (from-to)2747-2757
Number of pages11
JournalEuropean Journal of Organic Chemistry
Issue number12
DOIs
StatePublished - Jan 1 1998

Keywords

  • Dyes
  • Electronic structure
  • Nonlinear optics
  • Polymethines

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Organic Chemistry

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