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  • 1
    Electronic Resource
    Electronic Resource
    Bis(1,3-dithiole) Polymethine Dyes for Third-Order Nonlinear Optics - Synthesis, Electronic Structure, Nonlinear Optical Properties, and Structure-Property Relations (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2747-2757 
    Details
    ISSN: 1434-193X
    Keywords: Polymethines ; Dyes ; Electronic structure ; Nonlinear optics ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of Medium Polarity on the Second-Order Polarizability of an Octupolar Chromophore: An ab initio Reaction Field Study of Triaminotrinitrobenzene (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 1267-1269 
    Details
    ISSN: 1434-193X
    Keywords: Nonlinear optics (NLO) ; Second-order polarizability ; Self-consistent reaction field (SCRF) ; Octupolar NLO chromophore ; Triaminotrinitrobenzene ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Self-Consistent Reaction Field theory (extended to include an ellipsoidal cavity for the solute and a multipolar expansion of the field) is used to investigate the influence of medium polarity on the second-order nonlinear optical response of the prototypical octupolar compound 1,3,5-triamino-2,4,6-trinitrobenzene, TATB. Despite the absence of any dipole moment in TATB, the effect of medium polarity is found to be significant; for instance, the βzzz tensor component of TATB is calculated to be twice as large in dichloromethane (electric permittivity ε = 9.1) as in the gas phase (ε = 1). This enhancement factor is similar to, though somewhat smaller than the one calculated for the dipolar counterpart of TATB, i.e. p-nitroaniline.
    Type of Medium: Electronic Resource
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