Cyanine-Like Dyes with Large Bond-Length Alternation

Authors

  • Dr. Karl J. Thorley,

    1. Department of Chemistry, University of Oxford, Chemistry Research Laboratory, Mansfield Road, Oxford, OX1 3TA (UK), Fax: (+44) 1865-285-002
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  • Dr. Joel M. Hales,

    1. School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332-0400 (USA)
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  • Hyeongeu Kim,

    1. School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332-0400 (USA)
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  • Dr. Shino Ohira,

    1. School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332-0400 (USA)
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  • Prof. Jean-Luc Brédas,

    Corresponding author
    1. School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332-0400 (USA)
    • Jean-Luc Brédas, School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332-0400 (USA)

      Joseph W. Perry, School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332-0400 (USA)

      Harry L. Anderson, Department of Chemistry, University of Oxford, Chemistry Research Laboratory, Mansfield Road, Oxford, OX1 3TA (UK), Fax: (+44) 1865-285-002

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  • Prof. Joseph W. Perry,

    Corresponding author
    1. School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332-0400 (USA)
    • Jean-Luc Brédas, School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332-0400 (USA)

      Joseph W. Perry, School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332-0400 (USA)

      Harry L. Anderson, Department of Chemistry, University of Oxford, Chemistry Research Laboratory, Mansfield Road, Oxford, OX1 3TA (UK), Fax: (+44) 1865-285-002

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  • Prof. Harry L. Anderson

    Corresponding author
    1. Department of Chemistry, University of Oxford, Chemistry Research Laboratory, Mansfield Road, Oxford, OX1 3TA (UK), Fax: (+44) 1865-285-002
    • Jean-Luc Brédas, School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332-0400 (USA)

      Joseph W. Perry, School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332-0400 (USA)

      Harry L. Anderson, Department of Chemistry, University of Oxford, Chemistry Research Laboratory, Mansfield Road, Oxford, OX1 3TA (UK), Fax: (+44) 1865-285-002

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Abstract

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.

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