n-Doping of Organic Electronic Materials Using Air-Stable Organometallics: A Mechanistic Study of Reduction by Dimeric Sandwich Compounds

Authors

  • Dr. Song Guo,

    1. School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, GA 30332-0400 (USA), Fax: (+1) 404-894-5909
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    • These authors contributed equally.

  • Dr. Swagat K. Mohapatra,

    1. School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, GA 30332-0400 (USA), Fax: (+1) 404-894-5909
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    • These authors contributed equally.

  • Alexander Romanov,

    1. Department of Chemistry, New Mexico Highlands University, Las Vegas, NM 87701 (USA)
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  • Prof. Tatiana V. Timofeeva,

    1. Department of Chemistry, New Mexico Highlands University, Las Vegas, NM 87701 (USA)
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  • Prof. Kenneth I. Hardcastle,

    1. Department of Chemistry, Emory University, Atlanta, GA 30322 (USA)
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  • Dr. Kada Yesudas,

    1. School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, GA 30332-0400 (USA), Fax: (+1) 404-894-5909
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  • Dr. Chad Risko,

    1. School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, GA 30332-0400 (USA), Fax: (+1) 404-894-5909
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  • Prof. Jean-Luc Brédas,

    1. School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, GA 30332-0400 (USA), Fax: (+1) 404-894-5909
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  • Prof. Seth R. Marder,

    Corresponding author
    1. School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, GA 30332-0400 (USA), Fax: (+1) 404-894-5909
    • School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, GA 30332-0400 (USA), Fax: (+1) 404-894-5909
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  • Dr. Stephen Barlow

    Corresponding author
    1. School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, GA 30332-0400 (USA), Fax: (+1) 404-894-5909
    • School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, GA 30332-0400 (USA), Fax: (+1) 404-894-5909
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Abstract

Several 19-electron sandwich compounds are known to exist as “2×18-electron” dimers. Recently it has been shown that, despite their air stability in the solid state, some of these dimers act as powerful reductants when co-deposited from either the gas phase or from solution and that this behavior can be useful in n-doping materials for organic electronics, including compounds with moderate electron affinities, such as 6,13-bis[tri(isopropyl)silylethynyl]pentacene (3). This paper addresses the mechanisms by which the dimers of 1,2,3,4,5-pentamethylrhodocene (1 b2), (pentamethylcyclopentadienyl)(1,3,5-trialkylbenzene)ruthenium (alkyl=Me, 2 a2; alkyl=Et, 2 b2), and (pentamethylcyclopentadienyl)(benzene)iron (2 c2) react with 3 in solution. Vis/NIR and NMR spectroscopy, and X-ray crystallography indicate that the products of these solution reactions are 3.− salts of the monomeric sandwich cations. Vis/NIR kinetic studies for the Group 8 dimers are consistent with a mechanism whereby an endergonic electron transfer from the dimer to 3 is followed by rapid cleavage of the dimer cation. NMR crossover experiments with partially deuterated derivatives suggest that the C[BOND]C bond in the 1 b2 dimer is much more readily broken than that in 2 a2; consistent with this observation, Vis/NIR kinetic measurements suggest that the solution reduction of 3 by 1 b2 can occur by both the mechanism established for the Group 8 species and by a mechanism in which an endergonic dissociation of the dimer is followed by rapid electron transfer from monomeric 1 b to 3.

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