Reactivity of an air-stable dihydrobenzoimidazole n-dopant with organic semiconductor molecules

Samik Jhulki, Hio Ieng Un, Yi Fan Ding, Chad Risko, Swagat K. Mohapatra, Jian Pei, Stephen Barlow, Seth R. Marder

Research output: Contribution to journalArticlepeer-review

32 Scopus citations


1,3-Dimethyl-2-(4-(dimethylamino)phenyl)-2,4-dihydro-1H-benzoimidazole, N-DMBI-H, is widely used as an air-stable n-dopant for organic semiconductors. Here, its reactivity is investigated with a variety of imide- and amide-containing semiconductor molecules that have reduction potentials in the range −0.54 to −1.10 V versus ferrocene. Reaction rates correlate poorly with these potentials. The more reactive of the imides form the corresponding radical anions cleanly, but kinetic isotope studies using N-DMBI-D indicate that the reaction proceeds via an initial hydride- or hydrogen-transfer step. For an amide- and ester-rigidified bis(styryl)benzene derivative the hydride-reduced product is stable under an inert atmosphere and can be observed directly; the radical anion can only be obtained in sub-stoichiometric yield and under certain reaction conditions. On the other hand, (N-DMBI)2 rapidly reduces all the imides and amides examined to the corresponding radical anions. The implications of these findings for dopant selection and use are discussed.

Original languageEnglish
Pages (from-to)1050-1065
Number of pages16
Issue number4
StatePublished - Apr 8 2021

Bibliographical note

Funding Information:
This work was supported by: the National Science Foundation (through DMR-1807797 and DMR-1729737); the United States-India Educational Foundation and Institute of International Education (through a Fulbright-Nehru Postdoctoral Fellowship to S.J. grant no. 2266/FNPDR/2017); the National Natural Science Foundation of China (through 21790360, 21722201, and 21420102005); the Office of Naval Research Young Investigator Program (N00014-18-1-2448); and the University of Kentucky Information Technology Department and the University of Kentucky Center for Computational Sciences (CCS) (for provision of supercomputing resources on the Lipscomb High-Performance Computing Cluster). We thank Khaled Al Kurdi for providing 3c, Ye-Xin Wang for assistance with ESR measurements, and Yadong Zhang for providing the oxidant used for Figure S13C. Conceptualization, J.P. S.B. and S.R.M.; Investigation, S.J. H.-I.U. Y.-F.D. and C.R.; Resources, S.K.M.; Writing – Original Draft, S.J. H.-I.U. and S.B.; Writing – Review and Editing, all authors; Funding Acquisition, C.R. J.P. S.R.M. and S.B.; Supervision, J.P. S.B. and S.R.M. S.K.M. S.B. and S.R.M. are inventors on a patent (U.S. patent 8,912,535) relating to the use of II2 as an n-dopant.

Publisher Copyright:
© 2021 Elsevier Inc.


  • SDG7: Affordable and clean energy
  • benzoimidazole
  • dopant
  • hydride transfer
  • kinetic isotope effect
  • mechanism
  • organic semiconductor
  • rylene diimide

ASJC Scopus subject areas

  • Chemistry (all)
  • Biochemistry
  • Environmental Chemistry
  • Chemical Engineering (all)
  • Biochemistry, medical
  • Materials Chemistry


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