Impact of substituent effects on the Raman spectra of structurally related N-substituted diketopyrrolopyrroles

Jesus Calvo-Castro, Monika Warzecha, Andrew J. McLean, Callum J. McHugh

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Abstract

Control over vibrational frequency modes is important in optimising the performance and behaviour of conjugated organic materials employed as charge transfer mediators and optical components in optoelectronic devices. Raman spectroscopy represents a powerful technique that can be employed to determine the structural implications of molecular substitution on photophysical properties in such conjugated organic environments. Herein, we report for the first time, the optimised geometries for a series of eight systematically varied N-substituted diketopyrrolopyrroles as well as their experimental and computed Raman spectra, with special emphasis placed upon their spectral band assignments. Clear out-of-plane structural re-arrangements, including pyramidalisation of the lactam nitrogens arising from intramolecular H-bonding interactions were observed upon N-substitution in the reported systems, leading to significant vibrational frequency shifts for ν(N-C) and ν(C=O) modes. In addition, mode scaling factors were determined and found to be comparable with those reported previously, employed using the same density functional. The following study addresses the implications of structural variation on the progression of those intense Raman modes which play a key role in tuning the photophysical properties of N-substituted diketopyrrolopyrrole systems and as such should be of broad interest to those developing functional materials based upon this molecular motif.

Original languageEnglish
Pages (from-to)8-16
Number of pages9
JournalVibrational Spectroscopy
Volume83
Early online date22 Dec 2015
DOIs
Publication statusPublished - 1 Mar 2016

Keywords

  • density functional theory
  • diketopyrrolopyrroles
  • M06-2X
  • raman
  • scaling factors

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  • Research Output

    • 3 Citations
    • 1 Article

    Intermolecular interactions and energetics in the crystalline π-π stacks and associated model dimer systems of asymmetric halogenated diketopyrrolopyrroles

    Calvo-Castro, J., Warzecha, M., Oswald, I. D. H., Kennedy, A. R., Morris, G., McLean, A. J. & McHugh, C. J., 13 Jan 2016, In : Crystal Growth and Design. 16, 3, p. 1531-1542 12 p.

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  • 11 Citations (Scopus)
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