Atomic-Level Insight into the Postsynthesis Band Gap Engineering of a Lewis Base Polymer Using Lewis Acid Tris(pentafluorophenyl)borane

Brett Yurash, Dirk Leifert, G. N.Manjunatha Reddy, David Xi Cao, Simon Biberger, Viktor V. Brus, Martin Seifrid, Peter J. Santiago, Anna Köhler, Bradley F. Chmelka, Guillermo C. Bazan, Thuc Quyen Nguyen

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)

Abstract

In this report, we investigate the binding properties of the Lewis acid tris(pentafluorophenyl)borane with a Lewis base semiconducting polymer, PFPT, and the subsequent mechanism of band gap reduction. Experiments and quantum chemical calculations confirm that the formation of a Lewis acid adduct is energetically favorable (ΔG° < -0.2 eV), with preferential binding at the pyridyl nitrogen in the polymer backbone over other Lewis base sites. Upon adduct formation, ultraviolet photoelectron spectroscopy indicates only a slight decrease in the HOMO energy, implying that a larger reduction in the LUMO energy is primarily responsible for the observed optical band gap narrowing (ΔEopt = 0.3 eV). Herein, we also provide the first spatially resolved picture of how Lewis acid adducts form in heterogeneous, disordered polymer/tris(pentafluorophenyl)borane thin films via one- (1D) and two-dimensional (2D) solid-state nuclear magnetic resonance. Notably, solid-state 1D 11B, 13C{1H}, and 13C{19F} cross-polarization magic-angle spinning (CP-MAS) NMR and 2D 1H{19F} and 1H{1H} correlation NMR analyses establish that BCF molecules are intercalated between branched C16H33 side chains with the boron atom facing toward the pyridyl nitrogen atoms of PFPT.

Original languageEnglish
Pages (from-to)6715-6725
Number of pages11
JournalChemistry of Materials
Volume31
Issue number17
DOIs
Publication statusPublished - Sep 10 2019
Externally publishedYes

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)
  • Materials Chemistry

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