Oxidation Pathways Involving a Sulfide-Endcapped Donor-Acceptor-Donor π-Conjugated Molecule and Antimony(V) Chloride

Saadia Chaudhry, Sean M. Ryno, Matthias Zeller, David R. McMillin, Chad Risko, Jianguo Mei

Research output: Contribution to journalArticlepeer-review

8 Scopus citations

Abstract

The oxidation pathways and products of a discrete, sulfide-endcapped donor-acceptor-donor (D/A/D) molecule, namely, propylenedioxythiophene-benzothiadiazole-propylenedioxythiophene, are investigated. The electrochemical and chemical oxidations proceed by two distinct routes. Specifically, electrochemical oxidation undergoes a sequential two-step, one-electron (1e - ) oxidation route with a 117 mV difference between consecutive half-wave potentials. In contrast, chemical oxidation by antimony(V) chloride (SbCl 5 ) causes the generation of four different oxidized species: (a) the 1e - oxidation state, (b) a decomposition product, (c) the 2e - oxidation state, and (d) a chloride adduct of the 2e - oxidation state. The decomposition product is generated by the reaction of the 1e - oxidation state with residual water, resulting in nucleophilic aromatic substitution at the sulfide group terminal positions. This reaction leads to the formation of a 2e - oxidized, oxygen atom (ketone) terminated decomposed molecule. The chloride adduct is determined to be produced by electrophilic chloronium ion (2e - ) oxidation by the SbCl 4 + complex, which is a product of SbCl 5 ligand disproportionation. The formation of the 2e - oxidized chlorine adduct shows to be linearly dependent on the molarity of SbCl 5 in dichloromethane, giving new insight into the concentration dependent reactivity of SbCl 5 as a 2e - oxidant. The electronic, optical, and magnetic properties and geometric structures of the 1e - and 2e - oxidized hexachloroantimonate salts are fully characterized by a combination of electrochemistry, X-ray crystallography, UV-vis-NIR, electron paramagnetic resonance, NMR spectroscopies, and density functional theory calculations. The aim of this study is to provide a thorough understanding of the redox pathways of a D/A/D π-conjugated organic molecule for potential application in organic electrochromic devices.

Original languageEnglish
Pages (from-to)3866-3874
Number of pages9
JournalJournal of Physical Chemistry B
Volume123
Issue number17
DOIs
StatePublished - May 2 2019

Bibliographical note

Publisher Copyright:
© 2019 American Chemical Society.

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry

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