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 language | English |
|---|---|
| Pages (from-to) | 3866-3874 |
| Number of pages | 9 |
| Journal | Journal of Physical Chemistry B |
| Volume | 123 |
| Issue number | 17 |
| DOIs | |
| State | Published - May 2 2019 |
Bibliographical note
Publisher Copyright:© 2019 American Chemical Society.
Funding
We acknowledge the startup fund provided by Purdue University to conduct this research. We thank Han Wang and Dr. Haiyan Wang in the Department of Materials Engineering at Purdue University for assisting us in setting up our electrochemistry station. We also thank Dr. Tong Ren for his input in the analysis of our DPV results. C.R. acknowledges the Office of Naval Research (Award Number N00014-16-1-2985) for funding the work at the University of Kentucky. Computing resources on the Lipscomb High Performance Computing Cluster were provided by the University of Kentucky Information Technology Department and Center for Computational Sciences (CCS), and on the Holly computing cluster by the University of Kentucky College of Arts & Sciences.
| Funders | Funder number |
|---|---|
| Office of Naval Research Naval Academy | N00014-16-1-2985 |
| Office of Naval Research Naval Academy | |
| Purdue Climate Change Research Center, Purdue University | |
| University of Kentucky |
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films
- Materials Chemistry