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

Author
Abstract
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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) 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 complex, which is a product of SbCl ligand disproportionation. The formation of the 2e oxidized chlorine adduct shows to be linearly dependent on the molarity of SbCl in dichloromethane, giving new insight into the concentration dependent reactivity of SbCl as a 2e oxidant. The electronic, optical, and magnetic properties and geometric structures of the 1e and 2eoxidized 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.

Year of Publication
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2019
Journal
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The journal of physical chemistry. B
Volume
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123
Issue
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17
Number of Pages
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3866-3874
Date Published
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2019
ISSN Number
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1520-6106
URL
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https://doi.org/10.1021/acs.jpcb.9b01389
DOI
:
10.1021/acs.jpcb.9b01389
Short Title
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J Phys Chem B
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