Quantifying Environmental Effects on the Solution and Solid-State Stability of a Phenothiazine Radical Cation

Aman Preet Kaur; Oliver C. Harris; N. Harsha Attanayake; Zhiming Liang; Sean R. Parkin; Maureen H. Tang; Susan Odom

doi:10.1021/acs.chemmater.9b05345

Quantifying Environmental Effects on the Solution and Solid-State Stability of a Phenothiazine Radical Cation

Aman Preet Kaur, Oliver C. Harris, N. Harsha Attanayake, Zhiming Liang, Sean R. Parkin, Maureen H. Tang, Susan Odom

Chemistry

Research output: Contribution to journal › Article › peer-review

16 Scopus citations

Abstract

Organic radical cations are important intermediates in a wide variety of chemical processes. To date, significant progress has been made to improve the stability of these charged materials for use in electrochemical energy storage applications, especially in redox flow batteries. Here, we report the synthesis and isolation of four radical cation salts of N-(2-(2-methoxyethoxy)ethyl)phenothiazine (MEEPT), synthesizing MEEPT-X where X is tetrafluoroborate (BF4-), hexafluorophosphate (PF6-), perchlorate (ClO4-), and bis(trifluoromethanesulfonyl)imide (TFSI-), and a comparison of their stability in solution and in the solid state. In the solution, UV-vis spectroscopy and rotating ring-disk electrode voltammetry show similar stability trends with respect to anion identity, with the TFSI- salt being the most stable. In the solid state, these compounds show remarkable stability in air and at elevated temperatures, with the ClO4- salt surviving after being heated at 90 °C overnight in air. The different trends in MEEPT-X stability with X highlight the importance of concentration and the environment on the overall stability.

Original language	English
Pages (from-to)	3007-3017
Number of pages	11
Journal	Chemistry of Materials
Volume	32
Issue number	7
DOIs	https://doi.org/10.1021/acs.chemmater.9b05345
State	Published - Apr 14 2020

Bibliographical note

Funding Information:
The Odom group thanks the Department of Energy, Office of Science, Basic Energy Sciences for funding through the Joint Center for Energy Storage Research for support of solution-based stability studies, and thanks the National Science Foundation for support through CHE CSDM-B (award number 1800482) for solid-state stability studies. APK thanks Mark Crocker and Robert Pace at the University of Kentucky for access to their TGA instrument. The Tang group thanks the National Science Foundation for support through the CBET division (award number 1751553) for RRDE experiments. SRP thanks the NSF MRI program (award number 1625732) for support for the purchase of an X-ray diffractometer.

Publisher Copyright:
Copyright © 2020 American Chemical Society.

ASJC Scopus subject areas

Chemistry (all)
Chemical Engineering (all)
Materials Chemistry

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10.1021/acs.chemmater.9b05345

Cite this

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title = "Quantifying Environmental Effects on the Solution and Solid-State Stability of a Phenothiazine Radical Cation",

abstract = "Organic radical cations are important intermediates in a wide variety of chemical processes. To date, significant progress has been made to improve the stability of these charged materials for use in electrochemical energy storage applications, especially in redox flow batteries. Here, we report the synthesis and isolation of four radical cation salts of N-(2-(2-methoxyethoxy)ethyl)phenothiazine (MEEPT), synthesizing MEEPT-X where X is tetrafluoroborate (BF4-), hexafluorophosphate (PF6-), perchlorate (ClO4-), and bis(trifluoromethanesulfonyl)imide (TFSI-), and a comparison of their stability in solution and in the solid state. In the solution, UV-vis spectroscopy and rotating ring-disk electrode voltammetry show similar stability trends with respect to anion identity, with the TFSI- salt being the most stable. In the solid state, these compounds show remarkable stability in air and at elevated temperatures, with the ClO4- salt surviving after being heated at 90 °C overnight in air. The different trends in MEEPT-X stability with X highlight the importance of concentration and the environment on the overall stability. ",

author = "Kaur, {Aman Preet} and Harris, {Oliver C.} and Attanayake, {N. Harsha} and Zhiming Liang and Parkin, {Sean R.} and Tang, {Maureen H.} and Susan Odom",

note = "Funding Information: The Odom group thanks the Department of Energy, Office of Science, Basic Energy Sciences for funding through the Joint Center for Energy Storage Research for support of solution-based stability studies, and thanks the National Science Foundation for support through CHE CSDM-B (award number 1800482) for solid-state stability studies. APK thanks Mark Crocker and Robert Pace at the University of Kentucky for access to their TGA instrument. The Tang group thanks the National Science Foundation for support through the CBET division (award number 1751553) for RRDE experiments. SRP thanks the NSF MRI program (award number 1625732) for support for the purchase of an X-ray diffractometer. Publisher Copyright: Copyright {\textcopyright} 2020 American Chemical Society.",

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AU - Parkin, Sean R.

AU - Tang, Maureen H.

AU - Odom, Susan

N1 - Funding Information: The Odom group thanks the Department of Energy, Office of Science, Basic Energy Sciences for funding through the Joint Center for Energy Storage Research for support of solution-based stability studies, and thanks the National Science Foundation for support through CHE CSDM-B (award number 1800482) for solid-state stability studies. APK thanks Mark Crocker and Robert Pace at the University of Kentucky for access to their TGA instrument. The Tang group thanks the National Science Foundation for support through the CBET division (award number 1751553) for RRDE experiments. SRP thanks the NSF MRI program (award number 1625732) for support for the purchase of an X-ray diffractometer. Publisher Copyright: Copyright © 2020 American Chemical Society.

PY - 2020/4/14

Y1 - 2020/4/14

N2 - Organic radical cations are important intermediates in a wide variety of chemical processes. To date, significant progress has been made to improve the stability of these charged materials for use in electrochemical energy storage applications, especially in redox flow batteries. Here, we report the synthesis and isolation of four radical cation salts of N-(2-(2-methoxyethoxy)ethyl)phenothiazine (MEEPT), synthesizing MEEPT-X where X is tetrafluoroborate (BF4-), hexafluorophosphate (PF6-), perchlorate (ClO4-), and bis(trifluoromethanesulfonyl)imide (TFSI-), and a comparison of their stability in solution and in the solid state. In the solution, UV-vis spectroscopy and rotating ring-disk electrode voltammetry show similar stability trends with respect to anion identity, with the TFSI- salt being the most stable. In the solid state, these compounds show remarkable stability in air and at elevated temperatures, with the ClO4- salt surviving after being heated at 90 °C overnight in air. The different trends in MEEPT-X stability with X highlight the importance of concentration and the environment on the overall stability.

AB - Organic radical cations are important intermediates in a wide variety of chemical processes. To date, significant progress has been made to improve the stability of these charged materials for use in electrochemical energy storage applications, especially in redox flow batteries. Here, we report the synthesis and isolation of four radical cation salts of N-(2-(2-methoxyethoxy)ethyl)phenothiazine (MEEPT), synthesizing MEEPT-X where X is tetrafluoroborate (BF4-), hexafluorophosphate (PF6-), perchlorate (ClO4-), and bis(trifluoromethanesulfonyl)imide (TFSI-), and a comparison of their stability in solution and in the solid state. In the solution, UV-vis spectroscopy and rotating ring-disk electrode voltammetry show similar stability trends with respect to anion identity, with the TFSI- salt being the most stable. In the solid state, these compounds show remarkable stability in air and at elevated temperatures, with the ClO4- salt surviving after being heated at 90 °C overnight in air. The different trends in MEEPT-X stability with X highlight the importance of concentration and the environment on the overall stability.

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Quantifying Environmental Effects on the Solution and Solid-State Stability of a Phenothiazine Radical Cation

Abstract

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