X-Shaped Oligomeric Pyromellitimide Polyradicals

Yilei Wu, Ji Min Han, Michael Hong, Matthew D. Krzyaniak, Anthea K. Blackburn, Isurika R. Fernando, Dennis D. Cao, Michael R Wasielewski, J. Fraser Stoddart

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

The synthesis of stable organic polyradicals is important for the development of magnetic materials. Herein we report the synthesis, isolation, and characterization of a series of X-shaped pyromellitimide (PI) oligomers (Xn-R, n = 2-4, R = Hex or Ph) linked together by single C-C bonds between their benzenoid cores. We hypothesize that these oligomers might form high-spin states in their reduced forms because of the nearly orthogonal conformations adopted by their PI units. 1H and 13C nuclear magnetic resonance (NMR) spectroscopies confirmed the isolation of the dimeric, trimeric, and tetrameric homologues. X-ray crystallography shows that X2-Ph crystallizes into a densely packed superstructure, despite the criss-crossed conformations adopted by the molecules. Electrochemical experiments, carried out on the oligomers Xn-Hex, reveal that the reductions of the PI units occur at multiple distinct potentials, highlighting the weak electronic coupling between the adjacent redox centers. Finally, the chemically generated radical anion and polyanion states, Xn-Hex•- and Xn-Hexn(•-), respectively, were probed extensively by UV-vis-NIR absorption, EPR, and electron nuclear double resonance (ENDOR) spectroscopies. The ENDOR spectra of the radical monoanions Xn-Hex•- reveal that the unpaired electron is largely localized on a single PI unit. Further reductions of Xn-Hex•- yield EPR signals (in frozen solutions) that can be assigned to spin-spin interactions in X2-Hex2(•-), X3-Hex3(•-), and X4-Hex4(•-). Taken together, these findings demonstrate that directly linking the benzene rings of PIs with a single C-C bond is a viable method for generating stabilized high-spin organic anionic polyradicals.

Original languageEnglish
Pages (from-to)515-523
Number of pages9
JournalJournal of the American Chemical Society
Volume140
Issue number1
DOIs
Publication statusPublished - Jan 10 2018

Fingerprint

Electron Spin Resonance Spectroscopy
Oligomers
Synthetic Chemistry Techniques
Paramagnetic resonance
Conformations
Electrons
X Ray Crystallography
Benzene
Oxidation-Reduction
Anions
Spectrum Analysis
Magnetic Resonance Spectroscopy
X ray crystallography
Magnetic materials
Nuclear magnetic resonance spectroscopy
Negative ions
Spectroscopy
Molecules
Experiments
polyanions

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

Cite this

Wu, Y., Han, J. M., Hong, M., Krzyaniak, M. D., Blackburn, A. K., Fernando, I. R., ... Stoddart, J. F. (2018). X-Shaped Oligomeric Pyromellitimide Polyradicals. Journal of the American Chemical Society, 140(1), 515-523. https://doi.org/10.1021/jacs.7b12124

X-Shaped Oligomeric Pyromellitimide Polyradicals. / Wu, Yilei; Han, Ji Min; Hong, Michael; Krzyaniak, Matthew D.; Blackburn, Anthea K.; Fernando, Isurika R.; Cao, Dennis D.; Wasielewski, Michael R; Stoddart, J. Fraser.

In: Journal of the American Chemical Society, Vol. 140, No. 1, 10.01.2018, p. 515-523.

Research output: Contribution to journalArticle

Wu, Y, Han, JM, Hong, M, Krzyaniak, MD, Blackburn, AK, Fernando, IR, Cao, DD, Wasielewski, MR & Stoddart, JF 2018, 'X-Shaped Oligomeric Pyromellitimide Polyradicals', Journal of the American Chemical Society, vol. 140, no. 1, pp. 515-523. https://doi.org/10.1021/jacs.7b12124
Wu Y, Han JM, Hong M, Krzyaniak MD, Blackburn AK, Fernando IR et al. X-Shaped Oligomeric Pyromellitimide Polyradicals. Journal of the American Chemical Society. 2018 Jan 10;140(1):515-523. https://doi.org/10.1021/jacs.7b12124
Wu, Yilei ; Han, Ji Min ; Hong, Michael ; Krzyaniak, Matthew D. ; Blackburn, Anthea K. ; Fernando, Isurika R. ; Cao, Dennis D. ; Wasielewski, Michael R ; Stoddart, J. Fraser. / X-Shaped Oligomeric Pyromellitimide Polyradicals. In: Journal of the American Chemical Society. 2018 ; Vol. 140, No. 1. pp. 515-523.
@article{c084f00240624cb4a4fd92d10dc172e6,
title = "X-Shaped Oligomeric Pyromellitimide Polyradicals",
abstract = "The synthesis of stable organic polyradicals is important for the development of magnetic materials. Herein we report the synthesis, isolation, and characterization of a series of X-shaped pyromellitimide (PI) oligomers (Xn-R, n = 2-4, R = Hex or Ph) linked together by single C-C bonds between their benzenoid cores. We hypothesize that these oligomers might form high-spin states in their reduced forms because of the nearly orthogonal conformations adopted by their PI units. 1H and 13C nuclear magnetic resonance (NMR) spectroscopies confirmed the isolation of the dimeric, trimeric, and tetrameric homologues. X-ray crystallography shows that X2-Ph crystallizes into a densely packed superstructure, despite the criss-crossed conformations adopted by the molecules. Electrochemical experiments, carried out on the oligomers Xn-Hex, reveal that the reductions of the PI units occur at multiple distinct potentials, highlighting the weak electronic coupling between the adjacent redox centers. Finally, the chemically generated radical anion and polyanion states, Xn-Hex•- and Xn-Hexn(•-), respectively, were probed extensively by UV-vis-NIR absorption, EPR, and electron nuclear double resonance (ENDOR) spectroscopies. The ENDOR spectra of the radical monoanions Xn-Hex•- reveal that the unpaired electron is largely localized on a single PI unit. Further reductions of Xn-Hex•- yield EPR signals (in frozen solutions) that can be assigned to spin-spin interactions in X2-Hex2(•-), X3-Hex3(•-), and X4-Hex4(•-). Taken together, these findings demonstrate that directly linking the benzene rings of PIs with a single C-C bond is a viable method for generating stabilized high-spin organic anionic polyradicals.",
author = "Yilei Wu and Han, {Ji Min} and Michael Hong and Krzyaniak, {Matthew D.} and Blackburn, {Anthea K.} and Fernando, {Isurika R.} and Cao, {Dennis D.} and Wasielewski, {Michael R} and Stoddart, {J. Fraser}",
year = "2018",
month = "1",
day = "10",
doi = "10.1021/jacs.7b12124",
language = "English",
volume = "140",
pages = "515--523",
journal = "Journal of the American Chemical Society",
issn = "0002-7863",
publisher = "American Chemical Society",
number = "1",

}

TY - JOUR

T1 - X-Shaped Oligomeric Pyromellitimide Polyradicals

AU - Wu, Yilei

AU - Han, Ji Min

AU - Hong, Michael

AU - Krzyaniak, Matthew D.

AU - Blackburn, Anthea K.

AU - Fernando, Isurika R.

AU - Cao, Dennis D.

AU - Wasielewski, Michael R

AU - Stoddart, J. Fraser

PY - 2018/1/10

Y1 - 2018/1/10

N2 - The synthesis of stable organic polyradicals is important for the development of magnetic materials. Herein we report the synthesis, isolation, and characterization of a series of X-shaped pyromellitimide (PI) oligomers (Xn-R, n = 2-4, R = Hex or Ph) linked together by single C-C bonds between their benzenoid cores. We hypothesize that these oligomers might form high-spin states in their reduced forms because of the nearly orthogonal conformations adopted by their PI units. 1H and 13C nuclear magnetic resonance (NMR) spectroscopies confirmed the isolation of the dimeric, trimeric, and tetrameric homologues. X-ray crystallography shows that X2-Ph crystallizes into a densely packed superstructure, despite the criss-crossed conformations adopted by the molecules. Electrochemical experiments, carried out on the oligomers Xn-Hex, reveal that the reductions of the PI units occur at multiple distinct potentials, highlighting the weak electronic coupling between the adjacent redox centers. Finally, the chemically generated radical anion and polyanion states, Xn-Hex•- and Xn-Hexn(•-), respectively, were probed extensively by UV-vis-NIR absorption, EPR, and electron nuclear double resonance (ENDOR) spectroscopies. The ENDOR spectra of the radical monoanions Xn-Hex•- reveal that the unpaired electron is largely localized on a single PI unit. Further reductions of Xn-Hex•- yield EPR signals (in frozen solutions) that can be assigned to spin-spin interactions in X2-Hex2(•-), X3-Hex3(•-), and X4-Hex4(•-). Taken together, these findings demonstrate that directly linking the benzene rings of PIs with a single C-C bond is a viable method for generating stabilized high-spin organic anionic polyradicals.

AB - The synthesis of stable organic polyradicals is important for the development of magnetic materials. Herein we report the synthesis, isolation, and characterization of a series of X-shaped pyromellitimide (PI) oligomers (Xn-R, n = 2-4, R = Hex or Ph) linked together by single C-C bonds between their benzenoid cores. We hypothesize that these oligomers might form high-spin states in their reduced forms because of the nearly orthogonal conformations adopted by their PI units. 1H and 13C nuclear magnetic resonance (NMR) spectroscopies confirmed the isolation of the dimeric, trimeric, and tetrameric homologues. X-ray crystallography shows that X2-Ph crystallizes into a densely packed superstructure, despite the criss-crossed conformations adopted by the molecules. Electrochemical experiments, carried out on the oligomers Xn-Hex, reveal that the reductions of the PI units occur at multiple distinct potentials, highlighting the weak electronic coupling between the adjacent redox centers. Finally, the chemically generated radical anion and polyanion states, Xn-Hex•- and Xn-Hexn(•-), respectively, were probed extensively by UV-vis-NIR absorption, EPR, and electron nuclear double resonance (ENDOR) spectroscopies. The ENDOR spectra of the radical monoanions Xn-Hex•- reveal that the unpaired electron is largely localized on a single PI unit. Further reductions of Xn-Hex•- yield EPR signals (in frozen solutions) that can be assigned to spin-spin interactions in X2-Hex2(•-), X3-Hex3(•-), and X4-Hex4(•-). Taken together, these findings demonstrate that directly linking the benzene rings of PIs with a single C-C bond is a viable method for generating stabilized high-spin organic anionic polyradicals.

UR - http://www.scopus.com/inward/record.url?scp=85040346156&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85040346156&partnerID=8YFLogxK

U2 - 10.1021/jacs.7b12124

DO - 10.1021/jacs.7b12124

M3 - Article

AN - SCOPUS:85040346156

VL - 140

SP - 515

EP - 523

JO - Journal of the American Chemical Society

JF - Journal of the American Chemical Society

SN - 0002-7863

IS - 1

ER -