On the Importance of Electronic Symmetry for Triplet State Delocalization

doi:10.1021/jacs.7b01204

Title: On the Importance of Electronic Symmetry for Triplet State Delocalization

Abstract

The influence of electronic symmetry on triplet state delocalization in linear zinc porphyrin oligomers is explored by electron paramagnetic resonance techniques. Using a combination of transient continuous wave and pulse electron nuclear double resonance spectroscopies, it is demonstrated experimentally that complete triplet state delocalization requires the chemical equivalence of all porphyrin units. These results are supported by density functional theory calculations, showing uneven delocalization in a porphyrin dimer in which a terminal ethynyl group renders the two porphyrin units inequivalent. When the conjugation length of the molecule is further increased upon addition of a second terminal ethynyl group that restores the symmetry of the system, the triplet state is again found to be completely delocalized. Finally, the observations suggest that electronic symmetry is of greater importance for triplet state delocalization than other frequently invoked factors such as conformational rigidity or fundamental length-scale limitations.

Authors:

^[1]; Bullard, George ^[2];

^[2]; Angiolillo, Paul J. ^[3];

^[2];

^[1]

Univ. of Oxford (United Kingdom). Centre for Advanced Electron Spin Resonance (CAESR)
Duke Univ., Durham, NC (United States). Dept. of Chemistry
Saint Joseph's Univ., Philadelphia, PA (United States). Dept. of Physics

Publication Date:: 2017-03-29

Research Org.:: Duke Univ., Durham, NC (United States); Univ. of Oxford, Oxford (United Kingdom)

Sponsoring Org.:: USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); European Research Counsel (ERC)

OSTI Identifier:: 1355067

Alternate Identifier(s):: OSTI ID: 1426483

Grant/Contract Number:: SC0001517; 320969

Resource Type:: Published Article

Journal Name:: Journal of the American Chemical Society

Additional Journal Information:: Journal Volume: 139; Journal Issue: 15; Journal ID: ISSN 0002-7863

Publisher:: American Chemical Society (ACS)

Country of Publication:: United States

Language:: English

Subject:: 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats


                    Richert, Sabine, Bullard, George, Rawson, Jeff, Angiolillo, Paul J., Therien, Michael J., and Timmel, Christiane R. On the Importance of Electronic Symmetry for Triplet State Delocalization.  United States: N. p., 2017. 
        Web.  doi:10.1021/jacs.7b01204.

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                    Richert, Sabine, Bullard, George, Rawson, Jeff, Angiolillo, Paul J., Therien, Michael J., & Timmel, Christiane R. On the Importance of Electronic Symmetry for Triplet State Delocalization.  United States.  doi:10.1021/jacs.7b01204.

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                    Richert, Sabine, Bullard, George, Rawson, Jeff, Angiolillo, Paul J., Therien, Michael J., and Timmel, Christiane R. Wed .  
        "On the Importance of Electronic Symmetry for Triplet State Delocalization".  United States.  doi:10.1021/jacs.7b01204.

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@article{osti_1355067,

  title        = {On the Importance of Electronic Symmetry for Triplet State Delocalization},

  author       = {Richert, Sabine and Bullard, George and Rawson, Jeff and Angiolillo, Paul J. and Therien, Michael J. and Timmel, Christiane R.},

  abstractNote = {The influence of electronic symmetry on triplet state delocalization in linear zinc porphyrin oligomers is explored by electron paramagnetic resonance techniques. Using a combination of transient continuous wave and pulse electron nuclear double resonance spectroscopies, it is demonstrated experimentally that complete triplet state delocalization requires the chemical equivalence of all porphyrin units. These results are supported by density functional theory calculations, showing uneven delocalization in a porphyrin dimer in which a terminal ethynyl group renders the two porphyrin units inequivalent. When the conjugation length of the molecule is further increased upon addition of a second terminal ethynyl group that restores the symmetry of the system, the triplet state is again found to be completely delocalized. Finally, the observations suggest that electronic symmetry is of greater importance for triplet state delocalization than other frequently invoked factors such as conformational rigidity or fundamental length-scale limitations.},

  doi          = {10.1021/jacs.7b01204},

  journal      = {Journal of the American Chemical Society},

  number       = 15,

  volume       = 139,

  place        = {United States},

  year         = {2017},

  month        = {3}

}

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DOI: 10.1021/jacs.7b01204

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Figure 1: Chemical structures (left), comparison of the transient cw EPR spectra (center) and proton Mims ENDOR spectra recorded at a field position corresponding to the Y− orientation (right). The EPR and ENDOR data were acquired in frozen MTHF at 20 K. Pulse lengths of 16 ns were applied inmore »

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Works referencing / citing this record:

Stepwise oxidations of a nickel( ii )–iron( iii ) heterobimetallic porphyrin dimer: structure, spectroscopic and theoretical investigation
journal, January 2019

Kumar, Amit; Banerjee, Sayantani; Sarkar, Sabyasachi
Dalton Transactions, Vol. 48, Issue 27
DOI: 10.1039/c9dt01776c

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Figure 1(p. 2)

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Title: On the Importance of Electronic Symmetry for Triplet State Delocalization

Abstract

Citation Formats

Figures / Tables:

Stepwise oxidations of a nickel( ii )–iron( iii ) heterobimetallic porphyrin dimer: structure, spectroscopic and theoretical investigation journal, January 2019

Stepwise oxidations of a nickel( ii )–iron( iii ) heterobimetallic porphyrin dimer: structure, spectroscopic and theoretical investigation
journal, January 2019