Electron donor-bridge-acceptor molecules with bridging nitronyl nitroxide radicals: Influence of a third spin on charge- and spin-transfer dynamics

Erin T. Chernick, Qixi Mi, Richard F. Kelley, Emily A Weiss, Brooks A. Jones, Tobin J Marks, Mark A Ratner, Michael R Wasielewski

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Abstract

Appending a stable radical to the bridge molecule in a donor-bridge- acceptor system (D-B-A) is potentially an important way to control charge- and spin-transfer dynamics through D-B-A. We have attached a nitronyl nitroxide (NN.) stable radical to a D-B-A system having well-defined distances between the components: MeOAn-6ANl-Ph(NN.)-Nl, where MeOAn = p-methoxyaniline, 6ANl = 4-(N-piperidinyl)-naphthalene-1,8-dicarboximide, Ph = phenyl, and Nl = naphthalene-1,8:4,5-bis(dicarboximide). MeOAn-6ANl, NN ., and Nl are attached to the 1, 3, and 5 positions of the Ph bridge. Using both time-resolved optical and EPR spectroscopy, we show that NN . influences the spin dynamics of the photogenerated triradical states 2,4(MeOAn+.-6ANl-Ph(NN.)-Nl -.), resulting in slower charge recombination within the triradical compared to the corresponding biradical lacking NN.. The observed spin-spin exchange interaction between the photogenerated radicals MeOAn +. and Nl-. is not altered by the presence of NN ., which only accelerates radical pair intersystem crossing. Charge recombination within the triradical results in the formation of 2,4(MeOAn-6ANl-Ph(NN.)-3*Nl), in which NN. is strongly spin-polarized. Normally, the spin dynamics of correlated radical pairs do not produce a net spin polarization; however, net spin polarization appears on NN. with the same time constant as describes the photogenerated radical ion pair decay. This effect is attributed to antiferromagnetic coupling between NN. and the local triplet state 3*Nl, which is populated following charge recombination. This requires an effective switch in the spin basis set between the triradical and the three-spin charge recombination product having both NN. and 3*Nl present.

Original languageEnglish
Pages (from-to)4356-4364
Number of pages9
JournalJournal of the American Chemical Society
Volume128
Issue number13
DOIs
Publication statusPublished - Apr 5 2006

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Genetic Recombination
Electrons
Spin dynamics
Spin polarization
Molecules
Naphthalene
Exchange interactions
Paramagnetic resonance
Switches
Spectroscopy
Ions
Spectrum Analysis
nitroxyl

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

@article{a8b4c9a7710041e392c63ad042c73297,
title = "Electron donor-bridge-acceptor molecules with bridging nitronyl nitroxide radicals: Influence of a third spin on charge- and spin-transfer dynamics",
abstract = "Appending a stable radical to the bridge molecule in a donor-bridge- acceptor system (D-B-A) is potentially an important way to control charge- and spin-transfer dynamics through D-B-A. We have attached a nitronyl nitroxide (NN.) stable radical to a D-B-A system having well-defined distances between the components: MeOAn-6ANl-Ph(NN.)-Nl, where MeOAn = p-methoxyaniline, 6ANl = 4-(N-piperidinyl)-naphthalene-1,8-dicarboximide, Ph = phenyl, and Nl = naphthalene-1,8:4,5-bis(dicarboximide). MeOAn-6ANl, NN ., and Nl are attached to the 1, 3, and 5 positions of the Ph bridge. Using both time-resolved optical and EPR spectroscopy, we show that NN . influences the spin dynamics of the photogenerated triradical states 2,4(MeOAn+.-6ANl-Ph(NN.)-Nl -.), resulting in slower charge recombination within the triradical compared to the corresponding biradical lacking NN.. The observed spin-spin exchange interaction between the photogenerated radicals MeOAn +. and Nl-. is not altered by the presence of NN ., which only accelerates radical pair intersystem crossing. Charge recombination within the triradical results in the formation of 2,4(MeOAn-6ANl-Ph(NN.)-3*Nl), in which NN. is strongly spin-polarized. Normally, the spin dynamics of correlated radical pairs do not produce a net spin polarization; however, net spin polarization appears on NN. with the same time constant as describes the photogenerated radical ion pair decay. This effect is attributed to antiferromagnetic coupling between NN. and the local triplet state 3*Nl, which is populated following charge recombination. This requires an effective switch in the spin basis set between the triradical and the three-spin charge recombination product having both NN. and 3*Nl present.",
author = "Chernick, {Erin T.} and Qixi Mi and Kelley, {Richard F.} and Weiss, {Emily A} and Jones, {Brooks A.} and Marks, {Tobin J} and Ratner, {Mark A} and Wasielewski, {Michael R}",
year = "2006",
month = "4",
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language = "English",
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journal = "Journal of the American Chemical Society",
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T1 - Electron donor-bridge-acceptor molecules with bridging nitronyl nitroxide radicals

T2 - Influence of a third spin on charge- and spin-transfer dynamics

AU - Chernick, Erin T.

AU - Mi, Qixi

AU - Kelley, Richard F.

AU - Weiss, Emily A

AU - Jones, Brooks A.

AU - Marks, Tobin J

AU - Ratner, Mark A

AU - Wasielewski, Michael R

PY - 2006/4/5

Y1 - 2006/4/5

N2 - Appending a stable radical to the bridge molecule in a donor-bridge- acceptor system (D-B-A) is potentially an important way to control charge- and spin-transfer dynamics through D-B-A. We have attached a nitronyl nitroxide (NN.) stable radical to a D-B-A system having well-defined distances between the components: MeOAn-6ANl-Ph(NN.)-Nl, where MeOAn = p-methoxyaniline, 6ANl = 4-(N-piperidinyl)-naphthalene-1,8-dicarboximide, Ph = phenyl, and Nl = naphthalene-1,8:4,5-bis(dicarboximide). MeOAn-6ANl, NN ., and Nl are attached to the 1, 3, and 5 positions of the Ph bridge. Using both time-resolved optical and EPR spectroscopy, we show that NN . influences the spin dynamics of the photogenerated triradical states 2,4(MeOAn+.-6ANl-Ph(NN.)-Nl -.), resulting in slower charge recombination within the triradical compared to the corresponding biradical lacking NN.. The observed spin-spin exchange interaction between the photogenerated radicals MeOAn +. and Nl-. is not altered by the presence of NN ., which only accelerates radical pair intersystem crossing. Charge recombination within the triradical results in the formation of 2,4(MeOAn-6ANl-Ph(NN.)-3*Nl), in which NN. is strongly spin-polarized. Normally, the spin dynamics of correlated radical pairs do not produce a net spin polarization; however, net spin polarization appears on NN. with the same time constant as describes the photogenerated radical ion pair decay. This effect is attributed to antiferromagnetic coupling between NN. and the local triplet state 3*Nl, which is populated following charge recombination. This requires an effective switch in the spin basis set between the triradical and the three-spin charge recombination product having both NN. and 3*Nl present.

AB - Appending a stable radical to the bridge molecule in a donor-bridge- acceptor system (D-B-A) is potentially an important way to control charge- and spin-transfer dynamics through D-B-A. We have attached a nitronyl nitroxide (NN.) stable radical to a D-B-A system having well-defined distances between the components: MeOAn-6ANl-Ph(NN.)-Nl, where MeOAn = p-methoxyaniline, 6ANl = 4-(N-piperidinyl)-naphthalene-1,8-dicarboximide, Ph = phenyl, and Nl = naphthalene-1,8:4,5-bis(dicarboximide). MeOAn-6ANl, NN ., and Nl are attached to the 1, 3, and 5 positions of the Ph bridge. Using both time-resolved optical and EPR spectroscopy, we show that NN . influences the spin dynamics of the photogenerated triradical states 2,4(MeOAn+.-6ANl-Ph(NN.)-Nl -.), resulting in slower charge recombination within the triradical compared to the corresponding biradical lacking NN.. The observed spin-spin exchange interaction between the photogenerated radicals MeOAn +. and Nl-. is not altered by the presence of NN ., which only accelerates radical pair intersystem crossing. Charge recombination within the triradical results in the formation of 2,4(MeOAn-6ANl-Ph(NN.)-3*Nl), in which NN. is strongly spin-polarized. Normally, the spin dynamics of correlated radical pairs do not produce a net spin polarization; however, net spin polarization appears on NN. with the same time constant as describes the photogenerated radical ion pair decay. This effect is attributed to antiferromagnetic coupling between NN. and the local triplet state 3*Nl, which is populated following charge recombination. This requires an effective switch in the spin basis set between the triradical and the three-spin charge recombination product having both NN. and 3*Nl present.

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