Picosecond Control of Photogenerated Radical Pair Lifetimes Using a Stable Third Radical

Noah E. Horwitz, Brian T. Phelan, Jordan N. Nelson, Matthew D. Krzyaniak, Michael R Wasielewski

Research output: Contribution to journalArticle

16 Citations (Scopus)

Abstract

Photoinduced electron transfer reactions in organic donor-acceptor systems leading to long-lived radical ion pairs (RPs) have attracted broad interest for their potential applications in fields as diverse as solar energy conversion and spintronics. We present the photophysics and spin dynamics of an electron donor - electron acceptor - stable radical system consisting of a meta-phenylenediamine (mPD) donor covalently linked to a 4-aminonaphthalene-1,8-dicarboximide (ANI) electron-accepting chromophore as well as an α,γ-bisdiphenylene-β-phenylallyl (BDPA) stable radical. Selective photoexcitation of ANI produces the BDPA-mPD+•-ANI-• triradical in which the mPD+•-ANI-• RP spins are strongly exchange coupled. The presence of BDPA is found to greatly increase the RP intersystem crossing rate from the initially photogenerated BDPA-1(mPD+•-ANI-•) to BDPA-3(mPD+•-ANI-•), resulting in accelerated RP recombination via the triplet channel to produce BDPA-mPD-3∗ANI as compared to a reference molecule lacking the BDPA radical. The RP recombination rates observed are much faster than those previously reported for weakly coupled triradical systems. Time-resolved EPR spectroscopy shows that this process is also associated with strong spin polarization of the stable radical. Overall, these results show that RP intersystem crossing rates can be strongly influenced by stable radicals nearby strongly coupled RP systems, making it possible to use a third spin to control RP lifetimes down to a picosecond time scale.

Original languageEnglish
Pages (from-to)2841-2853
Number of pages13
JournalJournal of Physical Chemistry A
Volume120
Issue number18
DOIs
Publication statusPublished - May 12 2016

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1-Naphthylamine
Ions
life (durability)
Electrons
ions
Spin dynamics
Magnetoelectronics
Spin polarization
Photoexcitation
Chromophores
Energy conversion
Solar energy
Paramagnetic resonance
3-phenylenediamine
solar energy conversion
electrons
Spectroscopy
spin dynamics
photoexcitation
Molecules

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

Picosecond Control of Photogenerated Radical Pair Lifetimes Using a Stable Third Radical. / Horwitz, Noah E.; Phelan, Brian T.; Nelson, Jordan N.; Krzyaniak, Matthew D.; Wasielewski, Michael R.

In: Journal of Physical Chemistry A, Vol. 120, No. 18, 12.05.2016, p. 2841-2853.

Research output: Contribution to journalArticle

Horwitz, Noah E. ; Phelan, Brian T. ; Nelson, Jordan N. ; Krzyaniak, Matthew D. ; Wasielewski, Michael R. / Picosecond Control of Photogenerated Radical Pair Lifetimes Using a Stable Third Radical. In: Journal of Physical Chemistry A. 2016 ; Vol. 120, No. 18. pp. 2841-2853.
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