TY - JOUR
T1 - Picosecond Control of Photogenerated Radical Pair Lifetimes Using a Stable Third Radical
AU - Horwitz, Noah E.
AU - Phelan, Brian T.
AU - Nelson, Jordan N.
AU - Krzyaniak, Matthew D.
AU - Wasielewski, Michael R.
N1 - Funding Information:
This work was supported by National Science Foundation grant no. CHE-1266201. N.E.H. thanks the Department of Energy Office of Science Graduate Fellowship Program for a fellowship. This research is supported in part by the Department of Energy Office of Science Graduate Fellowship Program (DOE SCGF), made possible in part by the American Recovery and Reinvestment Act of 2009, administered by ORISE-ORAU under contract no. DE-AC05-06OR23100.
Publisher Copyright:
© 2016 American Chemical Society.
PY - 2016/5/12
Y1 - 2016/5/12
N2 - 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.
AB - 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.
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U2 - 10.1021/acs.jpca.6b02621
DO - 10.1021/acs.jpca.6b02621
M3 - Article
C2 - 27108738
AN - SCOPUS:84969780583
VL - 120
SP - 2841
EP - 2853
JO - Journal of Physical Chemistry A
JF - Journal of Physical Chemistry A
SN - 1089-5639
IS - 18
ER -