TY - JOUR
T1 - Photoinitiated long-lived charge separation with near-unity quantum yield in donor-acceptor1-acceptor2 systems for artificial photosynthesis
AU - Han, Won Sik
AU - Veldkamp, Brad S.
AU - Dyar, Scott M.
AU - Eaton, Samuel W.
AU - Wasielewski, Michael R.
PY - 2017
Y1 - 2017
N2 - We report the synthesis and photophysical characterization of isomeric donor-acceptor1-acceptor2 (D-A1-A2) triads each comprising a perylene donor (D) connected by a xylene bridge to a naphthalene-1,8-dicarboximide primary acceptor (NMI, A1) that is, in turn, covalently linked to a naphthalene-1,4:5,8-bis(dicarboximide) secondary acceptor (NDI, A2) through a benzene ring at its ortho, meta or para positions (Per-Xy-NMI-x-NDI). Selective photoexcitation of Per produces both Per+• and NDI‒• simultaneously with time constants of ∼50 ps in benzonitrile and ∼80 ps in toluene with a >98% yield. This is much faster than expected for single-step electron transfer from 1*Per to NDI and is consistent with a two-step mechanism, 1*Per-Xy-NMI-x-NDI → Per+•-Xy-NMI‒•-x-NDI → Per+•-Xy-NMI-x-NDI‒•, in which the second step is much faster than the first step. In addition, preserving long-lived charge separation in these systems is found to depend on inhibiting charge recombination by a triplet radical ion pair recombination pathway.
AB - We report the synthesis and photophysical characterization of isomeric donor-acceptor1-acceptor2 (D-A1-A2) triads each comprising a perylene donor (D) connected by a xylene bridge to a naphthalene-1,8-dicarboximide primary acceptor (NMI, A1) that is, in turn, covalently linked to a naphthalene-1,4:5,8-bis(dicarboximide) secondary acceptor (NDI, A2) through a benzene ring at its ortho, meta or para positions (Per-Xy-NMI-x-NDI). Selective photoexcitation of Per produces both Per+• and NDI‒• simultaneously with time constants of ∼50 ps in benzonitrile and ∼80 ps in toluene with a >98% yield. This is much faster than expected for single-step electron transfer from 1*Per to NDI and is consistent with a two-step mechanism, 1*Per-Xy-NMI-x-NDI → Per+•-Xy-NMI‒•-x-NDI → Per+•-Xy-NMI-x-NDI‒•, in which the second step is much faster than the first step. In addition, preserving long-lived charge separation in these systems is found to depend on inhibiting charge recombination by a triplet radical ion pair recombination pathway.
KW - Donor-acceptor
KW - Photochemistry
KW - Radical pairs
KW - Transient absorption spectroscopy
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U2 - 10.1016/j.tet.2017.06.021
DO - 10.1016/j.tet.2017.06.021
M3 - Article
AN - SCOPUS:85020876140
VL - 73
SP - 4925
EP - 4935
JO - Tetrahedron
JF - Tetrahedron
SN - 0040-4020
IS - 33
ER -