TY - JOUR
T1 - Toward Improved Charge Separation through Conformational Control in Copper Coordination Complexes
AU - Griffin, Paul J.
AU - Charette, Bronte J.
AU - Burke, John H.
AU - Vura-Weis, Josh
AU - Schaller, Richard D.
AU - Gosztola, David J.
AU - Olshansky, Lisa
N1 - Funding Information:
P.J.G. gratefully acknowledges the UIUC Department of Chemistry for a PhD4 fellowship, and B.J.C. gratefully acknowledges the University of Illinois’ Office of the Vice Chancellor for Diversity, Equity & Inclusion for the Illinois Distinguished Postdoctoral Fellowship. The authors gratefully acknowledge Dr. Toby Woods for assistance in collecting low-temperature EPR spectra and Dr. Alec Follmer for helpful discussions. This work was performed, in part, at the Center for Nanoscale Materials, a U.S. Department of Energy Office of Science User Facility, and supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.
Publisher Copyright:
© 2022 American Chemical Society. All rights reserved.
PY - 2022/7/13
Y1 - 2022/7/13
N2 - The continued development of solar energy as a renewable resource necessitates new approaches to sustaining photodriven charge separation (CS). We present a bioinspired approach in which photoinduced conformational rearrangements at a ligand are translated into changes in coordination geometry and environment about a bound metal ion. Taking advantage of the differential coordination properties of CuIand CuII, these dynamics aim to facilitate intramolecular electron transfer (ET) from CuIto the ligand to create a CS state. The synthesis and photophysical characterization of CuCl(dpaaR) (dpaa = dipicolylaminoacetophenone, with R = H and OMe) are presented. These ligands incorporate a fluorophore that gives rise to a twisted intramolecular charge transfer (TICT) excited state. Excited-state ligand twisting provides a tetragonal coordination geometry capable of capturing CuIIwhen an internal ortho-OMe binding site is present. NMR, IR, electron paramagnetic resonance (EPR), and optical spectroscopies, X-ray diffraction, and electrochemical methods establish the ground-state properties of these CuIand CuIIcomplexes. The photophysical dynamics of the CuIcomplexes are explored by time-resolved photoluminescence and optical transient absorption spectroscopies. Relative to control complexes lacking a TICT-active ligand, the lifetimes of CS states are enhanced ∼1000-fold. Further, the presence of the ortho-OMe substituent greatly enhances the lifetime of the TICT∗ state and biases the coordination environment toward CuII. The presence of CuIdecreases photoinduced degradation from 14 to <2% but does not result in significant quenching via ET. Factors affecting CS in these systems are discussed, laying the groundwork for our strategy toward solar energy conversion.
AB - The continued development of solar energy as a renewable resource necessitates new approaches to sustaining photodriven charge separation (CS). We present a bioinspired approach in which photoinduced conformational rearrangements at a ligand are translated into changes in coordination geometry and environment about a bound metal ion. Taking advantage of the differential coordination properties of CuIand CuII, these dynamics aim to facilitate intramolecular electron transfer (ET) from CuIto the ligand to create a CS state. The synthesis and photophysical characterization of CuCl(dpaaR) (dpaa = dipicolylaminoacetophenone, with R = H and OMe) are presented. These ligands incorporate a fluorophore that gives rise to a twisted intramolecular charge transfer (TICT) excited state. Excited-state ligand twisting provides a tetragonal coordination geometry capable of capturing CuIIwhen an internal ortho-OMe binding site is present. NMR, IR, electron paramagnetic resonance (EPR), and optical spectroscopies, X-ray diffraction, and electrochemical methods establish the ground-state properties of these CuIand CuIIcomplexes. The photophysical dynamics of the CuIcomplexes are explored by time-resolved photoluminescence and optical transient absorption spectroscopies. Relative to control complexes lacking a TICT-active ligand, the lifetimes of CS states are enhanced ∼1000-fold. Further, the presence of the ortho-OMe substituent greatly enhances the lifetime of the TICT∗ state and biases the coordination environment toward CuII. The presence of CuIdecreases photoinduced degradation from 14 to <2% but does not result in significant quenching via ET. Factors affecting CS in these systems are discussed, laying the groundwork for our strategy toward solar energy conversion.
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U2 - 10.1021/jacs.2c02580
DO - 10.1021/jacs.2c02580
M3 - Article
C2 - 35762527
AN - SCOPUS:85134426825
SN - 0002-7863
VL - 144
SP - 12116
EP - 12126
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
IS - 27
ER -