| Autor: |
Griffin PJ; Department of Chemistry, University of Illinois Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, United States., Charette BJ; Department of Chemistry, University of Illinois Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, United States., Burke JH; Department of Chemistry, University of Illinois Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, United States., Vura-Weis J; Department of Chemistry, University of Illinois Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, United States., Schaller RD; Center for Nanoscale Materials, Argonne National Laboratory, Lemont, Illinois 60439, United States., Gosztola DJ; Center for Nanoscale Materials, Argonne National Laboratory, Lemont, Illinois 60439, United States., Olshansky L; Department of Chemistry, University of Illinois Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, United States. |
| Abstrakt: |
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 Cu I and Cu II , these dynamics aim to facilitate intramolecular electron transfer (ET) from Cu I to the ligand to create a CS state. The synthesis and photophysical characterization of CuCl(dpaa R ) (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 Cu II when 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 Cu I and Cu II complexes. The photophysical dynamics of the Cu I complexes 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 Cu II . The presence of Cu I decreases 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. |
