Excited-state structure of copper phenanthroline-based photosensitizers
[2];
[3];
[2];
[5];
[4]
- Southern Federal University Rostov-on-Don (Russia)
- University of Zurich (Switzerland)
- Paul Scherrer Institute, Villigen (Switzerland); ETH Zurich (Switzerland)
- Paul Scherrer Institute, Villigen (Switzerland)
- Argonne National Laboratory (ANL), Argonne, IL (United States); Northwestern University, Evanston, IL (United States)
Cu diimine complexes present a noble metal free alternative to classical Ru, Re, Ir and Pt based photosensitizers in solution photochemistry, photoelectrochemical or dye-sensitized solar cells. Optimization of these dyes requires understanding of factors governing the key photochemical properties: excited state lifetime and emission quantum yield. The involvement of exciplex formation in the deactivation of the photoexcited state is a key question. Here, we investigate the excited-state structure of [Cu(dmp)2]+ and [Cu(dsbtmp)2]+ (dmp = 2,9-dimethyl-1,10-phenanthroline, dsbtmp = 2,9-di-sec-butyl-3,4,7,8-tetramethyl-1,10-phenanthroline) using pump–probe X-ray absorption spectroscopy (XAS) and DFT. Features of XAS that distinguish flattened tetrahedral site and 5-coordinated geometry with an additional solvent near Cu(II) center are identified. Pump–probe XAS demonstrates that for both complexes the excited state is 4-coordinated. For [Cu(dmp)2]+ the exciplex is 0.24 eV higher in energy than the flattened triplet state, therefore it can be involved in deactivation pathways as a non-observable state that forms slower than it decays. For [Cu(dsbtmp)2]+ the excited-state structure is characterized by Cu–N distances of 1.98 and 2.07 Å and minor distortions, leading to a 3 orders of magnitude longer excited-state lifetime.
- Research Organization:
- Argonne National Laboratory (ANL), Argonne, IL (United States). Argonne Leadership Computing Facility (ALCF)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES)
- Grant/Contract Number:
- AC02-06CH11357
- OSTI ID:
- 1982187
- Alternate ID(s):
- OSTI ID: 1832953
- Journal Information:
- Physical Chemistry Chemical Physics. PCCP, Vol. 23, Issue 47; ISSN 1463-9076
- Publisher:
- Royal Society of ChemistryCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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