Excited-state structure of copper phenanthroline-based photosensitizers

Alexander Guda, Johannes Windisch, Benjamin Probst, Jeroen A. Van Bokhoven, Roger Alberto, Maarten Nachtegaal, Lin X. Chen, Grigory Smolentsev*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


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. 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.

Original languageEnglish (US)
Pages (from-to)26729-26736
Number of pages8
JournalPhysical Chemistry Chemical Physics
Issue number47
StatePublished - Dec 21 2021

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry


Dive into the research topics of 'Excited-state structure of copper phenanthroline-based photosensitizers'. Together they form a unique fingerprint.

Cite this