Symmetry-Breaking Charge Transfer of Visible Light Absorbing Systems: Zinc Dipyrrins

Zinc dipyrrin complexes with two identical dipyrrin ligands absorb strongly at 450–550 nm and exhibit high fluorescence quantum yields in nonpolar solvents (e.g., 0.16–0.66 in cyclohexane) and weak to nonexistent emission in polar solvents (i.e., <10–3, in acetonitrile). The low quantum efficienc...

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Published inJournal of physical chemistry. C Vol. 118; no. 38; pp. 21834 - 21845
Main Authors Trinh, Cong, Kirlikovali, Kent, Das, Saptaparna, Ener, Maraia E, Gray, Harry B, Djurovich, Peter, Bradforth, Stephen E, Thompson, Mark E
Format Journal Article
LanguageEnglish
Published United States American Chemical Society 25.09.2014
Subjects
Absorption
Charge transfer
Decay
Excitation spectra
Ground state
Nanomaterials
Solvents
Zinc
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Summary:Zinc dipyrrin complexes with two identical dipyrrin ligands absorb strongly at 450–550 nm and exhibit high fluorescence quantum yields in nonpolar solvents (e.g., 0.16–0.66 in cyclohexane) and weak to nonexistent emission in polar solvents (i.e., <10–3, in acetonitrile). The low quantum efficiencies in polar solvents are attributed to the formation of a nonemissive symmetry-breaking charge transfer (SBCT) state, which is not formed in nonpolar solvents. Analysis using ultrafast spectroscopy shows that in polar solvents the singlet excited state relaxes to the SBCT state in 1.0–5.5 ps and then decays via recombination to the triplet or ground states in 0.9–3.3 ns. In the weakly polar solvent toluene, the equilibrium between a localized excited state and the charge transfer state is established in 11–22 ps.
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USDOE Office of Science (SC), Basic Energy Sciences (BES)
DE SC0001013
ISSN:1932-7447
1932-7455
DOI:10.1021/jp506855t