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Issue 32, 2020
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Spectroscopy and excited state dynamics of nearly infinite polyenes

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Abstract

Steady-state and transient absorption spectra with <50 fs time resolution were obtained for two conjugated polymers, both with ≈200 conjugated double bonds (N), constrained in planar, stable, polyene frameworks. Solutions of the polymers exhibit the same S2 → S1 → S* → S0 decay pathway observed for the N = 11–19 polyene oligomers and for zeaxanthin homologues with N = 11–23. Comparisons with the excited state dynamics of polydiactylene and a much longer, more disordered polyene polymer (poly(DEDPM)) show that the S2, S1, and S* lifetimes of the four polymers are almost identical. The S* signals in the polymers are assigned to absorption from vibrationally excited ground states. In spite of significant heterogeneities and variations in conjugation lengths in these long polyenes, their S0 → S2 absorptions are vibronically-resolved in room temperature solutions with electronic origins at ≈600 nm. The limiting wavelength for the S0 → S2 transitions is consistent with the persistence of bond length alternation in the electronic ground states and a HOMO–LUMO band gap in polyenes with N ≈ 200. The coincidence of the well-resolved S0 → S2 electronic origins and the convergence of the excited state lifetimes in the four polymers point to a common, “nearly infinite” polyene limit.

Graphical abstract: Spectroscopy and excited state dynamics of nearly infinite polyenes

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Article information


Submitted
06 May 2020
Accepted
28 Jul 2020
First published
29 Jul 2020

Phys. Chem. Chem. Phys., 2020,22, 17867-17879
Article type
Paper

Spectroscopy and excited state dynamics of nearly infinite polyenes

V. Šebelík, M. Kloz, M. Rebarz, M. Přeček, E. Kang, T. Choi, R. L. Christensen and T. Polívka, Phys. Chem. Chem. Phys., 2020, 22, 17867
DOI: 10.1039/D0CP02465A

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