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Change of Quadrupole Moment upon Excitation and Symmetry Breaking in Multibranched Donor‐Acceptor Dyes

Published inChemPhysChem, vol. 21, no. 15, p. 1718-1730
Publication date2020
Abstract

Upon photoexcitation, a majority of quadrupolar dyes, developed for large two-photon absorption, undergo excited-state symmetry breaking (ES-SB) and behave as dipolar molecules. We investigate how the change of quadrupole moment upon S 1  <- S 0  excitation, ? Q , influences the propensity of a dye to undergo ES-SB using a series of molecules with a A -π- D -π- A motif where D is the exceptionally electron-rich pyrrolo[3,2-b]pyrrole and A are accepting groups. Tuning of ? Q is achieved by appending a secondary acceptor group, A? , on both sides of the D core and ES-SB is monitored using a combination of time-resolved IR and broadband fluorescence spectroscopy. The results reveal a clear correlation between ? Q and the tendency to undergo ES-SB. When A is a stronger acceptor than A? , ES-SB occurs already in non-dipolar but quadrupolar solvents. When A and A? are identical, ES-SB is only partial even in highly dipolar solvents. When A is a weaker acceptor than A? , the orientation of ? Q changes, ES-SB is observed in dipolar solvents only and involves major redistribution of the excitation over the D -π- A  and D - A? branches of the dye.

Research group
Funding
  • Swiss National Science Foundation - 200020‐184607
Citation (ISO format)
SZAKACS, Zoltan et al. Change of Quadrupole Moment upon Excitation and Symmetry Breaking in Multibranched Donor‐Acceptor Dyes. In: ChemPhysChem, 2020, vol. 21, n° 15, p. 1718–1730. doi: 10.1002/cphc.202000253
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Article (Accepted version)
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ISSN of the journal1439-4235
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Creation08/13/2020 9:12:00 AM
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