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Gas‐Phase Ion Fluorescence Spectroscopy of Tailor‐made Rhodamine Homo‐ and Heterodyads: Quenching of Electronic Communication by π‐Conjugated Linkers
Author(s) -
Petersen Anne Ugleholdt,
Kjær Christina,
Jensen Cecilie,
Brøndsted Nielsen Mogens,
Brøndsted Nielsen Steen
Publication year - 2020
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.202008314
Subject(s) - chromophore , photochemistry , conjugated system , chemistry , dipole , ion , rhodamine , chemical physics , ionic bonding , fluorescence , alkyl , organic chemistry , physics , quantum mechanics , polymer
While many key photophysical features are understood for electronic communication between chromophores in neutral compounds, there is limited information on the effect of charges in practically relevant ionic chromo/fluorophores. Here we have chosen positively charged rhodamines and prepared a selection of homo‐ and heterodimers with alkyl or π‐conjugated, acetylenic bridges. Protonated molecules were transferred as isolated ions to gas phase where there is no solvent screening of charges, and fluorescence spectra were measured with a custom‐made ion‐trap setup. Our work reveals strong polarization of the π‐spacer (induced dipole/quadrupole) when it experiences the electric field from one/ two dyes. Hence, π‐spacers provide efficient shielding of charges by reducing the Coulomb interaction, whereas two dye cations polarize each other when connected by an alkyl. The screening influences the Förster resonance energy transfer efficiency that relies on the dipole–dipole interaction.