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Counterion Migration Driven by Light-Induced Intramolecular Charge Transfer

[Image: see text] A series of D−π–A(+) pyridinium compounds, in which D = −NPh(2) and A(+) = −PyMe(+) are linked by various amounts of linear phenyl spacers, were strategically designed and synthesized. Their characterization revealed the presence of excited-state intramolecular charge transfer (ESI...

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Autores principales: Lin, Ta-Chun, Liu, Zong-Ying, Liu, Shih-Hung, Koshevoy, Igor O., Chou, Pi-Tai
Formato: Online Artículo Texto
Lenguaje:English
Publicado: American Chemical Society 2021
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8395631/
https://www.ncbi.nlm.nih.gov/pubmed/34467293
http://dx.doi.org/10.1021/jacsau.0c00107
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author Lin, Ta-Chun
Liu, Zong-Ying
Liu, Shih-Hung
Koshevoy, Igor O.
Chou, Pi-Tai
author_facet Lin, Ta-Chun
Liu, Zong-Ying
Liu, Shih-Hung
Koshevoy, Igor O.
Chou, Pi-Tai
author_sort Lin, Ta-Chun
collection PubMed
description [Image: see text] A series of D−π–A(+) pyridinium compounds, in which D = −NPh(2) and A(+) = −PyMe(+) are linked by various amounts of linear phenyl spacers, were strategically designed and synthesized. Their characterization revealed the presence of excited-state intramolecular charge transfer (ESICT) that triggers a corresponding response from the counterion. In medium and strong polar solvents, the fast solvent relaxation occurring after ESICT overwhelms the counterion effect, showing typical emission solvatochromism. In weakly polar solvents, ESICT induces counteranion migration for electrostatic stabilization, the time scale of which is dependent on the radius of the counteranion, the length of the π-linker, and the viscosity of the solvent. In low-viscosity organic solvents such as toluene, counteranion migration occurs within several tens to hundreds of picoseconds, resulting in a time-dependent continuous emission that can be resolved from the spectral temporal evolution. Concrete evidence for this is provided by the chemical synthesis of a D−π–A(+) pyridinium–sulfur trioxide(–) zwitterion, where anion migration is restricted due to its internally locked ion pair. As a result, only a single emission band can be observed. These comprehensive studies prove that the ion migration process may be significant for a wide range of ESICT-type ionic fluorophores. Such an ionic movement, triggered by optically pumped ESICT of the D−π–A(+) dyad, is similar to the molecular machine driven by the redox reaction, but with a facile access and fast response.
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spelling pubmed-83956312021-08-30 Counterion Migration Driven by Light-Induced Intramolecular Charge Transfer Lin, Ta-Chun Liu, Zong-Ying Liu, Shih-Hung Koshevoy, Igor O. Chou, Pi-Tai JACS Au [Image: see text] A series of D−π–A(+) pyridinium compounds, in which D = −NPh(2) and A(+) = −PyMe(+) are linked by various amounts of linear phenyl spacers, were strategically designed and synthesized. Their characterization revealed the presence of excited-state intramolecular charge transfer (ESICT) that triggers a corresponding response from the counterion. In medium and strong polar solvents, the fast solvent relaxation occurring after ESICT overwhelms the counterion effect, showing typical emission solvatochromism. In weakly polar solvents, ESICT induces counteranion migration for electrostatic stabilization, the time scale of which is dependent on the radius of the counteranion, the length of the π-linker, and the viscosity of the solvent. In low-viscosity organic solvents such as toluene, counteranion migration occurs within several tens to hundreds of picoseconds, resulting in a time-dependent continuous emission that can be resolved from the spectral temporal evolution. Concrete evidence for this is provided by the chemical synthesis of a D−π–A(+) pyridinium–sulfur trioxide(–) zwitterion, where anion migration is restricted due to its internally locked ion pair. As a result, only a single emission band can be observed. These comprehensive studies prove that the ion migration process may be significant for a wide range of ESICT-type ionic fluorophores. Such an ionic movement, triggered by optically pumped ESICT of the D−π–A(+) dyad, is similar to the molecular machine driven by the redox reaction, but with a facile access and fast response. American Chemical Society 2021-01-25 /pmc/articles/PMC8395631/ /pubmed/34467293 http://dx.doi.org/10.1021/jacsau.0c00107 Text en © 2021 The Authors. Published by American Chemical Society https://pubs.acs.org/page/policy/authorchoice_ccbyncnd_termsofuse.htmlThis is an open access article published under a Creative Commons Non-Commercial No Derivative Works (CC-BY-NC-ND) Attribution License (https://pubs.acs.org/page/policy/authorchoice_ccbyncnd_termsofuse.html) , which permits copying and redistribution of the article, and creation of adaptations, all for non-commercial purposes.
spellingShingle Lin, Ta-Chun
Liu, Zong-Ying
Liu, Shih-Hung
Koshevoy, Igor O.
Chou, Pi-Tai
Counterion Migration Driven by Light-Induced Intramolecular Charge Transfer
title Counterion Migration Driven by Light-Induced Intramolecular Charge Transfer
title_full Counterion Migration Driven by Light-Induced Intramolecular Charge Transfer
title_fullStr Counterion Migration Driven by Light-Induced Intramolecular Charge Transfer
title_full_unstemmed Counterion Migration Driven by Light-Induced Intramolecular Charge Transfer
title_short Counterion Migration Driven by Light-Induced Intramolecular Charge Transfer
title_sort counterion migration driven by light-induced intramolecular charge transfer
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8395631/
https://www.ncbi.nlm.nih.gov/pubmed/34467293
http://dx.doi.org/10.1021/jacsau.0c00107
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