Ion Pair-pi Interactions
| Autor: | Tomasz Adam Wesolowski, Kaori Fujisawa, Eric Vauthey, Naomi Sakai, Stefan Matile, Marie Humbert-Droz, Romain Letrun |
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| Rok vydání: | 2015 |
| Předmět: |
Ions
Molecular Structure 010405 organic chemistry Chemistry Context (language use) General Chemistry Electron Cell-Penetrating Peptides Chromophore Hydrogen-Ion Concentration 010402 general chemistry Antiparallel (biochemistry) 01 natural sciences Biochemistry Hydrocarbons Aromatic Catalysis 0104 chemical sciences Ion Colloid and Surface Chemistry Ion binding Chemical physics Excited state ddc:540 Atomic physics Ground state |
| Zdroj: | JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Journal of the American Chemical Society, Vol. 137, No 34 (2015) pp. 11047-11056 Journal of the American Chemical Society |
| ISSN: | 0002-7863 |
| DOI: | 10.1021/jacs.5b05593 |
| Popis: | We report that anion−π and cation−π interactions can occur on the same aromatic surface. Interactions of this type are referred to as ion pair−π interactions. Their existence, nature, and significance are elaborated in the context of spectral tuning, ion binding in solution, and activation of cell-penetrating peptides. The origin of spectral tuning by ion pair−π interactions is unraveled with energy-minimized excited-state structures: The solvent- and pH-independent red shift of absorption and emission of push–pull fluorophores originates from antiparallel ion pair−π attraction to their polarized excited state. In contrast, the complementary parallel ion pair−π repulsion is spectroscopically irrelevant, in part because of charge neutralization by intriguing proton and electron transfers on excited push–pull surfaces. With time-resolved fluorescence measurements, very important differences between antiparallel and parallel ion pair−π interactions are identified and quantitatively dissected from interference by aggregation and ion pair dissociation. Contributions from hydrogen bonding, proton transfer, π–π interactions, chromophore twisting, ion pairing, and self-assembly are systematically addressed and eliminated by concise structural modifications. Ion-exchange studies in solution, activation of cell-penetrating peptides in vesicles, and computational analysis all imply that the situation in the ground state is complementary to spectral tuning in the excited state; i.e., parallel rather than antiparallel ion pair−π interactions are preferred, despite repulsion from the push–pull dipole. The overall quite complete picture of ion pair−π interactions provided by these remarkably coherent yet complex results is expected to attract attention throughout the multiple disciplines of chemistry involved. |
| Databáze: | OpenAIRE |
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