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Nuclear Spin Singlet States in Photoactive Molecules: From Fluorescence/NMR Bimodality to a Bimolecular Switch for Spin Singlet States
Author(s) -
Yang Shengjun,
McCormick Jeffrey,
Mamone Salvatore,
Bouchard LouisS.,
Glöggler Stefan
Publication year - 2019
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.201814198
Subject(s) - singlet state , chemistry , photochemistry , tetraphenylethylene , molecule , singlet fission , fluorescence , singlet oxygen , triplet state , nuclear magnetic resonance , excited state , atomic physics , physics , organic chemistry , quantum mechanics , oxygen , aggregation induced emission
Nuclear spin singlet states are silent states in nuclear magnetic resonance (NMR). However, they can be probed indirectly and offer great potential for the development of contrast agents for magnetic resonance imaging (MRI). Introduced here are two novel concepts: Firstly, the bimodal NMR/fluorescence properties of 13 C 2 ‐tetraphenylethylene. It possesses a long‐lived singlet state in organic solvents, and it shortens upon the addition of water. This simultaneously increases the aggregation‐induced emission (AIE) of the molecule, resulting in a substantial enhancement of fluorescence. Secondly, introduced is a bimolecular switch for singlet states based on 3‐ 2 H ‐coumarin containing an isolated proton. Upon UV‐light exposure, a dimer forms, leading to a coupling between two previously isolated protons. A nuclear spin singlet state can now be populated. Excitation with a wavelength of 254 nm results in partial ring cleavage of the molecule back to its monomer.