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Planarized Intramolecular Charge Transfer: A Concept for Fluorophores with both Large Stokes Shifts and High Fluorescence Quantum Yields
Author(s) -
Haberhauer Gebhard,
Gleiter Rolf,
Burkhart Christoph
Publication year - 2016
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201503927
Subject(s) - quantum yield , intramolecular force , fluorescence , excited state , stokes shift , chemistry , quantum , charge (physics) , ground state , chemical physics , excitation , photochemistry , atomic physics , molecular physics , computational chemistry , physics , quantum mechanics , stereochemistry
Fluorophores were successfully used in several areas of chemistry and biochemistry. For many purposes, however, it is necessary that the fluorescence compound features a high fluorescence quantum yield as well as a large Stokes shift. The latter is, for example, achieved by the use of a twisted intramolecular charge‐transfer (TICT) compound, which shows a twisted geometry in the excited state. However, the higher the twisting is, the lower becomes in general the fluorescence quantum yield as the resulting emission from the twisted state is forbidden. In order to escape this dilemma, we propose the model of planarized intramolecular charge‐transfer (PLICT) states. These compounds are completely twisted in the ground states and planar in the excited states. By means of quantum chemical calculations (time‐dependent (TD)‐B3LYP and CC2) and experimental studies, we could demonstrate that 1‐aminoindole and its derivatives form photoinduced PLICT states. They show both very large Stokes shifts ( ν ˜ =9000–13 500 cm −1 , i.e., λ =100–150 nm) and high fluorescence quantum yields. These characteristics and their easy availability starting from the corresponding indoles, make them very attractive for the use as optical switches in various fields of chemistry as well as biological probes.