Controlling the Fluorescence Properties of Diarylethene-based Photochromic Systems

Doctoral thesis, 2022

Diarylethene (DAE) photoswitches are one of the most promising families of photochromic molecules because of their outstanding photophysical/photochemical properties. This class of compounds, which can photoisomerize between an open colorless and a closed colored form, has been applied in various fields in this thesis work, spanning one-color fluorescence intensity modulation, all-photonic full-color reproduction, light-induced color changes for molecular logic gates and information processing. Particularly, all systems presented can be all-photonically controlled, which is extremely beneficial as light is a sustainable resource from nature that is non-invasive, clean, and waste free that also allows for remote operation.
The first part of the thesis deals with introducing the light-induced isomerization process of the diarylethene derivatives. Through the isomerization of DAEs, intrinsic one-color “on-off” fluorescent intensity modulation as well as dynamic multicolor changes can be realized in the designed systems. In paper I, the diarylethene derivative Dasy is applied as a fluorescent probe aiming at phase-sensitive (lock-in) detection for high-contrast cell studies using fluorescence microscopy. The rapid switching fluorescence signal of Dasy can be successfully discriminated from strong fluorescence background using amplitude modulated red light. In paper II, a photoswitch cocktail mixture is designed where the color of the system can be tuned dynamically only by light-controlled isomerizations of the two monomer photoswitches.
The second part of the thesis focuses on discussing Förster Resonance Energy Transfer (FRET) based photoswitching systems where the emission is controlled through FRET processes by harnessing the different absorption and emission properties of the open and closed isomers of the DAE derivatives. In paper III, the FRET process can be orthogonally controlled by selective isomerization of two individual DAE acceptors, which results in an all-photonic full color red-green-blue (RGB) emissive system. In paper IV, a photoswitch triad is used as a sequential molecular logic gate where the emission output can be controlled by two mechanisms, both inherent and FRET controlled intensity change.