Aryne-Enabled Synthesis of 1,8-Disubstituted Thioxanthones for Conformationally Gated Metal-Ion Sensing
Year: 2026
Type: preprint
Abstract: Conformational changes in a chromophore can strongly influence its fluorescence properties. Here, we report the development of thioxanthone-based fluorescent sensors designed to suppress the characteristic butterfly-like deformation of the thioxanthone core upon metal-ion binding. To access the required 1,8-disubstituted scaffolds, we developed an efficient aryne-based synthesis of multisubstituted thioxanthones from readily available o -iodoaryl triflates and N , N , N’ , N’- tetramethylthiourea. Subsequent functionalization provided a series of thioxanthones bearing metal-coordinating substituents at the 1,8-positions. Evaluation of the resulting compounds identified a probe exhibiting pronounced and spectrally distinct fluorescence responses to Zn 2+ and Ca 2+ with high ON/OFF ratios, enabling clear discrimination between the two metal ions. Time-dependent DFT (TD-DFT) calculations for a simplified Zn 2+ complex indicated that coordination stabilizes a nearly planar thioxanthone structure and enhances the oscillator strength of the emissive transition. These results demonstrate the utility of controlling the butterfly-like deformation of the thioxanthone core for metal-ion-responsive fluorescence sensing.
Source: ChemRxiv
Authors: Riku Arakaki, Mayu Kawada, Suguru Yoshida
Institution: Tokyo University of Science
Language: English
Subfield: Spectroscopy
Field: Chemistry
Domain: Physical Sciences
Open Access status: green
Award: G2955517606
OpenAlex ID: W7221981836