# Responsive Supramolecular Sensors Based on Pillar[5]arene–BTD Complexes for Aqueous Sensing: From Static Quenching to Anion and DNA Recognition

## TL;DR

Scientists developed a new type of sensor using supramolecular complexes that can detect anions and DNA in water by changing their fluorescence.

## Contribution

The study introduces pillar[5]arene–BTD complexes as a novel platform for aqueous sensing through fluorescence changes.

## Key findings

- BTD derivatives show intense visible emission and strong solvatochromism.
- Complexation with pillar[5]arenes leads to static fluorescence quenching confirmed by simulations.
- Anion or DNA binding disrupts the complex, restoring fluorescence for sensing applications.

## Abstract

We report the design and investigation of supramolecular
guest–host
systems based on cationic pillar[5]­arene macrocycles and fluorescent
2,1,3-benzothiadiazole (BTD) derivatives. The BTD guests, obtained
through Sonogashira cross-coupling, display intense visible emission,
large Stokes shifts, and strong solvatochromism, while the pillar[5]­arene
hosts enable selective recognition in aqueous media. Spectrofluorimetric
titrations and NMR experiments revealed the formation of 1:1 inclusion
complexes between dianionic BTD derivatives and cationic pillar[5]­arenes,
with binding constants on the order of 105 M–1. Static fluorescence quenching was observed upon complexation, in
agreement with molecular docking simulations (ΔG ≈ −8.5 kcal mol–1) that highlighted
the role of electrostatic and π–π interactions.
Proof-of-concept sensing studies demonstrated that competitive binding
of anions or DNA induces disassembly of the nonemissive BTD 4⊂P­[5]­A complex, restoring the intrinsic fluorescence
of the guest. These results establish pillar[5]­arene–BTD assemblies
as promising supramolecular platforms for responsive fluorescence
sensing in aqueous environments.