Fluorescent calixarene scaffolds for NO detection in protic media

Here, we present the first fluorescent water-soluble
conjugated calixarene scaffolds that are capable of detection of NO
gas. Two different scaffolds, one based on a 5,5’-Bicalixarene
structure and its isomer bearing separate calixarene moieties, have
been synthesized. While the fluorescence of both isomers is
quenched upon either passing of NO gas or generating it in-situ from
diethylamine NONOate, the bicalixarene-based scaffold showed a
significantly stronger response. We also present an example of a
dye encapsulation strategy to achieve the detection of NO at longer
wavelengths than in the parent calixarene host. Finally, a conjugated
polymer bearing 5,5’-Bicalixarene scaffold has also been prepared
and demonstrated enhanced sensitivity compared with the monomer
due to the molecular wire effect.