Molecular Cursor Caliper: A Fluorescent Sensor for Dicarboxylate Dianions

We
report here the fluorescent sensing of both aromatic and linear
saturated dicarboxylate anions (DC2–) (as their tetrabutylammonium salts) with different lengths and
shapes in acetonitrile using a single fluorescent probe, i.e., the
bis-calix[4]­pyrrole-appended 9,14-diphenyl-9,14-dihydrodibenzo­[a,c]­phenazine (DPAC-bisC4P) incorporating a vibration-induced emission (VIE) phenazine core.
Fluorescence titration studies revealed that treating DPAC-bisC4P with dicarboxylate guests capable of forming pseudomacrocyclic host–guest
complexes via multiple hydrogen-bonding interactions between the dicarboxylates
and calix[4]­pyrrole moieties led to a blue-shift in the emission of
the phenazine core. The binding-based fluorescence-tuning features
of DPAC-bisC4P allow the underlying binding events and
inferred structural changes to be monitored in the form of different
chromaticity outputs. The analyte-induced differences in the fluorescence
response to DC2– cover a wide range
within the chromaticity diagram and can be visualized readily. The
present system thus functions as a rudimentary dicarboxylate anion
sensor. It highlights the potential benefits associated with combining
a tunable VIE core with noncovalent binding interactions and thus
sets the stage for the development of new fluorescent chemosensors
where a single chemical entity responds to different analytes with
a high level of tunability.