New thiosemicarbazide-linked acridines
3a–c
were prepared and investigated as chemosensors for the detection of biologically and environmentally important anions. The compounds
3a–c
were found selective for fluoride (F
−
) with no affinity for other anions, i.e.
−
OAc, Br
−
, I
−
, HSO
4
−
, SO
4
2−
, PO
4
3−
, ClO
3
−
, ClO
4
−
, CN
−
and SCN
−
. Further, upon the gradual addition of a fluoride anion (F
−
) source (tetrabutylammonium fluoride), a well-defined change in colour of the solution of probes
3a–c
was observed. The anion-sensing process was studied in detail via UV–visible absorption, fluorescence and
1
H-NMR experiments. Moreover, during the synthesis of acridine probes
3a–c
nickel fluoride (NiF
2
), a rarely explored transition metal fluoride salt, was used as the catalyst. Theoretical studies via density functional theory were also carried out to further investigate the sensing and anion (F
−
) selectivity pattern of these probes.