Design of Two Pyrazole-Based Sensors with Similar Configuration and Different Fluorescent Response to Anions

Three-Fold C 3-Symmetric Off-On Fluorescent Chemo-Sensors for Fluoride

Three novel C 3-symmetric tris-salicylaldimine Schiff base based "off-on" fluorescence sensors have been designed and synthesized. The synthetic approach involves a simple imine bond (C = N) formation between 1,3,5-tris(4'-aminophenyl)benzene (TAPB) and 3,5-substituted salicylaldehydes. The presence of salicylaldehyde units on periphery of the tris-salicylaldimine Schiff bases masks the fluorescence of TAPB core. Interestingly, binding of fluoride ions to the salicylaldehyde units turns the fluorescence "on" in visible region. Fluoride ion detection limits for the present sensors have been calculated to be in the range of 0.17-3.0 ppm, which depends on the nature of the salicylaldehyde units.

Synthesis, spectroscopy studies, and theoretical calculations of new fluorescent probes based on pyrazole containing porphyrins for Zn(II), Cd(II), and Hg(II) optical detection

New pyrazole-porphyrin conjugates were successfully prepared from a reaction of β-porphyrin-chalcone derivatives with phenylhydrazine in acetic acid followed by an oxidative step. This fast and efficient synthetic approach provided the expected compounds in yields up to 82%. The sensing ability of the new porphyrin-pyrazole derivatives to detect the metal ions Ag(+), Na(+), K(+), Mg(2+), Ca(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), Hg(2+), Pb(2+), and Cr(3+) was studied by spectrophotometric and spectrofluorimetric titrations. In the presence of Zn(2+), the conjugates exhibit changes in the emission spectra that are desired for a ratiometric-type fluoroionophoric detection probe. The studies were extended to gas phase, where the pyrazole-porphyrin conjugates show ability to sense metal ions with high selectivity toward Cu(2+) and Ag(+), and in poly(methyl methacrylate) doped films with promising results for Zn(2+) detection.

Rational design of a rapid fluorescent approach for detection of inorganic fluoride in MeCN–H2O: a new fluorescence switch based on N-aryl-1,8-naphthalimide

A desilylation based sensor showed high selectivity and sensitivity to fluoride in MeCN–H₂O media.

Excimer–monomer switch: a reaction-based approach for selective detection of fluoride

Desilylation triggered excimer–monomer switch based on 1,8-naphthalimide was used as a sensing strategy for detection of fluoride.

A new N-imidazolyl-1,8-naphthalimide based fluorescence sensor for fluoride detection

A chemosensor is reported with high sensitivity and selectivity for detection of fluoride anion. The recognition mechanism is attributed to a fluoride-triggered disruption of the hydrogen bond between imidazole and naphthalimide moieties, resulting in a noncoplanar geometry with low fluorescence.

Selective ratiometric fluorescence detection of acetate based on a novel Schiff base derivative

A ratiometric fluorescence and colorimetric probe based on 5,5'-methylene-bis-salicylaldehyde-p-nitrophenylhydrazone (1), which was characterized by (1)H NMR, mass spectrometer and elemental analysis, was prepared through Schiff base reaction. The probe exhibited visible color changes from yellow to purple upon interacting with acetate ion. Particularly, the compound showed ratiometric fluorescence response to acetate with significant blue shift about 150 nm from 410 nm to 560 nm. Thence, the probe 1 was a selective ratiometric fluorescence probe for acetate ion in DMSO solution.