The non fluorescent meso diaminophenyl 1, 3, 5, 7-tetramethyl BODIPY dye has been investigated and employed for picric acid sensing in constructive way by regenerating its fluorescence through PET hindrance. Strong enhanced emission signal was obtained as consequence of electrostatic association between BODIPY probe and picric acid with specific recognition among other explosive nitro aromatics. The probe shows 1:1 binding stoichiometry with picric acid and detection limit up to 0.65ppb.
A new acridine based photoinduced electron transfer based fluorescent chemosensor for the detection of nitroaromatic compounds is reported. The probe exhibited high selectivity and sensitivity for the detection of picric acid over trivial explosive in CH3OH.
Three novel iminocoumarin derivatives with high quantum yield are synthesized from 3-benzimidazole substituted coumarin and different aromatic aldehydes. The photophysical behavior of the synthesized compounds was studied using UV-visible and fluorescence spectroscopy in polar and non-polar solvents. The compounds show absorption maxima at around 450 nm and emission maxima at around 500 nm. The quantum yields of compounds in dichloromethane and chloroform are more than 0.90. The absorption, emission and quantum yield of compounds are dependent on the polarity of solvents. Along with an intense absorption, these compounds show shoulder absorption peak in the studied solvents. The solvent polarity plots revealed the charge transfer process in the synthesized molecules from donor to acceptor. Density Functional Theory and Time Dependent Density Functional Theory computations have been used to have more understanding of the structural, molecular, electronic and photophysical parameters of the dyes. The dyes were characterized by FT-IR, (1)H NMR, (13)C NMR and mass spectral analysis.
Donor-π- acceptor styryl chromophores based on indole core were synthesized by Knoevenagel condensation of N-ethyl indole-3-carbaldehyde and different active methylene compounds. The absorption and emission properties of these dyes in different solvents were studied. The dyes displayed a broad absorption maximum in the UV and visible region between 397 and 469 nm with FWHM, 50 to 75 nm. Due to the extended π - conjugated systems this styryl chromophores shows strong intramolecular charge transfer characteristics. The dyes showed solid state emission and emission in solid state was red shifted as compared to their emission in less polar solvents. Density Functional Theory [B3LYP/6-311 + G(d)] computations were used to correlate the structural, molecular, electronic and photo physical parameters of styryl dye with experimental study. Synthesized dyes were confirmed by using FT-IR, H NMR,C NMR and HRMS spectral analysis.
Research Highlights1) Two new fluorescent PET chemosensors were designed and synthesised from acridine core. 2) Sensors can be used to monitor Cu 2+ and Al 3+ in CH 3 CN.3) The detection limits for 7a-Cu 2+ and 7b-Al 3+ were calculated to be 2.8 x 10 -7 M and 5.8 x 10 -7 M, respectively. 4) Binding study of metals to the probes showed that the nature of receptor plays very important role in the selective detection of metal ions.Abstract: Two novel acridine based chemosensors 7a and 7b were synthesized and configured as "fluorophore-spacer-receptor" systems based on photoinduced electron transfer. The probes 7a and 7b exhibited high selectivity and sensitivity for the detection of Cu 2+ and Al 3+ respectively over commonly coexistent metal ions in CH 3 CN. The binding association constants (Ka) of 7a-Cu 2+ and 7b-Al 3+ were obtained to be 4.0 x 10 4 M -1 and 1.7 x 10 4 M -1 in CH 3 CN, and the corresponding detection limits were calculated to be 2.8 x 10 -7 M and 5.8 x 10 -7 M, respectively. The fluorescence response of 7a-Cu 2+ and 7b-Al 3+ with respect to pH change was studied and the result demonstrated fluorescence enhancement was observed in the pH range of 7.0 -9.0. The chromophores were characterized by FT-IR, 1 H-NMR, 13 C-NMR and HR Mass spectral analysis.
Carboxylic acid substituted fluorescein derivatives were synthesized from 2,4-dihydroxy carboxylic acid and phthalic anhydride or trimellitic anhydride. The photophysical properties like absorption, emission and fluorescence quantum yields of these fluorophores were studied. The conjugation studies of these fluorophores with different proteins at different concentrations were carried out. The effect of pH on photophysical properties was studied at different pH ranges from 5 to 12. The change in the absorption and emission with respect to viscosity of medium was also studied. The changes in the electronic transition, energy levels, and orbital diagram of the fluorescein derivatives were computed using the TD-DFT computations and co-related with experimental photophysical data.
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