Novel pyrene-and anthracene-based Schiff base derivatives P1 and A1 were synthesized via a one-pot reaction and utilized as fluorescence turn-on sensors towards Cu 2+ and Fe 3+ ions, respectively, and for aggregation induced emissions (AIEs). P1 in CH 3 CN and A1 in THF illustrated the fluorescence turn-on sensing towards Cu 2+ and Fe 3+ ions, respectively, via chelation enhanced fluorescence (CHEF) through excimer (P1-P1* and A1-A1*) formation. The 2 : 1 stoichiometry of the sensor complexes (P1 + Cu 2+ and A1 + Fe 3+ ) were calculated from Job plots based on UV-Vis absorption titrations. In addition, the binding sites of sensor complexes (P1 + Cu 2+ and A1 + Fe 3+ ) were well established from the 1 H NMR titrations and supported by the fluorescence reversibility by adding metal ions and PMDTA sequentially.The detection limits (LODs) and the association constant (K a ) values of P1 + Cu 2+ and A1 + Fe 3+ sensor responses were calculated by standard deviations, linear fittings and from their fluorescence binding isotherms. More importantly, P1 + Cu 2+ and A1 + Fe 3+ sensors were found to be active in wide ranges of pHs (1-14 and 2-14, respectively). Moreover, the time effect along with the enhancements of quantum yield (F) and time resolved photoluminescence (TRPL) decay constant (s) towards sensor responses were investigated. Similarly, P1 in CH 3 CN and A1 in THF showed AIEs by increasing the aqueous media concentration from 0% to 90%, with altered fluorescence peak shifts (red and blue shifts, respectively). As well as s value enhancements, the F values of 0.506 and 0.567 (with 630-and 101-fold enhancements) were acquired for P1 in CH 3 CN : H 2 O (20 : 80) and A1 in THF : H 2 O (40 : 60), respectively.
Novel thieno-imidazole based polymer P showed both colorimetric and ratiometric detections of Hg(2+) as well as fluorometric detection of Zn(2+) via fluorescence turn-on response with augmented lifetime. Its model polymer M did not show any such sensing capability under similar conditions, which further confirmed the unique sensitivity of P toward Hg(2+) and Zn(2+) via the chelation of metal ions to both "S" and "N" heteroatoms.
Simple pyridyl-salicylimine derivatives (F1, F2 and F3) are reported for the first time as fluorescence "turn-on" sensors for distinct detections of Zn(2+), Al(3+) and OH(-) ions in mixed-aqueous media CH3CN/H2O with volume ratios of 6/4 and 3/7 (at pH = 7 and 25 °C) via internal charge transfer (ICT), chelation enhanced fluorescence (CHEF), and deprotonation mechanisms. F1 and F2 show diverse turn-on sensing applications to Zn(2+), Al(3+) and OH(-) ions, but F3 exhibited the fluorescence turn-on sensing to Al(3+) and OH(-) ions in CH3CN/H2O (6/4; vol/vol). F1+Zn(2+) and F2+Zn(2+) complexes revealed the reversibilities and ratiometric displacements of Zn(2+) with ethylene diamine tetra acetic acid (EDTA) and Al(3+) ions, respectively, in CH3CN/H2O (6/4; vol/vol). On the other hand, F1, F2 and F3 in CH3CN/H2O (3/7; vol/vol) showed sensitivities only to Al(3+) ions but negligible selectivities to OH(-) ions. Stoichiometry of all sensor complexes were calculated as 1 : 1 by job's plots based on UV/Vis and PL titrations. The complex formation and binding sites of all sensor materials were well characterized by (1)H, (13)C NMR, and mass (FAB) spectral analysis. Detection limits were calculated from standard deviations and linear fitting calculations. The association constant (log K(a)) values of sensor complexes were evaluated from the fluorescence binding isotherms. The fluorescence decay constant (τ) values were estimated from time resolved fluorescence studies. Time, temperature, pH and solvent concentration effects towards sensor responses were fully investigated in this report.
Two novel dithieno-benzo-imidazole-based compounds (M2 and A2) showed remarkable sensitivities towards Pb(2+) by 12-fold enhancement and 10-fold decay of fluorescence, respectively, in aqueous solutions. Substituent effects of different dithieno-benzo-imidazole-based moieties (M1, M2, A1 and A2) on the quantum yields, fluorescence lifetimes and sensitivities to Pb(2+) along with the reversibilities by S(2-) were investigated.
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