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In this paper, we studied the effect of increasing the conjugation in compound 3 on the proton transfer and aggregation‐induced emission properties. Compound 3 exhibited the dual absorption peak at 420 nm and 320 nm, which was redshifted by 50 nm compared to compound 2 (previous report). Compound 3 emits exhibited a peak at 530 nm with a Stokes' shift of 110 nm after photoexcitation at 420 nm. In a high polarity medium, the absorption and emission spectra of compound 3 showed redshifts of 50 nm and 20 nm, respectively. Further, compound 3 displayed the aggregation‐induced emission enhancement in THF/H2O (60 % v/v). Additionally, the proton transfer process in compounds 2 and 3 was evaluated through theoretical calculations via determining the relative free energies of possible tautomeric forms. It was determined that the small energy barriers for compound 2 in the S1 state suggested the presence of the proton transfer process; however, high energy barriers and high stabilization and Boltzmann population of 3.KK tautomeric form at S0 and S1 state for compound 3 discommoded the proton transfer process. Further, the aggregated form of compound 3 (20 μM; CH3OH/HEPES buffer (4 : 1; v/v) pH=7.04) was utilized to recognize Cu2+ ions with the lowest detection limit of 1.5 nM and Stern‐Volmer binding constant of 2.8×105 M−1. A noted decrease in the hydrodynamic size of compound 3 from 400 nm to 40 nm in the presence of Cu2+ ions confirmed the disaggregation with a decrease in emission intensity. Compound 3 was also employed as a Cu2+ ions recognizer in different collected samples with good percentage recovery. [ABSTRACT FROM AUTHOR]

• A novel Schiff base was synthesized and prepared for the detection of Cu2+, F-, and CN- ions using CH 3 CN as the medium. • The chemosensor exhibits a red shift in the presence of Cu2+, F-, and CN- ions. • A naked eye color change from colorless to faint yellow was observed in the presence of F-, and CN- ions. • The binding ratio (1:1) was determined by Job's plot between the chemosensor and ions. The development of selective chemosensor for the detection of detrimental analytes in the environment is crucial due to their catastrophic effects. In this study, a novel Schiff base derived from naphthalimide and salicylaldehyde was designed and prepared for the detection of Cu2+, F-, and CN- ions in CH 3 CN as medium. The chemosensor exhibits a red shift in the presence of Cu2+, F-, and CN- ions accompanied by naked eye color change in the presence of F- and CN- ions. On the other hand, a "turn-off" response was observed in the presence of ion Cu2+, F-, and CN- ions in the fluorescent spectrum. The good anti-interference characteristics, strong binding, and low limit of detection (LOD) of the chemosensor revealed its sensitivity against Cu2+, F-, and CN- ions i.e. 1.25 × 10-5 M, 1.07 × 10-6 M, and 0.98 × 10-6 M, respectively. The binding ratio (1:1) was determined by Job's plot between the chemosensor and ions. In addition, the binding of ions with the chemosensor was proposed which was further supported by time-dependent density functional theory (TD-DFT) and IR spectrum data. [Display omitted] [ABSTRACT FROM AUTHOR]

• Interplay of ESIPT, ICT and AIEE phenomena on single platform was observed. • Mixed aqueous medium was used for the sensing of F − and P2O74− ions. • The lowest detection limits for F − and P2O74− ions were calculated to be 41 nM and 23 nM. • Aggregation-disaggregation process of probe 1 and probe 1 + F −/P2O74− ions was investigated. In this study, the Schiff base (probe 1) was designed and synthesized, using the moieties of benzothiazole and salicylaldehyde as signaling units. UV–visible and emission spectroscopy has been identified to study interaction of probe 1 with various anions. Absorption bands at 290 and 360 nm for probe 1 (20 µM; CH 3 CN) were observed and two fluorescence peaks at 415 and 540 nm obtained with excitation at 360 nm in CH 3 CN. Probe 1 (20 µM) developed a yellow color in presence of F − and P 2 O 7 4− ions in their tetrabutylammonium salts. For both the ions, the corresponding absorption measurements revealed bathochromic shift of 85 nm. When complexed with anions, emission changes show that probe 1 acts as a " turn-on " sensor. Probe 1 shows detection limit (LOD) of 35.4 and 15.4 nM for F − and P 2 O 7 4−, respectively. 1H NMR titration analyses revealed more about their mode of binding with probe 1. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Naphthalimide-benzimidazole conjugate was studied for selective detection of Hg2+ ions in aqueous medium. • Detection of limit was found to be 7.1 nM. • Mass spectrometry confirmed 2:1 stoichiometry between 9 and Hg2+ ions. • DFT calculations were found in good agreement with experimental results. A chemosensor, 6-(1-cyclohexyl-1 H -benzo[ d ]imidazol-5-yl)-2-(2-(diethylamino)ethyl)-1 H -benzo[ de ]isoquinoline-1,3(2 H)-dione (9), containing 1 H ,3 H -benzo[ de ]isochromene-1,3-dione and 1-cyclohexyl-1 H -benzo[ d ]imidazole moieties has been designed and found to be selective towards Hg2+ ions over-tested wide-range of metal ions. Compound 9 shows the absorption and emission peaks at 370 nm and 540 nm, respectively. The addition of Hg2+ ions to compound 9 (20 μM; H 2 O, p H = 7.4) prompted the formation of a 2:1 ligand–metal complex, 9 -Hg2+, which shows a significant blue-shifted emission enhancement to 495 nm, due to the mechanism of ligand to metal charge transfer. The formation of compound 9 and Hg2+ ions complex has also been confirmed through mass spectrometry and 1H NMR titrations. The photophysical properties of the compound and its complex corroborated with Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TDDFT) calculations. [ABSTRACT FROM AUTHOR]

Benzophenone azine based schiff base exhibiting AIE and ESIPT phenomenon has been synthesised and studied the photophysical behaviour towards detection of Al 3+ ions. The results showed that compound 2 exhibit feeble excited state intramolecular proton transfer emission in CH 3 CN and undergo aggregation induced emission in >70% H 2 O-CH 3 CN. The compound 2 shows significant hydrodynamic diameter change from 20 nm to 200 nm upon increasing the H 2 O volume ratio in CH 3 CN. Compound 2 shows colorimetric and “ off-on ” emission response for Al 3+ , with detection limit of 2.7 × 10 −7  M in CH 3 OH. The association of compound 2 to Al 3+ also causes restriction in intramolecular motion induced emission. The hydrodynamic diameter of compound 2 increases from 335 nm to 625 nm in the presence of Al 3+ ion in CH 3 OH. [ABSTRACT FROM AUTHOR]

Thiazolidine based probe 1 has been synthesized for selective estimation of Cu 2+ ions amongst other metal ions viz., Zn 2+ , Co 2+ , Ca 2+ , K + , Ni 2+ , Mn 2+ , Fe 2+ , Hg 2+ , Na + , Pb 2+ , Ba 2+ , Fe 3+ , Al 3+ , Cr 3+ . The probe 1 has opened new absorption channels at 300 nm and 500 nm in the presence of Cu 2+ ions. The ratiometric response has been observed in the presence of Cu 2+ ions due to emission quenching at 425 nm and enhancement at 485 nm that resulted in “ON–OFF–ON” type sensing. The probe 1 has been used to estimate Cu 2+ ions between 50 nM and 15 µM, which is much lower than recommended by WHO in drinking water (30 µM). The probe 1 has also shown selective ratiometric absorption behavior towards CN − ions in CH 3 CN: H 2 O: 1:1. The ratiometric behavior of the probe 1 in the presence of Cu 2+ and CN − ions has mimicked as XOR logic function at λ em 485 nm and YES logic gate at λ abs 300 nm. The sensing mechanisms of the probe 1 toward Cu 2+ and CN − ions have been theoretically supported by DFT and TD-DFT calculations. Probe 1 has been used for its practical aplicability to sense Cu 2+ and CN − through dip coating method. [ABSTRACT FROM AUTHOR]

• The dyad 1 exhibited yellow absorption at 475 nm, and displayed a bright colour change with Cu2+ ions. • The dyad 1.Cu2+ complex showed ratiometric absorption response in CH 3 OH. • Presence of Al3+ and Hg2+ ions to dyad 1 exhibited " turn-on " emission response in CH 3 OH. • Al3+ ions induced hydrolysis of dyad 1 and showed coordination to the reacting unit to cause " turn-on " emission at 445 nm. • Hg2+ ions inhibit the PET phenomenon of dyad 1 and resulted in " turn-on " emission at 355 nm. The development of single molecular chemosensor with chromo-fluorescent properties have advantages of easy and cost-effective analysis. Moreover, designing and synthesizing such chemosensors for multi-metal ions has become a challenge. We have designed a new NBD based dyad with dual channel mode as a chromogenic sensor for Cu2+, and a fluorogenic sensor for Al3+ and Hg2+ ions. The dyad 1 showed the absorption peaks at 475 nm, 440 nm and 320 nm. In the presence of Cu2+ ions, dyad 1 showed an instant colour change from yellow to blue with a redshift of 150 nm to new absorption band at 595 nm. However, the weak emission of dyad 1 at 355 nm showed a " turn-on " response for Hg2+ and Al3+ ions. In the presence of Hg2+ ions, dyad 1 showed emission enhancement at 355 nm. Whereas, the presence of Al3+ ions from 0 to 4 μM, increase in intensity at 355 nm and on further addition of Al3+ ions from 4 to 15 μM, quenching at 355 nm with the concomitant increase in intensity at 445 nm was observed. The detection limit of Cu2+ ions was found to be 17.6 nM, and Hg2+/Al3+ was 20 nM/67.6 nM. Further, the DFT calculation was performed to complement the experimental results. Thus, dyad 1 showed the chromogenic response for Cu2+ and fluorogenic response for Al3+ ions. [ABSTRACT FROM AUTHOR]