A simple 1,8-naphthalimide based Schiff base probe NDSM has been designed and synthesized for the specific detection of Fe3+ based on a fluorimetric mode.

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A new family of extended π‐conjugated dihydrobenzopyrazoloquinoline (DBPQ) and dihydroindenopyrazolopyridine (DIPP) molecules were synthesized, and their photophysical and electrochemical properties were studied. The DBPQ derivatives showed significantly higher molar absorption coefficients, and their absorption and emission wavelengths were red‐shifted with respect to those of the corresponding DIPP derivatives in chloroform solution. Dyes with no substitution and methoxy, nitro, and fluoro‐substituted derivatives showed poor dependence on solvent polarity. At the same time, DBPQ and DIPP derivatives with dimethylamino groups exhibited strong solvatochromism in the emission spectra. Due to the presence of a vinyl link with a cylindrical π‐cloud on the donor (dimethylamino group) molecule, they showed efficient positive solvatochromism with high quantum yields on increasing solvent polarity from non‐polar to polar solvents. Aggregation‐induced emission (AIE) properties were also investigated. AIE studies show that the emission of DBPQ and DIPP derivatives in the presence of THF/H2O mixture increased due to aggregation. However, DBPQ and DIPP derivatives were still strongly emissive in the solid state. Dimethylamino substituted derivatives exhibited acidochromism, which was caused by the addition of TFA and pTsA leading to prominent red‐shifts in the emission spectra owing to the protonation at the pyridine segment.

Synthesis of two new and straight forward phenanthridine based fluorophores (PA1 and PA2) have been described. The molecular structure of PA1 and PA2 was confirmed by spectroscopic studies (1 H NMR, 13 C NMR and HRMS). The dyes are further characterized by comprehensive photophysical study, and their data are critically analyzed. The fluorescence properties of these DÀ A chromophores are highly influenced by the position of the hydroxyl substitution and the solvent polarity. These probes exhibited an arsenal of advantageous features such as higher Stokes shift values and appreciable photostability. Compounds PA1 and PA2 are found to be indicating fluorescent ratiometric detection towards primary amines (PAs) with high selectivity and sensitivity. With this background, sensing of PAs was extended to biogenic amines as they have primary amine functionality. As expected, these fluorophores have excellent detection ability towards neurotransmitters, such as dopamine (DA) and serotonin (SN) with a low limit of detection (LOD) such as 1.61 nM and 0.31 nM respectively. The sensing mechanism of the probe PA1 with PAs are based on the nucleophilic addition and confirmed through investigation by 1 H NMR titration, mass analysis and theoretical calculations. Moreover, sensor probe PA1 based test paper strip was developed, which could detect DA conveniently when visualized under 365 nm UV lamp.

We prepared and characterized an array of polarity-sensitive fluorescent dyes (7 and 9a, 9b and 9c). Fluorescent dyes are based on imidazole core, suitably functionalized with a conjugated push-pull system....