Acid-base equilibria were studied for 4-hydroxycoumarin, 7-hydroxy-4-methylcoumarin and their thione derivatives in different media for their ground and lowest energy singlet and triplet excited states. The ethoxylated and/or methoxylated derivatives were also investigated. Characterization involves¯uorescence spectra, quantum yields, lifetimes, phosphorescence spectra, lifetimes, and triplet±triplet absorption spectra. From their pK a values it was found that 4 and 7-hydroxycoumarins are more acidic in their lowest excited singlet states than in S 0. The origin and character of the lowest singlet and triplet excited states is discussed.

Herein, we designed two uorescent Tetrasubstituted Benzene sulfonyl appended Thiacalix[4]arene receptors named PK 1-2 which sensitively and selectively detect Sulfosulfuron among other herbicides and pesticides. The detection limit (LOD) was found to be 0.21 ppm and 0.35 ppm, and the Enhancement constant (Ks) was determined 7.07 X 10 4 M − 1 and 5.55 X 10 4 M − 1 for PK 1 and PK 2 respectively. Using the Non-linear regression method, the Association constant was obtained as 2.1 X 10 4 M − 1 and 2.23 X 10 4 M − 1 whereas the binding ratio was found to be 1:1 for both PK 1-2 respectively. Additionally, the interference studies show the selective nature of receptors for Sulfosulfuron among its sulfonylurea family. To further con rm the binding mechanism computational investigation was carried out, which validates the 1:1 binding ratio. The receptors were found to be recyclable in nature with simple Acid-Base treatment. This new approach of using Supramolecules as uorescent probes for sensitive and selective detection of herbicides are rare in the literature.

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In order to study various environmental pollutants among the class of nitro aromatic compounds, a new and novel sensor derived from a cyclotriveratrylene derivative has been developed which rapidly detects 4-nitrophenol from among the class of nitro aromatic compounds via spectrofluorimetric method. The newly derrivaritized cyclotriveratrylene compound is successfully confirmed by using the available techniques of 1H NMR, 13C NMR and ESI-MS. The newly developed molecule was named 4C7NbF-CTV. The complexation behaviour of 4C7NbF-CTV with various nitro aromatic compounds was studied. In the absorption spectra a shift was observed, which indicated that 4-nitrophenol interact with 4C7NbF-CTV. An enhanced intensity of fluorescence of 4C7NbF-CTV was observed on adding 4-nitrophenol.