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An organic solid-state near-infrared (NIR)-emitter (λem = 738 nm) exhibiting large Stokes shift (Δλ = 293 nm) through the excited-state intramolecular proton transfer phenomenon has been synthesized and characterized. The present discovery points to the possibility of achieving a new family of solid-state NIR emitters starting from simple aldehyde and amine precursors.

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New pyrene and anthracene based copper complexes 4 and 7 respectively were designed, synthesized and characterized. The fluorescence behaviour of both 4 and 7 were evaluated towards nitro aromatics and anions. Both 4 and 7 possess high selectivity for the detection of well-known explosive picric acid (PA) by showing maximum fluorescence affinity. Furthermore, complex 4 showed similar sensing efficiency towards PA at different pH ranges. It was also used for real world applications, as illustrated by the very fast detection of PA from soil samples observed directly by naked eye.

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Using 4-substituted derivatives of phenol-based compartmental Schiff-base hydroxyl-rich ligand, four multifunctional binuclear Zn(II) complexes have been synthesized and characterized. The photophysical properties of these complexes were explored in the solid state, in solutions, and in poly(methyl methacrylate) (PMMA) matrix, which revealed their good potential as tunable solid state emitters. Some of these complexes acted as efficient catalysts for the transesterification of esters and canola oil showing their potential in biodiesel generation. Mechanistic investigations using ESI-MS revealed that the transesterification catalyzed by these complexes proceeds through two types of acyl intermediates.

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Benzimidazole based compound 3 is designed and synthesized. The compound 3 is evaluated as fluorogenic sensor for metal ions in mixed aqueous solutions. Among all the metal ions tested, the compound 3 selectively senses Zn(2+) ions. The imine bond of 3 gets cleaved by Zn(2+) ions. Thus, 3 behave as 'turn on' fluorescent chemodosimeter for Zn(2+) ions with limit of detction in micromolar range. Furthurmore, we demonstated that 3 can detect Zn(2+) ions in cells of Allium cepa. Graphical Abstract Benzimidazole based ligand 3 is designed and synthesized which behave as chemodosimeter for Zn(2+) ions. We further demonstrated that 3 can detect Zn(2+) ions in cells of Allium cepa.

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New carbazole based AIEE material is synthesized with fluoro group which shows ESIPT induced AIEE in H2O:THF (80:20, v/v). The material selectively recognizes Cu(2+) and CN(-) ions in contrasting modes with detection limits of 5 × 10(-6)Mol L(-1) and 12×10(-5)Mol L(-1) respectively and acts as a dual action chemosensor. The recognition of copper has also been observed in human serum, thus facilitating the detection of increased level of free Cu(2+) ions and its quantification in human serum.

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Based on the mechanism of hydrolytic cleavage of Schiff bases, a 1-aminopyrene based fluorescent chemodosimeter, 3, is reported for the selective detection of Nb(5+) ions in solution. Among the 21 metal ions tested, the chemodosimeter shows a selective fluorogenic 'turn-on' response toward Nb(5+) ions in mixed aqueous media.

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New melamine based ligand with pyrene as a fluorophore is synthesized and characterized. The sequential addition of Au(3+) ions and ascorbic acid to the solution of in EtOH-H2O (9.5 : 0.5 v/v) generates gold microparticles (AuMPs). However, the particle size distribution and fluorescence behaviour on sequential additions are different and contribute to the construction of a new logic based molecular dual channel keypad lock system.

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The zinc complex of a new triphenylene based receptor is evaluated for its anti-oxidant activity which is better in comparison to that of commercially available anti-oxidants.

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New hetero-oligophenylene derivative (2) was synthesized which exhibits aggregation-induced emission enhancement (AIEE) in H(2)O/THF (80:20). The aggregates serve as a biological probe for three different proteins, that is bovine serum albumin (BSA), cytochrome c, and lysozyme, and DNA in contrasting modes. Further, among 29 metal ions tested, the contrasting fluorescence behavior of aggregates of 2 is observed with only Pb(2+) and Pd(2+) ions. Multiple output logic circuits based upon the fluorescence behavior between BSA and cytochrome c and between Pb(2+) and Pd(2+) ions are constructed.

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A new pentaquinone-based chemosensor armed with phenolic moieties has been synthesized. The fluorescence behaviour of the chemosensor in the presence of different chemical inputs mimics the functions of a digital encoder.

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Synthetic strategies are described to synthesize the calix[4]arene diamine 4 of partial cone (paco) conformation, which on condensation with 9-anthracene carbaldehyde forms the chemosensor 5 in paco conformation. The chemosensor 5 undergoes fluorescence enhancement in the presence of Ni(2+) ions.

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New thiacalix[4]crown derivatives 4 and 5 of 1,3-alternate conformation possessing anthracene and quinoline moieties respectively were synthesised and examined for their cation recognition abilities toward different cations by fluorescence spectroscopy. Selective optical recognition with fluorescence amplification was observed for Fe(3+)/K(+) and Hg(2+)/K(+) in chemosensors 4 and 5 respectively. Further it was observed that the formation of 4·Fe(3+) complex triggers the decomplexation of K(+) ion. Similar allosteric behaviour between Hg(2+) and K(+) was observed in chemosensor 5.

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A new fluorescent chemosensor 3 based on calix[4]arene of partial cone conformation possessing dansyl moieties has been synthesized. The chemosensor demonstrates selective optical recognition of Hg(2+) ions in mixed aqueous media and mimics the operation of a traffic signal based on the R-S Latch Logic circuit with pH, Hg(2+) and Cl(-)/Br(-)/I(-) as chemical inputs.

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A new bispyrenyl azadiene derivative has been synthesized and examined for its cation recognition abilities toward different cations. The ligand shows strong affinity for Hg(2+) ions over other cations such as Cu(2+), Pb(2+), Zn(2+), Ni(2+), Cd(2+), Ag(+), K(+), Na(+) and Li(+). An "Off-On" type of fluorescent behaviour was observed with simultaneous presence of Cu(2+) and Hg(2+) ions. An ion selective electrode (ISE) is also formed which showed excellent selectivity to Hg(2+) over all the other cations tested. The lower limit of detection is 7.08 x 10(-6) M.

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A chemosensor based on the thiacalix[4]arene of 1,3-alternate conformation has been designed and synthesized. The binding behavior of this chemosensor has been studied toward different metal ions by fluorescence spectroscopy, and it was observed that the chemosensor selectively senses Cu(2+) ions. The chemical inputs of Cu(2+) and F(-) in a sequential manner generate an output which mimics the functions of a security keypad lock.

RESUMEN

A new fluorescent chemosensor based on the calix[4]arene of partial cone conformation possessing a dansyl moiety has been synthesized. The chemosensor demonstrates selective optical recognition of Hg(2+) and Cu(2+) in two contrasting modes. The receptor exhibited ratiometric sensing of Hg(2+) and "ON-OFF" type of fluorescence behavior in the presence of Cu(2+). The compound behaves as a fluorescent molecular switch upon chemical inputs of Hg(2+) and Cu(2+) ions.