Adenine-linked naphthalimide: A case of selective colorimetric as well as fluorometric sensing of F- and anion-activated moisture detection in organic solvents and CO2-sensing

Compounds 1, 2 and 3 with a common strategy of variation of substituent at the 4-position of naphthalimide have been designed and synthesized. Of the three structures, compound 1 has been established as F^- sensor in CH₃CN involving a color change from colorless to pink. The pink color is discharged in the presence of water or any polar protic solvent. By comparison, while compound 3 did not show any response towards anions, compound 2 under identical conditions exhibited color change from light yellow to pink in presence of several basic anions such as F^-, AcO^- and H₂PO₄^-. This emphasizes the importance on structural tuning in establishing a new effective sensor for a particular anion. F^--induced deprotonation of 1 and its reprotonation with water has been employed as the working principle to detect the moisture content in various organic solvents. In addition, F^--activated CO₂ sensing via color and fluorescence changes have been demonstrated using chemosensor 1. Compound 1 and F^- coated paper exhibit color change on heating and cooling. Writing on this 1.F^- coated paper using AcO^- ion as ink and its appearance/disappearance on heating/cooling has been possible successfully.

Simultaneous dual-colour tracking lipid droplets and lysosomes dynamics using a fluorescent probe

After entering a cell, most small molecule fluorescent probes are dispersed in the cytoplasm before they then accumulate in a specific organelle or subcellular zone. Molecules that can enter two or more organelles with high selectivity are all but unknown. In this work, we report a naphthalimide-based fluorescent probe, NIM-7, that allows lipid droplets and lysosomes to be labelled simultaneously and with high specificity. These subcellular entities can then be visualized readily through yellow and red fluorescence, using different excitation and detection channels. NIM-7 allows 3D imaging and quantitative visualizing of lipid droplets and lysosomes. It is also able to track simultaneously the movement of lipid droplets and lysosomes in real-time. We also report here that NIM-7 can be used to image both different cell lines and zebrafish embryos.

Bimodal detection of carbon dioxide using fluorescent molecular aggregates

Fluorescent aggregates of a cyano-substituted phenylenevinylene derivative (R-1) have been used as a bimodal probe for the easy and fast detection of CO₂.

A diquat-containing macrocyclic anion acceptor in pure water

A self-assembled diquat-containing tetracationic macrocycle is obtained in a high yield, which demonstrates its anion recognition ability in pure water.

Unprecedented rearrangement of diketopyrrolopyrroles leads to structurally unique chromophores

Diketopyrrolopyrroles possessing thienyl, furyl and benzofuryl substituents undergo unprecedented skeletal rearrangement in the presence of trimethylsilyl bromide resulting in the formation of thieno[2,3-f]isoindole-5,8-diones and furo[2,3-f]isoindole-5,8-diones. These relatively small dyes possess favorable photophysical properties with the emission maxima within the range of 573-624 nm, large fluorescence quantum yields, moderate sensitivity of emission to solvent polarity and a HOMO-LUMO gap of ca. 1.8 eV.

Selective Recognition of Fluoride by using a Benzobisimidazolium Derivative through Aggregation-Induced Fluorescence

A new benzobisimidazolium derivative (1) bearing four naphthalene moieties was synthesized and demonstrated as an F- ion-selective fluorescent chemosensor. The fluorescence of 1 in acetonitrile (CH3CN) is significantly stronger with F- and acetate (CH3CO2-), but not with other anions (Cl-, Br-, I-, HSO4-, and H2PO4-). The fluorescence of 1 is enhanced selectively with F- in the presence of a small amount of water. Our DFT calculations indicate that the electrostatic interactions between the positively charged benzobisimidazolium moieties and F- play an important role in the formation of stable aggregates. The formation of stable aggregates of 1 with F- in CH3CN is a key step for the selective sensing of F-, and the fluorescence of the aggregates is further enhanced in a mixture of 95 % CH3CN and 5 % water, which can be attributed to the aggregation-induced emission.

Synthesis and application of a new class of D–π–A type charge transfer probe containing imidazole – naphthalene units for detection of F− and CO2

A new class of D–π–A type charge transfer probe, 3 and 4, containing imidazole – naphthalene moieties as donor and acceptor, respectively, has been synthesized via a Suzuki coupling reaction.

Off-On-Off fluorescence behavior of an intramolecular charge transfer probe toward anions and CO2

The photophysical behavior of a newly developed fluorescent probe, tricyanoethylphenyl phenanthroimidazole (TCPPI) has been studied. Upon interaction of different class of anions TCPPI displayed naked-eye sensitive fluorescence "turn-on" response to detect selectively F(-) (0.98μM, 18.62ppb) and CN(-) (1.12μM, 29.12ppb) anions in acetonitrile (MeCN). Job's plot analysis revealed a 1:1 binding stoichiometry between probe and anions. The spectral data analysis and 1H NMR titration studies suggested about the affinity of F(-) and CN(-) anions with moderately acidic -NH fragment of imidazolyl unit of probe through deprotonation and H-bonding interaction. Moreover, the anion activated probe upon interaction with CO2 revived photophysical properties of probe, "On-Off-On" type fluorescence and enabled anion-induced CO2 sensing in the medium.

A fluorescent probe for relay recognition of homocysteine and Group IIIA ions including Ga(iii)

Relay fluorescence recognition of homocysteine and gallium ions was realized by sequential chemodosimeter and chemosensor approaches for the first time.

An efficient ICT based fluorescent turn-on dyad for selective detection of fluoride and carbon dioxide

A new intramolecular charge transfer based fluorescent turn-on ratiometric probe exhibiting high sensitivity for F⁻ and CO₂.

Synthesis and characterization on novel fluorescent sensors for Pd2+/Pd0 with high selectivity

Novel chemosensors based on triaryl 1H-imidazo[4,5-b]pyrazine with high selectivity for palladium (Pd⁰/Pd²⁺) detection have been synthesized simply.

Why vertically π-expanded imidazo[1,2-a]pyridines are weak fluorescence emitters: experimental and computational studies

Two novel π-expanded analogs of imidazo[1,2-a]pyridine are studied by spectroscopic, kinetic and DFT methods. Low fluorescence quantum yield has been attributed to intersystem crossing.

Anion-activated, thermoreversible gelation system for the capture, release, and visual monitoring of CO2

Carbon dioxide (CO2) is an important green house gas. This is providing an incentive to develop new strategies to detect and capture CO2. Achieving both functions within a single molecular system represents an unmet challenge in terms of molecular design and could translate into enhanced ease of use. Here, we report an anion-activated chemosensor system, NAP-chol 1, that permits dissolved CO2 to be detected in organic media via simple color changes or through ratiometric differences in fluorescence intensity. NAP-chol 1 also acts as a super gelator for DMSO. The resulting gel is transformed into a homogeneous solution upon exposure to fluoride anions. Bubbling with CO2 regenerates the gel. Subsequent flushing with N2 or heating serves to release the CO2 and reform the sol form. This series of transformations is reversible and can be followed by easy-to-discern color changes. Thus, NAP-chol 1 allows for the capture and release of CO2 gas while acting as a three mode sensing system. In particular, it permits CO2 to be detected through reversible sol-gel transitions, simple changes in color, or ratiometric monitoring of the differences in the fluorescence features.

A simple BODIPY-aniline-based fluorescent chemosensor as multiple logic operations for the detection of pH and CO2gas

4-Aniline BODIPY dye was developed as a highly sensitive fluorescent chemosensor for the detection of pH and CO₂gas.

Pentacyclic coumarin-based blue emitters – the case of bifunctional nucleophilic behavior of amidines

Esters of coumarin-3-carboxylic acids undergo addition to DBU and DBN leading to the formation of a 6-membered ring.