Naphthalimide-based new architecture for fluorescence turn-on sensing of Cu2+ and colorimetric detection of F-/CN.

A new molecular structure 1 has been developed on naphthalimide motif. The amine and triazole binding groups have been employed at the 4-position of naphthalimide to explore the sensing behavior of molecule 1. Single crystal x-ray diffraction and other spectroscopic techniques confirm the identity of 1. Compound 1 exhibits high selectivity and sensitivity for Cu2+ ions in CH3CN. The binding of Cu2+ shows âˆ¼ 70-fold enhancement in emission at 520 nm. The binding follows 1:1 interaction and the detection limit is determined to be 6.49 × 10-7 M. The amine-triazole binding site in 1 also corroborates the detection of F- through a colour change in CH3CN. Initially H-bonding and then deprotonation of amine -NH- in the presence of F- are the sequential steps involved in F- recognition with a detection limit of 4.13 × 10-7 M. Compound 1 is also sensible to CN- like F- ion and they are distinguished by Fe3+ ion. Cu2+-ensemble of 1 fluorimetrically recognizes F- among the tested anions and vice-versa. The collaborative effect of amine and triazole motifs in the binding of both Cu2+ and F-/CN- has been explained by DFT calculation.

New Cyanostyrylcopillar[5]arene Derivative: Synthesis, Photophysical Study, Chromogenic Detection of Aliphatic Amines, and Biofilm-Antibiofilm Activity.

The synthesis, characterization, and application of a new cyanostyrylcopillar[5]arene 1 is reported. Single-crystal X-ray diffraction and other spectroscopic techniques confirm the identity of the new copillar 1. The X-ray diffraction study reveals that the copillar 1 exhibits a 1D supramolecular chain in the solid state involving π···π interactions along the crystallographic c-axis and 1D chains are further connected by interchain C-H···π interactions to establish 2D supramolecular layers within the crystallographic bc-plane. 2D supramolecular chains on further packing introduce a 3D structure with void spaces filled with hexane molecules. Through minimal deviation in the dihedral angle, the cyano-substituted ethylenic group in 1 shows a conjugation with the phenolic -OH, favoring intramolecular bond conjugation (ITBC) and colorimetrically detects the aliphatic amines over aromatic amines in CH3CN. Among the aliphatic amines, tertiary amines are differentiated from primary and secondary amines by the naked eye through color change. Both in solution and solid states, 1 displays vapor phase detection of volatile aliphatic amines. Antibacterial activity analysis shows that while 1 exhibits the antibiofilm action against Gram-positive pathogenic bacteria, Staphylococcus aureus, it promotes biofilm formation by Gram-negative pathogenic bacteria, Pseudomonas aeruginosa.

Nanoarchitectonics with Positionally Isomeric Coumarin Carbamates: Structure-Gelation Study, F- Recognition, Dye Removal and Excellent Oil-Spill Recovery.

Coumarin carbamates with cholesteryl group 1 and 2 have been designed, synthesized and characterized. The isomeric compounds show different gelation behaviors in organic solvents such as toluene and CH3 CN. Rheological studies reveal the different viscoelastic properties of the gels. Gels of the isomers differ in morphology. While an intertwined fibre-like structure is noted for the toluene gel of 1, rod like fibres are observed for toluene gel of 2. The positional alteration of carbamate group around coumarin changes the polarity of the isomers and hence influences the packing of molecules to establish different 3D networks for gel formation as explained by DFT study. Gels of the isomers show multiple applications with different attributes. Toluene gel of 1 is found to be F- -responsive and undergoes gel-to-sol phase transition due to the disruption of intermolecular hydrogen bonding through deprotonation. Under the condition, toluene gel of 2 is anion stable. Compound 1 also shows measurable interaction with F- over other anions in CH3 CN as interpreted by UV-vis and emission spectral changes. Based on phase-selective gelation (PSG) property, both 1 and 2 is deployed to remove cationic dye from water. Further, only gelator 2 is useful for oil spill recovery, whereas isomer 1 is not suitable in this regard.

A naphthalimide-linked new pyridylazo phenol derivative for selective sensing of cyanide ions (CN-) in sol-gel medium.

Napthalimide-linked pyridylazo derivatives 1 and 2 have been designed and synthesized. Compound 1 acts as a gelator in DMF-H2O (1 : 1, v/v). The brown gel is photostable and shows good viscoelastic properties. The value of G' is almost 10 times higher than that of G'' over the entire range of frequencies at a constant strain of 1%. The SEM image shows the presence of densely stacked flakes. In comparison, compound 2, devoid of free phenolic -OH, does not show gelation properties under identical conditions. However, the brown gel of 1 shows selective sensing of CN- ions over a series of anions involving phase change through the deprotonation mechanism. While the brown gel of 1 is selectively ruptured in the presence of CN- to the sol, compound 1 in solution shows measurable UV-vis and emission changes in the presence of CN- over the other anions and validates the visual sensing of CN-. In the test-kit application, the yellow paper strip turned into pinkish-red upon contact with CN-.

Anthracene labeled poly(pyridine methacrylamide) as a polymer-based chemosensor for detection of pyrophosphate (P2O74-) in semi-aqueous media.

To develop fluorophore-labelled pyridinium-based macromolecular architectures for fluorometric and colorimetric detection of anions, two polymers P1 and P2 are synthesized. Linear polymer P1 and cross-linked polymer P2, prepared from N-methacryloyl-3-aminopyridine monomers via free radical polymerization followed by quaternization of the pyridine ring nitrogen with anthracene as a fluorescent marker, have been successfully employed in anion sensing. P1 exhibits excellent sensing of HPPi in aqueous DMSO. In addition to the enhancement of fluorescence emission of the anthracene moiety, P1 exclusively shows excimer/exciplex emission in the presence of HPPi over other anions and exhibits selectivity to HPPi with a detection limit of about 1.63 ppm. Cross-linked P2 exhibits naked-eye detection of PPi/HPPi over other anions studied via indicator displacement assay (IDA).

Effect of Substitution at Amine Functionality of 2,6-Diaminopyridine-Coupled Rhodamine on Metal-Ion Interaction and Self-Assembly.

2,6-Diaminopyridine-coupled rhodamines 1 and 2 have been synthesized, and the effect of substitution on amine functionality toward metal-ion interactions and self-assembly is thoroughly investigated. Both the compounds effectively recognize different metal ions of biological significance fluorimetrically and colorimetrically with a high degree of selectivity and sensitivities. While compound 1 is sensitive to Fe3+ ions, compound 2 is responsive to both Fe3+ and Al3+ ions in aqueous CH3CN (4/1, v/v; 10 mM tris HCl buffer, pH 6.8). The sensing mechanism involves the metal-ion chelation-induced spirolactam ring opening of the rhodamine scaffold that results in both color and fluorescence changes, while the extent of interactions with the metal ions is truly governed by the chemical structure of the compounds. Both 1 and 2 are proficient in detecting Fe3+ and Al3+ ions in human lung cancer cells (A549). As new findings, unlike 1, compound 2 formed a faint pink gel in the toluene-hexane mixture solvent (1:1, v/v), and the gel state of 2 selectively recognizes Ag+ ions by exhibiting a phase change from gel to purple sol. Experimental findings establish the role of the formamide moiety in forming the self-assembly.

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.

Dosimetric Chromogenic Probe for Selective Detection of Sulfide via Sol-Gel Methodology.

Dinitrobenzenesulfonyl-protected naphthyl azo pyridine conjugate 1 has been designed and synthesized. Compound 1 acts as a nongelator in dimethyl sulfoxide (DMSO)-H2O (1:1, v/v) while its hydroxy counterpart 2 can form a nice gel in the same solvent. In the presence of sulfide, compound 1 undergoes rapid sulfonate ester hydrolysis and results in the formation of azo-naphthol 2 that responds in instant gelation. Such deprotection was extremely selective to sulfide; other analytes did not show measurable response. The sensing mechanism has been established by various spectroscopic techniques. Compound 1 in solution (DMSO-H2O) also shows a selective response toward sulfide over a series of other anions with a color change. Preparation of test kit with compound 1 allows detection of sulfide in solution and vapor states. Such kind of dosimetric sensing of chemical analytes by improvising the protection/deprotection of functional groups in gelator structure is rare in the literature, and to the best of our knowledge, this is the first example of a stimuli-responsive low-molecular-weight gelator which dosimetrically senses sulfide over other nucleophilic substrates.

Cholesterol-Appended Benzimidazolium Salts: Synthesis, Aggregation, Sensing, Dye Adsorption, and Semiconducting Properties.

A series of cholesterol-appended benzimidazolium salts 1-9 have been designed and synthesized. They have been explored in gel chemistry. The gelation of the benzimidazolium salts is dependent on the nature of the counteranions. In addition, the gelation behavior of the gelators is linked with the presence of both π-stacking and cholesteryl motifs. Whereas bisbenzimidazolium salt 2 forms a gel in dimethylsulfoxide/H2O (1:1, v/v) itself, under similar conditions, monobenzimidazolium salts 4 and 6 exhibit gelation in the presence of F- ions and validate the visual sensing of F-. As an application, the gel phase of 2 efficiently removes toxic dyes from waste water. Furthermore, all gels show thermally activated semiconducting property within a wide voltage window.

α-Amino Acid Derived Benzimidazole-Linked Rhodamines: A Case of Substitution Effect at the Amino Acid Site toward Spiro Ring Opening for Selective Sensing of Al3+ Ions.

α-Amino acid derived benzimidazole-linked rhodamines have been synthesized, and their metal ion sensing properties have been evaluated. Experimentally, l-valine- and l-phenylglycine-derived benzimidazole-based rhodamines 1 and 2 selectively recognize Al3+ ion in aqueous CH3CN (CH3CN/H2O 4/1 v/v, 10 mM tris HCl buffer, pH 7.0) over the other cations by exhibiting color and "turn-on" emission changes. In contrast, glycine-derived benzimidazole 3 remains silent in the recognition event and emphasizes the role of α-substitution of amino acid undertaken in the design. The fact has been addressed on the basis of the single-crystal X-ray structures and theoretical calculations. Moreover, pink 1·Al3+ and 2·Al3+ ensembles selectively sensed F- ions over other halides through a discharge of color. Importantly, compounds 1 and 2 are cell permeable and have been used as imaging reagents for the detection of Al3+ uptake in human lung carcinoma cell line A549.

Nano-Pelargonidin Protects Hyperglycemic-Induced L6 Cells against Mitochondrial Dysfunction.

Nano-encapsulation of several natural products has become an important tool in enhancing the bioavailability of some modern drugs against many diseases. Pelargonidin is an anthocyanidin found in many fruits and vegetables. Pelargonidin is loaded with poly-lactide-co-glycolic-acid, a non-toxic biodegradable polymer, to produce nano-pelargonidin. Size, morphology, zeta potential, and planar uniformity of formulated nano-pelargonidin were determined by atomic force microscopy and dynamic light scattering. The time required for cellular entry, folds of nano-pelargonidin, and drug encapsulation efficiency of poly-lactide-co-glycolic-acid were also ascertained. Relative functional efficacy of nano-pelargonidin and pelargonidin was evaluated by examining markers such as pyruvate kinase, glucokinase, calcium ion level, ATP/ADP ratio, mitochondrial membrane potential, cytosolic release of mitochondrial cytochrome-c, and structural analysis of mitochondrial DNA in controlled and experimental sets of alloxan-induced hyperglycemic L6 cells. Expressions of mitochondrial apoptotic proteins, such as bcl2 and caspase3, and glucose signalling cascades, such as GLUT4, IRS1, IRS2, and PI3, were analyzed. Nano-pelargonidin at a nearly 10-fold reduced dose significantly enhanced protection, presumably due to its smaller size, ability of faster entry, and drug delivery at target-specific sites. Thus, nano-pelargonidin can be used in formulating protective drugs for therapeutic management of mitochondrial dysfunction often encountered in diabetic conditions.

New Six-Membered pH-Insensitive Rhodamine Spirocycle in Selective Sensing of Cu2+ through C-C Bond Cleavage and Its Application in Cell Imaging.

A new rhodamine-based chemosensor 1 with a six-membered spirocyclic ring has been synthesized, which exhibits excellent pH stability and shows selective "turn-on" fluorescent detection of Cu2+ ions over a series of other metal ions including Cu+ ions. The expansion of spirocycle improves the stability and selectivity of the chemosensors in sensing of metal ions. Till today only few rhodamine structures R1-R5 with thiourea-, hydrazine amide-, or pyrrole-decorated six-membered spirocyclic rings are known that exhibit metal-ion sensing via C-N bond cleavage of the spiro ring. In this context, rhodamine compound that responds to the metal ion through C-C bond cleavage of the six-membered spiro ring is completely unknown. The present example is a first-time report that demonstrates selective sensing of Cu2+ ions through C-C bond cleavage over the conventional existing systems in the literature. The chemosensor 1 is cell permeable and can detect Cu2+ in live cells using confocal microscopy in the biologically relevant pH range with high photostability.

Pyridinium-based tripodal chemosensor in visual sensing of AMP in water by indicator displacement assay (IDA).

A simple pyridinium-based tripodal chemosensor, 1, effectively recognizes AMP over ATP and ADP through indicator displacement assay (IDA) technique in water at pH 6.4. The good recognition of 1 is due to the better accommodation of AMP at the core of 1 as well as functional interaction involving hydrogen bonding and charge-charge interaction. The sensor 1 also recognizes intracellular AMP.

O-tert-butyldiphenylsilyl coumarin and dicoumarol: a case toward selective sensing of F- ions in organic and aqueous environments.

O-tert-Butyldiphenylsilyl coumarin 1 and 2 dicoumarol have been synthesized and their anion binding properties have been examined in organic and aqueous organic solvents. Compound 1 senses F(-) selectively over the other anions examined in CHCl3 by exhibiting a greater increase in emission. In contrast, compound 2 shows similar selectivity in CHCl3 giving ratiometric change in emission as well as color. In addition, both 1 and 2 are capable of detecting F(-) in water ensuing the cleavage of Si-O bonds. They also show cell permeability and demonstrate their abilities to detect F(-) in a living system.

Ortho-phenylenediamine-based open and macrocyclic receptors in selective sensing of H2PO4(-), ATP and ADP under different conditions.

Ortho-phenylenediamine-based open and macrocyclic receptors have been designed and synthesized. The open receptor 1 and the macrocyclic receptor 2 fluorimetrically distinguish H(2)PO(4)(-) from the other anions examined in CH(3)CN with appreciable binding constant values. As practical applications, they are also sensible to nucleotides in aq. CH(3)CN (1 : 1, v/v). The receptor 1 shows significant emission change upon complexation of ATP and ADP. ADP is selectively distinguished by a ratiometric change in emission. In contrast, the macrocyclic receptor 2, under similar conditions, shows good binding with ATP over the others.

Cholesterol appended pyridinium ureas: a case of gel making and breaking for selective visual readout of F-.

Cholesterol appended pyridinium ureas 1 and 2 have been designed and synthesized. The unsymmetrical urea-based chemosensor 1 fluorimetrically distinguishes F(-) from the other anions examined in both CH(3)CN and DMSO with appreciable binding constant values. The pyridinium - based symmetrical compound 2 acts as a low molecular weight gelator (LMWG) in CHCl(3) and is capable of detecting F(-) visually by breaking the gel. On the contrary, the chemosensor 1 in DMSO in the presence of tetrabutylammonium fluoride undergoes a change from sol to gel state that produces an unambiguous visual readout of F(-).

Pyridinium-based fluororeceptors as practical chemosensors for hydrogen pyrophosphate (HP2O7(3-)) in semiaqueous and aqueous environments.

The pyridinium-based fluororeceptor 1 and the sensor bead 2 recognize hydrogen pyrophosphate effectively through the 'Indicator Displacement Assay' (IDA) technique over a series of other anions in aq CH(3)CN (CH(3)CN/H(2)O = 4:1, v/v, pH = 6.5). The sensor bead 2 is also capable of sensing the same anion selectively in pure water.

A rhodamine appended tripodal receptor as a ratiometric probe for Hg2+ ions.

A new rhodamine appended tripodal receptor 1 has been designed and synthesized. The receptor selectively recognizes Hg(2+) ions in CH(3)CN-water (4:1, v/v; 10 µM tris HCl buffer, pH 7.0) by displaying a ratiometric change in emission. Additionally, the visual detection is possible by a sharp change in color. The receptor shows in vitro detection of Hg(2+) ions in human cervical cancer (HeLa) cells.

Pyridinium-based symmetrical diamides as chemosensors in visual sensing of citrate through indicator displacement assay (IDA) and gel formation.

The design and synthesis of pyridinium-based symmetrical diamides 1 and 2 along with their anion binding studies through 'indicator-diplacement assay' are reported. Both the chemosensors effectively respond in in CH(3)CN-H(2)O (4 : 1 v/v) at pH = 6.3 for the selective naked-eye detection of citrate. Additionally, chemosensor 2 (c = 6.29 × 10(-3) M) forms a stable gel only with citrate in CH(3)CN, which validates its visual sensing.

(rac)-1,1'-binaphthyl-based simple receptors designed for fluorometric discrimination of maleic and fumaric acids.

(rac)-1,1'-Binaphthyl-based simple receptors 1 and 2 have been designed, synthesized and studied theoretically. The receptors utilize naphthyridine as the binding motifs for complexation of dicarboxylic acids in CHCl(3). The emission of the BINOL moiety was monitored experimentally to ascertain the selectivity and sensitivity of the receptors. Receptor 1 distinguishes maleic acid from isomeric fumaric acid by exhibiting different fluorescence behavior and demonstrates stronger binding in the excited state. Modulation of the binding sites of 1 leads to a new receptor structure 2, which was found to be less efficient in distinguishing maleic from fumaric acid, fluorometrically. Both 1 and 2 also recognize other hydroxy di- and tricarboxylic acids. The binding interactions were monitored by (1)H NMR, fluorescence and UV-vis spectroscopic methods. Structures of apo-hosts, guests and host-guest complexes were determined using force-field based conformational searching. Low energy ensembles were grouped into geometrically similar families, and low energy structures from each family were verified using B3LYP/6-31G*/PB-SCRF(CHCl(3)) calculations. The atomistic calculations provide insight into the differential dicarboxylic acid binding behavior of receptors 1 and 2.