Semi-aqueous Medium Research Articles

TICT fluorescent probe for Al3+: Sequential detection of PPi, ATP and ADP in semi-aqueous medium and real-life applications.

A ditopic Schiff base ligand, H2L has been synthesized and characterized by all spectroscopic techniques. It is highly selective and specific towards Al3+ in semi aqueous medium (DMF/H2O mixture) by exhibiting a drastic increase in the fluorescence intensity. The emission studies, spectroscopic data, life time and quantum yield results have been used to understand its binding mode, explore its specificity and establish its efficacy. The intensity difference is remarkable in physiological pH range. Due to its reversible behavior this ditopic fluorescent chemosensor can be used multiple times to make it cost effective. Detection limit for this chemosensor was found to be 0.65μM. Experiments with TLC plates show that it can be used as a practical and portable sensor for studying environmental samples in real life. The L-Al3+ complex generated in the solution acts as a sensor to sequentially detect pyrophosphate groups present in inorganic pyrophosphates, ATP and ADP among other anions by turning off the fluorescence. Inhibit logic gate and its corresponding truth table has been developed to aid in further exploiting its multidimensional applications.

Azo dye featuring triazole appended organosilicon multifunctionalized sensor: Paradigm for detection of Cu+2and Fe+2 ions

This work embodies the derivatization of functional organic fragments with triethoxysilyl motif to afford organotriazole silanes (5a-5e) using copper-catalyzed alkyne azide cycloaddition reaction under strictly anhydrous conditions. Furthermore, when compound 5e was employed for the sensorial aptitude towards wide spectrum of transition metal ions, UV–Vis absorption analysis substantiates the selective binding with Fe2+ and Cu2+ ions. This sensor unveils unassailable binding ability, high sensitive and selectivity in semi aqueous media. LOD values for recognition of Fe2+ and Cu2+ ions were estimated to be 0.11 μM and 0.12 μM respectively and on the basis of the Job's plot, the feasible binding approach of the receptor with these ions have also been proposed.

Organometallic Chemistry in Industry: A Practical Approach

Mercury Contamination represents a major environmental and health concern for which new eco-friendly solutions are desired. Azide–alkyne cycloaddition and Claisen Schmidt reaction were attempted to trigger a flavanone based bis-siloxyl hybrid materials. The synthesized bis-organosilicon compound was used as receptor for recognition of Hg (II) ions in semi aqueous medium. The presence of silicon makes the receptor impetus and has benefits in the field of nanochemistry. All the final compounds were recognized by spectroscopic techniques like IR, NMR and further corroborate by mass spectrometry.

Quinoline-ampyrone functionalized azo dyes as colorimetric and fluorescent enhancement probes for selective aluminium and cobalt ion detection in semi-aqueous media

Two azo dyes (E)-4-((6-hydroxyquinolin-5-yl)diazenyl)-1,5-dimethyl-2-phenyl-1H-pyrazol-3(2H)-one (6QD) and (E)-4-((8-hydroxyquinolin-5-yl)diazenyl)-1,5-dimethyl-2-phenyl-1H-pyrazol-3(2H)-one (8QD) have been designed and synthesized. The structure of both dyes was confirmed by FTIR, NMR spectroscopy and mass spectrometry. The absorption and emission spectral analysis of 6QD and 8QD confirmed their selective turn-on behaviour towards Al3+ and Co2+ ions, respectively in MeOH:H2O (v/v = 1:1, HEPES buffer, pH = 7.2) at room temperature. The emission intensity of 6QD enhanced remarkably by 148-fold upon binding with Al3+ ion due to chelation-enhanced fluorescence (CHEF) effect and inhibition of photoinduced electron transfer (PET) phenomenon in the molecule. Emission behaviour of 8QD operates on CHEF and intramolecular charge transfer (ICT) mechanisms in presence of Co2+ ion which induced 26-fold enhancement in emission intensity of 8QD. Colorimetric studies showed prominent visual response for Al3+ and Co2+ ions allowing the real time analysis of these ions in their corresponding solutions. Other coexisting metal ions do not interfere with the detection of these metal ions. Job’s plot analyses revealed 1:1 binding stoichiometry for complexes 6QD-Al3+ and 8QD-Co2+. Association constants of complexes 6QD-Al3+ and 8QD-Co2+ were found to be 1.2 × 106 and 4 × 106 M−1, respectively which suggest good association of both probes with respective metal ions. The limit of detection of 6QD and 8QD was determined to be 1 × 10−8 M and 9.1 × 10−8 M respectively, which demonstrates the high sensitivity towards corresponding metal ions. Reversible studies confirmed that both probes 6QD and 8QD could be used as secondary sensor for EDTA2− anion. Furthermore, pH based absorption studies revealed that 6QD and 8QD can act as naked eye colorimetric probe for detection of hydroxyl ions at pH > 9.

Rationally designed imidazole derivative as colorimetric and fluorometric sensor for selective, qualitative and quantitative cyanide ion detection in real time samples.

A new imidazole derivative of 1,2-diaminoanthraquinone and fluorene-2-carboxaldehyde was designed as a sensor B2 to selectively detect the cyanide (CN-) ion through colorimetric and/or fluorometric methods. The photochemical characterizations of sensor B2 were tested using absorption and emission spectral studies in CH3CN-H2O (8:2) semi-aqueous medium. An excited state proton transfer process (ESIPT) was proved by theoretical and spectral studies. The colorimetric and fluorescence detection limit of CN- ion was found to be 5.3×10-6M and 4.11×10-8M, respectively. 1H NMR titration, electrochemical and DFT studies were supported the removal of -NH proton from B2. In order to utilize this sensor in real-time applications, we developed a test cassette which is coated with sensor B2 detected the presence of CN- ion in the food sample with endogenous cyanide ion.

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).

A phenanthro[9,10-d]imidazole-based optical sensor for dual-responsive turn-on detection of acidic pH and Cu2+ in chicken blood and living cells

A phenanthro[9,10-d]imidazole-based organic optical sensor (PIQPy) for dual-responsive turn-on detection of both acidic pH and Cu2+ in semi-aqueous media was described. PIQPy was weak fluorescence (nearly turn-off) in pure ethanol solution but exhibited typical aggregation-induced emission phenomenon (moderate turn-on) in water/EtOH mixture. More interestingly, PIQPy further displayed a dual enhancement (strong turn-on) for both acidic pH and Cu2+ with highly fluorescent intensity. pKa value of PIQPy for pH responding was 6.89, which suggests that PIQPy was an ideal biosensor for pH sensing. In addition, the super lower limit of detection for Cu2+ were found to be 37.69 nM which also nearly 500-fold lower than Cu2+ concentration in blood (15.7–23.6 μM). Therefore, PIQPy was successfully used to detect Cu2+ in chicken blood. Furthermore, these dual-responsive turn-on signals to both acidic pH and Cu2+ were also successfully implemented in HeLa cells, which proved that PIQPy was capable of imaging pH fluctuations and simultaneous Cu2+ in living cells.

Isophthaloyl-Based Selective Fluorescence Receptor for Zn (II) Ion in Semi-Aqueous Medium.

A novel Isophthaloyl-based symmetrical (12E,21E)-N1',N3'-bis(2-hydroxybenzylidene) isophthalohydrazide, receptor (1) was synthesized and characterized using various spectroscopic technique. The reorganization ability of receptor (1) was evaluated in semi-aqueous medium and shows significant enhancement in fluorescence intensity for Zn (II) ion over various metal ions in CH3CN:H2O (1:1, v/v). The 1:2 binding stoichiometry between receptor (1) and Zn (II) ion was established using Job's plot and the proposed complex structure was calculated by applying Density Functional Theory (DFT) method. The binding constant (Ka) of receptor (1) with Zn (II) ion was established with the Benesi-Hildebrand plot, Scatchard and Connor's plot and the values are 1.00 × 104M-1, 1.05× 104M-1 and 1.05× 104M-1 respectively. The limit of detection (LOD) and limit of quantification (LOQ) of receptor (1) and Zn (II) ion was 0.292μM and 0.974μM respectively. The binding mode was due to photo-induced electron transfer (PET) and the coordination of Zn (II) ion with C = N hydroxyl group of receptor (1). Electrochemical analysis of metal free receptor (1) and with Zn (II) ion also confirmed the formation of complex.

A novel chromone based colorimetric sensor for highly selective detection of copper ions: Synthesis, optical properties and DFT calculations

In this work, a new chromone based colorimetric sensor (ChrCS) was developed for highly selective detection of copper ions in semi-aqueous media. Evaluation of color and spectral changes displayed by the developed sensor shows that the sensor can be applied to detect copper ions in the presence of other competing metal ions and anions. The developed sensor, which contains biologically active chromone ring, shows excellent selectivity at microlevel for Cu2+ with a color change from colorless to yellow. Job's plot based on spectroscopic data showed the complex formation between ChrCS and Cu2+ ions has the stoichiometric ratio of 1:1 (ChrCS-Cu2+ complex). In addition, the binding constant of the ChrCS to Cu2+ was determined using the Benesi-Hildebrand equation. Furthermore, the test papers of the developed ChrCS were successfully prepared and employed to detect different concentration Cu2+ (10-3 M to 10-7 M) in aqueous solution. Importantly, sensor ChrCS was applied to detect Cu2+ ions in real water samples. To better understand the optical character of ChrCS and the effect of metal ion titration, density functional theory (DFT) calculations at the B3LYP/6-31 + G(d,p) level were performed for ChrCS and its complex ChrCS-Cu2+. Furthermore, on the basis of the Job's plot analysis DFT calculations, and reversible nature of the developed sensor, the sensing mechanism was demonstrated.

A new azo-azomethine sensor for detection of CN- and AcO- anions: Highly selective chemosensor for naked eye detection of sodium diclofenac.

New azo-azomethine sensor, HL, has been synthesized and characterized using standard spectroscopic methods. HL was found to sense CN- and AcO- in DMSO and semi-aqueous media over other anions such as F-, Cl-, Br-, I-, H2PO4- and HSO4-. The anions recognition ability of HL was also evaluated using UV-Vis absorption and 1H NMR spectroscopy. Importantly, HL can detect CN- and AcO- in DMSO even at 0.7 ppm and 1.3 ppm, respectively. The binding stoichiometry between HL and the mentioned anions was found to be 1:1 with binding constants of 8.81 × 103 M-1 and 3.64 × 104 M-1 for CN- and AcO-, respectively. Successfully, HL was used for the detection of sodium diclofenac over the other opiate drugs such as codeine phosphate, noscapine hydrochloride, papaverine hydrochloride, and morphine sulfate. The designed chemosensor has also shown highly promising results for the qualitative and quantitative detection of sodium diclofenac in oral pills.

A novel sulfur-incorporated naphthoquinone as a selective “turn-on” fluorescence chemical sensor for rapid detection of Ba2+ ion in semi-aqueous medium

A sulfur-functionalised analogue of the naturally available 1,4-naphthoquinone (N) has been synthesized and evaluated as a sensitive and highly selective fluorimetric sensor against the environmentally toxic barium (II) ion in a semi-aqueous medium. The host ligand exhibits a distinct enhancement in its native fluorescence in the presence of barium ions in ethanol/H2O (1:1,v/v). Its sensing activity was further corroborated by a minimum interference offered by a diverse array of other competing metal cations during the fluorimetric sensing of barium ions. The stoichiometry of N:Ba2+ ion system was calculated from the Benesi-Hildebrand plot to be 2:1 with a binding constant of 3.29 mM. The detection limit of the potential fluorescence probe N against aqueous barium ions was observed to be 4.22 mM. In conclusion we propose that sulfur-containing naphthoquinone act as a potential turn-on fluorescence sensor for the selective detection of toxic barium ions in semi-aqueous medium.

Fluorescence “turn-on” sensor for highly selective recognition of Cu2+ ion and its application to living cell imaging

A new, bis-thiophene based Schiff base receptor A2 has been synthesized and rationally designed as rapid and highly selective fluorescence sensor for Cu2+ ion in a semi-aqueous medium. Structural characterization of A2 was confirmed by NMR, FT-IR and HRMS spectral techniques. The receptor A2 shows the colorimetric response from yellow to colorless and fluorescence “turn-on” with Cu2+ ions under visible and UV light. Both the UV–Vis and fluorescence studies were confirmed the formation of 1:1 stoichiometry complex with an estimated association constant of 1.07 × 10−5 M−1. The sensor could work in the pH range of 4.0–8.0 without interference in the presence of other interfering ions. The lowest detection limits by colorimetric and fluorescence techniques were found to be 1.18 × 10−7 M and 8.8 × 10−8 M respectively. Further, the probe was applied to image the intracellular Cu2+ ions in the HeLa cell line. The sensing mechanism was studied by ESI-mass analysis and DFT calculations.

Removal of phosphate in presence of interfering sulphate and arsenate by a tripodal thiourea receptor by precipitation through crystallization in semi-aqueous medium

A cyanuric acid platform based tripodal thiourea receptor, L shows encapsulation of phosphate, sulphate and arsenate anions in semi-aqueous medium. Solution phase 1H NMR showed selective recognition of phosphate anion in presence of various anions (e.g. Cl−, Br−, I−, NO3−, HSO4−, CH3CO2− and H2PO4− as TBA salts) in DMSO-d6 at 298 K. L showed partial removal and separation of phosphates from semi-aqueous solution in the presence of interfering arsenate and sulphate via precipitation through crystallization. In the absence of phosphate, L is found to remove/separate arsenate from semi-aqueous medium in presence of sulphate which is the first report of partial removal of arsenate from semi-aqueous medium by a neutral anion receptor. In absence of phosphate and arsenate anions, L could partially remove sulphate anions from mixture of other anions from semi-aqueous solution. All the extracted complexes were characterized by NMR, PXRD, TEM-EDX and Single crystal X-Ray diffraction analysis.

Coumarin-based fluorescent chemodosimeter for selective sensing of hydrazine in semi-aqueous medium

Coumarin-based fluorescent chemodosimeter for selective sensing of hydrazine in semi-aqueous medium

Highly selective CHEF-type chemosensor for lutetium (III) recognition in semi-aqueous media.

A simple phosphoryl quinolone (L) based sensor has been synthesized for the selective recognition of Lu3+ by spectrofluorimetric method. In methanol-water (1:1, v/v), the ligand L exhibits a weak emission peak at 400 nm upon excitation at 280 nm. Upon interaction with various f-metal and other selected metals from s, p, and d-block elements, the fluorescence of L is selectively enhanced in the presence of Lu3+ due to the chelation enhanced fluorescence (CHEF) effects. The quantum yield (φ) of L (φ = 0.063) is enhanced to φ = 0.118 upon chelation with Lu3+ ion. From the titration experiment, the limit of detection (LOD) of sensor L to recognize Lu3+ is estimated down to 24.2 nM, which is much lower than the WHO guidelines (76 μM) in drinking water. The formation of host-guest complexation between L and Lu3+ in 2:1 binding stoichiometry is studied by Job's method and the binding constant is estimated by band fit analysis (logKf = 5.1). Further, the coordination behaviour between L and Lu3+ is well supported by FT-IR, 1H NMR, 13C NMR, 31P NMR, ESI mass spectral data and the theoretical results.

A fluorescein-based chemosensor for “turn-on” detection of Hg2+ and the resultant complex as a fluorescent sensor for S2− in semi-aqueous medium with cell-imaging application: experimental and computational studies

A fluorescein hydrazone based probe selectively recognizes Hg2+ ion with live cell imaging application.

Chromenone-rhodamine conjugate for naked eye detection of Al3+ and Hg2+ ions in semi aqueous medium

ABSTRACTChromenone-rhodamine conjugate 1 has been synthesized and its metal ion binding properties have been studied in CH3CN/water (3:1, v/v; 10 mM HEPES buffer; pH = 6.85). Compound 1 senses multiple metal ions such as Al3+ and Hg2+ by exhibiting turn on fluorescence and color change (colorless to pink). Al3+ and Hg2+ ions have been distinguished with the aid of tetrabutylammonium iodide (TBAI). While in the presence of I− the pink color of the 1.Hg2+ complex was completely discharged; under identical conditions the pink color of 1.Al3+ complex was retained.

A novel nanomolar highly selective fluorescent probe for imaging mercury (II) in living cells and zebrafish

A novel fluorescent probe, PES, which contains a bisethylsulfane moiety, displayed high specificity for Hg2+ detection. With Hg2+, PES showed significant blue fluorescence enhancement, while the metal ions Al3+, Ag+, Cr3+, Ca2+, Cu2+, Co2+, Cd2+, Fe3+, Fe2+, Mn2+, Mg2+, Ni2+, Zn2+, and Pb2+ exhibited only negligible fluorescence change. PES has been found to be an effective quantitative detector (LOD, 57 nM) for Hg2+ in semi-aqueous medium based on the Hg2+-induced removal of bisethylsulfane. It resulted in a turn-on blue fluorescence response. The fluorescence enhancement induced by Hg2+ was observed over the pH range of 4–10. Our fluorescence cell-imaging experiments revealed the applicability of the new probe, PES, to be a reliable and effective fluorescent marker for Hg2+ in living cells.

A highly selective pH switchable colorimetric fluorescent rhodamine functionalized azo-phenol derivative for thorium recognition up to nano molar level in semi-aqueous media: Implication towards multiple logic gates.

A new rhodamine functionalized Schiff base (3',6'-bis(diethylamino)-2-((Z)-(5-((E)-(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)diazenyl)-2,4-dihydroxybenzylidene) amino)spiro[isoindoline-1,9'-xanthen]-3-one (1) has been synthesized and was characterized spectroscopically. The optical properties of the schiff base have been studied using UV-vis and fluorescence spectra. Schiff base 1 displayed a selective behaviour towards Th4+ ions, as evidenced by UV-vis and fluorescence spectra. It shows visible colour change from orangish-yellow to red upon addition of Th4+ ions. A strong new emission band at 586 nm and about 24-fold enhancement in fluorescence intensity was observed upon binding with Th4+ which could be quenched by subsequent addition of oxalate and chromate ions. Probe 1 also acts as a reversible pH sensor in the highly acidic region (pH < 4, pKa = 2.01) via the photophysical response to pH as well as visible detectable colour change from orangish-yellow to red to pink. The absorbance and emission intensities of 1 diminished in the pH region from 4 to 11.5 and could be recovered by adding acid to adjust the pH < 4. Probe 1 exhibited high binding constant (8.595 × 106 M-1) and low limit of detection (1.122 × 10-9) compared to most previously reported sensors for Th4+ ions. Furthermore, two multiple logic gates i.e. 3 and 5 input, have been constructed.

ATP Induced Modulation in π–π Stacking Interactions in Pyrene Based Zinc Complexes: Chemosensor Study and Quantitative Investigation of Apyrase Activity

Fluorescent zinc complexes of 1,2-disubstituted benzimidazole (R1–R3) have been synthesized and characterized using single crystal X-ray diffraction. The ligands L1–3 were found to be less emissive due to photoinduced electron transfer (PET) mechanism originated from the electron pair of benzimidazole nitrogen. The complexation of ligands with Zn(II) not only enhances the fluorescent intensity; it also orients the ligands to a new packing. It was observed that the aromatic unit plays a decisive role in the packing of the molecules. The complex R1 has extended the coordination through C–H···π interaction, whereas complex R2 involved C–H···π interaction and C–H···Br interaction for packing in supramolecular architecture. Among these complexes, R3 showed the most interesting noncovalent interaction pattern involving C–H···π interaction, C–H···Br interaction, and π–π stacking between pyrene rings. These noncovalent interactions govern photophysical properties that are sensitive toward the microenvironment. Thus, by altering these interactions, the selective sensing for a particular analyte can be achieved. The complexes R1 and R2 have shown enhanced emission intensity upon interacting with adenosine triphosphate (ATP) competitively in the presence of some other tested anions. A ratiometric change in emission spectra of the complex R3 was observed upon binding with ATP in semiaqueous medium offering the lowest detection limit of 15 nM. Upon interaction with ATP, the π–π stacking between pyrene rings breaks and results in a decrease in excimer emission at 470 nm and increases in monomeric emission intensity at 410 nm. The AFM (Atomic force microscopy) images of receptor R3 show that upon addition of ATP to the R3 solution, solvent mediated aggregation takes place, which results in the ratiometric detection. In the dimethylformamide solvent system, aggregates were formed, whereas in a water/tetrahydrofuran solvent system the clear solution was converted to a highly viscous gel. To investigate the applications of the prepared sensor, the fluorescence response of HeLa cells enriched with ATP was observed using fluorescence microscopy. The fluorescence modulation of the sensor in living cells makes the receptor practically applicable in a biological environment. Quantitative analysis of apyrase activity has shown that the presented sensor R3 is capable of monitoring the hydrolysis process in the biological system.