Benzimidazole-based imine-linked chemosensor: chromogenic sensor for Mg2+ and fluorescent sensor for Cr3+

A novel organic chromo-fluorogenic optical sensor for detecting chromium ions

Sensing trivalent chromium ion (Cr(III)) is widely applied in different areas, such as clinical analysis, marine, environmental monitoring, or even chemical industry applications. Cr(III) has a significant role in the physiological process of human life. It is classified as an essential micronutrient for living organisms. Herein, we developed and designed a novel optical Cr(III) ions sensor film. The investigated sensor has a relatively small dynamic range of 1.24 × 10-3 to 0.5 μM. We report a highly sensitive optical sensor film for Cr(III) ions based on diethyl 3,4-diaminothieno[2,3-b]thiophene-2,5-dicarboxylate (3D) probe. The optical characteristics of the chemical probe exhibit substantial emission at 460 nm under 354 nm excitation. Besides, the interaction of the Cr(III) ions with 3D involves a complex formation with a 2:1 (metal: ligand) ratio, which is convoyed by the main peak enhancement that centered at 460 nm of 3D, and the main peak is red-shifted to 480 nm. The easily discernible fluorescence enhancement effect is a defining characteristic of the complexation reaction between the 3D probe and Cr(III). On the basis of the substantial fluorescence mechanism caused by the formation of a (Cr(III)-3D complex, which inhibits the photo-induced electron transfer (PET) process, the devised optical sensor was proposed. This film exhibits exceptional sensitivity and selectivity due to its notable fluorescence properties, stock shift of less than 106 nm, and detection capabilities at a significantly low detection limit of 0.37 × 10-3 μM. The detection procedure is executed by utilizing a physiological pH medium (pH = 7.4) with a relative standard deviation RSDr (1 %, n = 3). In addition, the 3D sensor demonstrates a high degree of affinity for Cr(III), as determined by the calculation of its binding constant to be 1.40 × 106. We present an impressive optical sensor that is constructed upon a three-dimensional molecule.

A fluorescent chemosensor for selective detection of chromium (III) ions in environmentally and biologically relevant samples

A simple single step one pot multicomponent reaction was performed to synthesize N-(tert-butyl)-2-(furan-2-yl)imidazo[1,2-a]pyridine-3-amine (TBFIPA). The synthesized TBFIPA was subjected to library of cations to study its ability for selective and sensitive detection of specific metal ions. Selective detection of chromium ions by TBFIPA were found from the significant hypsochromic shift (335 nm → 285 nm) in the UV-Visible spectra. The fluorescent TBFIPA displays complete quenching of fluorescence under UV lamp (365 nm) only in the presence of chromium without the interference of common metal ions. Binding constant (ka) obtained from Benesi-Hildebrand plot is 0.21 × 105 M-1, limit of detection (LOD) and limit of quantification (LOQ) of TBFIPA toward Cr3+ ions are 4.70 × 10-7 M and 1.56 × 10-7 M, respectively. The mechanism proposed during complex formation were supported by stoichiometric Job continuous variation plot, 1H NMR titration and ESI-MS spectroscopic data. All the experimental confirmation for complex formation were corroborated with theoretical DFT studies optimized using RB3LYP/6-31G(d) basis set. The selectivity and sensitivity of TBFIPA toward Cr3+ ions are found suitable to design a user-friendly silica based portable test kit. Alongside, TBFIPA was successfully utilized for imaging onion epidermal cells. Furthermore, the results obtained for biological, environmental, and industrial samples provided solid evidence to estimate chromium ions using TBFIPA in these real samples.

A carboethoxy quinoline-Derived Schiff base chemosensor: Crystal structure, selective Hg2+ ion detection and its computational study

Environmental monitoring of mercury (Hg2+) ions has become increasingly important as a result of their detrimental effects on biological organisms at all levels. To recognize toxic metal ions, utmost effort has been devoted to developing new materials that are highly selective, ultra-sensitive, and provide rapid response. In this context, a new chemosensor, 2-imino [N - (N-amido phenyl)]-6-methoxy-3-carbethoxy quinoline (L), has been synthesized by combining 2-formyl-6-methoxy-3-carbethoxy quinoline and benzhydrazide and it has been extensively characterized by NMR, FTIR, ESI-Mass and SCXRD analysis. Probe L has excellent specificity and sensitivity toward Hg2+ ions in semi-aqueous solutions, with a detection limit of 0.185 μM, regardless of the presence of other interfering cations. Chromogenic behavior was demonstrated by the L when it changed the color of the solution from colorless to light yellow, a change that can be observed visually. The probe L forms a 1:1 stochiometric complex with an estimated association constant (Ka) of 6.74 × 104 M-1. The 1H NMR change and density functional theory calculations were analyzed to improve our understanding of the sensing mechanism. Also, an inexpensive and simple paper-based test kit has been developed for the on-site detection of mercury ions in water samples.

A novel fluorescent "Off-On" probe based on phenanthro[9,10-d]imidazole conjugated polymers (PIPF) for Cr3+ detection with high selectivity and sensitivity

Trivalent chromium (Cr3+) causes serious environmental pollution, degradation of the quality of edible agricultural products and human diseases. A novel phenanthro[9,10-d]imidazole-derived conjugated polymers (PIPF) was obtained from 4-(5,10-dibromo-1H-phenanthro[9,10-d]imidazol-2-yl)phenol and diethyl 4,4'-(2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9H-fluorene-9,9-diyl)dibutyrate by Suzuki polymerization reaction, which was reasonably demonstrated by 1H NMR spectroscopy, infrared spectroscopy and quantum chemical calculations. The PIPF exhibits a "turn-on" fluorescence response to Cr3+ in DMSO/H2O (98:2, v/v) with naked-eye detection. The limit of detection for Cr3+ was calculated to be 0.073 μM with a linear range of 3-9 μM. The possible mechanism of the PIPF-based Cr3+ fluorescence "turn-on" sensor is due to the inhibition of the PET process by the coordination of Cr3+ to the hexaalkyl ester carbon chain of PIPF (RCOO-). The high sensitivity, good selectivity, and utility of this sensor indicated that PIPF-based "turn-on" fluorescence sensor is a potential fluorescence application for measuring Cr3+ in environmental samples.

Synthesis and photophysical investigation of Schiff base as a Mg2+ and Zn2+ fluorescent chemosensor and its application

In view of the fluorescent switching properties and anti-fatigue properties of diarylethene, a diarylethene fluorescent chemosensor for the immediate detection of zinc ion (Zn²⁺ ) and magnesium ion (Mg²⁺ ) in acetonitrile was synthesized in this article. The structure of 1o was determined by performing spectroscopy and elemental analysis. The presence of Zn²⁺ or Mg²⁺ made the chemosensor 1o show an obvious "turn-on" fluorescent signal (bright yellow-green for Mg²⁺ and bright cyan for Zn²⁺ ). The fluorescent change caused by the 1:1 binding of 1o and Zn²⁺ or Mg²⁺ might be due to hindering the excited-state intramolecular proton transfer (ESIPT) process, which were bolstered by Benesi-Hildebrand analysis, Job's plot curves, proton nuclear magnetic resonance (¹ H-NMR) titration and mass spectrometry. The limits of detection were acquired from the standard curve plots for Mg²⁺ at 44.6 nM and for Zn²⁺ at 14 nM. Based on the fluorescent behaviors, a logic gate was constructed with the emission intensity at 528/518 nm as output signal, the ultraviolet-visible (UV-vis) lights, Mg²⁺ /Zn²⁺ and EDTA as input signals. Exogenous Zn²⁺ and Mg²⁺ fluorescent bioimaging were performed on Hela cells with 1o, indicating its potential application in biodiagnostic analysis. In particular, 1o was manufactured into test paper, and Zn²⁺ or Mg²⁺ can be conveniently, efficiently and qualitatively identified by the fluorescent color variation of the test strips.

A Novel Triazole Schiff Base Derivatives for Remediation of Chromium Contamination from Tannery Waste Water

Tannery industries are one of the extensive industrial activities which are the major source of chromium contamination in the environment. Chromium contamination has been an increasing threat to the environment and human health. Therefore, the removal of chromium ions is necessary to save human society. This study is oriented toward the preparation of a new triazole Schiff base derivatives for the remediation of chromium ions. 4,4′-((1E)-1,2-bis ((1H-1,2,4-triazol-3-yl) imino)ethane-1,2-diyl) diphenol was prepared by the interaction between 3-Amino-1H-1,2,4-triazole and 4,4′-Dihydroxybenzil. Then, the produced Schiff base underwent a phosphorylation reaction to produce the adsorbent (TIHP), which confirmed its structure via the different tools FTIR, TGA, ¹HNMR, ¹³CNMR, GC-MS, and Phosphorus-31 nuclear magnetic resonance (³¹P-NMR). The newly synthesized adsorbent (TIHP) was used to remove chromium oxyanions (Cr(VI)) from an aqueous solution. The batch technique was used to test many controlling factors, including the pH of the working aqueous solution, the amount of adsorbent dose, the initial concentration of Cr(VI), the interaction time, and the temperature. The desorption behaviour of Cr(VI) changes when it is exposed to the suggested foreign ions. The maximum adsorption capacity for Cr(VI) adsorption on the new adsorbent was 307.07 mg/g at room temperature. Freundlich’s isotherm model fits the adsorption isotherms perfectly. The kinetic results were well-constrained by the pseudo-second-order equation. The thermodynamic studies establish that the adsorption type was exothermic and naturally spontaneous.

Synthesis, Characterization and Applications of Schiff Base Chemosensor for Determination of Cr(III) Ions

The development of a highly sensitive, selective, and efficient sensor for the determination and detection of Cr(III) ions remains a great challenge. Recently, some fluorescent chemosensors have been developed for the recognition of Cr(III) ions. But, the main drawbacks of the reported fluorescent chemosensors are the lack of selectivity and interference of anions and other trivalent cations. Herein, we designed and synthesized a novel thiazole-based fluorescent and colorimetric Schiff base chemosensor SB2 for the detection of Cr(III) ion by chemodosimetric approach. Using different analytical techniques including UV-vis, ¹³C-NMR, ¹H-NMR, and FT-IR analysis the chemosensor SB2 was structurally characterized. The fully characterized chemosensor SB2 was used for the spectrofluorimetric and colorimetric detection of Cr(III) ions. Interestingly, chemosensor SB2 upon interaction with various metal cations including Ni²⁺, Na⁺, Cd²⁺, Ag⁺, Mn²⁺, K⁺, Zn²⁺, Cu²⁺, Hg²⁺, Co²⁺, Pb²⁺, Mg²⁺, Sn²⁺, Al³⁺ and Cr³⁺ displays highly selective and sensitive fluorescent (turn-on) and colorimetric (yellow to colorless) response toward Cr(III) ions. The fluorescence and UV-vis techniques confirmed the selective hydrolysis of azomethine group (-C = N-) of Schiff base chemosensor SB2 by Cr(III) ions. As a result, the fluorescence enhancement was observed that is corresponding to 2-hydroxy-1-nepthaldehyde (fluorophore). The chemosensor SB2 exhibits high interference performance towards Cr(III) ions over other metal cations in a wide pH range. Mover, the quite low detection limit was calculated to be 0.027 µg ml-1 (0.5 µM) (3σ/slop), lower than the maximum tolerable limits of Cr(III ions (10 µM) in drinking water permitted by the United States Environmental Protection Agency (EPA). These results show that chemosensor SB2 has great potential to detect selectively Cr(III) ions in the agricultural, environmental and biological analysis system.

A chalcone-based fluorescent chemosensor for detecting Mg2+ and Cd2

SBOD (sodium (E)-2-(3-[5-bromothiophen-2-yl]-3-oxoprop-1-en-1-yl)-4,6-dichlorophenolate) was designed and synthesized as a chalcone-based fluorescent turn-on chemosensor for Mg²⁺ and Cd²⁺ . SBOD selectively detected Mg²⁺ and Cd²⁺ through the increase in effective fluorescence. Detection limits of SBOD for Mg²⁺ and Cd²⁺ were calculated to be 3.8 μM and 2.9 μM, respectively. The binding modes of SBOD for Mg²⁺ and Cd²⁺ were determined to be 1:1 by ESI-MS and Job plot. Association mechanisms for SBOD to Mg²⁺ and Cd²⁺ were illustrated by ESI-MS, UV-vis, fluorescence spectroscopy, and calculations.

Zn2+ detection of a benzimidazole 8-aminoquinoline fluorescent sensor by inhibited tautomerization

A new fluorescent chemosensor based on 8-aminoquinoline L1 bearing a benzimidazole moiety was synthesized, which exists as two predominant tautomers L1A and L1B in diluted DMSO-d6 solution. Among various metal ions, L1 showed a highly selective and sensitive turn-on fluorescence response to the presence of Zn2+ ions in methanol. The detection limit for Zn2+ by L1 was calculated to be 1.76 × 10-7 M. The 1 : 1 complexation ratio of the L1-Zn complex was confirmed through Job plot measurements. Complexation studies were performed by FT-IR, NMR and HR-ESI MS measurements and DFT calculations. With the gained insight, it was possible to successfully apply L1 in water sample analysis.

Sulfur-doped carbon dots synthesis under microwave irradiation as turn-off fluorescent sensor for Cr(III)

This study synthesized a facile and high sensitive fluorescent probe based on sulfur-doped carbon dots (S-CDs) using a one-step microwave irradiation method. The probe exhibited a strong blue emission and a high quantum yield (QY) of 36.40%. In the detection, the presence of trivalent chromium (Cr(III)) strongly quenched the PL intensity of S-CDs by the inner filter effect (IFE) quenching mechanism of Cr(III) on the S-CDs. The S-CDs exhibited good sensitivity to turn-off Cr(III) detection with a linear range concentration of 0–45 μM and a detection limit of 0.17 μM. Furthermore, the proposed method has been successfully applied for Cr(III) detection in natural water samples with the 93.68–106.20% recoveries.

A Study of the Interaction of a New Benzimidazole Schiff Base with Synthetic and Simulated Membrane Models of Bacterial and Mammalian Membranes

Biological membranes are complex dynamic systems composed of a great variety of carbohydrates, lipids, and proteins, which together play a pivotal role in the protection of organisms and through which the interchange of different substances is regulated in the cell. Given the complexity of membranes, models mimicking them provide a convenient way to study and better understand their mechanisms of action and their interactions with biologically active compounds. Thus, in the present study, a new Schiff base (Bz-Im) derivative from 2-(m-aminophenyl)benzimidazole and 2,4-dihydroxybenzaldehyde was synthesized and characterized by spectroscopic and spectrometric techniques. Interaction studies of (Bz-Im) with two synthetic membrane models prepared with 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and DMPC/1,2-dimyristoyl-sn-glycero-3-phosphoglycerol (DMPG) 3:1 mixture, imitating eukaryotic and prokaryotic membranes, respectively, were performed by applying differential scanning calorimetry (DSC). Molecular dynamics simulations were also developed to better understand their interactions. In vitro and in silico assays provided approaches to understand the effect of Bz-Im on these lipid systems. The DSC results showed that, at low compound concentrations, the effects were similar in both membrane models. By increasing the concentration of Bz-Im, the DMPC/DMPG membrane exhibited greater fluidity as a result of the interaction with Bz-Im. On the other hand, molecular dynamics studies carried out on the erythrocyte membrane model using the phospholipids POPE (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine), SM (N-(15Z-tetracosenoyl)-sphing-4-enine-1-phosphocholine), and POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) revealed that after 30 ns of interaction, both hydrophobic interactions and hydrogen bonds were responsible for the affinity of Bz-Im for PE and SM. The interactions of the imine with POPG (1-Palmitoyl-2-Oleoyl-sn-Glycero-3-Phosphoglycerol) in the E. coli membrane model were mainly based on hydrophobic interactions.

Selective colorimetric and electrochemical detections of Cr(III) pollutant in water on 3-mercaptopropionic acid-functionalized gold plasmon nanoparticles

Gold plasmon nanoparticle (AuNP) was applied to the detection and the quantification of pollutant Cr(III) in water. It was synthesized by the chemical reduction of tetrachloroauric(III) acid with sodium citrate as a reducing and capping agent and was modified with 3-mercaptopropanoic acid (3-mpa) to improve the sensing recognition for the metal ion in the colorimetric detection. The 3-mpa-deposited AuNP selectively bound Cr(III) among the other 14 metal cations, resulting in the redshift of the gold plasmon band from 521 nm to 670 nm. The colorimetric quantification examination of the Cr(III) using the plasmon intensity approved the high sensitivity with the low limit of detection (0.34 ppb). Meanwhile, for the electrochemical detection, AuNP was electrochemically deposited on indium tin oxide glass substrate, modified with 3-mpa, attached Cr(III), and subsequently capped with 3-mpa-deposited AuNP. The cathodic current peak at -0.84 V versus the metal ion concentration revealed the linearity at a wide concertation range of 200-5000 ppb. As a result, the proposed colorimetric and electrochemical sensing techniques, which are the simple and facile detectors, can be complementarily employed with a high selectivity, sensitivity and wide analyte concentration range for the quantification of Cr(III) in aqueous solutions.

Sensitive and rapid detection of Cr3+ in live cells by a red turn-on fluorescent probe

A new probe RB-CR for the detection of Cr³⁺ was constructed based on the conjugation between rhodamine B and phenylthiourea. The Cr³⁺ could trigger opening of the rhodamine spirolactam of RB-CR upon complexation selectively, sensitively and rapidly, resulting in a pronounced enhancement of absorption and fluorescence signal. Further fluorescence imaging study has suggested that RB-CR could be applied as a probe for Cr³⁺ surveillance in living HepG2 cells with low cytotoxicity, which provide us the feasibility of exploring the Cr³⁺ recognition process by the turn-on fluorescence response.

Systematic approach of chromone skeleton for detecting Mg2+, ion: Applications for sustainable cytotoxicity and cell imaging possibilities

The systematic studies of chromone appended novel chemosensors, favored to Mg²⁺ ion detection, these were analyzed and characterized by different spectroscopic techniques such as NMR, mass spectroscopy, FTIR and optical techniques. The binding demeanor of the ligands was executed with the library of metal ions and shown the good coordination with Mg²⁺ ion to the ligand's cavity. Both ligands demonstrated good binding behavior with Mg²⁺ ion. The ligands represented 1: 1 stoichiometry with Mg²⁺ ions through Job's plot. The low limit of detection of Mg²⁺ ion was determined as 2.56 × 10^-6 and 1.28 × 10^-6 for L_a and L_b respectively. No interference was occurred in Inference study by foreign metal ions that supported the specific detection of Mg²⁺ ion among the other metal ions. Further, the cytotoxicity assay test of these chromone appended ligands revealed that both ligands and their respective compound with Mg²⁺ ion shown negligible toxicity with HeLa cancer cell line. Further, due to the fluorescence properties of the ligands, with or without Mg²⁺ ion was successfully tested in bioimaging experiment of HeLa cancer cell lines and found that ligands with Mg²⁺ ions represented good imaging with HeLa cancer cell.

Novel benzimidazole-based conjugated polyelectrolytes: synthesis, solution photophysics and fluorescent sensing of metal ions

Two benzimidazole-based conjugated polyelectrolytes (+)-PPBIPV and (-)-PPBIPV which have opposite charges on their side chains were synthesized via Heck coupling reaction and characterized by 1H-NMR, UV-vis and PL spectroscopy. These two polyelectrolytes are both consisted of benzimidazole derivatives and phenylenevinylene units. The absorption and emission spectra reveal that the polymers both have solvent-dependency and concentration-dependency, and they exhibit aggregation effect in aqueous solution. In the respect of ion detection, the aqueous solution of (+)-PPBIPV has excellent selectivity and sensitivity for Fe3+. Moreover, Pd2+ can almost completely quench the fluorescence of (+)-PPBIPV in methanol solution, and its quenching constant KSV is 5.93×104 M-1. For (-)-PPBIPV, Sn2+ can double the fluorescence intensity of its aqueous solution, while (-)-PPBIPV has good identification for Fe3+ in methanol with a KSV = 3.44×105 M-1. Hence, two polyelectrolytes have considerable potential to become effective fluorescent sensing materials for some specific metal ions. All of the stoichiometric relationships between metal ions and conjugated polyelectrolytes were calculated using Benesi-Hildebrand equation.

Colorimetric Detection of Multiple Metal Ions Using Schiff Base 1-(2-Thiophenylimino)-4-(N-dimethyl)benzene

In this paper, a Schiff base ligand 1-(2-thiophenylimino)-4-(N-dimethyl)benzene (SL1) bearing azomethine (>C=N-) and thiol (-SH) moieties capable of coordinating to metals and forming colored metal complexes was synthesized and examined as a colorimetric chemosensor. The sensing ability toward the metal ions of Cu2+, Cr3+, Fe2+ Ni2+, Co2+, Mg2+, Zn2+, Fe2+, Fe3+, NH4VO3 (V5+), Mn2+, Hg2+, Pb2+, and Al3+ was investigated in a mixture of H2O and dimethylformamide (DMF) solvent using the UV–Visible spectra monitoring method. The synthesized Schiff base ligand showed colorimetric properties with Cr3+, Fe2+, Fe3+, and Hg2+ ions, resulting in a different color change for each metal that could be identified easily with the naked eye. The UV–Vis spectra indicated a significant red shift (~69–288 nm) from the origin after the addition of the ligand to these metal ions, which may be due to ligand-to-metal charge-transfer (LMCT). On applying Job’s plot, it was indicated that the ligand binds to the metal ions in a 2:1 ligand-to-metal molar ratio. SL1 behaves as a bidentate ligand and binds through the N atom of the imine group and the S atom of the thiol group. The results indicate that the SL1 ligand is an appropriate coordination entity and can be developed for use as a chemosensor for the detection of Cr3+, Fe2+, Fe3+, and Hg2+ ions.

Highly sensitive and selective light-up fluorescent probe for monitoring gallium and chromium ions in vitro and in vivo

Here reported an NBDT sensor could be effectively responsive to gallium and chromium for bio-imaging in vivo.

Potentially toxic elements and environmentally-related pollutants recognition using colorimetric and ratiometric fluorescent probes

A safer detection or sensing of toxic pollutants is one among several environmental contamination issues, across the globe. The ever-increasing industrial practices and controlled or uncontrolled release of toxic pollutants from various industrial sectors is a key source of this environmental problem. Significant research efforts have been or being made to tackle this problematic issue to fulfill the growing needs of the modern world. Despite many useful aspects, heavy metals are posing noteworthy toxicological concerns and human-health related issues at various levels of the ecosystem. In this context, notable efforts from various regulatory authorities, the increase in the concentration of these toxic heavy metals in the environment is of serious concern, so real-time monitoring is urgently required. Herein, we reviewed fluorescent sensor based models and their potentialities to address the detection fate of hazardous pollutants including chromium, manganese, cobalt, nickel, copper, and zinc as model elements. The novel aspects of turn-on/off fluorescent sensors have also been discussed from a state of the art viewpoint. In summary, comprehensive literature regarding fluorescent sensor based models and their potentialities to detect various types of toxic pollutants is reviewed.

Highly Selective Detection of Cr3 + Ion with Colorimetric & Fluorescent Response Via Chemodosimetric Approach in Aqueous Medium

So far, very few numbers of chemosensors for Cr³⁺ ion have been reported. However, the main drawback of reported receptors are the lack of selectivity and other trivalent cations such as Fe³⁺, Al³⁺ and anions like F^- and ^-OAc frequently interfere with such assays. This paper present the synthesis, characterization & sensor studies of Schiff base containing naphthalene moiety which selectively detect Cr³⁺ ion by chemodosimetric approach. Using FT-IR, ¹H NMR, ¹³C NMR and ESI mass spectroscopic techniques the probe was characterized. This receptor exhibit more selectivity and sensitivity towards Cr³⁺ than other divalent and trivalent cations like Mn²⁺, Zn²⁺, Co²⁺, Ni²⁺, Cd²⁺, Cu²⁺, Hg²⁺, Fe³⁺, and Al³⁺ ions. After the addition of chromium ion the receptor get change from yellow to colorless in aqueous medium. But no color change was observed on the addition of other metal ions. Using UV-Vis and PL studies, it was confirmed that the selective hydrolysis of imine group of receptor by Cr³⁺ ions takes place with high fluorescence enhancement that is corresponding to 1-naphthylamine. Receptor acts as selective chemodosimeter for Cr³⁺ ions with 2:1 stoichiometry and micro molar detection limit. This chemodosimetric approach was applied successfully for bio-imaging of HeLa cells.

A new fluorene-based Schiff-base as fluorescent chemosensor for selective detection of Cr3+ and Al3

2-((9H-fluoren-2-ylimino) methyl)phenol (F3) was synthesized by condensation reaction of 9H-fluoren-2-amine and 2-hydroxybenzaldehyde in EtOH and characterized by its melting point, ¹H-,¹³C NMR and molecular mass. F3 exhibits a high selectivity for detection of Cr³⁺ and Al³⁺ ions as a fluorescent chemosensor and showed a single emission band at 536nm upon excitation at 333nm according to fluorescence emission studies. The addition of Cr³⁺ and Al³⁺ make a significant increase in fluorescent intensity at 536nm in CH₃CN, while other metal ions have almost no influence on the fluorescence. The fluorescence enhancement was attributed to the inhibited CN isomerization and the obstructed excited state intra-molecular proton transfer (ESIPT) of compound F3. Job's plot and DFT calculations data showed that the binding stoichiometries of F3 with Cr³⁺ and Al³⁺ are 2:1. The association constants (K_a) for Cr³⁺ and Al³⁺ were calculated and found to be 8.33×10⁴M^-1 and 5.44×10⁴M^-1, respectively. The detection limits were also calculated for Cr³⁺ and Al³⁺ and found to be 2.5×10^-7mol/L and 3.1×10^-7mol/L, respectively.

A distal vinyl shift (DVS) through quadruple domino reaction: synthesis of N-vinyl benzoheterocyclic scaffolds

An unprecedented Distal Vinyl Shift (DVS) through quadruple domino reaction has been disclosed via the synthesis of N-vinyl benzoheterocyclic scaffolds.

C, Israel V. M. V. E, Selvakumar PM. Development of a fluorescent chemosensor towards sensing and separation of Mg2+ ions in chlorophyll and hard water

A dyad receptor bearing a disulfide spacer and a naphthol terminal group has been designed for sensing of Mg²⁺ ions and the receptor incorporated polysulphone membrane is used to remove Mg²⁺ ions present in hard water.

Luminescent Zn(II) Coordination Polymers for Highly Selective Sensing of Cr(III) and Cr(VI) in Water

Three photoluminescent zinc coordination polymers (CPs), {[Zn₂(tpeb)₂(2,5-tdc)(2,5-Htdc)₂]·2H₂O}_n (1), {[Zn₂(tpeb)₂(1,4-ndc)(1,4-Hndc)₂]·2.6H₂O}_n (2), and {[Zn₂(tpeb)₂(2,3-ndc)₂]·H₂O}_n (3) (tpeb = 1,3,5-tri-4-pyridyl-1,2-ethenylbenzene, 2,5-tdc = 2,5-thiophenedicarboxylic acid, 1,4-ndc = 1,4-naphthalenedicarboxylic acid, and 2,3-ndc = 2,3-naphthalenedicarboxylic acid) were prepared from reactions of Zn(NO₃)₂·6H₂O with tpeb and 2,5-H₂tdc, 1,4-H₂ndc, or 2,3-H₂ndc under solvothermal conditions. Compound 1 has a two-dimensional (2D) grid-like network formed from bridging 1D [Zn(tpeb)]_n chains via 2,5-tdc dianions. 2 and 3 possess similar one-dimensional (1D) double-chain structures derived from bridging the [Zn(tpeb)]_n chains via pairs of 1,4-ndc or 2,3-ndc ligands. The solid-state, visible emission by 1-3 was quenched by Cr³⁺, CrO₄^2-, and Cr₂O₇^2- ions in water with detection limits by the most responsive complex 3 of 0.88 ppb for Cr³⁺ and 2.623 ppb for Cr₂O₇^2- (pH = 3) or 1.734 ppb for CrO₄^2- (pH = 12). These values are well below the permissible limits set by the USEPA and European Union and the lowest so far reported for any bi/trifunctional CPs sensors. The mechanism of Cr³⁺ luminescence quenching involves irreversible coordination to free pyridyl sites in the CP framework, while the Cr⁶⁺ quenching involves reversible overlap of the absorption bands of the analytes with those of the excitation and/or emission bands for 3.

Fluorescent probes and bioimaging: alkali metals, alkaline earth metals and pH

All living species and life forms have an absolute requirement for bio-functional metals and acid-base equilibrium chemistry owing to the critical roles they play in biological processes. Hence, a great need exists for efficient methods to detect and monitor biometals and acids. In the last few years, great attention has been paid to the development of organic molecule based fluorescent chemosensors. The availability of new synthetic fluorescent probes has made fluorescence microscopy an indispensable tool for tracing biologically important molecules and in the area of clinical diagnostics. This review highlights the recent advances that have been made in the design and bioimaging applications of fluorescent probes for alkali metals and alkaline earth metal cations, including lithium, sodium and potassium, magnesium and calcium, and for pH determination within biological systems.

ZnO decorated with organic nanoparticles based sensor for the ratiometric selective determination of mercury ions

Fully characterized organic nanoparticles (R1) decorated on the surface of ZnO (N1), used for selective nanomolar determination of mercury ions.

A highly selective and sensitive acylhydrazone-based turn-on optical sensor for Al3+

The fluorescence turn-on probing of Al³⁺ in ethanol was realized by the utilization of a type of conjugated acylhydrazone-based compound.