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Three simple dipodal artificial acyclic symmetric receptors

Three azine oligomeric esters were synthesized, characterized by IR, UV, 1H, 13C{1H} and GPC technique, and applied to chemosensor application. The sensitivity response of the oligomers towards the metal ion was evaluated for a metal ion series. The results have shown selective and sensitive “turn off” fluorescence response towards Fe3+ ion in DMF/H2O (1:1, pH: 7.4, fluorophore: 5 μM) solution. The binding stoichiometry and binding constant of the fluorophores were calculated using the Stern–Volmer equation and Benesi–Hildebrand plots, respectively. The quenching of fluorophores on the addition of Fe3+ ion indicates the capability of fluorophore towards quantitative analysis of Fe3+. The dimer of oligomers was theoretically studied using DFT, B3LYP/6-311G level basic set to support and explain the quenching mechanism of LMCT, PET process and to explain the DC, AC electrical studies results. The electrical conductivity measurements of solid-state, I2 doped and undoped oligomers were carried out and the conductivity gradually increases with increase in iodine vapor contact time of oligomers. The electrical conductivity was related with band gap and charge density values of imine nitrogen obtained by Huckel calculations. The dielectric measurements at different temperatures and frequencies were made by two probe method. Among the oligomers, EBHAP has recorded a high dielectric constant at the low applied frequency of 50 Hz at 373 K due to loosely attached π bonds resulting good polarization.

The PVA–NH4SCN polymer membranes were prepared by simple solution casting technique by passing ultrasound waves during the preparation. The polymer membranes were subjected to X-ray diffraction analysis and scanning electron microscopy. The X-ray diffraction pattern confirmed the incorporation of a salt into the polymer matrix. The scanning electron microscopy images showed the morphological changes of the polymer membrane. The polymer electrolyte (designated as UPVA20) incorporated with the 20 wt.% of the salt had the highest electrical conductivity in the order of 10–4 S cm–1. It was concluded from the dielectric, tangent and modulus spectra that the UPVA20 membrane was good at its properties. Thus, electric double layer capacitor was constructed with UPVA20 membrane as the separator. The capacitance value of the electric double layer capacitor determined from cyclic voltammetry was found to be 1652 mF g–1. The ultrasound assisted preparation of polymer membranes were good at performance when compared with the polymer membranes of ultrasound unassisted preparation. Among all the polymer electrolytes, UPVA20 polymer membrane had high conductivity, potential stability and capacitance.

A hybrid material reduced graphene oxide based organic nanocomposite was synthesized from graphite by modified Hummers method, which is further chemically reduced to form reduced graphene oxide (rGO) and with resorcinol through a solvothermal process a reduced graphene oxide-resorcinol (rGO-R) nanocomposite was obtained. The synthesized materials surface morphology and structural compositions were studied through X-ray diffraction (XRD) and scanning electron microscope (SEM) and their optical properties were studied through UV-visible spectroscopy and photoluminescence. The material was further used as a fluorescent chemosensor to detect cerium ion under aqueous conditions. The rGO-R composite's sensing abilities were studied by following parameters viz. pH, reversibility, time and the interference of other probable competing ions. The sensing follows both the photo-induced electron transfer and intramolecular charge transfer processes. © 2021 Chemical Publishing Co.. All rights reserved., Department of Science and Technology, Ministry of Science and Technology, India, डीएसटी: SERB-EMR/2016/005692

Graphene Oxide/Nickel Oxide nanocomposite (GN) has been synthesized and characterized using SEM, FTIR, XRD, UV and PL studies. The nanocomposite showed good antibacterial properties against Methicillin Resistant Staphylococcus aureus and A. baumannii. The capability of the nanocomposite as a chemosensor was analyzed towards the sensing of natural amino acids. This nanocomposite acts as a potential fluorescent chemosensor for L-Leucine through Photoinduced Electron Transfer (PET) mechanism without any interference from the potentially competing other amino acids.

Among diverse nanomaterials, graphene oxide (GO) and reduced graphene oxide (rGO)-based nanomaterials have encountered generous attention because of their ubiquitous advantages such as photo-stability, nontoxicity, water-solubility, bio-compatibility, eco-friendliness, and cost-effectiveness. Unfortunately, the inadequacy of functional groups in graphene-based nanomaterials seriously obstructs the complexing ability with regard to analytes in the field of fluorescent chemosensors. Therefore, graphene oxide and reduced graphene oxide-based materials were functionalized/modified using organic fluorophores, organic acids, polymers, organic dyes, inorganic nanoparticles, macrocyclic compounds, rotaxanes, DNA, metal oxides, chemodosimeter molecules, etc. They find extensive applications in the field of fluorescence sensing as chemosensors, wherein they either perform as fluorophores or quenchers. The functionalization is typically supported by covalent and noncovalent interactions including electrostatic forces, π–π interaction, and hydrogen bonding to furnish effective photophysical properties for fluorescent chemosensor applications. In this mini review, we critically discuss the sensitive and selective recognition of biologically and environmentally important metal ions, anions, neutral molecules, and small biological scaffolds via divergent signalling phenomena such as photoinduced electron transfer (PET), fluorescence resonance energy transfer (FRET), intramolecular charge transfer (ICT), energy transfer (ET), excited state intramolecular proton transfer (ESIPT), aggregation induced emission (AIE), and displacement approach. Most of the discussed functionalized graphene oxide materials show high sensitivity toward various analytes compared to other potential fluorescent chemosensors.

A quinoline-benzimidazole conjugate 1 has been synthesized as a potential probe to discriminate the TiO2 anatase and rutile nanoparticles by fluorimetry. Probe 1 exhibits selective TiO2 sensing through a photoinduced electron transfer process (PET) and the ratiometric sensing response by intramolecular charge transfer (ICT) mechanism. The binding ratio and the association constants were also calculated. The limit of detection of TiO2 nanoparticles by probe 1 was upto micro molar concentrations.

A simple fluorescent chemosensor 2-(furan-2-yl)-4,5-diphenyl-1H-imidazole (P1) based on an imidazole furan conjugate has been designed, synthesized and characterized. Fluorimetric studies on chemosensor P1 showed excellent selectivity toward Cu2+ ions over other metal ions in aqueous media through a “turn on−off” process. A possible reverse photoinduced electron transfer mechanism is proposed. The viability of P1 to Cu2+ has been demonstrated by live cell imaging.

In this work, two naphthalene scaffolds dangling around a benzene moiety as a colorimetric and fluorimetric probe for Fe3+ in aqueous media have been reported. Recognition processes of Fe3+ were shown to be scarcely influenced by other coexisting metal ions. The probe exhibits a turn on colorimetric and a turn off fluorimetric detection of Fe3+ ions. The association constant for sensor 1–Fe3+ complex was found as Ka = 1.12 × 105 M–1 with the detection limit of 1.7 nM. The chemosensor has been utilized for bioimaging of E. coli cells.

A visible light-driven Cu3SnS4/rGO (CTS/rGO) composite photocatalyst was prepared using ball milling (B) and solvothermal (S) method. CTS prepared by both the methods was preferentially oriented along the (1 1 2) plane exhibiting a tetragonal structure. The SEM image indicates an irregular structure and flower-like appearance in the morphology of CTS samples prepared by ball milling and solvothermal process, respectively. The impact on the morphological structure of CTS by incorporating rGO in both the methods of preparation has been analysed. UV–vis-DRS shows that the incorporation of rGO effectively influences the light response performance of the composite material in visible light. The photoluminescence (PL) spectra reveal that the composite photocatalyst can either effectually detach the electron–hole pairs and curtail their recombination or enhance the recombination based on the method of preparation owing to the phase purity of the prepared sample. Degradation of the model pollutant methylene blue (MB) was used to study the photocatalytic activity of the samples. The influence of rGO incorporation on the functioning of CTS as a photocatalyst has been studied. The species trapping experiments depicted the prominent role of h+ active species in the photocatalytic degradation of MB. The mechanism of photocatalysis in the presence of CTS/rGO has been discussed in detail.

New quinoline-based thiazole derivatives QPT and QBT were synthesized and characterized by various spectroscopic and single-crystal X-ray crystallographic studies. The metal-sensing properties of the probes were further examined by absorption and fluorescence spectrometry. The fluorescence intensity of QPT and QBT was remarkably quenched during the addition of Fe3+, Fe2+, and Cu2+ ions in THF/H2O (1:1) at pH = 7.4 in HEPES buffer, while the addition of other metal ions did not affect the fluorescence intensity of the ligands. The detection ability of the probes QPT and QBT was further investigated by titration with various equivalents of metal ions, optimized pH ranges for detection, and reversibility with Na2EDTA for biological applications.

Pyrene-phenylglycinol tangled ratiometric sensor (R)-1 was developed for the detection of Al3+ ion over other metal ions. Ratiometric behaviour of (R)-1 for Al3+ ion explained through monomer emission and excimer quenching leads to avoiding the π-π interactions of bis-pyrene rings. Pull-push to push-pull binding mechanism is successfully explained by DFT and sensing of Al3+-ions demonstrated in living cells. The LOD of (R)-1 for Al3+ downs to nanomolar concentrations which is lower than the allowed concentration of drinking water set by the (World Health Organization) WHO.

Presence of heavy metals in industrial discharge warrants the adoption of efficient and cost-effective treatment technologies. In this work, lichen Parmotrema tinctorum biomass was utilized as biosorbent for removal of Ni (II) from metal finishing industry effluents. Optimal adsorption was observed at pH 7, stirring speed of 300 rpm, 120 min incubation from independent batch experiments. Adsorption isotherm at optimal conditions followed Langmuir model (R2 > 0.974) with a maximum adsorption capacity of 33.92 mg g−1. Adsorption kinetics could be described with pseudo-first-order model (R2 > 0.98). Fourier transform infrared spectroscopy of pristine and metal loaded P. tinctorum biomass indicated electrostatics and ionic interaction in the adsorption process. Biosorbent treated water showed no inhibition against agriculturally important microorganisms like Phosphobacter sp. and Azospirillum sp. in microbial toxicity assay. Similarly, biosorbent treated water offered better germination and growth for Vigna radiata than the untreated water in greenhouse phytotoxicity assessment. Though the result suggests detoxification of industrial effluents following P. tinctorum biosorption, reusability of treated wastewater in agricultural practice warrants multi-tiered ecotoxicity assessment, and long-term environmental impact analysis.

Graphene oxide-rhodamine B hydrazide (GO-RhB) nanocomposite was prepared by a simple chemical method and characterized by various spectroscopic and analytical techniques. GO-RhB nanocomposite potentially detects Cr3+ ion (excitation/emission = 550 nm/572 nm) via fluorescence turn "on-off" approach. This composite showed high binding affinity (106 M-1) with Cr3+ and a+ limit of detection (LOD) down to picomolar concentration (LOD = 85.6 pM). As far as we know, this is the first report for the sensing of Cr3+ ion at picomolar concentration. GO-RhB selectively senses Cr3+ ion without any interference of other coexisting metal ions. In addition, this composite exhibited the dynamic nature of quenching in the presence of Cr3+ ion, which is confirmed by the Stern-Volmer plot, fluorescence temperature profiles, and decay time experiments. The GO-RhB nanocomposite-based fluorescent probe was successfully applied to the quantitative detection of Cr3+ ion in milk sample (linear range = 2 to 10 nM) with better performance than other existing methods. Besides, this GO-RhB composite showed better antibiofilm activity against Acinetobacter baumannii and methicillin-resistant Staphylococcus aureus (MRSA) by using the Congo red agar and tube method.

In this work, graphene oxide-p-Phenylenediamine nanocomposites of two different ratios of Graphene oxide: p-Phenylenediamine (1:1 and 1:5) were prepared and characterized by using analytical, spectroscopic and microscopic studies (GO-pPD 11 and GO-pPD 15). These nanocomposites were employed as fluorescent chemosensors for sensing potential cations. Remarkably, graphene oxide-p-Phenylenediamine nanocomposites of ratio 1:1 (GO-pPD 15) was selective and sensitive to Ag+ ions, whereas the graphene oxide-p-Phenylenediamine nanocomposites of ratio 1:5 (GO-pPD 15) was selective to Ce3+ions. A possible mechanism as switch “off-on” is proposed built on the inhibition of the photo induced electron transfer process in both the fluorescent probes in detecting the metal ions. In addition, interference studies were performed with the help of competitive complexation analysis and no significant interference were found by other potentially competing cations. The pH studies revealed that both the chemosensors can be used at the physiological pH for the ion detection and also the detection time was within 2–3 min. Both the chemosensors show good reversibility and hence the sensors can be used for multiple times. The newer nanocomposites were then utilized in the real water sample analysis as to check its real level application purpose.

Heavy metal pollution in the water bodies causes a serious threat to all living beings. Extended exposure of heavy metals such as nickel (Ni) ions causes cancer. Henceforth, the current study investigated the removal of Ni ions from the electroplating effluent using nanocomposites namely, Graphene Oxide (GO) and Reduced Graphene Oxide (rGO) in the presence of various factors such as contact time, pH, agitation speed and sorbent dosage. Further, it was determined the rate kinetic model and adsorption equilibrium isotherms. The study also focused on comparing the removal efficiency of two nanocomposites. The maximum sorption efficiency were found to be 90.8% and 84.4% at optimized pH (8), contact time (180–1440 m), RPM (250–300) and adsorbent dosage (0.2 mg/L) for GO and rGO respectively. Furthermore, toxicity of treated and untreated effluent were tested against Phosphobacter and Azospirillium using GO and rGO and found that the treated effluent was non-toxic. The contribution of this study to agriculture in using recycled effluent for crop cultivation was being verified by seed germination of Lablab purpureus seeds watered with treated and untreated effluent. Finally we concluded that the results of treated water can be used for cultivation as there was healthy growth of plants.

A simple rhodanine derived fluorophoric unit has been designed for selective detection of Ag+ and I- ions in DMSO-H2O medium. The sensor R1 showed an obvious “turn-on” fluorescence response toward Ag+ due to the inhibition of both C-N single bond free rotation, internal charge transfer (ICT) and the formation of chelation enhanced fluorescence (CHEF) effects. The fluorescence quantum yield (Φ) was increased from 0.0013 to 0.032 for receptor R1 upon the Ag+-complexation. In addition, the 1:1 complexing stoichiometry was employed based on Job’s plot analysis with detection limit of 24.23 × 10−7 M. Conversely, receptor R1+Ag+ particularly detects I- ion over other co-existing anions by the “turn-off” fluorescence response due to the formation of AgI, displacing the receptor R1 with the quantum yield of 0.0014. The detection limit was calculated to be 22.83 × 10−7 M. The sensing behaviour of receptor R1 toward Ag+ was also supported by density functional theory (DFT) calculations. Moreover, the sensing ability of reported receptor R1 could be exercised in multifarious applications like paper strip, silica-supported analysis, staining test for latent finger print, logical behaviour, smartphone-assisted quantitative detection and real water samples studies.

In this report, a new design is proposed for the detection of silver ions using Graphene Oxide-Titanium oxide (GO/TiO₂) composite. The GO was synthesized by modified Hummers method and the composite is synthesized by chemical reflux method. The surface morphology of the composite was analyzed using a scanning electron microscope (SEM), and it is clearly observed that TiO₂ spheres are adsorbed on the surface of GO in a disordered manner. X-ray Diffraction (XRD) results confirm the presence of TiO₂ on GO. Photoluminescence (PL) spectra show the reduced recombination of charge carriers in the (GO/TiO₂) composite. The resulting composite selectively detects silver ions over other potentially competing metal ions with no notable interference monitored by fluorescence.

A novel bis-anthracene molecule linked to bis-pyridine by xylylene dibromide (APC) was synthesized as a potent sensor for the detection of Al3+ ions. Receptor APC exhibits high affinity towards Al3+ ions through fluorescence ‘off–on’ behaviour in HEPES-buffered THF–H2O (1 : 1, (v/v) HEPES = 50 mM, pH = 7.4) solution with a detection limit of 0.89 × 10−6 M. The affinity between receptor APC and Al3+ ions can be attributed to the photoinduced electron transfer (PET) mechanism. Furthermore, the receptor APC can be employed for the detection of Al3+ ions in various effluent water samples and in microbial bioimaging.

A simple carbazole derived Schiff base fluorescent chemosensor (C1) has been synthesized and characterized successfully to recognize sequentially Fe3+ ion and an amino acid, arginine (Arg). The chemosensor (C1) shows specific response “on-off-on” towards Fe3+ and Arg among different competing cations and amino acids. Interestingly, the fluorescence emission got turned-off for C1-Fe3+ complex and turned-on for the detection of arginine. The binding ability of sensor C1 with Fe3+ and arginine was advocated using fluorometric titrations, Job’s plot, B-H plot and density functional theory studies (DFT). The significant color changes of sensor C1 from aqua blue to transparent blue to aqua blue were monitored under UV-lamp of 365 nm during the sensing process, which additionally supported the complex formation. The sensor C1 accomplishes the lowest detection limit of 12.22×10-9 M and binding constant of 2.09×104 M-1 for Fe3+ detection. This efficient fluorescent candidate was utilized for the detection of Fe3+ in applications such as molecular logic gate, smart-phone based on-site detection, live cell bio-imaging and real sample analysis.

A quinoline-naphthalene duo-based Schiff base probe (R) was synthesized and characterized by the usual spectroscopic and single-crystal X-ray crystallographic techniques. Probe R detects Al3+ and HSO3− ions via the fluorescent turn-on approach by dual pathways i.e., i) when probe R interacts with Al3+, the restriction of C N single bond rotation, blocking of both photoinduced electron transfer (PET) and C N isomerization were observed, and ii) when the sensor R interacts with HSO3−, imine (CH = N) bond was cleaved via hydrolysis and produced the respective aldehyde and amine behaving as a chemodosimeter. The binding stoichiometric ratio of R + Al3+ (1:1) was confirmed by Job’s plot, emission titration profile, NMR, and mass spectrometric analyses. This probe R is highly selective to both Al3+ -ions and HSO3− -ions, without any interference of other potentially competing cations and anions. Limit of detection (LOD) and quantification (LOQ) of R with Al3+ and HSO3− were downed to nanomolar concentrations, which is much lower than the recommended level of drinking water/food fixed by the World Health Organization (WHO). Furthermore, probe R was utilized in the detection of Al3+ and HSO3− ions in highly contaminated real samples, bioimaging in E. coli cells, multiple-targeting molecular logic gate, and in bovine serum albumin (BSA) binding.

In this work, we have successfully synthesized superparamagnetic nanocomposites, Ce4–xSr1+xFe5–xZnxO14+δ (0 ≤ x ≤ 0.45) (CSFZ) (TA1–TA4: x = 0, 0.15, 0.30, and 0.45) via the Nitrate–citrate sol–gel method. X-ray diffraction studies show the formation of single-phase nanocomposites (NCs) and the average crystallite size is found to be 18 nm. Energy-dispersive X-ray spectroscopy analysis supports the formation of the desired product with the expected composition. The scanning electron microscopy image shows that the prepared samples are in spherical shape and highly porous in nature. Most of the particle sizes present in the image are in the range of 5–20 nm. The optical studies show an intense peak at 583 nm corresponding to the instantaneous existence of both Fe2+ and Fe3+ intervalence electronic charge transition bands. X-ray photoelectron spectra analysis confirms the presence of elements with their preferred oxidation state. The superparamagnetic nature of the prepared sample was confirmed by vibrating...

A binaphthyl derived fluorescent probe (S)-1 was developed for dual channel detection of Ni2+ and Al3+ ions. The sensing of Ni2+ and Al3+ ions takes place by two pathways: (i) fluorescent turn-on response via the blocking of the photoinduced electron transfer process and (ii) red-shifted fluorescent enrichment via the intramolecular charge transfer process. All these findings were supported by NMR, mass spectrometry, and theoretical studies. In addition, sensing of Al3+ ions was successfully applied into live cells for bioimaging studies and logic gate applications.

A new hybrid material, graphene oxide- Resorcinol (GO-R) is synthesized from graphite following the modified Hummers method, characterized and utilized as a fluorescent chemosensor to detect Cerium ion under aqueous conditions. The effect of pH, reversibility, time and the interference of other potentially competing ions have been studied. The sensing follows both the photo induced electron transfer and intramolecular charge transfer processes.

N1,N5-bis(pyridin-2-ylmethylene)naphthalene-1,5-diamine (L1) Schiff base conjugate was synthesized by the condensation reaction of 1,5-diamino naphthalene (1,5-DAN) and 2-pyridine carboxaldehyde and spectroscopically evidenced by 1H NMR, 13C NMR and Mass spectrum. The developed Schiff base conjugate was used as a fluorescent chemosensor for the selective recognition of bismuth (Bi3+) ions in the midst of various interfering heavy transition metal ions such as Ag+, Hg2+ and Cu2+ with marked fluorescence enhancement. Based on “switch-on” intramolecular charge transfer (ICT) approach, chemosensor L1 showed specific response towards bismuth ions with a low detection limit of 1.5 × 10−8 M and a high binding constant 7.11 × 105 M−1. Simultaneously, the experimental (Job’s plot, Mass spectrum, and FT-IR) and theoretical (B3LYP-D3/6–311++G(d,p)) analysis were performed for promising the 1:1 binding mode of L1 + Bi3+ complex formation. The chemosensor L1 has been successfully demonstrated in practical applications such as water and food samples, bacterial imaging and logic gate operation producing satisfactory results.

A simple quinoline-based fluorescent chemosensor 1 capable of detecting Ag+ ion in aqueous media was developed. Chemosensor 1 exhibits high selectivity and sensitivity toward Ag+ ion as fluorescence off-on behavior in HEPES buffered MeOH-H2O (1:1, (v/v) HEPES = 50 mM, pH = 7.4) solution. Chemosensor 1 binds with Ag+ ion through intra-molecular charge transfer (ICT), resulting in enhancement and quenching of peaks demarcated by isoemissive point. The practical application of chemosensor 1 in bio imaging and water studies have been demonstrated in this study.

A simple thiophene based fluorescent probe 1 was prepared for the detection of Ag+ in aqueous solution. Probe 1 exhibits high selectivity and sensitivity toward Ag+ as fluorescence “ off-on” behavior in HEPES buffered MeOH-H2O (1:1, (v/v) HEPES = 50 mM, pH = 7.4) solution. The detection limit was calculated to be 1.28 × 10−7M with an association constant of 1.58 × 106 M−1 by fluorescence titration experiments. The probe was also demonstrated to detect Ag+ in real samples and in living cells.

A pyrene scaffold bearing a phenol molecule has been designed and synthesized as a chemosensor L1 by an aldol type of condensation reaction. The sensor showed high sensitivity and selectivity for Al3+ ions by the enhancement of fluorescene intensity and distinguishes from the other potentially competing metal ions. The effect of pH, time and the reversibility of the sensor are studied. The fluorescence experiments suggested that the proposed binding of L1 and Al3+ ion is in a 1:1 stoichiometry. The chemosensor’s direct application in the electrosorptive removal of Al3+ ion and several other biological applications including the bio-imaging of bacterial cells were examined.

Two mononuclear complexes of Co(II) (1) and Ni(II) (2) and a chloro bridged binuclear copper(II) complex (3) of 2-benzoylpyridine-4-methoxybenzoylhydrazone have been synthesized in order to explore their biological activities, such as DNA binding, protein-binding, antioxidant activity and anticancer activity. Analytical and spectroscopic techniques have been used to characterize the complexes. The molecular structures of 2 and 3 have been obtained by single crystal XRD. Interaction of the ligand and the complexes with calf thymus DNA (CT-DNA) has been explored by absorption and emission titrations, which revealed that the compounds interacted with CT-DNA through intercalation. Absorption titration and biological studies revealed that the complexes interact with BSA through different binding modes to different extents. The radical scavenging ability of the ligand and the complexes was studied against DPPH radicals. The ligand and its metal complexes were tested for potential cytotoxicity towards human breast cancer (MCF-7) and lung cancer (A-549) cell lines.

Quinoline and imidazole derivatives have been playing a significant role in functional bioactivities and were potentially used as antibacterial, antifungal, anticancer, and anti-inflammatory drugs. Owing to the limitation of drug resistance, herein we synthesized thio-, chloro-, and hydroxyl-functionalized various imidazoquinolines by molecular hybridization approach. All the imidazoquinoline derivatives were examined for their antibacterial activity against selected bacterial pathogens by the agar well diffusion method. In addition, the anti-oxidant efficacy of imidazoquinolines was also tested using ferric reducing antioxidant power (FRAP). Among them, electron-withdrawing (-Cl) substituent containing imidazoquinoline 5f showed higher antibacterial and anti-oxidant activities than other imidazoquinolines and reached the effectiveness of the standard. In addition, compounds 4f, 5e, and 3f showed moderate antibacterial activity and other derivatives displayed weak activity against various pathogens. Molecular docking studies were also performed on selected imidazoquinoline derivatives (3f, 4f, and 5f), which showed high docking score and strong binding energy values. These results revealed that thio-imidazoquinoline could assist as a prototype for the designing of multidrug-resistant antibiotics against various microbial organisms., Thio-imidazoquinolines; Hydroxy-imidazoquinolines; Chloro-imidazoquinolines; 2-Chloro-3-formylquinolines; Antibacterial; Antioxidant; Molecular docking; Multidrug-resistant.

We report the modular design and synthesis of an amine dangled Schiff base quinoline–morpholine conjugate (QMC) for highly selective detection of Pb2+ ions via fluorimetry. The sensing strategy of QMC towards Pb2+ ion exhibits a large blue shift with fluorescent enhancement via the intramolecular charge transfer (ICT) process. At the same time, QMC coordination with Pb2+, the C N single bond rotation between quinoline and morpholine rings and the C N isomerization process were blocked. Best of our knowledge, this is the first blue shifted turn-on fluorescent chemosensor for Pb2+ ion via the ICT process. Furthermore, QMC selectively detects Pb2+ ion without any interference with alkali, alkaline earth, and transition metal ions, and limit of detection (LOD) downs to 13 μM, which is a permissible level of Pb2+ ion in drinking water reported by WHO. The 1:2 binding stoichiometry between QMC and Pb2+ was confirmed by fluorimetric, 1H NMR titration, mass spectrometry, and theoretical studies. Finally, QMC was potentially applied for the sensing of Pb2+ ions in milk, red wine, live cells and an INHIBIT molecular logic function was constructed by using Pb2+ and EDTA as chemical inputs.

We report herein synthesis and characterization of four new organoruthenium(II) complexes of the type [RuH(CO)(PPh3)2(L1,2)]Cl (1, 3) and [Ru(CO)(Cl)2(AsPh3)(L1,2)] (2, 4) derived from the reaction of [RuHCl(CO)(EPh3)3] (E = P or As) with 2-(pyridine-2yl)benzoxazole (L1) and 2-(pyridine-2yl)benzthiazole (L2). Single-crystal X-ray diffraction data of 2 proved octahedral geometry of the complexes with a 1:1 ratio between the metal and the coordinated ligands. The binding affinities of 1-4 toward calf-thymus DNA (CT-DNA) and BSA were thoroughly studied by various spectroscopic techniques. Furthermore, the coordination compounds exhibit catecholase-like activities in the aerial oxidation of 3,5-di-tert-butylcatechol to the corresponding o-quinone and phosphatase-like activities in the hydrolysis of 4-nitrophenyl phosphate to 4-nitrophenolate ion. The kinetic parameters have been determined using Michaelis–Menten approach. The highest kcat values suggested that coordination compounds exhibit higher rates of catalytic efficacy.

A simple chalcone based dual analyte fluorescent probe FPC for Al3+ and HSO3- ions was developed. FPC detects both the analytes through a "turn off-on" approach and by the PET and ICT mechanism. FPC showed high selectivity and sensitivity for Al3+ and HSO3- ions detection over other interfering and competing metal ions. In addition, the LOD of FPC for sensing Al3+ and HSO3- ions was found to be 1.60×10-7M and 0.17×10-6M respectively. An electrochemical desalination technique was employed for the complete removal of Al3+ ions from the environmental water samples by using the probe FPC.

Naphthalene based salen type fluorescent chemosensors have been designed and synthesized for the highly selective detection of silver ions by fluorimetry. These probes 1, 2 and 3 sense Ag+ over other cations as fluorescence ‘on-off’ behaviour. A possible mechanism is proposed, where the heavy atom effect of silver ion overcomes the effect of CN isomerization and intramolecular restricted torsional rotation through the CC single bond between the naphathalene and the benzene moieties. These chemosensors are further utilized to detect Ag+ as strip tests and solid supported silica gel material. These results are further supported by the theoretical calculations.