Tripodal Receptor Research Articles

A captivating approach to elevate the detection of Al3+ ions incorporates the utilization of a tripodal receptor intricately embellishing the surface of zinc oxide

The FDA (Food and Drug Administration, (USA)) lists ZnO as a material that is widely acknowledged to be safe. ZnO NPs with a range of tiny particle sizes were made using the precipitation process. ZnO nanoparticles' surface is embellished with a tripodal sensor containing naphthol units. The assembly with the same receptor decorated on ZnO NPs is contrasted with the cation detection capabilities of the purified tripodal receptor. The UV–visible spectrophotometric analysis was conducted to study the state transitions of the receptor and the decorated ZnO receptor. A positive selectivity to Al3+ cations is determined by the fluorescence study under ideal circumstances. The particle size and surface morphologies are determined by DLS and SEM analysis for the same receptor − TP1 and embellished with a tripodal receptor TP2. Using a fluorescence switch-on Photoinduced Electron Transfer (PET) mechanism, the receptor coated on ZnO detects the presence of Al3+ ions with specificity. The binding constant value was determined using the B-H plot equation. Binding stoichiometry for [TP1-Al3+, TP2-Al3+] showed a 1:1 ratio. The fluorescence switches ON-OFF process of the ZnO surface adorned − TP2 with Tripodal receptor- TP1 was used to create molecular logic gates, which can function as a module for sensors and molecular switches. The addition of Na2EDTA in the solution of the [TP1; TP2 − Al3+] complex resulted in a noticeable reduction in the emission of fluorescence. This finding offers compelling support for the reversibility of the chemosensor. To enable the practical application of this sensor, we have developed a cassette containing receptors TP1 and TP2. Successfully, it can detect Al3+ metal ions. We performed a comprehensive assessment of the dependability and appropriateness of our approach in measuring the concentration of Al3+ ions in wastewater produced by important industrial procedures.

Tripodal receptor cross-linked polymer as a promising adsorbent for iodine vapor capture and adsorption from water

A cross-linked tripodal receptor polymer was synthesized using a Friedel-Crafts polymerization reaction which showed an iodine vapor capture capacity of 2.47 g g−1 at 80 °C with remarkable iodine adsorption per unit BET surface area of 86 wt/(m2/g). UV–Vis spectral analysis confirmed that the polymer adsorbent rapidly adsorbs iodine from water. Importantly, the polymer exhibited reversible iodine adsorption allowing the polymer to be reused several times without losing the adsorption efficiency. We also investigated the adsorption capability of the synthesized polymer TPP as a filtration material for practical applications. Through dynamic adsorption experiments using a syringe pump setup, we demonstrated that a mere 40 mg of the TPP polymer effectively purifies 20 ml of a 2.5 mM aqueous iodine solution. Our findings underscore the exceptional adsorption efficiency of the TPP polymer, as evidenced by the successful removal of iodine molecules from the solution. These results not only highlight the potential of the TPP polymer for its utility in environmental remediation applications particularly for the treatment of effluents from nuclear reactors.

Tuning of the Anion Affinity and Selectivity of Tripyrromethane‐Based Receptors by Simple Structural Modification

AbstractTripyrromethane‐based tripodal compounds 1–3 were synthesized as anion receptors. It was revealed by 1H NMR spectroscopic analyses carried out in CDCl3 that tripyrromethane 1 with an ester group was capable of recognizing F−, Cl−, Br−, and H2PO4− with relatively high selectivity for F−. By contrast, receptor 2 having an additional hydrogen bond donor of an amide group binds F− and H2PO4− with much improved affinity relative to receptor 1. On the other hand, receptor 3 bearing formyl groups on its two pyrrole subunits showed markedly enhanced selectivity for F− presumably due to the increased acidity of the pyrrolic NHs and the resulting strengthened intermolecular hydrogen bonds. In addition, tripodal receptors 1–3 were found to bind H2PO4−, a tetrahedral oxyanion, more efficiently than 2‐dimensional macrocyclic calix[4]pyrrole 4.

Biomass-Derived Core-Shell Carbon Dots with Embedded Tripodal Receptors for the Selective Recognition of Mefenamic Acid in Pharmaceutical Formulations and Urine.

A tripodal amine (TPA) with -OH, N, and S donors is synthesized to functionalize a core-shell carbon dot composite (FCDs@SiO2-TPA) for sensing application. The TPA is characterized by spectroscopic and spectrometric techniques, and the composite is characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive X-ray spectra (EDS) techniques. The composite has the ability to recognize mefenamic acid (MFA) selectively even in the presence of other drugs like ibuprofen sodium, acetylsalicylic acid, naproxen sodium, diclofenac sodium, and ketoprofen. It can also be used for the quantification of MFA by recording the emission quenching response of the sample at λexc. = 350 nm and λems. = 460 nm (linear range = 1-8 μM and LOD = 197 nM). The density functional theory calculations and 1H NMR titration suggest quenching of the emission signal due to photoinduced electron transfer via hydrogen bonding between the probe and MFA. The composite FCDs@SiO2-TPA has been demonstrated as a reliable and cost-effective sensing probe for the detection of MFA in pharmaceutical formulations, water samples, and cow urine samples.

Urea- and Thiourea-Based Receptors for Anion Binding.

ConspectusOver the past five decades, significant progress has been made in the field of anion recognition with a diverse variety of synthetic receptors because of the fundamental importance of anions in chemical, environmental, and biological processes. In particular, urea- and thiourea-based molecules offering directional binding sites are attractive receptors for anions due to their ability to bind anions employing primarily hydrogen-bonding interactions under neutral conditions and have gained a recent paramount attention in the area of supramolecular chemistry. The presence of two imine (-NH) groups on each urea/thiourea functionality in these receptors gives them potential for excellent binding of an anion, mimicking the natural binding process in living cells. The increased acidity offered by thiocarbonyl groups (C═S) in a thiourea-functionalized receptor could enhance its anion binding ability as compared to its analogous urea-based receptor containing a carbonyl (C═O) group. During the last several years, our group has been involved in exploring a wide variety of synthetic receptors, and we have studied them with anions experimentally and computationally. In this Account, we will highlight the overall summary of our group's efforts focusing on anion coordination chemistry of urea- and thiourea-based receptors with varying linkers (rigid and flexible), dimensions (dipodal and tripodal), and functionalities (bifunctional, trifunctional, and hexafunctional). Depending on the linkers and attached groups, bifunctional-based dipodal receptors can bind anions forming 1:1 or 1:2 complexes. A dipodal receptor with flexible aliphatic or rigid m-xylyl linkers forms a cleft to bind a single anionic species in the pocket. However, a dipodal receptor with p-xylyl linkers binds anions in both 1:1 and 1:2 binding modes. As compared to a dipodal receptor, a tripodal receptor provides a more organized cavity for an anion, forming predominantly a 1:1 complex, while the binding strength and selectivity are influenced by linking chains and terminal groups. A hexafunctional-based tripodal receptor bridged with o-phenylene groups provides two clefts that can host two small anions or one large anion. However, a hexafunctional receptor with p-phenylene groups as linkers binds two anions, one at an inner pocket and the other at an outer pocket. It was shown that the presence of suitable chromophores at the terminal groups makes the receptor useful for the naked-eye detection for certain anions (e.g., fluoride, acetate) in solution. The field of anion binding chemistry is rapidly growing, and this Account aims to provide fundamental aspects influencing the binding strength and selectivity of anionic species with abiotic receptors which might eventually be useful for the development of new devices for binding, sensing, and separating biologically and environmentally important anions.

Anion-exchange facilitated selective extraction of sulfate and phosphate by overcoming the Hofmeister bias.

Selective recognition and removal of sulfate and phosphates from aqueous media in the presence of highly competing anions is very demanding because of their biological and environmental implications. In this paper, we present the anion recognition approach for the selective and efficient extraction of sulfate by nitrophenyl-functionalized tris-urea receptors (L1-L2) from highly competitive aqueous media with an equivalent concentration of nitrate and other anions. Tetrabutylammonium hydroxide has been used for the first time as a phase transfer anionic extractant for sulfate-exchange from the aqueous phase to the organic phase (dichloromethane) containing a tris-urea receptor (L1-L3). The sulfate extraction efficacy of L2 (≈84-90%) was observed to be higher than those of L1 (≈76-82%) and L3 (≈68-75%) in competitive extraction experiments. In contrast, an analogous nitrophenyl-functionalized tris-thiourea receptor (L4) has been recognized for the selective and efficient extraction of phosphates from aqueous media in the presence of several competing anions including sulfate and nitrate, with ≈85-92% extraction efficiency. In this case, tetrabutylammonium acetate has been used as a phase transfer anionic extractant for phosphate exchange between the two immiscible phases. Due to the higher acidity of tris-thiourea -NH groups in comparison to the analogous tris-urea, tetrabutylammonium hydroxide could deprotonate a hydrogen bond donating -NH group of the thiourea receptor and phosphate extraction was observed to be inefficient in such a case. Several liquid-liquid extraction (LLE) experiments have been carried out to establish the selective removal of sulfate and phosphates by the tripodal receptors from competitive aqueous media having different combinations of two or more anions. The LLE products obtained from organic phases were characterized by NMR (1H, 13C, 31P, and 19F) spectroscopy to affirm the oxoanion selectivity of the receptors and purity of the complexes. The tripodal receptors can easily be recycled for successive extraction cycles by simply washing the LLE products (oxoanion complexes) with a methanol-water (1 : 1, v/v) solvent system followed by filtration.

Selective recognition and extraction of arsenate by a urea-functionalized tripodal receptor from competitive aqueous media.

A second-generation hydrogen bond donor (HBD) anion receptor with an inner amide cavity and an outer urea cavity can selectively and efficiently extract arsenate (AsO43-) from water in the presence of competitive oxoanions and halides. The X-ray structure showed encapsulation of AsO43- in a π-stacked dimeric capsular assembly of the receptor, the first crystallography-based example of pentavalent AsO43- trianion recognition by a HBD receptor.

Host-guest complexes vs. supramolecular polymers in chalcogen bonding receptors: an experimental and theoretical study.

We describe here a comparative study between two tripodal anion receptors based on selenophene as the binding motif. The receptors use benzene or perfluorobenzene as a spacer. The presence of the electron-withdrawing ring activates the selenium atom for anion recognition inducing the formation of self-assembled supramolecular structures in the presence of chloride or bromide anions, which are bonded by the cooperative action of hydrogen and chalcogen bonding interactions. DOSY NMR and DLS experiments provided evidence for the formation of the supramolecular structures only in the presence of a perfluorobenzene based anion receptor while the analogous benzene one shows the classical anion/receptor complex without the participation of the selenium atom. The energetic and geometric features of the complexes of both receptors with the Cl and Br anions have been studied in solution. These results combined with the molecular electrostatic potential (MEP) surface plots allow us to rationalize the quite different behaviors of both receptors observed experimentally.

Tripodal aroyl hydrazone based AIE fluorescent sensor for relay detection Hg2+ and Br− in living cells

The efficient detection of toxic substances is a very important task. Herein, a tripodal receptor TM employing three aroyl hydrazone moieties as binding sites has been designed and used for the selective determination of Hg2+ and Br−. The TM shows AIE properties and could selectively relay fluorescent response for Hg2+ and Br−. The detection limit (LOD) for Hg2+ and Br− is found to be 4.95 × 10−8 M and 1.7 × 10−6 M. More interestingly, the TM could be used for fluorescent sensing Hg2+ and Br− in living cells with high sensitivities.

Highly Efficient, Tripodal Ion-Pair Receptors for Switching Selectivity between Acetates and Sulfates Using Solid-Liquid and Liquid-Liquid Extractions.

A tripodal, squaramide-based ion-pair receptor 1 was synthesized in a modular fashion, and 1H NMR and UV-vis studies revealed its ability to interact more efficiently with anions with the assistance of cations. The reference tripodal anion receptor 2, lacking a crown ether unit, was found to lose the enhancement in anion binding induced by presence of cations. Besides the ability to bind anions in enhanced manner by the “single armed” ion-pair receptor 3, the lack of multiple and prearranged binding sites resulted in its much lower affinity towards anions than in the case of tripodal receptors. Unlike with receptors 2 or 3, the high affinity of 1 towards salts opens up the possibility of extracting extremely hydrophilic sulfate anions from aqueous to organic phase. The disparity in receptor 1 binding modes towards monovalent anions and divalent sulfates assures its selectivity towards sulfates over other lipophilic salts upon liquid–liquid extraction (LLE) and enables the Hofmeister bias to be overcome. By changing the extraction conditions from LLE to SLE (solid–liquid extraction), a switch of selectivity from sulfates to acetates was achieved. X-ray measurements support the ability of anion binding by cooperation of the arms of receptor 1 together with simultaneous binding of cations.

Design, synthesis and evaluation of a tripodal receptor for phosphatidylinositol phosphates

Phosphatidylinositol phosphates (PIPs) are membrane phospholipids that play crucial roles in a wide range of cellular processes. Their function is dictated by the number and positions of the phosphate groups in the inositol ring (with seven different PIPs being active in the cell). Therefore, there is significant interest in developing small-molecule receptors that can bind selectively to these species and in doing so affect their cellular function or be the basis for molecular probes. However, to date there are very few examples of such molecular receptors. Towards this aim, herein we report a novel tripodal molecule that acts as receptor for mono- and bis-phosphorylated PIPs in a cell free environment. To assess their affinity to PIPs we have developed a new cell free assay based on the ability of the receptor to prevent alkaline phosphatase from hydrolysing these substrates. The new receptor displays selectivity towards two out of the seven PIPs, namely PI(3)P and PI(3,4)P2. To rationalise these results, a DFT computational study was performed which corroborated the experimental results and provided insight into the host–guest binding mode.

C3V symmetric tripodal molecular pocket for linear anions: Selective colorimetric detection of azide through N4-Cu-π···hole interactions.

Tris(3-amino propyl)amine (TRPN) based C3v symmetric tripodal molecular pocket, L has been prepared and mono copper complex of L, (1) having Cu-N4-π··· hole as recognizing elements, becoming a potential and selective colorimetric chemo sensor for perfect linear recognition of N3-, generate a Cu-NNN- π··· hole unit inside the tripodal pocket. Systematic spectrometric and naked-eye colorimetric studies reveal that, this chemo sensor is also colorimetrically recognizing the cyanide ion by its cavity via Cu-N4-π···hole interactions; nevertheless, when azide anion is entering as a guest into the molecular pocket of 1 which is already hosted cyanide anion, then host displaces cyanide ion, subsequently azide is getting inside the cavity. The strength of the copper complex, 1 towards azide and cyanide are found to be 2.36×103M-1, and 1.87×103 M-1 respectively in 7:3 acetonitrile:water solvent medium. Further, the ability of cyanide displacement by azide in complex 1 is found to be 2.53×103 M-1. To the best of our knowledge, this is the first example of naked-eye detection of azide via cyanide displacement assay by a tripodal receptor.

Altered metal ion selectivity in signalling with heterocyclic tripodal receptor appended rhodamine-B derivatives

The rhodamine derivatives (2–7) were shown to exhibit metal ion complexation induced photophysical ‘turn-on’ signalling responses, where the selectivity in signalling were driven by stereo-electronic environment of the receptor units that structurally differ as derivatization of different heterocyclic units. The chromogenic and fluorogenic spectral enhancements of two order higher in logarithmic scale were observed in these tripodal receptor incorporated amino-ethyl-rhodamine probes, where substitution of a 2-[2-[(thiophen-2-yl-methyl)-(2-pyridinylmethyl)-amino]-ethyl]- (as in 3) has shown selectivity for Hg(II) ion, a 2-[2-[(furan-2-yl-methyl)-(2-pyridinyl methyl)-amino]-ethyl]- (as in 5) for Al(III) ion and a 2-[2-[(phen-2-ylmethyl)-(2-pyridinylmethyl)-amino]-ethyl]- (as in 7) for Fe(III) ion respectively. The higher order of association constants (log Ka > 9.0) of complexation, high sensitivity of detection(LOD < 2 nM) and higher rate of interaction between probe and metal ion (k ~ 0.001 s−1) have showed potential of these probes in selective detection of corresponding metal ions. In general, the investigations on complexation induced photophysical signalling in these probes in terms of selectivity and sensitivity of detection, association constants of complex formation, reversibility in signalling, execution at different pH range, kinetics of spiro-ring opening and theoretical structure elucidation have therefore put insights on their coordination mediated stereo-electronic environment to establish a rationality in structure-function correlation.

Most Efficient Tris(3-Aminopropyl) Amine Based Electron Deficient Tripodal Receptor for Azide.

Investigation on strength of the tris(2-amino ethyl) amine and tris (3-amino propyl) amine backboned tripodal receptors, L and L1 (incorporated with tripodal C3ν frame, thio urea-amide linkage and π-hole assisting functionality) which are premeditated to explore the prospect for a particular anion recognition are studied. UV-Vis, 1H- NMR, and IR spectroscopy studies indicates that both the receptors sensing azide anion, colorimetrically and binds azide anion stronger than any other anions such as acetate, and cyanide. In particular the receptor L1 shows the highest binding strength towards azide anion. To the best of our knowledge this is the first receptor showing highest binding ability with azide anion. We used Molecular Electrostatic Potential Surface analyses to support our spectroscopic findings. The association constant and limits of detection for receptor L1 with azide is found to be 8.4X105M-1 and 3.16X10-6 M respectively. The observed highest binding strength of L1 with azide is, could be due to the cooperative effect of extended traditional hydrogen bonding via thiourea-amide functionality, anion-π interaction and C3ν suitable framework.

Development of a synthetic strategy for Water soluble tripodal receptors: Two novel fluorescent receptors for highly selective and sensitive detections of Fe3+ and Cu2+ ions and biological evaluation

A general synthetic strategy is developed to synthesize water soluble receptors by employing tripodal system based on a cyclotriphosphaze platform. The developed model is successfully synthesized and characterized by using elemental analysis, FT-IR, MALDI-TOF, 1H NMR, 13C NMR and 31P NMR techniques. The fluorescence sensing performance of prepared water soluble tripodal systems were evaluated by UV/Vis and fluorescence spectroscopies. According to obtained results, two novel water-soluble sensing platforms were selective and sensitive fluorescence receptors for detections of Fe3+ and Cu2+ ions in both the absence and presence of competitive ions. In addition, the iron receptor also displays biological function, therefore, the cytotoxicity and fluorescence microscopy experiments were applied and it was demonstrated that compound 3 was non-cytotoxic, and can be used as fluorescence imaging sensors for Fe3+ in living cells. According to obtained results, proposed synthetic strategy could be applied to develop water soluble receptors for not only iron and/or copper ions but also many different metal ions of interest using a variety of fluoroionophores.

Selective encapsulation and extraction of hydrogenphosphate by a hydrogen bond donor tripodal receptor

Intramolecular N–H⋯OC hydrogen bonding between the inner amide groups dictates the receptor–anion complementarity in a tripodal receptor towards selective encapsulation of hydrogenphosphate in the outer urea cavity by multiple hydrogen bonds.

Design and synthesis of a tripodal receptor for the selective detection of Fe3+

The tripodalreceptor (Ty) was synthesized from naphthol and tren units.The metal ionrecognition property of the tripodalreceptor Ty was analysed using UV–Visible and fluorescence techniques. The structure of Ty receptor is confirmed by FT-IR and NMR spectral data. The Elemental and surface morphology were determined by EDAX and SEM analysis.Fluorescence analysis revealed a positive selectivity towards Fe3+ ions, in minimal conditions. Thereceptor Ty selectively recognizes Fe3+ ions through fluorescence switch-on process in which a bright green luminescence was observed on binding with Fe3+ ions. Further, thebinding stoichiometry for [Ty-Fe3+] exhibited 1:1 ratio and the binding constant value was found to be 5.1127 × 106 M−1.

Selective fluorescence sensing of H2PO4- by the anion induced formation of self-assembled supramolecular polymers.

The utilization of anions to induce the formation of self-assembled supramolecular polymers in solution is an undeveloped area of host-guest chemistry. We report in this manuscript a comparative study of two tripodal anion receptors by hydrogen or halogen bonding interactions to form self-assembled supramolecular structures induced by the presence of anions. DOSY NMR and DLS experiments provided evidence for the formation of supramolecular structures in solution in both halogen and hydrogen bond donors with H2PO4- anions. The nucleation and elongation constants obtained using the thermodynamic model indicate that the polymers grow following an isodesmic mechanism. Emission studies demonstrate that only the formation of the supramolecular polymer between the halogen bond donor receptor and H2PO4- anions results in the appearance of the excimer emission band.

Anion templated crystal engineering of halogen bonding tripodal tris(halopyridinium) compounds

Crystal engineering of halogen bonding tripodal receptors is found to be highly dependent on solvent and choice of anion.

A GFP-chromophore-based C3V-symmetric tripodal receptor with selective recognition of Hg(ii), Fe(iii) and Cr(iii)

A GFP-chromophore tripodal receptor with a diameter of cavity = 2.7–3.5 Å selectively captures Hg2+, Fe3+ or Cr3+ ions.