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In the present work, a new triazine-based intermediate containing bis(2-pyridylmethyl)amine and benzothiazole units was designed and synthesized with the purpose of selective and sensitive cation detection. The related sensor candidate IV was characterized chemically and photophysically with the assistance of FTIR, UV–Vis, fluorescence, DLS, 1H- and 13C-NMR spectroscopic techniques along with HRMS data. Photophysical studies of this sensor molecule exhibited aggregation dependent emission enhancement with polarity increment that have been explained on the basis of aggregation induced emission phenomenon. Within this context, DMSO:H2O (50:50, v/v) was determined as the most appropriate solvent mixture and the chemosensor has been found to detect Zn2+ selectively in this aqueous medium by fluorescence enhancement. The detection limit of the turn-on sensor IV for Zn2+ was found to be 0.011 μmol L−1. Along with the support of HRMS data, the binding stoichiometry of IV to Zn2+ was revealed as 1:1 from the Job's plot analysis and the binding constant of IV − Zn2+ complex was calculated as 9.31 × 106 M−1 by Benesi-Hildebrand plot. Moreover, the linear response range between the values of 50–1000 μmol L−1 for Zn2+ ions was observed and selective detection of Zn2+ among other competitive metal ions including Cd2+ was provided. The newly synthesized sensor that may offer a different perspective was successfully applied to determine Zn2+ in real sample with good recovery and reproducibility. [ABSTRACT FROM AUTHOR]

As one of the most important minerals in the body, potassium is vital for the heart and neurons. Methods that can non‐invasively and accurately monitor changes in potassium balances would benefit disease diagnoses as well as offer insight into pathologies. Among the sensing approaches, fluorescent probes serve as a unique detection method for its simplicity, tunable detection range, and bioimaging ability. The design of new probes with highly selective K+ receptors and transduction functionality remains a challenge that is motivated by numerous sensing and detection applications. In this minireview, fluoroionophores are summarized that undergo transduction, producing fluorescence signals when interacting with, e. g. potassium ions. The properties of ionophores (afford selective interaction with potassium) and fluorophores (generate signal read‐out) are discussed. Molecular structure design and sensing mechanisms are included along with cell imaging applications. The selectivity towards K+ and the absorption/emission characteristics of the probes are of particular interest. [ABSTRACT FROM AUTHOR]

A novel click derived fluorescence signaling system bearing two different coumarin derivatives connected via a triazole linkage has been developed as a fluorescent chemosensor with high selectivity toward Ca 2+ and Fe 3+ ions. A significant increase in fluorescence was observed when coumarin derivatives upon complexation with Ca 2+ , whereas fluorescence quenching was observed upon complexation with Fe 3+ . The fluorescence enhancement/quenching in the sensor is governed by a photoinduced electron transfer (PET) process in which the energy level ordering of the excited states is altered by the formation of 1:1 complexes of Ca 2+ /Fe 3+ with the coumarin derivatives. [ABSTRACT FROM AUTHOR]

A novel sensing concept for the selective detection of ammonia over amines is introduced. For the first time, the reversible fluorescence-based NH 3 sensor makes use of an ammonium-sensitive fluoroionophore instead of commonly utilized pH indicators. NH 3 diffuses into the sensor where a buffered internal electrolyte generates the corresponding ammonium ion, which is then detected by an ion selective NIR fluoroionophore. [ABSTRACT FROM AUTHOR]

A new malonate possessing two pyrene moieties was synthesized as a fluoroionophore, and its structure and fluorescence spectroscopic properties were investigated. When excited at 344 nm in acetonitrile/chloroform (9:1, v/v), the synthesized bispyrenyl malonate has the fluorescence of intramolecular excimer (λem = 467 nm) emissions and not a pyrene monomer emission (λem = 394 nm). A large absolute fluorescence quantum yield was obtained in the solid state (ΦPL = 0.65) rather than in solution (ΦPL = 0.13). X-ray crystallography analysis clarified the molecular structure and alignment of the bispyrenyl malonate in the crystal phase, elucidating its fluorescence spectroscopic properties. Such analysis also suggests there are intramolecular C--H•••π interactions and intermolecular π•••π interactions between the pyrenyl rings. Interestingly, the synthesized bispyrenyl malonate exhibits excellent fluorescence sensing for the Cu2+ ion. Remarkable fluorescence intensity enhancement was only observed with the addition of the Cu2+ ion. [ABSTRACT FROM AUTHOR]

New podand-type fluoroionophores having two pyrene moieties: 2,2´-bis(1-pyrenylacetyloxy)diphenyl sulfide (3), 2,2´-bis(1-pyrenylacetyloxy)diphenyl sulfoxide (4), and 2,2´-bis(1-pyrenylacetyloxy)diphenyl sulfone (5), have been synthesized by connecting two 1-pyrenecarbonylmethyl groups with the two hydroxy groups of 2,2´-dihydroxydiphenyl sulfide, sulfoxide, and sulfone, respectively. Their complexation behavior toward alkali metal ions was examined by fluorescence spectroscopy. Among these fluoroionophores, compound 4, having a sulfinyl group, showed high selectivity toward Li+.

A new macromolecule possessing two dansyl moieties and based on 2-[4-(2-aminoethylthio)butylthio]ethanamine was prepared as a fluorescent sensor and its mercury sensing properties toward various transition metal, alkali, and alkali earth ions were investigated. The designed compound exhibited pronounced Hg2+-selective ON-OFF type fluorescence switching upon binding. The new compoundprovided highly selective sensing to Hg2+ in acetonitrile-water solvent mixtures with a detection limit of 2.49 x 10-7 M or 50 ppb. The molecular modeling results indicated that ions-recognition of the sensor originated from a self assembly process of the reagentand Hg2+ to form a helical wrapping structure with the favorable electrostatic interactions of Hg2+coordinated with sulfur, oxygen, nitrogen atoms and aromatic moieties.

Small-molecule fluorescent probes play a myriad of important roles in chemical sensing. Many such systems incorporating a receptor component designed to recognise and bind a specific analyte, and a reporter or transducer component which signals the binding event with a change in fluorescence output have been developed. Fluorescent probes use a variety of mechanisms to transmit the binding event to the reporter unit, including photoinduced electron transfer (PET), charge transfer (CT), Förster resonance energy transfer (FRET), excimer formation, and aggregation induced emission (AIE) or aggregation caused quenching (ACQ). These systems respond to a wide array of potential analytes including protons, metal cations, anions, carbohydrates, and other biomolecules. This review surveys important new fluorescence-based probes for these and other analytes that have been reported over the past five years, focusing on the most widely exploited macrocyclic recognition components, those based on cyclam, calixarenes, cyclodextrins and crown ethers; other macrocyclic and non-macrocyclic receptors are also discussed. [ABSTRACT FROM AUTHOR]

Novel N - n -butyl-1,8-naphthalimide derivatives with mono- or di-substitution to the C-4 position containing a N atom and a carbonyl have been synthesized as a efficient silver(I) fluorescent sensor. The ligand structures were confirmed by IR, NMR, MS, and elemental analysis. A highly sensitive spectrofluorometric method based on chelation-assisted fluorescence quenching was developed for trace-level detection, estimation and speciation studies of silver(I) in ethanol-water. The ligand exhibits emission and excitation maxima at 525 nm and 420 nm, respectively. The novel fluorescent sensor exhibited selective binding toward Ag(I) and pH insensitivity over a biologically relevant range. The interference of foreign ions was observed to be negligible. [ABSTRACT FROM AUTHOR]

The decay pathways with relative quantum efficiencies for photoexcited trans -aminostilbenes in dilute organic solutions at ambient temperature are reviewed. Like the case of the parent trans -stilbene, fluorescence and the vinylene C C torsion are two important decay pathways for trans -aminostilbenes. However, a new pathway, that is, formation of a TICT state by twisting the phenylene-amino C N bond, dominates the excited-state deactivation of some trans -aminostilbenes in medium and/or highly polar solvents. On the basis of the quantum yields of fluorescence (Ф f ) and the trans → cis isomerization (Ф tc ) in solvents of different polarity, the TICT-forming activity of trans -aminostilbenes could be readily probed. The TICT states could be unambiguously characterized with ring-bridged model compounds, profiles of the emission spectra, and variable–temperature emission spectra. The interplay among fluorescence, the trans → cis isomerization, and the TICT state formation strongly depend on the nature and position of the amino group(s), the solvent polarity, and the other substituents that significantly perturb the steric and/or electronic properties. This provides a unique opportunity toward the design of novel fluorescent probes, light-emitting materials, and molecular switches. [ABSTRACT FROM AUTHOR]

4,5-Bis(hydroxymethyl) acridine (sensor 1) has been discovered and synthesized as a simple-structured Pd 2+ fluorescent probe. Sensor 1 showed highly selective recognition toward Pd 2+ over other examined metal ions in aqueous solution. Under the optimized condition, fluorescence intensity was linearly proportional to the concentration of Pd 2+ in the 0–1 μM concentration range with detection limits of 0.021 μM. The EDTA-adding and stoichiometry experiments indicated that sensor 1 was a reversible chemosensor for Pd 2+ with a 2:1 ligand/metal complex at neutral pH. Moreover, the sensor 1 was also successfully applied to determination of Pd 2+ in water samples and palladium-containing catalyst, which made it attractive for sensing applications. [ABSTRACT FROM AUTHOR]

A series of malonamides possessing two quinoline moieties were synthesized and characterized as fluoroionophores for the Zn 2+ ion. We focused on the relationship between the substituents introduced to the C2-position of the malonamides and their Zn 2+ ion-selectivity, exploiting the structural effect of the substituents in the design of the fluoroionophores with high selectivity. The substituents introduced to the malonamides were the methyl, benzyl and naphthalenylmethyl groups. In dimethyl sulfoxide solvent, all substituted bisquinolinyl malonamides showed excellent fluorescence sensing for the Zn 2+ ion, while unsubstituted bisquinolinyl malonamide 1 displayed ratiometric sensing for the Co 2+ ion. N , N ′-Bis(8-quinolyl)-2-methyl-2-naphthalenylmethyl malonamide 4 exhibited the highest Zn 2+ ion-selectivity against the Cd 2+ ion. Although the substituents introduced into the C2-position are spatially distant from the quinoline recognition moiety, this study indicated that they greatly influenced the ion selectivities of the bisquinolinyl malonamides. Furthermore, it was demonstrated that visible fluorescence analyses could be performed on malonamide 4 . [ABSTRACT FROM AUTHOR]

Abstract: Fluorescence spectroscopy has great potential for on-site and real-time monitoring of pollutants in aquatic environments; however, its application to environmental aquatic samples has been extremely limited. In this study, a novel fluoroionophore based on a BODIPY-terpyridine conjugate was developed and applied to determine Zn concentrations in urban runoff. The fluoroionophore selectively bound to Zn2+ in water, which led to an instant red-shift of the fluorescence peak of the fluoroionophore from 539 nm to 567 nm that could be seen by the naked eye. Zn concentrations could be quantified using the ratio of fluorescence intensities, and the detection limit was 9 μg/L, which is sufficiently low for environmental aquatic samples. To demonstrate applicability of the method to environmental samples, we measured Zn concentrations in urban runoff samples with a complex matrix (∼60 mg/L dissolved organic carbon and ∼20 mS/cm electrical conductivity). The total and dissolved fractions of Zn in the samples could be determined by fluorescence spectroscopy and its relative error was estimated to be less than 30% by inductively coupled plasma-atomic emission spectroscopy analysis. The proposed method is rapid and easy-to-use with simple pretreatment for Zn determination in environmental aquatic samples with complex matrices. [Copyright &y& Elsevier]

A new fluorescent sensor for the highly sensitive and selective determination of La3+ ion is developed. The sensing membrane was prepared by incorporating N,N′-bis(dansylamidoethyl)-N,N′-bis(2-pyridylmethyl)propylenediamine (L) as fluoroionophore in the plasticized PVC membrane containing o-NPOE as plasticizer. The proposed sensor displays a wide calibration range of 5.0×10−9 to 5.0×10−4 M with a low limit of detection of 2.0×10−9 M in a solution of pH 6.0. This sensor has a relatively fast response time of less than 2min. In addition to high stability and reproducibility, it shows a unique selectivity toward La3+ ion with respect to common coexisting cations. The sensor can be regenerated by exposure to a solution of EDTA. The proposed sensor was successfully applied to the determination of La3+ in aqueous solutions. [ABSTRACT FROM AUTHOR]

Abstract: A new acridine fluoroionophore containing two iminodiacetic acid ligands, Acridinyl Tetra Acid (ATA), was synthesized. The fluorescence sensing behavior of ATA toward metal ions was investigated in buffered aqueous media. The presence of Cu2+ resulted in significant quenching of the fluorescence emission from ATA, while other metal ions posed little interferences, if any. The fluorescence response was concentration-dependent and can be well described by the modified Stern–Volmer equation. A good linear relationship (R 2=0.9952) was observed up to 3.0×10−6 molL−1 Cu2+ ions. The detection limit, calculated following the 3σ IUPAC criteria, was 1.24×10−7 molL−1. The presence of Cu2+ induces the formation of a 1:1 ligand/metal complex at neutral pH. [Copyright &y& Elsevier]

Abstract: A novel fluorescent chemical sensor for the highly sensitive and selective determination of Fe3+ ions in aqueous solutions is prepared. The iron sensing system was prepared by incorporating 5-(8-hydroxy-2-quinolinylmethyl)-2,8-dithia-5-aza-2,6-pyridinophane (L) as a neutral Fe3+-selective fluoroionophore in the plasticized PVC membrane containing sodium tetraphenylborate as a liphophilic anionic additive. The response of the sensor is based on the strong fluorescence quenching of L by Fe3+ ions. At pH 5.5, the proposed sensor displays a calibration curve over a wide concentration range from 6.0×10−4 to 1.0×10−7 M, with a relatively fast response time of less than 2min. In addition to a high stability and reproducibility, the sensor shows a unique selectivity toward Fe3+ ion with respect to common coexisting cations. The proposed fluorescence optode was applied to the determination of iron(III) content of straw of rice, spinach and different water samples. The fluorescent sensor was also used as a novel probe for Fe3+/Fe2+ speciation in aqueous solution. [Copyright &y& Elsevier]

Abstract: We have developed a series of fluoroionophores from diamine-salicylaldehyde (DS) derivatives and studied their spectra diversity when interacting with a variety of metal cations. Based on our results, 2-((E)-(2-(dimethylamino)ethylimino)methyl)-4-(4-methoxystyryl)phenol (I) can specifically chelate Zn+2 in both organic and semi-aqueous solution. Furthermore, 2-((E)-(2-(dimethylamino)ethylimino)methyl)-4-((E)-2-(pyridin-4-yl)vinyl)-phenol (II) is an excellent metal recognizer, successfully identifying Zn+2 from acetates, chloride and perchlorate salts. In addition, control compound (E)-N-(2-methoxy-5-((E)-2-(pyridin-4-yl)vinyl)benzylidene)-N′,N′-dimethyl-ethane-1,2-diamine (IV) also showed specific metal response to Cd+2 from Cd(OAc)2 over other anions. This anionic-dependent metal binding behavior was imparted by the pyridine moiety, which supports extra intermolecular metal-fluorophore complexation. Fluoroionophores I and II were preliminarily tested for cellular metal staining in general fluorescence and ratio fluorescence methods. [Copyright &y& Elsevier]

Abstract: A novel fluorescent probe with naphthalimide as fluorophore and di(2-picolyl)amino unit as receptor for Cu(II) was designed and synthesized. In water/acetonitrile solution, the presence of Cu2+ ions induced significant blue shift on the maximum absorption band as well as complete fluorescence quenching due to the formation of a 1:1 metal–ligand complex. It exhibited high selectivity toward Cu(II) and no interference from other metal ions was observed. The structure of the complex was characterized by single crystal X-ray diffraction experiments. The results of this research demonstrate successfully that excellent sensing properties can be achieved by a small organic compound with very simple structure. This is also the first single crystal structure which reveals directly the coordination pattern of fluorescent probe bearing di-2-picoly-amine unit with Cu(II). [Copyright &y& Elsevier]

Abstract: Two novel macromolecules based on 2-[3-(2-aminoethylsulfanyl)propylsulfanyl]ethanamine covalently bound to one and two units of rhodamine-B moieties, 1 and 2, were prepared and utilized as fluoroionophores and chromophores for the optical detection of Hg2+ ions. The sensors were readily prepared by a conventional two-step synthesis. Especially, sensor 1 exhibits high sensitivity and selective OFF–ON fluorescence enhancement and chromogenic change upon binding to Hg2+, which served as a “naked-eye” indicator by a noticeable color change of the solution (from colorless to pink–red color). 1 is shown to discriminate various competing metal ions, particularly Ag+ and Cu2+, as well as Cd2+, Na+, Li+, K+, Ba2+, Co2+, Ni2+, Mg2+, Mn2+ and Al3+, with a detection limit of 10ppb. [Copyright &y& Elsevier]

Abstract: A novel fluorometric sensor bearing three dansyl moieties based on tris[2-(2-aminoethylthio)ethyl]amine was prepared by a simple approach using a conventional two-step synthesis. The sensor exhibits highly Hg2+-selective ON–OFF fluorescence quenching behavior in aqueous acetonitrile solutions and is shown to discriminate various competing metal ions, particularly Cu2+, Ag+, and Pb2+ as well as Ca2+, Cd2+, Co2+, Fe3+, Mn2+, Na+, Ni2+, and Zn2+, with a detection limit of 1.15×10−7 M or 23ppb. [Copyright &y& Elsevier]

Abstract: A new acridine fluoroionophore containing two diethanolamine ligands, 4,5-bis(N,N-di (2-hydroxyethyl)iminomethyl)acridine (BHIA), was designed and synthesized based on the fluorophore-spacer-receptor format. And its fluorescent sensing behavior towards metal ions was investigated in buffered aqueous media. The presence of Cd2+ induces the formation of a 1:1 ligand/metal complex at neutral pH, which exhibits enhanced emission at 454nm. The fluorescence intensity is linear with the Cd2+ concentration in the range of 1.0×10−6 to 3.0×10−5 M (R =0.9967). Experimental results show a low interference response towards other metal ions. The selective switch-on fluorescence response of BHIA to Cd2+ makes it suitable for sensing of Cd2+ in aqueous solution. The detection limit is 1.3×10−7 M. Moreover, the results indicated that BHIA was a reversible chemosensor for Cd2+, which makes it attractive for sensing applications. [Copyright &y& Elsevier]

New podand-type fluoroionophores having two pyrene moieties: 2,2′-bis(1-pyrenylacetyloxy)diphenyl sulfide (3), 2,2′-bis(1-pyrenylacetyloxy)diphenyl sulfoxide (4), and 2,2′-bis(1-pyrenylacetyloxy)diphenyl sulfone (5), have been synthesized by connecting two 1-pyrenecarbonylmethyl groups with the two hydroxy groups of 2,2′-dihydroxydiphenyl sulfide, sulfoxide, and sulfone, respectively. Their complexation behavior toward alkali metal ions was examined by fluorescence spectroscopy. Among these fluoroionophores, compound 4, having a sulfinyl group, showed high selectivity toward Li+. [ABSTRACT FROM AUTHOR]

Abstract: A novel fluorescence chemical sensor for the highly sensitive and selective determination of Pb2+ ions in aqueous solutions is described. The preliminary potentiometric and spectrofluorimetric complexation studies in solution revealed that the lipophilic ligand 5,8-bis((5′-chloro-8′-hydroxy-7′-quinolinyl)methyl)-2,11-dithia-5,8-diaza-2,6-pyridinophane (L2) forms a highly stable and selective [PbL2]2+ and [Pb(L2)2]2+ complexes which results in a strong fluorescence quenching of the ligand. Thus, a novel fluorescence Pb2+ sensing system was prepared by incorporating L2 as a neutral lead-selective fluoroionophore in the plasticized PVC membrane containing tetrakis(p-chlorophenyl) borate as a liphophilic anionic additive. The response of the sensor is based on the strong selective fluorescence quenching of L2 by Pb2+ ions. At pH 5.5, the proposed sensor displays a calibration curve over a wide concentration range of 3.0×10−7 to 2.5×10−2 M with a relatively fast response time of less than 5min. In addition to high stability, reversibility and reproducibility, the sensor shows a unique selectivity towards Pb2+ ion with respect to common coexisting cations. The proposed fluorescence optode was successfully applied to the determination of lead in plastic toys and tap water samples. [Copyright &y& Elsevier]

A new macromolecule possessing two dansyl moieties and based on 2-[4-(2-aminoethylthio)butylthio]ethanamine was prepared as a fluorescent sensor and its mercury sensing properties toward various transition metal, alkali, and alkali earth ions were investigated. The designed compound exhibited pronounced Hg2+-selective ON-OFF type fluorescence switching upon binding. The new compound provided highly selective sensing to Hg2+ in acetonitrile-water solvent mixtures with a detection limit of 2.49 × 10-7 M or 50 ppb. The molecular modeling results indicated that ions-recognition of the sensor originated from a self assembly process of the reagent and Hg2+ to form a helical wrapping structure with the favorable electrostatic interactions of Hg2+coordinated with sulfur, oxygen, nitrogen atoms and aromatic moieties. [ABSTRACT FROM AUTHOR]

We discuss an interpretation of the emission signal of a class of dimethylaminobenzonitrile (DMABN) derivatives, based on a stochastic model approach. This study is prompted by the interest in building relatively simple theoretical tools for understanding the static and dynamic properties of metal chelation-controlled fluorescent molecular systems with internal flexibility and solvation effects, which can be used as fluorescent sensors of metal ions. We proceed by extending a stochastic modeling approach, previously used for DMABN, in which internal degrees of freedom are coupled to an effective solvent relaxation variable. The model is based on an integrated approach that combines stochastic methods and QM calculations. The static and dynamic properties of the molecule are obtained by a combination of a continuum treatment and a detailed solute dynamics. Simple computational approximations lead to a semianalytical treatment of the resulting equations, which reproduce correctly the static spectra at room temperature of 4-(1-aza-4,7,10-trioxacyclododecyl) benzonitrile (DMABN-Crown4) and 4-(1-aza-4,7,10,13-tetraoxacyclododecyl) benzonitrile (DMABN-Crown5) in solvents with different polarity. A qualitative analysis of the dynamic spectra of the DMABN-Crown4 is also presented. A discussion is finally provided on how combined quantum and classical methods can be used to define a general robust and reliable computational approach for predicting fluorescence properties of organic molecules in solution. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 [ABSTRACT FROM AUTHOR]

Dichlorofluorescein derivatives with two aza-crown ether binding units were prepared by the Mannich reaction and their chemosensing behaviors toward transition metal ions were investigated. An 18-crown-6 ether derivative exhibited pronounced Cu2+-selective fluorescence signaling, with selectivity over other common physiologically important alkali, alkaline earth and transition metal ions. The compound also displayed 1:1 complex formation with Cu2+ ion, with a detection limit of 2.9×10−6 M in an aqueous 50% DMSO solution at pH 7, showing that it may offer potential as a chemosensor for the detection of submillimolar Cu2+ ions in physiological environments. A 15-Crown-5 ether analogue also revealed selective Cu2+ signaling, although with somewhat diminished selectivity compared with its 18-crown-6 counterpart. [Copyright &y& Elsevier]

Abstract: A novel macromolecule based on 2-[3-(2-aminoethylthio)propylthio]ethanamine covalently bound to two 7-nitrobenzo-2-oxa-1,3-diazolyl moieties was prepared as a fluoroionophore and a chromophore for the selective optical detection of Hg2+. The sensor was prepared in two steps and its fluoroionophoric and chromophoric properties toward various transition metal, alkali, and alkali earth cations were investigated. Compound 4 selectively binds Hg2+, and the binding is indicated by both fluorescence quenching and a chromogenic change which can be detected by the naked eye. In an 80:20 acetonitrile/water solvent mixture, 4 acts as an ON–OFF fluorescence switch upon Hg2+ binding, exhibiting efficient quenching and a detection limit of 10−7 M or 20ppb. [Copyright &y& Elsevier]

The recent advances in the development of fluorescent heteroditopic ligands of metal ions are reviewed. The scientific endeavour in this area is fuelled partly by the need for sensing technologies that are (1) targeting substances over large concentration ranges and (2) capable of analysing multiple analytes simultaneously. These objectives are largely not attainable using monotopic coordination platforms. The investigations of the fluorescent heteroditopic ligands of metal ions have revealed surprisingly intricate interplays between metal coordination at two different sites and the photophysical states that are accessible through those systems. The chemical complexity of fluorescent heteroditopic ligands of metal ions warrants further investigations on the fundamental science front in order to fully acquire their potential for meeting our practical needs. [ABSTRACT FROM AUTHOR]

Abstract: A new multichromophoric cyclodextrin substituted with benzothiadiazoyl-triazole moiety has been synthesized by a one-pot click reaction between azido-cyclodextrin and TMS-ethynyl benzothiadiazole in the presence of TBAF. This fluorescent chemosensor exhibits a high selectivity to Ni2+ among a series of cations in CH3CN solution. The association constant for the 1:1 complex was determined to be 2.88×107 M−1. [Copyright &y& Elsevier]

Abstract: Novel coronene fluoroionophores, N,N′-dipropyl-5,11-bis[4-(1-aza-18-crown-6)phenyl]cornene-2,3,8,9-tetracarboxy diimide (4), and N,N′-dipropyl-5,11-bis[4-(calix[4]azacrown-5-crown-5)phenyl]coronene-2,3,8,9-tetracarboxy diimide (6), were prepared by reacting N,N′-dipropyl-5,11-bis(p-chlorophenyl)coronene-2,3,8,9-tetracarboxy diimide (3) with 1-aza-18-crown-6 or calix[4] azacrown-5-crown-5. Alternating copolymers, 5 and 7, with a similar repeating unit were prepared by reacting 7,16-diaza-18-crown-6 or calix[4]bisazacrown-5 with compound 3. The fluoroionophoric characteristics were investigated by binding alkali, alkali earth metal and various metal ions. The model and polymeric fluoroionophores exhibited significant decreasing fluorescence effects with K+, Ag+ and Ba2+, which were attributed to photoinduced charge transfer (PCT). [Copyright &y& Elsevier]

Abstract: This article describes the design, synthesis and characterization of an optical sensor suitable for practical measurement of ionized calcium in serum and whole blood samples. The key to the development of this sensor is the identification of a chemically very stable, nitrogen-containing, calcium selective ionophore, coupled with a fluorophore having the correct spectral and electron accepting properties. The slope of the sensor is about 34%/mM in the typical clinically significant range of 0.32–2.2mM. This sensor has been implemented into the disposable cartridge, used for commercially available OPTI CCA analyzer with precision better than ±0.02mM (1S.D.). The sensor displays excellent stability against hydrolysis and oxidation, leading to less than 0.02mM measurement error after 9 months of wet storage at room temperature, up to 30°C. [Copyright &y& Elsevier]

Materials containing new chromoionophores consisting of crown residue and azole moiety as parts of macrocycles were encapsulated by the sol-gel procedure in silica xerogel matrices and proposed as chemical recognition elements especially for such metal ions as Li+, Cs+ and Cu2+. Action of these recognition elements is in principle based on changes of reflectance. The recognition elements containing 21membered chromogenic derivatives of unsubstituted imidazole and 4-methylimidazole are able to distinguish in aqueous solution whether the Li+ concentration ratio is lower or higher then 1. In the case of Cu2+ complexes with 18-membered macrocyclic chromoionophore in which phenol residue was replaced by imidazole and 21-membered chromogenic derivative of 4-methylimidazole, values of the EPR parameters g and A suggast participation of two oxygen and two nitrogen atoms of the ligend in the equatorial plane of the tetragonally distorted octahedral environment of the central ion. [ABSTRACT FROM AUTHOR]

Abstract: Heterocycles have been modified in various ways in the search for new functions, but few examples are known of crown ethers incorporating heterocycles in macro-ring systems. Here we report a simple and versatile synthesis of crown ether-bearing heterocycles. An acylurea moiety in the heterocycles is efficiently transformed to ‘crown ether’ of various ring sizes. The products included a Ca2+-selective fluoroionophore. Our simple methodology is expected to provide many novel functional heterocyclic compounds, including fluoroionophores and candidate pharmaceuticals. [Copyright &y& Elsevier]

Abstract: New dioxocyclam derivatives bearing two anthracene fluorophores were prepared, and their fluoroionophoric properties toward transition metal ions were investigated. Chemosensor 2 having anthrylacetamide moieties exhibited pronounced Hg2+- and Cu2+-selective fluoroionophoric properties in aqueous acetonitrile solution over other representative transition metal ions, as well as alkali and alkaline earth metal ions. Chemosensor 2 also exhibited Hg2+ and Cu2+ selectivity under competitive conditions in the presence of physiologically and environmentally important metal ions. The detection limits for the sensing of Hg2+ and Cu2+ ions were 7.8×10−6 and 1.5×10−6 M, respectively, in aqueous 95% acetonitrile solution. [Copyright &y& Elsevier]

Abstract: Lipophilic H+-selective fluorophores such as Nile Blue derivatives are widely used in ISE-based pH sensors and bulk optodes, and are commonly dissolved in a plasticized matrix such as PVC. Unfortunately, leaching of the active sensing ingredients and plasticizer from the matrix dictates the lifetime of the sensors and hampers their applications in vivo, especially with miniaturized particle based sensors. We find that classical copolymerization of Nile Blue derivatives containing an acrylic side group gives rise to multiple reaction products with different spectral and H+-binding properties, making this approach unsuitable for the development of reliable sensor materials. This limitation was overcome by grafting Nile Blue to a self-plasticized poly(n-butyl acrylate) matrix via an urea or amide linkage between the Nile Blue base structure and the polymer. Optode leaching experiments into methanol confirmed the successful covalent attachment of the two chromoionophores to the polymer matrix. Both polymerized Nile Blue derivatives have satisfactory pH response and appropriate optical properties that are suitable for use in ion-selective electrodes and optodes. Plasticizer-free Na+-selective microsphere sensors using the polymerized chromoionophores were fabricated under mild conditions with an in-house sonic microparticle generator for the measurement of sodium activities at physiological pH. The measuring range for sodium was found as 10−1–10−4 M and 1–10−3 M, for Nile Blue derivatives linked via urea and amide functionalities, respectively, at physiological pH. The observed ion-exchange constants of the plasticizer-free microsphere were log K exch =−5.6 and log K exch =−6.5 for the same two systems, respectively. Compared with earlier Na+-selective bulk optodes, the fabricated optical sensing microbeads reported here have agreeable selectivity patterns, reasonably fast response times, and more appropriate measuring ranges for determination of Na+ activity at physiological pH in undiluted blood samples. [Copyright &y& Elsevier]

Abstract: A new chemosensor with a phenanthroimidazole subunit based upon calix[4]arene-diamide has been synthesized, and its Mg2+-selective fluoroionophoric properties were investigated in an aqueous DMSO solution. The compound exhibited a pronounced Mg2+-selective fluoroionophoric behavior over other physiologically relevant metal ions. A significant red shift in fluorescence emission (Δλ =86nm) provided the ratiometric determination as well as naked-eye detection of Mg2+ ions. [Copyright &y& Elsevier]

Abstract: Bis(pyrene) derivative of diazatetrathia-crown ether has been prepared and its Hg2+-selective fluoroionophoric properties were investigated. The compound showed a pronounced Hg2+-selectivity and other metal ions except for Cu2+ showed almost no discernible responses. The Hg2+-selectivity of the compound was also confirmed by the competitive experiments performed in the presence of physiologically important metal ions and the detection limit was found to be 1.6×10−6 M. The prominent selective and efficient fluorescence quenching behavior could be utilized as a new chemosensing system for the analysis of toxic Hg2+ ions in aqueous environment. [Copyright &y& Elsevier]

Abstract: A novel fluoroionophore 1 based on 2,2′-binaphthalene bearing two monoaza-15-crown-5 ethers at 8- and 8′-positions was prepared. UV–vis and fluorescence responses of 1 upon the addition of alkali and alkaline earth metal cations were evaluated in 15% MeOH–MeCN. Receptor 1 showed unique response for Ba2+ due to the formation of an intramolecular sandwich complex. [Copyright &y& Elsevier]

Abstract: The synthesis and metal binding properties of cation-sensitive fluorescent indicators intended for biological applications are described. The increase of the crown ether ring size enhances the affinity for larger cations, but weakens the fluorescent response and selectivity. A compound having a 15-crown-5 chelator directly attached to a 2,7-difluoroxanthenone fluorophore loads into live cells and responds to sodium ion concentration changes with large fluorescence increases in the visible wavelength range. [Copyright &y& Elsevier]

The chelating ligand (2,2′-C12H8O2)P(CH2CH2O)4P(2,2′-O2C12H8) reacts with both Ru(bpy)2(O3SCF3)2 and Mo(CO)4(C7H8) to form the new metallacrown ether complexes cis-[Ru(bpy)2((2,2′-C12H8O2)P(CH2CH2O)4P(2,2′-O2C12H8))](O3SCF3)2 (1) and cis-[Mo(CO)4((2,2′-C12H8O2)P(CH2CH2O)4P(2,2′-O2C12H8))] (2). The X-ray crystal structures for both complexes indicate that the metallacrown ether ring oxygen atoms point their lone pairs towards the cavity in the cis-metallacrown ether ring. The effect of interactions of the metallacrown ether complex with selected monoatomic cations (Li+, Na+ and Hg2+) on the emissive properties of the Ru(bpy)2 2+ chromophore were studied by steady-state and time-dependent emission spectroscopy. Our results suggest that complex 1 interacts weakly with Li+, Na+ and Hg2+, and subtle changes are observed in its photophysical properties. These changes are discussed in terms of excited-state parameters obtained from a Franck–Condon analysis of the emission spectra. [Copyright &y& Elsevier]

The photophysical and complexing properties of a series of fluoroionophores based on coumarin 343 linked to monoaza-crown ethers are presented. Aiming to modify the selectivity of the fluorescing probe, the complexing cavity is rigidified by the incorporation of benzo groups. Complexation of alkaline-earth cations (magnesium and calcium) induces marked modifications of the photophysical properties of the probes in acetonitrile and in ethanol, whereas the alkaline cations induce only very weak modifications. The stoichiometry of the complexes is 1:1, except for C343-crown and C343-benzocrown in acetonitrile, where two complexes can be formed with calcium. The results obtained show that rigidification of the complexing cavity improves selectivity, favouring the complexation of Mg2+ and Ca2+ versus Li+. Competition between Mg2+ and Ca2+ has also been studied. [Copyright &y& Elsevier]

N-(9-methylanthracene)-25,27-bis(1-propyloxy)-4-tert-butylcalix[4]arene-azacrown-3 (I) was synthesized and tested as a fluoroionophore for the selective detection of lithium cations. The efficiency of photoinduced electron transfer in this fluoroionophore is sensitive to the presence of lithium ions. When exposed to lithium ions in a 75:25 (v/v) dichloromethane/THF solvent mixture, the molecule acted as an “off–on” fluorescence switch exhibiting a >106-fold enhancement in fluorescence emission intensity. Selectivity studies demonstrated that I effectively discriminates against sodium and potassium: log KLi,Na=−3.8 and log KLi,K=−2.3. [Copyright &y& Elsevier]

A new fluorogenic ionophore has been prepared by conjugating calix[4]-crown-5 ether with boron–dipyrromethene fluorophore. The ionophore exhibited a pronounced selective ON–OFF type response toward Ca2+ ions over other physiologically important metal ions of Na+, K+, and Mg2+. The interaction with Ca2+ ions resulted in very efficient quenching of fluorescence at 507 nm excited by relatively long wavelength irradiation at 480 nm. The selectivity ratios toward Ca2+ ions over other tested physiologically important metal ions were larger than 180 in aqueous 95% MeOH solution. [Copyright &y& Elsevier]

N-(9-methyl-anthracene)-25,27-bis(1-propyloxy)calix[4]arene azacrown-5 (II) and its model compound N-(9-anthrylmethyl)aza-18-crown-6 (I) were synthesized and tested as fluoroionophores for the selective detection of potassium ions with a view to the use of II in the fabrication of potassium ion sensors. Compound II consists of a 1,3-alternate calix[4]arene group covalently linked to an azacrown ether that is N-substituted with a fluorescent anthracene group. This compound acts as an ‘off–on’ fluorescent indicator for ion complexation. In dichloromethane solution, compound II exhibits good sensitivity to potassium ions and forms a 1:1 fluoroionophore–ion complex. Studies demonstrate that II is selective for potassium over other alkali metal cations, with excellent selectivity over sodium and lithium (log KK,Na∼log KK,Li≤−3.5) and moderate selectivity over rubidium and cesium (log KK,Rb∼log KK,Cs∼−1). Sensitivity of II to potassium is considerably enhanced in dichloromethane in comparison to methanol/dichloromethane mixtures, presumably due to two effects: a hydrogen-bonding interaction of methanol with the azacrown nitrogen atom, and poor solvation of the ion by dichloromethane, the latter creating a driving force for complexation. [Copyright &y& Elsevier]

A new benzothiazolyl functionalized ionophore based upon the calix[4]arene-crown-5 ether has been prepared and its fluoroionophoric properties toward Ca2+ ions were investigated. The compound exhibited a pronouncedly selective fluoroionophoric behavior toward Ca2+ ions among the surveyed physiologically important metal ions of Na+, K+, and Mg2+. Detection limit for Ca2+ ions was found to be 9×10−5 M in dioxane–water (80:20, v/v) solution. [Copyright &y& Elsevier]