Cyclams bearing diametrically disubstituted pyrenes as Cu2+- and Hg2+-selective fluoroionophores

New cyclam derivatives having diametrically disubstituted pyrene fluorophores were prepared and their fluoroionophoric properties toward transition metal ions were investigated. The compounds exhibited significant selectivity toward Hg2+ and Cu2+ ions in switching-off type responses in aqueous methanol or acetonitrile solution. Dipyrene-diamide derivative 3, having extra binding sites of the amide function, exhibited more pronounced chemosensing behavior toward Hg2+ and Cu2+ ions than its parent, dipyrene derivative 2. Detection limits for the analysis of Hg2+ and Cu2+ ions of dipyrene-diamide derivative 3 were 1.45x10(-6) and 1.30x10(-6) M, respectively. The diametrically disubstituted dipyrene-cyclam 2 may be utilized as a new starting platform for the design of other supramolecular fluorescent signaling systems having switching or chemosensing behaviors toward transition metal ions.     

Diametrically disubstituted cyclam derivative having Hg2+-selective fluoroionophoric behaviors

[reaction: see text] A new fluoroionophore has been synthesized by appending two signaling pyrenylacetamide subunits on the binding motif of 1,8-dimethylcyclam. The designed compound exhibited highly selective and sensitive fluoroionophoric behavior toward Hg(2+) ions of excimer emission in aqueous dioxane (dioxane/H(2)O = 1:9, v/v) solution with a detection limit of 1.3 x 10(-)(6) M. The "ON-OFF" type signaling behavior of the fluoroionophore is due to the metal ion induced conformational changes from folded to open-winged conformations by exploiting the two nearby appended pyrenyl fluorophores.     

New Hg2+-selective chromo- and fluoroionophore based upon 8-hydroxyquinoline

A new 8-hydroxyquinoline derivative having an appended boron-dipyrromethene function has been prepared, and its metal ion sensing properties were investigated. The designed compound exhibited pronounced Hg(2+)-selective on-off-type fluoroionophoric properties among the representative transition- and heavy-metal ions in aqueous dioxane solution. The fluorescence was efficiently quenched more than 98% with 5 equiv of Hg(2+) ions, and the detection limit was found to be 5 x 10(-)(6) M in a dioxane-water (1:3, v/v) solvent system. The ionophore also showed a selective chromogenic behavior toward Hg(2+) ions by changing the color of the solution from light amber to red, which can be detected with the naked eye.     

Simultaneous determination of Cu2+, Zn2+, Cd2+, Hg2+ and Pb2+ by using second-derivative spectrophotometry method

A new method of simultaneous determination of Cu2+, Zn2+, Cd2+, Hg2+ and Pb2+ is proposed here by using the second-derivative spectrophotometry method. In pH=10.35 Borax-NaOH buffer, using meso-tetra (3-methoxyl-4-hydroxylphenyl) porphyrin ([T-(3-MO-4-HP)P]) as chromomeric reagent, micelle solution was formed after Tween-80 surfactant was added into the solution containing Cu2+, Zn2+, Cd2+, Hg2+ and Pb2+ ions. The original absorption spectrum of the above complexes was obtained after heating in the boiling water for 25 min. The second-derivative absorption peaks of five metal-porphyrin complexes can be separated from the original absorption spectrum by using chemometric tool. In this way, Cu2+, Zn2+, Cd2+, Hg2+ and Pb2+ ions can be determined simultaneously. Under the optimal conditions, the linear ranges of the calibration curve were 0-0.60, 0-0.60, 0-0.40, 0-0.80 and 0-0.48 μg mL(-1) for Cu2+, Zn2+, Cd2+, Hg2+ and Pb2+, respectively. The molar absorptivity of these color systems were 1.38×10(5), 1.01×10(5), 3.24×10(5), 1.07×10(5) and 1.29×10(5)Lmol(-1)cm(-1). The method developed in this paper has advantages in selectivity, sensitivity, operation and can effectively resolve spectra overlapping problem. This method has been applied to determine the real samples with satisfactory results.     

Fluorogenic Hg2+-selective chemodosimeter derived from 8-hydroxyquinoline

[reaction: see text] A new thioamide derivative of 8-hydroxyquinoline-benzothiazole was prepared, and its fluorogenic chemodosimetric behaviors toward transition-metal ions were investigated. The thioamide derivative showed highly Hg2+-selective fluorescence enhancing properties (167-fold) in 30% aqueous acetonitrile solution. The selective and sensitive signaling behaviors were found to originate from the Hg2+ ion induced transformation of the very weak fluorescent thioamide derivative into a highly fluorescent amide analogue.     

Rhodamine-based Hg2+-selective chemodosimeter in aqueous solution: fluorescent OFF-ON

[reaction: see text] N-(Rhodamine-6G)lactam-N'-phenylthiourea-ethylenediamine (1) was developed as a fluorescent and colorimetric chemodosimeter in aqueous solution with a broad pH span (5 approximately 10) and high selectivity toward Hg2+ but no significant response toward other competitive cations, such as Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Pb2+, Cd2+, Ca2+, Mg2+, K+, Na+, etc. The Hg2+-promoted ring opening of spirolactam of the rhodamine moiety induced cyclic guanylation of the thiourea moiety, which resulted in the dual chromo- and fluorogenic observation (OFF-ON).     

A novel 5-mercapto triazole Schiff base as a selective chromogenic chemosensor for Cu2+

A novel colorimetric cation sensor bearing phenol, thiol and HCN groups was designed and synthesized. In a DMSO/H2O (9:1, v/v) solution, the sensor exhibited highly selective recognition of Cu2+ among a range of metal ions tested. In the presence of Cu2+, solutions of the sensor underwent a dramatic color change from colorless to yellow, while the presence of other metal cations such as Zn2+, Pb2+, Cd2+, Ni2+, Co2+, Fe3+, Hg2+, Ag+ and Ca2+ had no effect on the color. The detection limit of the sensor toward Cu2+ is 8.0×10(-7) M and an association constant Ka of 4.3×10(5) M(-1) was measured. The sensing of Cu2+ by this sensor was found to be reversible, with the Cu2+-induced color being lost upon addition of EDTA.     

A new Hg(2+) -selective fluorescent sensor based on a 1,3-alternate thiacalix[4]arene anchored with four 8-quinolinoloxy groups

A new thiacalix [4]arene derivative in a 1,3-alternate conformation bearing four quinolinoloxy groups through propyl chains has been synthesized, and its metal ion-binding and fluorescence-sensing properties were investigated in both THF and 10% H2O-THF systems. The designed ligand exhibited pronounced Hg2+ -selective on-off type fluoroionophoric properties among the representative transition and heavy metal ions including Cu2+. The detection limit for Hg2+ was found to be 2.0 x 10(-6) M in the mixed H2O-THF system. Detailed spectral studies including 1H NMR and MALDI-TOF mass spectroscopy reveal the unusual formation of a tetramercury complex with the ligand, in which the four propyl arms containing the quinolinoloxy groups adopt a "tetrapodand" conformation enclosing one Hg2+ ion each in the four cavities thus formed.     

Cu2+ colorimetric sensing and fluorescence enhancement and Hg2+ fluorescence diminution in "scorpionate"-like tetrathienyl-substituted boron-dipyrrins

Four novel tetrathienyl-substituted boron-dipyrrin-type (BODIPY-type) complexes, 3-(R')-4,4-di(R')-8-R-4-bora-3a,4a-diaza-s-indacene (4a, R = 2-T, R' = 2-T; 4b, R = 3-T, R' = 2-T; 5a, R = 2-T, R' = 3-T; 5b, R = 3-T, R' = 3-T; T = thienyl) have been prepared and fully characterized to explore patterns of stoichiometric Mn+ recognition in solution. Treatment of the respective parent BF2 dipyrrin with 2- or 3-thienyllithium gave the unexpected asymmetric tetrathienyl-substituted products in 8.5-35% yield. Compounds 4a and 4b bear a neutral "scorpionate"-like [SSS] tridentate binding pocket. Extensive NMR and UV-vis spectroscopic studies were performed on 4a-5b; 5a, 4b, and 5b were structurally characterized. The PhiF values for 4a-5b all decrease compared to the BF2-containing parent molecules (0.00058, 0.012, 0.00090, and 0.0051, respectively), with lambda(abs,max) values (epsilon, M(-1) cm(-1)) of 563 (44,000), 553 (29,000), 539 (33,000), and 531 (44,000) nm, respectively, and Stokes' shifts of 25-36 nm. Upon treatment with metal ion (Ca2+, Cs+, Mn2+, Co2+, Cu2+, Ag+, Zn2+, Cd2+, Hg2+, Pb2+) perchlorate salts, the solution of 4b undergoes rapid pink-to-clear switch-off behavior upon Cu2+ addition (10 microM scale) with smaller effects seen for 4a. Further, there were 2- to 19-fold Cu2+ fluorescence enhancements for these ligands. Cu2+- and Hg2+-L (L = 4a-5b) binding was modeled, and response patterns for Mn+-L 1:1 molar solutions upon Cu2+ addition were measured. Upon treatment with Hg2+, all ligand solutions show a significant fluorescence decrease accompanied by minor absorption increases. The UV-vis spectroscopic detection limit for Cu2+ and Hg2+ is approximately 270 ppb and approximately 1.7 ppm, respectively; the naked eye detection limit for Cu2+ with 4b (1.0 x 10(-5) M) is approximately 23 microM. DFT calculations gave HOMO-LUMO gaps of 478 (4a), 462 (4b), 448 (5a), and 442 nm (5b). Molecular orbital diagrams for 4a-5b revealed that the HOMO and LUMO electron density is distributed onto the 3-position-thienyl group and to a lesser degree the B(thienyl)2 moiety.     

Evaluation of a carbon paste electrode modified with organofunctionalised SBA-15 nanostructured silica in the simultaneous determination of divalent lead, copper and mercury ions

The performance of a carbon paste electrode (CPE) modified with SBA-15 nanostructured silica organofunctionalised with 2-benzothiazolethiol in the simultaneous determination of Pb(II), Cu(II) and Hg(II) ions in natural water and sugar cane spirit (cacha?a) is described. Pb(II), Cu(II) and Hg(II) were pre-concentrated on the surface of the modified electrode by complexing with 2-benzothiazolethiol and reduced at a negative potential (-0.80 V). Then the reduced products were oxidised by DPASV procedure. The fact that three stripping peaks appeared on the voltammograms at the potentials of -0.48 V (Pb2+), -0.03 V (Cu2+) and +0.36 V (Hg2+) in relation to the SCE, demonstrates the possibility of simultaneous determination of Pb2+, Cu2+ and Hg2+. The best results were obtained under the following optimised conditions: 100 mV pulse amplitude, 3 min accumulation time, 25 mV s(-1) scan rate in phosphate solution pH 3.0. Using such parameters, calibration graphs were linear in the concentration ranges of 3.00-70.0 x 10(-7) mol L(-1) (Pb2+), 8.00-100.0 x 10(-7) mol L(-1) (Cu2+) and 2.00-10.0 x 10(-6) mol L(-1) (Hg2+). Detection limits of 4.0 x 10(-8) mol L(-1) (Pb2+), 2.0 x 10(-7) mol L(-1) (Cu2+) and 4.0 x 10(-7) mol L(-1) (Hg2+) were obtained at the signal noise ratio (SNR) of 3. The results indicate that this electrode is sensitive and effective for simultaneous determination of Pb2+, Cu2+ and Hg2+ in the analysed samples.     

New Hg2+ and Cu2+ selective chromo- and fluoroionophore based on a bichromophoric azine

[graph: see text] A new probe, 1,4-bis(1-pyrenyl)-2,3-diaza-1,3-butadiene, selectively senses Hg2+ and Cu2+ through two different channels: the yellow-deep-pink color change and the enhancement of the fluorescence with the red shift of the excimer emission, which can visually be discernible by a green fluorescence in the presence of Hg2+ and an orange fluorescence in the presence of Cu2+.     

"Turn-on" fluorescent sensor for Hg2+ via displacement approach

A new Cu2+ compound Cu- NB, (where H2 NB is bis(2-hydroxyl-naphthalene-carboxaldehyde) benzil dihydrazone) was synthesized as a highly selective fluorescence chemosensor for the detection of Hg2+ in aqueous media through a displacement "turn-on" signaling strategy. Whereas the coordination of Cu2+ resulted in a considerable quenching of the typical luminescence of the naphthol rings in Cu-NB, the addition of Hg2+ ion led to a dramatic increase in the emission intensity of Cu-NB at about 530 nm (excitation at 430 nm). The competitive fluorescent experiments showed that alkali, alkaline earth metal ions, the group 12 metals Zn2+, Cd2+, the first-row transition-metal ions such as Mn2+, Fe2+, Co2+, and Ni2+, as well as Pb2+ could not inhibit the Hg2+-binding fluorescent enhancement. It is postulated that the existence of Cu2+ in the luminescent probe Cu-NB could turn away the interferences of other metal cations from Hg2+ detection. The optical responses of the free ligand upon addition of Cu2+ ion, and of the Hg-H2NB compound upon the addition of Cu2+ were also investigated for comparisons.     

An optode sensor for Cu2+ with high selectivity based on porphyrin derivative appended with bipyridine.

A porphyrin derivative (fluorophore) appended with bipyridine (ionophore) has been applied for preparation of a Cu2+-sensitive optical chemical sensor, which is based on fluorescence quenching of porphyrin derivative entrapped in a poly(vinyl chloride) membrane by the energy transfer process. The sensor exhibits a linear response toward Cu2+ in the concentration range 2.0 x 10(-8) - 1.0 x 10(-5) M, with a working pH range from 6.0 to 8.0 and a high selectivity. The detection limit is 5 x 10(-9) M. The response time for Cu2+ is less than 5 min with concentrations lower than 5 x 10(-6) M. The optode can be regenerated using 0.3 M EDTA (pH 9) and acetate buffer solution. The effect of the composition of the sensor membrane was studied, and the experimental conditions were optimized. The sensor has been used for direct determination of Cu2+ in water samples with satisfied results.     

A fluorescent probe for Hg2+sensing in solutions and living cells with a wide working pH range简

In this paper, 2-carboxybenzaldehyde rhodamine B thiohydrazine(1) was synthesized and developed as a fluorescent probe to recognize Hg2+in DMF/H2 O(1:9, v/v) solution with high selectivity. The probe can be applied to the quanti?cation of Hg2+with a linear concentration range covering from 1.0×10-7mol/L to 1.0×10-5mol/L(R2= 0.9985) and a detection limit of 4.2×10-8mol/L. The experiment results show that the response of probe 1 to Hg2+is pH-independent in a wide range from 4.0 to 9.0. Moreover, the probe 1 exhibits excellent selectivity toward Hg2+over other common metal cations. Most importantly, the probe can be employed to monitor Hg2+in living cells using fluorescent imaging technique with satisfied results.     

Copper(II)-selective electrode using 2,2'-dithiodianiline as neutral carrier

Poly(vinyl chloride) membrane electrode, that is highly selective and sensitive to Cu(II) ions, was developed by using 2,2'-dithiodianiline and dibutyl phthalate as carrier and plasticizer, respectively. The electrode exhibits good potentiometric response for Cu(II) over a wide concentration range (5.0x10(-2)-7.0x10(-7) mol l(-1)) with Nernstian slope of 30+/-1 mV per decade. The response time of the electrode is 10 s and it has been used for a period of one month and exhibits good selectivity towards Cu(2+) in comparison to alkali, alkaline earth, transition and heavy metal ions, with no interference caused by Pb(2+), Cd(2+) and Fe(+2) which are known to interfere with many other copper electrodes.     

Chemodosimetric Hg2+-selective signaling by mercuration of dichlorofluorescein derivatives

The chemodosimetric behavior of dichlorofluorescein derivatives toward Hg(2+) ions was investigated. Simple chemodosimetric systems showed selective and efficient signaling behaviors toward micromolar concentrations of Hg(2+) ions over other common interfering metal ions in an aqueous environment. The signaling mechanism is selective mercuration of the 4',5'-position of the xanthene moiety, which results in efficient chromogenic and fluorogenic signaling of Hg(2+) ions in aqueous environment.     

1-(2-methoxybenzylidene)-4-phenylthiosemicarbazide as OFF-ON fluorescent chemodosimeter for detection of Cu2+ in acetonitrile-water binary solvents

A novel fluorescent chemodosimeter, 1-(2-methoxybenzylidene)-4-phenylthiolsemicarbazide, was studied. In 90:10 (v/v) mixture of CH3CN and water binary solution, it exhibits high selectivity toward Cu2+ but very low response toward other competitive cations. The Cu2+ promoting cyclization of the thiosemicarbazide to 1,2,4-triazole-3(4H)-thione ring results in observation of the turn-on fluorescence.     

Extraction and photometric determination of microamounts of Zn2+, Cd2+ and Hg2+ with 1-(2-quinolylazo)-2-acenaphthylenol

1-(2-Quinolylazo)-2-acenaphthylenol (QAAc) combines with Zn(II), Cd(II) and Hg(II), giving deep red 1:2 complexes which are extractable in CCl(4)and other organic solvents. Spectrophotometric methods based on the reactions are sensitive and fairly selective, the Sandell's sensitivities being 8.8 x 10(-4), 2.4 x 10(-3) and 3.3 x 10(-3) microg/cm(2) for Zn(II), Cd(II) and Hg(II) respectively.     

Ratiometric determination of Hg2+ ions based on simple molecular motifs of pyrene and dioxaoctanediamide

A new podand-type dioxaoctanediamide-based chemosensor having two pyrene moieties was prepared, and its fluoroionophoric behaviors toward transition-metal ions were investigated. Pyrene-appended dioxaoctanediamide 1 showed a selective fluorescence quenching toward Hg2+ ions over other transition-metal ions in an aqueous methanol solution. Unique responses in pyrene monomer and excimer emissions allowed selective ratiometric determination of Hg2+ ions in aqueous environments, and the detection limit was found to be 1.6 x 10(-6) M. [structure: see text]     

Co2+-selective membrane electrode based on the Schiff Base NADS

A new PVC membrane electrode for cobalt(II) ions based on a recently synthesized Schiff base of 5-((4-nitrophenyl)azo)- N-(2',4'-dimethoxyphenyl)salicylaldimine is reported. The electrode exhibits a Nernstian response for Co(2+) ions over a wide concentration range (9.0 x 10(-7)-1.0 x 10(-2) M) with a slope of 29(+/-1). The limit of detection is 8.0 x 10(-7) M. The proposed sensor revealed good selectivities over a wide variety of other cations including hard and soft metals. This electrode could be used in a pH range of 3.5-6.0. It was used as an indicator electrode in potentiometric titrations of cobalt(II) ions and can be used in the direct determination of Co(2+) in aqueous solutions.