A quinoline-polyamine conjugate as a fluorescent chemosensor for quantitative detection of Zn(II) in water

A simple ligand (L1), a diethylenetriamine bearing two end quinoline fragments, was synthesized. Without metal cations, L1 shows no fluorescence at pH 2-13; however, Zn²⁺ addition creates strong fluorescence at pH 5-12. The emission intensity exhibits linear and stoichiometrical response to the Zn²⁺ amount. No remarkable emission enhancement was, however, observed for other cations.     

A highly selective and sensitive fluorescent PET (photoinduced electron transfer) chemosensor for Zn(II)

The naphthalimide derivative 1 was designed as a fluorescence PET sensor for Zn(II); 1 showed excellent selectivity for Zn(II) at pH 7.4, even in the presence of other competitive cations, the emission, being pH independent above pH 3.5, was switched on upon Zn(II) recognition.     

Selective sensing of Zn(II) ion by a simple anthracene-based tripodal chemosensor

A new and an easy-to-make simple tripodal shaped chemosensor 1, comprising an anthracene moiety as a fluorophore and amide, alcohol functionalities as ligating groups has been designed and synthesized for Zn(II). In CH₃CN containing 0.1% DMSO, upon excitation at 370 nm, the chemosensor 1 exhibited an emission at 412 nm, which increased to a large extent upon complexation of Zn(II). Among the other metal ions examined in the study, Cd²⁺ moderately perturbed the emission of 1 under similar conditions.     

A potential fluorescent Hg(II) chemosensor

An imidazole-based ligand has been evaluated for a potential fluorescent Hg(II) sensing probe. In water-acetonitrile solvent system, the ligand exhibits a unique selectivity towards Hg(II), which not only modulates fluorescence intensity but also shifts the emission band. The fluorescence reduction and the emission shift correlate with Hg(II) concentrations.     

A fluorescent chemosensor for Zn(II). Exciplex formation in solution and the solid state

The macrocyclic phenanthrolinophane 2,9-[2,5,8-triaza-5-(N-anthracene-9-methylamino)ethyl]-[9]-1,10-phenanthrolinophane (L) bearing a pendant arm containing a coordinating amine and an anthracene group forms stable complexes with Zn(II), Cd(II) and Hg(II) in solution. Stability constants of these complexes were determined in 0.10 mol dm(-3) NMe(4)Cl H(2)O-MeCN (1:1, v/v) solution at 298.1 +/- 0.1 K by means of potentiometric (pH metric) titration. The fluorescence emission properties of these complexes were studied in this solvent. For the Zn(II) complex, steady-state and time-resolved fluorescence studies were performed in ethanol solution and in the solid state. In solution, intramolecular pi-stacking interaction between phenanthroline and anthracene in the ground state and exciplex emission in the excited state were observed. From the temperature dependence of the photostationary ratio (I(Exc)/I(M)), the activation energy for the exciplex formation (E(a)) and the binding energy of the exciplex (-DeltaH) were determined. The crystal structure of the [ZnLBr](ClO(4)).H(2)O compound was resolved, showing that in the solid state both intra- and inter-molecular pi-stacking interactions are present. Such interactions were also evidenced by UV-vis absorption and emission spectra in the solid state. The absorption spectrum of a thin film of the solid complex is red-shifted compared with the solution spectra, whereas its emission spectrum reveals the unique featureless exciplex band, blue shifted compared with the solution. In conjunction with X-ray data the solid-state data was interpreted as being due to a new exciplex where no pi-stacking (full overlap of the pi-electron cloud of the two chromophores - anthracene and phenanthroline) is observed. L is a fluorescent chemosensor able to signal Zn(II) in presence of Cd(II) and Hg(II), since the last two metal ions do not give rise either to the formation of pi-stacking complexes or to exciplex emission in solution.     

A novel selective fluorescent chemosensor for Cu（Ⅱ）

A novel fluorescence enhancement Cu~(2 ) chemosensor derived from coumarin was prepared.Emission study found that it exhibits evident Cu~(2 )-amplified fluorescence prior to Co~(2 ),Pb~(2 ),Mg~(2 ),Mn~(2 ),Ni~(2 ),Zn~(2 ),Fe~(3 ),Ag~ and Cd~(2 ),and the largest emission enhancement factor is about 9 at a ratio of 2:1 (chemosensor 1/Cu~(2 )).     

Turn-on fluorescence sensing of nucleoside polyphosphates using a xanthene-based Zn(II) complex chemosensor

Fluorescence sensing with small molecular chemosensors is a versatile technique for elucidation of function of various biological substances. We now report a new fluorescent chemosensor for nucleoside polyphosphates such as ATP using metal-anion coordination chemistry. The chemosensor 1-2Zn(II) is comprised of the two sites of 2,2'-dipicolylamine (Dpa)-Zn(II) as the binding motifs and xanthene as a fluorescent sensing unit for nucleoside polyphosphates. The chemosensor 1-2Zn(II) selectively senses nucleoside polyphosphates with a large fluorescence enhancement (F/F(o) > 15) and strong binding affinity (K(app) approximately = 1 x 10(6) M(-1)), whereas no detectable fluorescence change was induced by monophosphate species and various other anions. The 'turn-on,' fluorescence of 1-2Zn(II) is based on a new mechanism, which involves the binding-induced recovery of the conjugated form of the xanthene ring from its nonfluorescent deconjugated state which was formed by an unprecedented nucleophilic attack of zinc-bound water. The selective and highly sensitive ability of 1-2Zn(II) to detect nucleoside polyphosphates enables its bioanalytical applications in fluorescence visualization of ATP particulate stores in living cells, demonstrating the potential utility of 1-2Zn(II).     

An effective fluorescent chemosensor for the detection of copper(II)

The fluorescent compound N-substituted 2,6-bis(benzimidazol-2-yl)pyidine (1) has been synthesized. The fluorescent characteristics of the compound 1 and 2,6-bis(benzimidazol-2-yl)pyidine (2) and the complexes formed between the two compounds and different metal ions have also been investigated. The results show that the compound 1 possesses a specific ability to form complex with Cu(2+) ion, but the compound 2 have not such a property. It is proposed that the specific recognition ability of compound 1 to Cu(2+) may be attributed to the cyclic configuration of this compound in polar solvent.     

A highly selective turn-on fluorescent chemosensor for copper(II) ion

A new pyrene derivative (1) containing a diaminomaleonitrile moiety exhibits high selectivity for Cu²⁺ detection. Significant fluorescence enhancement was observed with chemosensor 1 in the presence of Cu²⁺. However, the metal ions Ag⁺, Ca²⁺, Cd²⁺, Co²⁺, Fe²⁺, Fe³⁺, Hg²⁺, Mg²⁺, Mn²⁺, Ni²⁺, Pb²⁺, and Zn²⁺ produced only minor changes in fluorescence values for the system. The apparent association constant (K_a) of Cu²⁺ binding in chemosensor 1 was found to be 5.55×10³ M⁻¹. The maximum fluorescence enhancement caused by Cu²⁺ binding in chemosensor 1 was observed over the pH range 5-7.5.     

Selective dendritic fluorescent sensors for Zn(II)

A series of dendritic 8-hydroxyquinoline (8-HQ) and 5-dialkyl(aryl)aminomethyl-8-HQ derivatives were synthesized and their fluoroionophoric properties toward representative alkali, alkaline earth, group IIIA and transition metal ions were investigated. Among the selected ions, Zn(II) enhanced the fluorescence of N-di-(methoxycarbonylethyl)aminoethyl-3-[4-(8-hydroxyquinolin-5-ylmethyl)piperazin-1-yl]-propanoic amide] (7) by 31-fold, while Al(III) caused enhancement to some extent. The absence of any significant fluorescence enhancement by the other ions examined renders 7a highly useful Zn(II)-selective fluorescent sensor.     

Anthracene-based macrocyclic fluorescent chemosensor for selective sensing of dicarboxylate

An anthracene-based macrocyclic receptor has been designed and synthesized for selective recognition of 1,4-phenylenediacetate (K_a = 3.34 × 10⁵ M^?1). The macrocycle binds 1,4-phenylenediacetate selectively at the charged sites of the receptor with a concomitant increase in fluorescence of anthracene. The interaction properties of the macrocycle were evaluated by ¹H NMR, UV–vis and fluorescence spectroscopic methods.     

A near IR di-styryl BODIPY-based ratiometric fluorescent chemosensor for Hg(II)

A novel BODIPY-based near-IR emitting probe as a selective and sensitive fluorophore for Hg(II) is synthesized. This versatile BODIPY fluorophore is functionalized for long wavelength emission at the 3 and 5 positions via a condensation reaction in which two dithiodioxomonoaza-based crown-containing phenyl units are conjugated to the BODIPY core as a chelating unit. This designed fluorophore, employing an ICT sensor can be used effectively to detect Hg(II) cations by way of a hypsochromic shift (∼90 nm) in both the absorption and emission spectra.     

Fluorescent macrocyclic chemosensor for Zn(II) detection at alkaline pH values

ABSTRACT

The new macrocyclic ligand L (28,29-dimethoxy-27-oxa-8,11,14,17,25,26-hexaazatetracyclo[22.2.1.1(2,6).1(19,23)]nonacosa-2,4,6(28),19,21,23(29),24,26(1)-octaene) has been synthesised. It contains a tetramine chain and the 2,5-bis(2-methoxy-3-metyl-phenyl)-1,3,4-oxadiazole (PPD-OMe) chromophore, acting as coordinating and sensing units, respectively.

The fluorescent emission of L depends on the pH being highly fluorescent at pH = 2 and not emitting from pH >10. The studies highlighted that L is a PET mediated emitting chemosensor, being the PET effect regulated by the degree of the tetraamine protonation.

L coordinates metal ions (Cu(II), Zn(II) and Cd(II)) in water giving rise to an OFF-ON fluorescent response for the presence of Zn(II) ion thus signalling its presence in the medium. This response is particularly notable at pH = 9 allowing to extend the Zn(II) sensing also in the alkaline pH field.     

Novel highly selective fluorescent chemosensors for Zn(II)

Two novel fluorescent Zn²⁺ chemosensors were synthesized in four steps from inexpensive starting materials. They exhibited very strong fluorescence responses to Zn²⁺ and had remarkably high selectivity to Zn²⁺ than other metal ions including Mg²⁺, Ca²⁺, Ni²⁺, Cu²⁺, and Cd²⁺. These two new molecules could be used as low-priced yet high-quality Zn²⁺ chemosensors.     

Poly(amine ester) dendrimer with naphthyl units as a fluorescent chemosensor for Al(III), Cu(II), and Zn(II).

A poly(amine ester) dendrimer with naphthyl units (G1N6) has been synthesized as a fluorescent chemosensor for metal ions. We investigated the metal-ion recognition of G1N6 by adding each of Ag(+), Al(3+), Ba(2+), Ca(2+), Cd(2+), Co(2+), Cu(2+), Fe(3+), Mg(2+), Ni(2+), and Zn(2+) in acetonitrile solution. Large changes were observed in the fluorescence spectra of G1N6 upon the addition of Al(3+), Cu(2+), and Zn(2+).     

A novel highly selective fluorescent chemosensor for Hg（Ⅱ） in fully aqueous media

A novel fluorescent Hg~(2 ) chemosensor based on dithia-dioxa-monoaza crown ether was synthesized in four steps from inexpensive starting materials.This new sensor exhibited very strong fluorescence response to Hg~(2 ) (F_(Hg~(2 ))/F_(free)>130) and it was highly selective to Hg~(2 ) over the other metal ions by more than 45-fold.     

Synthesis of triazolyl anthracene as a selective fluorescent chemosensor for the Cu(II) ion

The Cu(I)-catalyzed azide-alkyne cycloaddition reaction (CuAAC) has been used to synthesize an anthracene-based fluorescent compound that undergoes strong fluorescence quenching in the presence of Cu(II). Fluorescence studies indicate that the compound forms a 1:1 complex and can be used to quantitatively determine micromolar concentrations of Cu(II) in aqueous solution.     

Ratiometric chemosensor for fluorescent determination of Zn2+ in aqueous ethanol

A new ratiometric and selective fluorescent chemosensor (1) for quantification of zinc ions in aqueous ethanol has been synthesized and investigated in this work. In an environmentally friendly media of 30% (v/v) water/ethanol and 10 mM Tris-HCl neutral buffer (pH 7.03), 1 displayed selective Zn²⁺ ratiometric fluorescence response, with a dynamic working range of 1.0-8.0 μM and a detection limit of 0.5 μM Zn²⁺. The determination of Zn²⁺ in synthesized water sample was also successful.     

An 2-(2'-aminophenyl)benzoxazole-based OFF-ON fluorescent chemosensor for Zn2+ in aqueous solution

A water-soluble fluorescent sensor, 1, based on the "receptor-spacer-fluorophore" [2-(2'-aminophenyl)benzoxazole-amide-2-picolylamine] sensor platform, demonstrates the high sensitivity for Zn(2+) with a 25-fold fluorescence enhancement upon chelation to Zn(2+) and also exhibits high selectivity to Zn(2+) over other metal ions. X-ray crystal structure of Zn(2+) complex reveals that the amide oxygen (O2) cooperates with 2-picolylamine unit (N3, N4) as a receptor bind Zn(2+).     

A new fluorescent chemosensor for copper(II) and molecular switch controlled by light

A novel fluorescent chemosensor with two 5-nitro-salicylaldehyde groups at the upper rim of calix[4]arene has been synthesized. The chemosensor can effectively recognize copper(II) ion. This system could be considered as a molecular switch. By alternating the light irradiation of mixed solution formed by the host and Cu²⁺, off-on-off fluorescent switching is carried out.