Synthesis and evaluation of two novel rhodamine-based fluorescence probes for specific recognition of Fec+ ion

Two low cytotoxic fluorescence probes Rb1 and Rb2 detecting Fe³⁺ were synthesized and evaluated. Rb1 and Rb2 exhibited an excellent selectivity to Fe³⁺, which was not disturbed by Ag⁺, Li⁺, K⁺, Na⁺, NH₄⁺, Fe²⁺, Pb²⁺, Ba²⁺, Cd²⁺, Ni²⁺, Co²⁺, Mn²⁺, Zn²⁺, Mg²⁺, Hg²⁺, Ca²⁺, Cu²⁺, Ce³⁺, AcO^?, Br^?, Cl^?, HPO₄^2?, HSO₃^?, I^?, NO₃^?, S₂O₃^2?, SO₃^2? and SO₄^2? ions. The detection limits were 1.87 × 10^?7 M for Rb1 and 5.60 × 10^?7 M for Rb2, respectively. 1:1 stoichiometry and 1:2 stoichiometry were the most likely recognition mode of Rb1 or Rb2 towards Fe³⁺, and the corresponding OFF–ON fluorescence mechanisms of Rb1 and Rb2 were proposed.     

Anthroneamine based chromofluorogenic probes for Hg2+ detection in aqueous solution

Anthroneamine derivatives 1–3 (H₂O:DMSO; 9:1, HEPES buffer, pH 7.0 ± 0.1) undergo highly selective fluorescence quenching with Hg²⁺. The observed linear fluorescence intensity change allows the quantitative detection of Hg²⁺ between 200 nM/40 ppb—12 μM/2.4 ppm even in the presence of interfering metal ions viz. Na⁺, K⁺, Mg²⁺, Ca²⁺, Ba²⁺, Cr³⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Ag⁺, Cd²⁺, Pb²⁺. Probes 1–3 and their Hg²⁺ complexes also show the broad pH resistance for their practical applicability.     

A voltammetric sensor for simultaneous determination of lead,cadmium and zinc on an activated carbon fiber rod

A simple, low cost and sensitive voltammetric sensor was developed for the simultaneous detection of Pb²⁺, Cd²⁺, and Zn²⁺ based on a disposable carbon fiber rod (CFR). The important factors to enhance the sensing property were creation of a clean surface by dealing with CFR at a high potential and electrochemical deposition of Bi film to improve the accumulation of heavy metal ions.     

Coumarin-based fluorescent chemosensor for the selective quantification of Zn2+ and AcO− in an aqueous solution and living cells

In this work, we report a novel fluorescence chemosensor HM based on the coumarin fluorophore for the quantification of Zn²⁺ and AcO^?. HM specifically binds to Zn²⁺ in the presence of other competing cations, and evident changes in UV–vis and fluorescence spectra in HEPES buffer are noticed. The in situ generated HM-Zn²⁺ complex solution exhibit a high selectivity toward AcO^? via Zn²⁺ displacement approach. The detection limits of HM for Zn²⁺ and HM-Zn²⁺ for AcO^? were estimated to be 7.24 × 10^?8 M and 9.41 × 10^?8 M, respectively. HM and the resultant complex HM-Zn²⁺ exhibit low cytotoxicity and cell-membrane permeability, which makes them capable of Zn²⁺ and AcO^? imaging in living Hep G2 cells. A B3LYP/6-31G(d,p) basis set was employed for optimization of HM and HM-Zn²⁺ complex.     

A sensitive tetraphenylethene-based fluorescent probe for Zn2+ ion involving ESIPT and CHEF processes

A new tetraphenylethene-based fluorescent probe 2-(quinolin-8-yliminomethyl)-4-triphenylvinyl-phenol (HL) for detecting Zn²⁺ ion through the excited state intramolecular proton transfer (ESIPT) and chelation enhanced fluorescence (CHEF) processes has been designed and synthesized. The results show that HL emits relatively strong blue fluorescence at 460 nm without Zn²⁺ ion, however, probe HL displays highly pink fluorescent emission at 600 nm when adding Zn²⁺ ion. The fluorescent emission of HL appears an extremely large Stokes shift, which effectively reduces the interference of background signal. The limit of detection of HL for Zn²⁺ ion can reach to 9.0 × 10^–8 M.     

Quinoline-based highly selective and sensitive fluorescent probe specific for Cd2+ detection in mixed aqueous media

Quinoline-based fluorescent probe as a recognition unit was designed and synthesized in this study. The probe R1 displayed excellent selectivity and sensitivity for cadmium ions (Cd²⁺) over a wide range of metal ions in acetonitrile-water (MeCN-H₂O) mixed solution. In order to better understand the recognition mechanism between probe and Cd²⁺, the density functional theory calculations were performed. Finally, the colorimetric experiment result was observed and conveniently monitored by the naked eye, and a visual detection limit of 4 × 10^?6 mol L^?1 was achieved. These experimental results indicated the promising potential of the probe to detect Cd²⁺ in biological system. Furthermore, the probe R1 was successfully used for the highly sensitive detection of Cd²⁺ in living cells.     

A novel colorimetric chemosensor based on quinoline for the sequential detection of Fe3+ and PPi in aqueous solution

A novel quinoline-functionalized Schiff-base derivative PY was designed and synthesized. Sensor PY displayed highly selective and sensitive fluorescence enhancement and naked-eye color change to Fe³⁺ in the presence of other competing cations. The mechanisms have been supported by Job’s plot evaluation, FT-MS and theoretical calculations. The in situ generated PY-Fe³⁺ complex solution exhibited a high selectivity toward PPi via Fe³⁺ displacement approach. The detection limits of sensor PY to Fe³⁺ and PY-Fe³⁺ complex to PPi were estimated to be 4.24 × 10^?8 M and 8.18 × 10^?8 M, respectively. This successive recognition feature of sensor PY makes it has a potential utility for Fe³⁺ and PPi detection in aqueous solution. A B3LYP/6-31G(d,p) basis set was employed for optimization of PY and PY-Fe³⁺ complex.     

A pyrene-based dual chemosensor for colorimetric detection of Cu2+ and fluorescent detection of Fe3+

A pyrene based chemosensor was designed and synthesized. The pyrene fluorophore was connected with a pyridine unit through a Schiff base structure to give the sensor (L). L was tested with a variety of metal ions and exhibited high colorimetric selectivities for Cu²⁺ and Fe³⁺ over other ions. Upon binding with Cu²⁺ or Fe³⁺, L showed an obvious optical color change from colorless to pink for Cu²⁺ or orange for Fe³⁺ over a wide pH range from 3 to 12. Moreover, the fluorescence of L at 370 nm decreased sharply after bonding with Fe³⁺, while other metal ions including Cu²⁺ had no apparent interference. Thus, using such single chemosensor, Cu²⁺ and Fe³⁺ can be detected independently with high selectivity and sensitivity. The limits of detection toward Cu²⁺ and Fe³⁺ were 8.5 and 2.0 μM, respectively. DFT calculation results also proved the formation of stable coordination complexes and the phenomenon of fluorescence quenching by Fe³⁺. Furthermore, L was also successfully used as a bioimaging reagent for detection of Fe³⁺ in living cells.     

A functional applied material on recognition of metal ion zinc based on the double azine compound

A colorimetric and fluorescent probe L has been designed and synthesized, which bearing the double azine moiety and showing a detection limit of 2.725 × 10^?7 M towards Zn²⁺. Based on the basic recognition mechanism of ESIPT and CHEF effect, the L has high selectivity and sensitivity to only Zn²⁺ (not Fe³⁺, Hg²⁺, Ag⁺, Ca²⁺, Co²⁺, Ni²⁺, Cd²⁺, Pb²⁺, Cr³⁺, and Mg²⁺) within the physiological pH range (pH = 7.0–8.4) and showed a fluorescence switch. Moreover, this detection progress occured in the DMSO/H₂O ～ HEPES buffer (80/20, v/v; pH 7.23) solution which can conveniently used on test strip.     

A novel highly selective ratiometric fluorescent sensor for relay recognition of Zn2+ and H2PO4−

A novel fluorescent sensor (AQTF1) based on the N-(quinolin-8-yl) tetrahydrofuran-2-carboxamide was designed and synthesized. This new sensor demonstrated high selectivity for the Zn²⁺ without the interference from Cd²⁺. The detection limit of this probe was calculated to be 10.8 nM for Zn²⁺. The in situ prepared AQTF1-Zn²⁺ complex was used for detection of H₂PO₄^? and displayed good selectivity from the common anions. Furthermore, the AQTF1 displayed good ratiometric response for the relay recognition for Zn²⁺ and H₂PO₄^?.     

Long-distance electronic interaction in a molecular wire consisting of a ferrocenyl–ethynyl unit bridging two [(η5-C5H5)(dppe)M] metal centers

Several multinuclear ferrocenyl–ethynyl complexes of formula [(η⁵-C₅H₅)(dppe)M^II?CC–(fc)_n–CC–M^II(dppe)(η⁵-C₅H₅)] (fc = ferrocenyl; dppe = Ph₂PCH₂CH₂PPh₂; 1: M^II = Ru²⁺, n = 1; 2: M^II = Ru²⁺, n = 2; 3: M^II = Ru²⁺, n = 3; 4: M^II = Fe²⁺, n = 2; 5: M^II = Fe²⁺, n = 3) were studied. Structural determinations of 2 and 4 confirm the ferrocenyl group directly linked to the ethynyl linkage which is linked to the pseudo-octahedral [(η⁵-C₅H₅)(dppe)M] metal center. Complexes of 1–5 undergo sequential reversible oxidation events from 0.0 V to 1.0 V referred to the Ag/AgCl electrode in anhydrous CH₂Cl₂ solution and the low-potential waves have been assigned to the end-capped metallic centers. The solid-state and solution-state electronic configurations in the resulting oxidation products of [1]⁺ and [2]²⁺ were characterized by IR, X-band EPR spectroscopy, and UV–Vis at room temperature and 77 K. In [1]⁺ and [2]²⁺, broad intervalence transition band near 1600 nm is assigned to the intervalence transition involving photo-induced electron transfer between the Ru³⁺ and Fe²⁺ metal centers, indicating the existence of strong metal-to-metal interaction. Application of Hush’s theoretical analysis of intervalence transition band to determine the nature and magnitude of the electronic coupling between the metal sites in complexes [1]⁺ and [2]²⁺ is also reported. Computational calculations reveal that the ferrocenyl–ethynyl-based orbitals do mix significantly with the (η⁵-C₅H₅)(dppe)Ru metallic orbitals. It clearly appears from this work that the ferrocenyl–ethynyl spacers strongly contribute in propagating electron delocalization.     

A highly selective colorimetric and fluorescent chemosensor for Cr2+ in aqueous solutions

A new rhodamine-based chemosensor was synthetized through a modified copper-catalyzed [3+2]-cycloaddition of an azidocoumarin with an alkynyl-rhodamine. Its sensing properties toward various metal cations in aqueous solutions were investigated by colorimetric changes, UV–vis and fluorescence spectroscopies. The sensor exhibited a high selectivity for Cr²⁺ over Cr³⁺ and other divalent cations such as Cu²⁺, Mg²⁺, Zn²⁺, Ca²⁺, Cd²⁺, Co²⁺, Hg²⁺ and Ni²⁺. The linear range of detection by fluorescence spectroscopy is 0.07–3.5 mM, with a detection limit of ca. 64 μM. The binding mode of Cr²⁺ with the sensor was rationalized through experimental evidences.     

A highly sensitive and selective naked-eye probe for detection of Fe3+ based on a 2,5-bis[3-benzyl-2-methylbenzothiazole]-croconaine

A highly sensitive and selective naked-eye probe, 2,5-bis[3-benzyl-2-methylbenzothiazole]-croconaine (BMC) for sensing of Fe³⁺ was synthesized and characterized. The BMC can selectively recognize Fe³⁺ among the test cations (Ni²⁺, Mg²⁺, Cu²⁺, Ca²⁺, Na⁺, K⁺, Cr³⁺, Ag⁺, Ba²⁺, Zn²⁺, Pb²⁺, Al³⁺, Fe³⁺, Cd²⁺, Co²⁺) in DMF/H₂O (4:1, v/v). The binding constant of BMC-Fe³⁺ was evaluated by using Benesi-Hildebrand plot. Simultaneously, the binding mode of BMC-Fe³⁺ was supporting by Job's plot, ESI-MS, FT-IR and ¹H NMR. Correspondingly, the morphology of chelate complex was investigated by FESEM. Moreover, Fe³⁺ and EDTA could be employed as inputs and the fluorescence emission intensity which was 816 nm as output so that a molecular logic gate could be realized.     

Synthesis of a new pyrene-devived fluorescent probe for the detection of Zn2+

A novel pyrene-based receptor bearing benzothiazole was synthesized as a good turn-on fluorescent sensor for the recognition of Zn²⁺. The probe showed an excellent selectivity for Zn²⁺over most other competing ions (eg, Cr³⁺, Li⁺, Cd²⁺, Al³⁺, Pb²⁺, Li⁺, Mg²⁺, Ag⁺, Ca²⁺, Ni²⁺, Mn²⁺, Fe³⁺, Hg²⁺, Ba²⁺, K⁺, Na⁺, Cu²⁺, Fe²⁺) in EtOH-HEPES (65:35, v/v, pH?=?7.20), which might be attributed to the photoinduced electron transfer (PET) mechanism. The formation of 1:1 stoichiometric PBZ-Zn²⁺ complex was determined based on the Job's plot, ¹H NMR titration and ESI-MS. The binding constant of the complex was 4.04?×?10⁴?M^?1 with a detection limit of 2.58?×?10^?7?M. The potential application of the PBZ in real water samples for recognizing Zn²⁺ was investigated. Bio-imaging study also revealed that PBZ could be applied to detecting Zn²⁺ in live cells. These results indicated that PBZ could be a favorable probe for Zn²⁺.     

Syntheses and structures of tetranuclear Zn（Ⅱ） complexes with in situ generated macrocyclic Schiff base ligands:Applications in Zn2+ sensing

Three novel Zn（II） complexes,[Zn₄L¹Cl₄]-3H₂O（1）,[Zn₄L²Cl₄]-2DMF（2） and[Zn₄L³Cl₄]H₂O（3）,have been synthesized and structurally characterized.In these complexes,interesting 32-membered dodecadentate macrocyclic ligands were generated in situ by ’2 + 2’ type condensation reactions between a tetraamine and various dialdehydes.All the complexes are isostructurally tetranuclear Zn（Ⅱ） complexes,containing endogenous alkoxo and phenoxo bridges.Applications of the macrocyclic ligands as Zn²⁺ sensors have been investigated.Take H₄L¹ for example,it exhibits a 4-fold fluorescence enhancement upon the addition of 2 equiv.of Zn²⁺ in MeOH.     

A simple highly sensitive and selective turn-on fluorescent chemosensor for the recognition of Pb2+

A simple highly sensitive and selective turn-on fluorescent chemosensor L based on bis-Schiff-base for Pb²⁺ ions was synthesized and characterized by spectroscopic techniques. L having high binding affinity towards Pb²⁺ ions of 2.10 × 10⁴ M^?1 selectively detects Pb²⁺ ions with almost no interference among various competitive ions by a 11-fold fluorescent enhancement in CH₃CN/H₂O (95:5, v/v) solution over a wide pH range. Moreover, sensor L displayed a lower detection limit of 3.80 × 10^?7 M, which is low enough for sensing sub-millimolar concentration of Pb²⁺ encountered practically.     

A lysosomal targeting fluorescent probe and its zinc imaging in SH-SY5Y human neuroblastoma cells

A fluorescent probe based PET mechanism was designed, and the probe could image endogenous release of Zn²⁺ upon H₂O₂ stimulation in SH-SY5Y cells.     

Luminescent CdSe-ZnS quantum dots as selective Cu2+ probe

Luminescent CdSe-ZnS quantum dots (QDs) were modified with bovine serum albumin (BSA) and used as selective copper ion probe. The fluorescence of the water-soluble QDs can be quenched only by Cu²⁺ and Fe³⁺ in physiological buffer solution. Approximate concentrations of other physiologically important cations, such as Zn²⁺, Na⁺ and K⁺ etc. have no effect on the fluorescence. Adding F⁻ to form the colorless complex FeF₆³⁻ can eliminate the interference of Fe³⁺. The detection limit of Cu²⁺ ions was 10 nM. The results can be explained in terms of strong binding of Cu²⁺ onto the surface of CdSe resulting in a chemical displacement of Cd²⁺ ions and the formation of CuSe on the surface of the QDs.     

Spectral studies of Fe(III) complexes of dipodal tridentate chelating agents

The dipodal ligands (Im) and (BIm) as well as complexes [FeLCl₃] [L = Im (1) and BIm (2)] have been prepared and studied using spectroscopic techniques. The magnetic moment, IR, electronic (ligand field), FAB-mass and NMR spectral data indicate a hexa-coordinate geometry around high-spin state Fe³⁺ where the ligands coordinate as a tridentate [N,N,N] chelating agent. ⁵⁷Fe-Mössbauer spectral data confirmed the presence of a ligand asymmetry around Fe³⁺ in a high-spin state electronic configuration (t_2g³,e_g², S = 5/2) with nuclear transition Fe(±3/2 → ±1/2) exhibiting Kramer's double degeneracy. The molecular computations provided the optimum energy perspective plots for the molecular geometries giving the important structural data.     

Synthesis and Applications of a New Polysiloxane-Immobilized Macrocyclic Ligand System

Abstract

Insoluble porous solid, macrocyclic 22-membered ring, 1-oxa-6,9,12,15,18-pentaaza-2,22-disilacyclododocosane polysiloxane ligand system has been prepared by the reaction of a macro-silane agent with tetraethylorthosilicate. The macro-silane agent was prepared by the reaction of imino-bis(N-2-aminoethylacetamide) ligand with 3-iodopropyltrimethoxysilane in 1:3 molar ratio. The new prepared polysiloxane system exhibits variable potentials for the extraction of metal ions (Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Ag⁺, Cd²⁺, Hg²⁺, and Pb²⁺) from aqueous solutions. The ligand system shows high capacity to extract silver, lead, and mercury. Chemisorption of the metal ions by the ligand system at the optimum conditions was found in the order Ag ⁺ > Pb²⁺ > Hg²⁺ > Cu²⁺ > Ni²⁺ > Fe³⁺ > Co²⁺ > Cd²⁺ > Zn²⁺.