Synthesis and properties of three novel rhodamine-based fluorescent sensors for Hg2+

Three novel rhodamine-based Hg~(2+) fluorescent sensors were designed and synthesized. The sensors could work in semi-aqueous solutions with nearly neutral p H and showed high selectivity and sensitivity to Hg~(2+) with remarkable fluorescence enhancement. For these three sensors, the linear working range broadened(0–80, 0–100 and 0–140 μmol/L, respectively) and the sensitivity increased(7.7, 15.5 and 17.6 folds of the fluorescence enhancement and 512, 66.2 and 37.6 ppb of the detection limit) with the rising of the thiourea-unit numbers. Furthermore the sensors exhibited excellent interference immunity to multiple environmentally and biologically relevant metal ions. Pond and tap water assay showed good practicability of the sensors. The number of the bound Hg~(2+) equaling to that of the thiourea units and the irreversible recognition process implied a new interaction way between Hg~(2+) and the sensor.     

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.     

A fluorescent PET chemosensor for Zn2+ cations based on 4-methoxy-1,8-naphthalimide derivative containing salicylideneamino receptor group

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Cyclometalated iridium(III) complexes containing 2-phenyl-2H-indazole ligand: Synthesis,photophysical studies,and DFT calculations

Heteroleptic cyclometalated iridium(III) complexes ( Ir1 – Ir5 ) featuring piz-based ligands and acetylacetone ancillary ligand are synthesized and characterized. Their photophysical and electrochemical properties were studied, and DFT calculations were used to further support the experiment results. All the complexes emit yellow color with quantum yields of 12.2–56.5% in dichloromethane solution at room temperature, and the emission originates from a hybrid ³MLCT/³ILCT/³LLCT excited state.     

A porphyrin derivative containing 2-(oxymethyl)pyridine units showing unexpected ratiometric fluorescent recognition of Zn2+ with high selectivity

A porphyrin derivative (1), containing two 2-(oxymethyl)pyridine units has been designed and synthesized as chemosensor for recognition of metal ions. Unlike many common porphyrin derivatives that show response to different heavy metal ions, compound 1 exhibits unexpected ratiometric fluorescence response to Zn²⁺ with high selectivity. The response of the novel chemosensor to zinc was based on the porphyrin metallation with cooperating effect of 2-(oxymethyl)pyridine units. The change of fluorescence of 1 was attributed to the formation of an inclusion complex between porphyrin ring and Zn²⁺ by 1:1 complex ratio (K = 1.04 × 10⁵), which has been utilized as the basis of the fabrication of the Zn²⁺-sensitive fluorescent chemosensor. The analytical performance characteristics of the proposed Zn²⁺-sensitive chemosensor were investigated. The sensor can be applied to the quantification of Zn²⁺ with a linear range covering from 3.2 × 10⁻⁷ to 1.8 × 10⁻⁴ M and a detection limit of 5.5 × 10⁻⁸ M. The experiment results show that the response behavior of 1 to Zn²⁺ is pH-independent in medium condition (pH 4.0-8.0) and show excellent selectivity for Zn²⁺ over transition metal cations.     

Colorimetric detection of Fe3+/2+ and fluorescent detection of Al3+ in aqueous media: applications and DFT calculations

Abstract

A new multifunctional colorimetric and fluorescent chemosensor 1 for Fe^3+/2+ and Al³⁺ has been synthesized in the one-step procedure. The sensor 1 detected both Fe²⁺ and Fe³⁺ through the color change from yellow to brown and Al³⁺ via turn-on fluorescence. The binding stoichiometries of sensor 1 with Fe^3+/2+ and Al³⁺ were proposed to be 1:1 with the analyses of ESI-mass and Job plot. Importantly, the detection limits of 1 for Fe^3+/2+ (2.11 and 2.70 μM) and Al³⁺ (3.44 μM) were lower than the EPA guideline (5.37 μM) for Fe^3+/2+ and WHO guideline (7.41 μM) for Al³⁺. Compound 1 was used to quantify ferric species (Fe³⁺) in real samples. Moreover, the sensing processes for Fe^3+/2+ and Al³⁺ were proposed with the spectroscopic studies and theoretical calculations.     

A novel rhodamine-based turn-on probe for fluorescent detection of Au3+ and colorimetric detection of Cu2+

In this work, we design and synthesize the novel probe RC through introduction the 1-aza-4,13-dithia-15-crown-5 ring into the structure of rhodamine 6G hydrazide, where the N atom of crown ring is responsible for quenching of rhodamine fluorescence. The compound obtained behaves as multifunctional cation sensor providing selective fluorescent response to Au³⁺ and selective colorimetric response to Cu²⁺ ions in aqueous acetonitrile (1/1, v/v) at pH 7.0. The use of 10^?5?M RC solution allowed reliable determination of target cations in the presence of a wide range of environmentally relevant ions with detection limits of 2?×?10^?6?M and 5?×?10^?7?M for gold and copper, respectively.     

A new perylene diimide-based colorimetric and fluorescent sensor for selective detection of Cu<Superscript>2+</Superscript> cation

A new perylene diimide (PDI) ligand (1) functionalized with a dipicolylethylenediamine (DPEN) moiety was synthesized and first used as a colorimetric and fluorometric dual-channel sensor to specifically detect the presence of Cu²⁺ over a wide range of other cations. The solution of 1 (10 μmol/L) upon addition of Cu²⁺ displayed distinguishing pink color compared with other cations including K⁺, Ni²⁺, Ca²⁺, Mn²⁺, Na⁺, Sr²⁺, Zn²⁺, Co²⁺, Cd²⁺, Mg²⁺, Cr³⁺, Ag⁺, and Ba²⁺, indicating the sensitivity and selectivity of 1 to Cu²⁺. Thus, the advantage of this assay is that naked-eye detection of Cu²⁺ becomes possible. Moreover, among these metal ions investigated, only Cu²⁺ quenched more than half fluorescent intensity of 1. The ESI-TOF spectrum of a mixture of 1 and CuCl₂ in combination of the fluorescence titration spectra of 1 (10 μmol/L) upon addition of various amounts of Cu²⁺ revealed the formation of a 2:1 metal-ligand complex through the metal coordination interaction. Supported by the National Natural Science Foundation of China (Grant Nos. 20872101 & 20772086)     

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 new Schiff-base as fluorescent chemosensor for selective detection of Cr3+: An experimental and theoretical study

A novel Schiff base fluorescent sensor N,N′-bis(salicylidene)-2,6-bis(4-aminophenyl)-4-phenylpyridine (P3) was synthesized through condensation of 2,6-bis(4-aminophenyl)-4-phenylpyridine and 2-hydroxybenzaldehyde. The obtained results from fluorescence analysis revealed that by excess of Cr³⁺ to P3, a remarkable increase was observed in the fluorescent intensity of the Schiff base at 663?nm with the ratio of CH₃CN/H₂O (95/5%), even though the other cations would likely have no impact on the fluorescence intensity. The cause of this trend might be ascribed to the formation of a 1:1 stoichiometric P3-Cr³⁺ complex, confirmed by Job's plot, which is resulted in preventing the photo-induced electron transfer (PET) process. From fluorescence titration, the association constant K_a was gained 2.28?×?10⁵?M^?1 and the limit of detection (LOD) was determined to be 1.3?×?10^?7?M. Furthermore, the optimized structure together with the electronic spectra of the proposed complex was determined by DFT and TDDFT calculations.     

Copper(II) complexes of bis(pyrazol-1-yl)methane - Synthesis, spectroscopic characterization, X-ray structure and DFT calculations

Two novel copper(II) complexes incorporating bis(pyrazol-1-yl)methane ligand (bpzm) have been synthesized. The compounds [CuCl(bpzm)₂(H₂O)]Cl·H₂O (1) and [Cu(N₃)₂(bpzm)]_n (2) have been studied by IR, UV-Vis spectroscopy and X-ray crystallography. The experimental studies on the compounds 1 and 2 have been accompanied computationally by the density functional theory (DFT) calculations.     

A chelating resin containing bis(2-benzimidazolylmethyl)amine: synthesis and metal-ion uptake properties suitable for analytical application

A new stable chelating resin was synthesized by incorporating the bis(2-benzimidazolyl methyl)amine into Merrifield polymer through CN covalent bond and characterized by elemental analysis, IR and thermal study. The sorption capacity of the newly formed resin for Ag(I), Cu(II), Fe(III), Hg(II) and Pb(II) as a function of pH have been studied. The resin exhibits no affinity for alkali or alkaline earth metals. In column operation it has been observed that Ag(I) in trace quantities can be separated from different complex matrices and Hg(II) can be removed from the river water spiked with Hg(II) at usual pH of natural waters.     

Study on the synthesis of novel fluorescent macrocyclic sensors and their sensitive properties for Cu2+ and Fe3+ in aqueous solution

In this work, we synthesised and characterised three novel fluorescence macrocyclic sensors containing optically active dansyl groups. The studies for the interaction of the synthesised compounds with various mental ions (Li⁺, Na⁺, K⁺, Ag⁺, Mg²⁺, Ca²⁺, Ba²⁺, Pb²⁺, Zn²⁺, Co²⁺, Cd²⁺, Hg²⁺, Ni²⁺, Cu²⁺, Mn²⁺, Cr³⁺, Al³⁺, Fe³⁺) were performed by fluorescence titration, Job’s plot, ESI-MS and DFT calculations. The results showed that the sensors 1a–1c displayed selective recognition for Cu²⁺ and Fe³⁺ ions and formed stoichiometry 1:1 complex through PET mechanism in DMSO/H₂O solution (1:1, v/v, pH 7.4 of HEPES). The binding constant (K) and detection limit were calculated.     

A highly selective fluorescent sensor for Cu based on 2-(2′-hydroxyphenyl)benzoxazole in a poly(vinyl chloride) matrix

This paper describes a copper selective optical chemical sensor based on static quenching of the fluorescence of 2-(2′-hydroxyphenyl)benzoxazole entrapped in a poly(vinyl chloride) (PVC) membrane. The effect of the composition of the sensing membrane was studied, and experimental conditions were optimized. The sensors exhibit stable response over the concentration range from 4.0 × 10⁻⁸ M to 5.0 × 10⁻⁵ M Cu²⁺ at pH 4.0-6.5, and a high selectivity. The response time for Cu²⁺ with concentration ≤5 × 10⁻⁶ M is less than 7 min. The optode can be regenerated using 0.1 M HCl and acetate buffer solution. The sensor has been used for direct measurement of copper content in river water samples with a relative error less than 4% with reference to that obtained by atomic absorption spectrometry.     

The X‐ray Single Crystal Structures of an Acid‐functionalized Bis(2‐picolyl)amine (bpa) Ligand with Palladium(II) and Zinc(II) Display Different Intermoleclar Interactions around the Common (H2O)2(anion)2 Motif

This work reports structural investigations on two metal complexes of the functionalized (p‐carboxylatobenzyl)‐bis(2‐picolyl)amine ligand 1 (HL). The complex {[HLPdCl]Cl × H₂O}₂ ( 2_Pd ) has a square‐planar coordination around the Pd ion. It forms discrete dimers by intermolecular hydrogen bonding involving the protonated ligand HL. The coordination around the Zn²⁺ ion in {[(H₂O)LZn]CF₃SO₃ × 2 H₂O}_∞ ( 3_Zn ) is best described as distorted trigonal‐bipyramidal. The N₃O₂ ligand sphere is composed of three nitrogen atoms from the bpa ligand, one water molecule, and a carboxylate oxygen atom from a neighbouring molecule, thus forming infinite chains along the crystallographic a axis. Further intermolecular interactions are based on the same (H₂O)₂(anion)₂ motif as for 2_Pd , but whereas the former forms discrete dimers, 3_Zn forms a more complicated two‐dimensional coordination polymer with additional intermolecular hydrogen bonds.     

Synthesis and characterization of new selective Zn fluorescent probes for functionalization: in vitro Cell imaging applications

Herein the synthesis and characterization of new, lipophilic highly Zn²⁺-selective fluorescent probes are reported. High affinity for zinc (K_d 1.1–8.0 nM) over other biologically relevant metals and mixtures of metals was observed. Excitation at 360 nm afforded an emission spectrum with maximum at 530 nm for the zinc bound complex. The linear relationship between fluorescence intensity and zinc concentration indicates that FZnA-probes can be used for quantification. The probes have been synthesized in 28–45% overall yield and the feasibility for further functionalization with biologically relevant side chains has been demonstrated. In vitro studies using PC12 cells and 10 μM of one of the novel probes (FZnA-Ada) visualized endogenous labile Zn²⁺ after 45 min incubation time.     

Ru(bpy)32+配合物及bpy上双取代基效应的DFT法研究

报道Ru(bpy)32+配合物取代基效应的量子化学密度泛函(DFT)法研究的结果。探讨Ru(bpy)32+的三个配体bpy(2,2′-联二吡啶)被取代基(-NH2,-OH,-NO2)对位双取代后对配合物电子结构及相关性质,如配位键长、光谱性质等的影响规律,为该类配合物的合成及性质分析提供理论参考。     

BODIPY based fluorescent turn-on sensor for highly selective detection of HNO and the application in living cells

On the basis of BODIPY platform, a terpyridyl-substituent BODIPY-Copper complex (Cu(II)-BTPY) was rationally designed and synthesized as a redox reaction fluorescent sensor for detecting HNO over reactive oxygen species (ROS) and reactive nitrogen species (RNS) with impressive selectivity in living cells under mild and neutral conditions. The BTPY exhibits relatively high fluorescence quantum efficiency as much as 34.8% and presents large stokes shift, about 62 nm. When a series of transition metal ions were exploited to investigate the fluorescence quench towards BTPY, copper ion (Cu²⁺) gave the optimal result. After the fluorescence of the probe being effectively quenched in the presence of Cu²⁺, it can be in turn recovered through the reduction of Cu²⁺ into Cu⁺ by HNO accompanying with a visually observable fluorescence response. Still, the sensing mechanism was evidently confirmed by EPR and ESI-MS measurement. In addition, the employment of BTPY for imaging dyes was also presented in vivo.     

Structures and Fluorescent Properties of Cadmium(II) Complexes with 1D and 2D Structures Based on Tridentate Benzimidazole Ligands

The cadmium(II) complexes [CdL1(m‐nba)₂] ( 1 ), [CdL1(p‐nba)₂] · C₂H₅OH ( 2 ), [CdL2(p‐nba)₂] · CH₃OH ( 3 ), and [CdL2(p‐nbat)₂] ( 4 ) containing the ligands L1 and L2 [L1 = 2,6‐bis(benzimidazol‐2‐yl)pyridine, L2 = bis(2‐benzimidazolylmethyl)amine] were synthesized and characterized (m‐nba, p‐nba, and p‐nbat are the anions of p‐nitrobenzoic acid, m‐nitrobenzoic acid, and p‐nitrobenzeneacetic acid, respectively). The complexes were investigated by X‐ray single crystal diffraction, elemental analysis as well as IR and fluorescence spectroscopy. Compounds 1 – 3 contain a distorted pentagonal bipyramidal coordination sphere with Cd^II coordinated by two carboxylate ligands in bidentate‐chelating mode, whereas complex 4 exhibits a distorted octahedral arrangement with one carboxylate ligand in bidentate‐chelating and the other in monodentate coordination mode. 1 and 2 form a 1D chain interplayed by hydrogen bonding and strong π–π stacking interactions. 3 and 4 vary from 1D chain into 2D single‐layer and double‐layer networks because of more extensive hydrogen bonding interactions. The complexes show emission maxima in the blue region in the solid state and emission bands are red‐shifted compared to those of the free ligands.     

Structure and liquid crystalline properties of 2-hydroxyazobenzenes. X-ray diffraction, infra-red and DFT theoretical studies

The family of 2′-hydroxy-4′-alkyloxyazobenzenes containing in position 4 either CH₃ or Cl group with varying number of carbon atoms in alkyl group was analysed from the point of view of liquid crystalline properties and intramolecular OHN hydrogen bonding. The phase transition diagrams show that insertion of the OH group in 2′ position leads to a marked extention of mesophases as compared with parent azobenzenes and appearance in addition to nematic of the smectic SmA phase in the case of 4-chloro-derivatives. The role of chelate conjugating OHN hydrogen bonds in modification of mesophases is discussed based on DFT theoretical and X-ray as well as infrared studies. The importance of the molecule pairing is emphasized. Most important feature of mesophases and crystalline state of compounds under study is appearance of a continuous absorption down to 500 cm⁻¹ which is absent in solutions and Ar matrices.