Sequential detection of copper(II) and cyanide by a simple colorimetric chemosensor

A simple colorimetric receptor 1 based on the combination of N-(5-nitro-2-pyridyl)-1,2-ethanediamine and 4-(diethylamino)-2-hydroxybenzaldehyde was synthesized for the sequential detection of Cu^2 + and CN⁻. The receptor 1 showed a distinct color change toward Cu^2 + from colorless to yellow. The detection limit of 1 for Cu^2 + (0.88 μM) was much lower than the World Health Organization guideline (31.5 μM) as the maximum allowable copper concentration in drinking water. In addition, 1-Cu^2 + complex could be used to detect cyanide by showing a color change from yellow to colorless, indicating the recovery of 1 from 1-Cu^2 +. Furthermore, the sensing mechanism of 1 for Cu^2 + was supported by theoretical calculations.     

Synthesis,structural studies,and oxidation catalysis of the manganese(II), iron(II), and copper(II) complexes of a 2-pyridylmethyl pendant armed side-bridged cyclam

The first 2-pyridylmethyl pendant armed structurally reinforced cyclam ligand has been synthesized and successfully complexed to Mn^2 +, Fe^2 +, and Cu^2 + cations. X-ray crystal structures were obtained for the diprotonated ligand and its Cu^2 + complex demonstrating pentadentate binding of the ligand with trans-II configuration of the side-bridged cyclam ring, leaving a potential labile binding site cis to the pyridine donor for interaction of the complex with oxidants and/or substrates. The electronic properties of these complexes were determined by means of solid state magnetic moment, with a low value of μ = 3.10 μ_B for the Fe^2 + complex suggesting that it has a trigonal bipyramidal coordination geometry, matching the crystal structure of the Cu^2 + complex, while the μ = 5.52 μ_B value for the Mn^2 + complex suggests that it is high spin octahedral. Cyclic voltammetry in acetonitrile revealed reversible redox processes in all three complexes, suggesting that catalytic reactivity involving electron transfer processes are possible for these complexes. Screening for oxidation catalysis using hydrogen peroxide as the terminal oxidant identified the Fe^2 + complex as the oxidation catalysts most worthy of continued development.     

An unusual emissive and colorimetric copper (II) detection by a selective probe based on a pseudo-crown cysteine dye: Solution and gas phase studies

An off-on-off emissive and colorimetric probe L, based on a Pseudo-Crown cysteine dye was designed for Copper (II). Compound L was studied in solution and in gas-phase (MALDI-MS) over alkaline, alkaline, earth-alkaline and transition metal ions (Li⁺, Na⁺, K⁺, Ca^2 +, Mg^2 +, Zn^2 +, Cu^2 +, Co^2 +, Ni^2 +, Pb^2 +, and Hg^2 +) in organic media. The recognition of Cu^2 + by L lead to red/dark red colored complexes, one emissive L₂Cu and another LCu, less emissive. In regards to fluorescent quantum yield in both cases an increase respective to L was visualized (2 fold for LCu and 7 fold for L₂Cu). The paramagnetic nature of both complexes was proved by the synthesis of both complex species, as well as, through ¹H NMR and FTIR. Compound L demonstrate to be able to detect and quantify the minimal amounts of 1.3 μM/3.3 μM of Cu^2 +.     

A NBD-based highly sensitive and selective colorimetric chemosensor for Ni2 + and Cu2 +

A new colorimetric chemosensor 1, containing the 7-nitrobenzo-2-oxo-1,3-diazolyl (NBD) moiety and the phenol one connected through Schiff-base linkage, has been synthesized. Sensor 1 showed remarkable color changes from pink to orange and pale brown, respectively, upon selective binding to Ni^2 + and Cu^2 + that can be identified by the naked-eye. The binding modes of sensor 1 to Ni^2 + and Cu^2 + were determined to be 1:1 stoichiometries using a Job plot and ESI-mass analysis. The sensor 1 showed high sensitivity toward Ni^2 + and Cu^2 + with the detection limits of 0.48 μM and 0.26 μM, respectively. The recognition properties of the sensor 1 toward Ni^2 + and Cu^2 + were explained by using photophysical experiments and theoretical calculations. Practically, sensor 1 functioned as a visible test strip for Ni^2 + and Cu^2 +.     

Design,synthesis, structure and magnetic behavior of a high spin binuclear Fe(III) complex of N-(1-ethanol)-N,N-bis(3-tert-butyl-5-methyl-2-hydroxybenxyl) amine

The Mannich reaction of 2-aminoethanol, 2-tert-butyl-4-methylphenol, and formaldehyde at the ratio sets of 1:2:2 provided a new ligand, N-(1-ethanol)-N,N-bis(3-tert-butyl-5-methyl-2-hydroxybenxyl)amine (H₃L). In the presence of base, H₃L reacted with FeCl₃·6H₂O to form a dinuclear Fe(III) complex [Fe₂L₂] 1. The value of μ_eff at room temperature (5.95 μ_B), is much less than the expected spin-only value (8.37 μ_B) of two high spin (hs) Fe³⁺ (S = 5/2) ions [μ = g[∑ ZS(S + 1)]^1/2], indicating there were strong interactions between Fe³⁺ ions. The effective magnetic moment (μ_eff) decreased abruptly with cooling to a minimum value of 0.1 μ_B at 2 K. It was worth noting that Fe³⁺ ions of 1 exhibited thermally induced quartet ? doublet spin transitions, and these transitions were abrupt. The magnetic behaviors of 1 denoted the occurrence of intramolecular anti-ferromagnetic interactions. J (? 13.58 cm^? 1) agrees with the result from Gorun–Lippard equation, ? J (cm^? 1) = Aexp(BP(Å) = 12.9).     

Highly selective recognition of mercury ions through the “naked-eye”

A new sensor 2-((E)-(3-(1H-imidazol-1-yl)propylimino)methyl)-5-(diethylamino)phenol (1) based on the combination of diethylaminosalicylaldehyde and imidazole groups was designed and synthesized as a Hg^2 + selective colorimetric chemosensor. Upon treatment of 1 with mercury ions, sensor 1 showed a color-change from colorless to yellow in a mixture of H₂O/DMF (5:95), while many other ions such as Al^3 +, Zn^2 +, Cd^2 +, Cu^2 +, Fe^2 +, Mg^2 +, Cr^3 +, Ag⁺, Co^2 +, Ni^2 +, Na⁺, K⁺, Ca^2 +, Mn^2 + and Pb^2 + had no influence. Notably, this chemosensor could distinguish clearly Hg^2 + from Cu^2 +, Ag⁺, Fe^2 + and Pb^2 +. The underlying signaling mechanism is a ligand-to-metal charge-transfer (LMCT) process. Compound 1 showed the serial formation of the 1:1 and the 1:2 complexation between 1 and Hg^2 +. This two-step binding mode was proposed based on the UV titration, ¹H NMR titration and ESI-mass studies.     

A 3D heterometallic Pb(II)-Na(I) coordination polymer as a sensitive and selective fluorescent sensor for detecting Fe3 +

A Pb(II)-Na(I) coordination polymer, {[Pb₃NaL₃](Me₂NH₂)₂(C₂H₅OH)_1.5(H₂O)_10.5}_n (1) (H₃L = 4,4′,4″-s-triazine-2,4,6-triyl-tribenzoic acid), was synthesized under solvothermal condition. This structure crystallizes in the orthorhombic system and shows a 3D pillar-layer network. Topologically, it shows complicate (3,4,5,6,7)-connected net with Schläfli symbol of (4²·6⁸·8⁹·10²)(4³·6²·8)₂(4³·6⁶·8)₂(4⁸·6⁶·8)(6³). Luminescent investigations reveal that 1 can detect Fe^3 + with relative high sensitivity and selectivity, and show broad linear range of 0–1000 μM, as well as low detection limits of 8.65 nM for Fe^3 +.     

Electrochemical syntheses and structures of lead(II) and bismuth(III) complexes of 4-(trimethylammonio)benzenethiolate

Two main-group metal complexes of the zwitterionic ammonium thiolate complexes, [M(Tab)₃](ClO₄)_n (Tab = 4-(trimethylammonio)benzenethiolate) (1: M = Pb, n = 2; 2: M = Bi, n = 3), were prepared by electrochemical oxidation of Pb or Bi electrode in MeCN containing Tab and Et₄NClO₄. Each M atom in 1 and 2 is coordinated by three S atoms of three Tab ligands, forming a trigonal pyramidal coordination geometry. The resulting [M(Tab)₃]ⁿ⁺ cations are interconnected by secondary M⋯S interactions to form two different 1D cationic chains. The electrochemical properties of 1 and 2 were also investigated by cyclic voltammetry.     

Structural characterization of ferromagnetic bridged-acetato and -dichlorido copper(II) complexes based on bicompartmental 4-t-butylphenol

The reaction of Cu(II) salts with 2,6-bis[bis(2-pyridylmethyl)aminomethyl]-4-t-butylphenol (L^t-Bu-OH) afforded two bridged-phenoxido/hydroxido complexes. The dinuclear bridged acetate species [Cu₂(μ-L^t-Bu-O)(μ-CH₃COO)](PF₆)₂ (1) and the 1D polymeric doubly-bridged-chlorido {[Cu₂(μ-L^t-Bu-OH)(μ-Cl)₂](ClO₄)₂·4H₂O}_n (2). The two complexes were structurally characterized. Both complexes revealed ferromagnetic interactions; moderate in complex 1 (J = + 30.8 cm^− 1) and very weak (J = + 2.25 cm⁻¹) in 2.     

Ascorbic acid-based quinoxaline derivative as a chromogenic chemosensor for Cu2 +

Detection of cationic species represents an important field due to its importance in biological and environmental processes. This communication shows the synthesis and application of an ascorbic acid-based quinoxaline derivative (1) in the colorimetric detection of Cu^2 + against several other cationic species, including Sr^2 +, Fe^2 +, Pb^2 +, Mn^2 +, Mg^2 +, Ni^2 +, Zn^2 +, Sn^2 +, Hg^2 +, Ca^2 +, Ba^2 +, Co^2 +, Cr^3 +, Al^3 +, and Fe^3 +. Based on experimental and theoretical results, a 1:2 binding model involving 1 and Cu^2 + is proposed.     

DNA and copper (II) governed fluorescence tuning of phenanthroline possessing Ru(II) complex. Interplay of electrostatic interactions

Tuning of the fluorescence properties of [Ru (bpy) ₂ (L₁)] ^2 + (1) [L₁ = 2-(2-methoxyphenyl)-1H–imidazo [4, 5-f] Kumar et al. (2010), Rawle et al. (1992) phenanthroline] by DNA and/or Cu^2 + ion have been investigated. Fluorescence of 1 gets enhanced upon binding to DNA owing to electrostatic interactions. The binding constant of 8.4 × 10⁴ has been evaluated. Cu^2 + ions though unable to alter the fluorescence intensity of free 1 but successfully sequestrate the DNA bound 1, evidently decreasing its fluorescence intensity. The reversibility of the sequestration process was ascertained by the recovery of the quenched fluorescence intensity via introduction of equimolar EDTA to the buffer system of DNA bound 1 and Cu^2 +.     

Synthesis,crystal structure and photoluminescent properties of a 3D Zn(II) coordination polymer

A new 3D coordination polymer [NH₂(CH₃)₂]₂[Zn₇L₄(DMF)₂(H₂O)₃]·19H₂O (1) (L = 2,3′,5,5′-biphenyl tetracarboxylic acid) has been solvothermally synthesized and structurally characterized by IR, elemental analysis and single-crystal X-ray diffraction. Single-crystal X-ray diffraction studies indicate that 1 exhibits 3D framework with a one-dimensional (1D) channel. The luminescence properties have been studied, and the results showed that 1 displays strong fluorescent emissions both in the solid state and in methanol suspension at room temperature. More interesting, the addition of Fe^3 + causes the fluorescence intensity of 1 to be weakened, which implies that it may be used as luminescent probes of Fe^3 +.     

First hexanuclear manganese(II) μ6-Cl centered carboxylate anion: Synthesis,structure and magnetic properties

Reaction of manganese(II) polymer [Mn₅Cl(OH)(Piv)₈(MeCN)(HPiv)(H₂O)]_n (1, HPiv is pivalic acid) and 2-benzoylpyridine (L) in MeCN produces the ionic complex [Mn₃(Piv)₅L₂(MeCN)]⁺[Mn₆Cl(Piv)₁₂]⁻ · MeCN (3) containing the unusual hexanuclear {Mn₆(μ₆-Cl)} anion. An analogous anion was also observed in the complex [Mn₆Cl(Piv)₁₂]⁻(NEt₄)⁺ · 5MeCN (4) prepared by the reaction of the polymer [Mn(Piv)₂(EtOH)]_n (2) with NEt₄Cl in MeCN. Complexes 3 and 4 were characterized by the X-ray diffraction and magnetic susceptibility.     

Turn-on fluorescent chemosensor for selective detection of Zn2 + in an aqueous solution: Experimental and theoretical studies

A new simple receptor 1 based on the combination of julolidine and 2-(aminomethyl)benzenamine groups was prepared. It exhibited a ‘turn-on fluorescence type’ mode with high selectivity in the presence of Zn^2 +. Noticeably, receptor 1 could clearly distinguish Zn^2 + from Cd^2 +. The mechanism of fluorescence enhancement of 1 for zinc was explained by theoretical calculations. Moreover, sensor 1 had a sufficiently low detection limit (10.9 μM), which is below than the WHO recommendation level (76 μM) for drinking water. Therefore, 1 can serve as a practical chemosensor for zinc ion in an aqueous solution.     

Highly sensitive colorimetric phosphorescent chemodosimeter for Hg2 + based iridium(III) complex with (Ph2PS)2N auxiliary ligand

A colorimetric phosphorescent iridium(III) complex chemodosimeter (Ir1) for Hg^2 + has been prepared and confirmed by NMR, MS, and crystal data, which displays a high selectivity and antidisturbance for Hg^2 + detection among relevant metal ions. Phosphorescent studies show that the luminescence intensity at 598 nm decreased to ca. 12%, while the luminescence intensity in 441 nm increased to ca. 195%. The ratio of Ir1 responding to Hg^2 + was determined to be 1:1 by UV–vis absorption and phosphorescent emission measurements. Further study demonstrates that the detection limit on phosphorescent response of the sensor to Hg^2 + is down to 10^− 6 M range. The mechanism study shows that the interaction between the S atom of ancillary ligand and Hg^2 + is responsible for the highly selective and sensitive phosphorescent senor for Hg^2 +.     

Azobenzene chemosensor based on nitrogen chelator for the detection of Cu (II) ion in aqueous medium

A bis-pyridine unit containing azobenzene chemosensor for Cu^2 + ion is designed and synthesized with good yield. The structure of the receptor I is determined by FT-IR, ¹H NMR, ¹³C NMR, ESI-MS and single crystal XRD. The receptor I is constructed on the basis of internal charge transfer (ICT) mechanism with bis-pyridine unit acting as the binding part for Cu^2 + ion. In solution, the proposed receptor I produces a cation induced 120 nm blue shift for Cu^2 + ion from 457 nm to 337 nm with remarkable colour change from red to colourless. Whereas no significant colour change is observed upon addition of other metal ions in aqueous HEPES buffer (pH 7.0). Moreover, spectroscopic studies confirm the formation of 1: 1 stoichiometry between the receptor I and Cu^2 + ion with an association constant of ca. 1.45 × 10⁶ M^− 1. The receptor I is highly specific to Cu^2 + ions in aqueous solution attributed to the rational design of the molecular structure.     

A 2-(2′-hydroxyphenyl)quinazolin-4(3H)-one derived enaminone for fluorescence detection of Pd2 +

A 2-(2′-hydroxyphenyl)quinazolin-4(3H)-one derived enaminone (QA) has been developed as a fluorescent probe. In PBS buffered (10 mM, pH = 7.4) water solution, QA displays high selectivity to Pd^2 + over other metal ions with a complete fluorescence quenching at 538 nm. Probe QA interacts with Pd^2 + through a 1:1 binding stoichiometry with a detection limit of 4.85 × 10^− 7 M. Potential applications of QA for Pd^2 + detection in real water samples and living cell imaging were also investigated.     

A new copper(II) selective fluorescence probe based on naphthalimide: Synthesis,mechanism and application in living cells

A new fluorescence probe L based on naphthalimide has been synthesized for selective and quantitative detection of Cu^2 + in CH₃CN:H₂O (4:1, v/v) solution. L exhibited a strong green fluorescence. Upon addition of 2 equiv. of Cu^2 +, the fluorescence emission shows a steady and smooth decrease until a plateau is reached with a 30-fold quenching of fluorescence intensity. In the presence of Cu^2 +, the absorbance peak of L maximum at 466 nm decreased, and a new absorption band at 600 nm appeared. Under the identical conditions, other physiological and environmental important metal ions induced negligible spectroscopic changes. The 1:2 stoichiometry binding mode of L with Cu^2 + was supported by the Benesi–Hildebrand analysis and ESI-MS spectra studies. The detection limit for Cu^2 + was estimated to be 64 ppb. Fluorescence microscopy experiments showed that L has practical application in living cells.     

Synthesis,crystal structures and cytotoxic activity of mononuclear nickel(II) and dinuclear zinc(II) complexes with ligand derived from S-benzyldithiocarbazate

Ni(L)₂ (1) and Zn₂(μ-OL)₂(L)₂ (2), (HL = S-benzyl-β-N-(2-bromobenzylidene) dithiocarbazate), were synthesized and characterized by elemental analysis and X-ray single-crystal diffraction analysis. 1 is a mononuclear neutral nickel(II) complex and the center nickel atom is chelated by donors of N₂S₂ possessing a distorted tetrahedral configuration, while in 2, the adjacent two complex molecules are linked through two O atoms to form a dimer and the center zinc atom is five-coordinate in a distorted trigonal–bipyramidal geometry. The cytotoxic activity study indicated that 2 showed potent cytotoxic activity against the human liver hepatocellular carcinoma (HepG2) cancer cell lines, with IC₅₀ 2.4 ± 0.2 μg·mL^− 1, which is slightly weaker than 5-fluoroacil (5-FU) (0.89 ± 0.21 μg·mL^− 1) as reference. A gel electrophoresis assay demonstrated the ability of the complex to cleave the pBR322 plasmid DNA.     

Turn-on selective fluorescent probe for trivalent cations

A novel fluorescent sensor 1 (1 = 10-(2-(((pyridin-2-yl)methylamino)methyl)phenol)methyl-anthracene) for trivalent cations has been synthesized and characterized. Both UV-vis and fluorescence spectroscopic studies demonstrated that the new receptor 1 was highly sensitive and selective toward trivalent cations, while there was no response to monovalent and divalent cations in methanol. Upon binding with trivalent cations, the emission bands of 1 red-shifted for all the trivalent cations from 411 nm to 421 nm and their fluorescence intensities were enhanced. In particular, Fe^3 + could be obviously discriminated from Fe^2 +. The binding modes of 1 and the trivalent cations (M^3 + ions) were found to be 1:1 and confirmed by Job plot, ¹H NMR titration and ESI-mass spectrometry analysis.