Dual functional rhodamine-immobilized silica toward sensing and extracting mercury ions in natural water samples

A reversible solid optical sensor (SGIR) for Hg(2+) based on silica gel was designed and synthesized. The binding and adsorption abilities of SGIR for metal cations were investigated with fluorophotometry and cold vapor atomic absorption spectrometry, respectively. The SGIR exhibits high selectivity for sensing Hg(2+) over other metal cations in aqueous media because the Hg(2+) ion selectively induces a ring opening of the rhodamine fluorophores, and the SGIR was also found to adsorb 72% of Hg(2+) ion. The determination of Hg(2+) in both tap and lake water samples displays satisfactory results, and the SGIR can also be easily recovered by treatment of a solution of TBA(+)OH(-).     

"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.     

Interaction of cysteine with Cu2+ and group IIb (Zn2+, Cd2+, Hg2+) metal cations: a theoretical study

The structure and energetics of complexes obtained upon interaction between cysteine and Zn2+, Cd2+, Hg2+ and Cu2+ cations were studied using quantum chemical density functional theory calculations with the 6-311++G** orbital basis set and relativistic pseudopotentials for the cations. Different coordination sites for metal ions on several cysteine conformers were considered. In their lowest energy complexes with the amino acid, the Zn2+ and Cd2+ cations appear to be three-coordinated to carbonyl oxygen, nitrogen and sulfur atoms, whereas the Cu2+ and Hg2+ ions are coordinated to both the carbonyl oxygen and sulfur atoms of one of the zwitterion forms of the amino acid. Bonds of metal cations with the coordination sites are mainly ionic except those established with sulfur, which show a small covalent character that become most significant when Cu2+ and Hg2+ are involved. The order of metal ion affinity proposed is Cu>Zn>Hg>Cd.     

Selective transport of silver ion through a supported liquid membrane using hexathia-18-crown-6 as carrier.

A facile supported liquid membrane (SLM) system for the selective and efficient transport of silver ion is introduced. The SLM used is a thin porous polyvinyldifluoride membrane impregnated with hexathia-18-crown-6 (HT18C6) dissolved in nitrophenyloctyl ether. HT18C6 acts as a specific carrier for the uphill transport of Ag+ ion as its picrate ion paired complex through the SLM. In the presence of thiosulfate ion as a suitable stripping agent in the strip solution, transport of silver occurs almost quantitatively after 4 h. The selectivity and efficiency of silver transport from aqueous solutions containing other Mn+ cations such as Mg2+, Ca2+, Co2+, Ni2+, Cu2+, Zn2+, Pb2+, Cd2+, Hg2+, Fe3+ and Cr3+ ions were investigated.     

Visual sensing of Ca2+ ion via photoreaction of fluorenyl ester-armed cyclen

Fluorenyl ester-armed cyclen gave fluorenone and related decomposition compounds upon photoirradiation. The reaction was effectively suppressed by the formation of an octacoordinated Ca2+ complex while Na+ and other alkali/alkaline earth metal cations had little influence. Since the production efficiency of fluorescent fluorenone related well to the concentration of the Ca2+ ion, the photoreaction of this armed cyclen offered the naked-eye detection of Ca2+ ion in aqueous samples.     

Obtention and characterization of a ciclesonide: methyl-beta cyclodextrin complex

Conformationally mobile, di-ionizable 1,2-dimethoxy-p-tert-butylcalix[4]arene ligands are synthesized and compared with 1,3-dimethoxyl analogues to probe the influence of regiochemistry on metal ion extraction efficiency and selectivity. Extraction of hard alkali metal and alkaline earth metal cations, intermediate Pb²⁺, and soft Hg²⁺ from aqueous solutions into chloroform are utilized to evaluate the effect of this structural variation on the ability of the ligands to complex monovalent and divalent metal ion species.     

Ratiometric Zn2+ sensor and strategy for Hg2+ selective recognition by central metal ion replacement

Strategies of both self-assembly and metal ion replacement were adopted in the development of new metal ion sensors for Zn2+ and Hg2+. Ligand BPBA, phenylene-bridged bis(pyrrol-2-ylmethyleneamine), could self-assemble to form a molecular square in the presence of Zn2+, which showed strong emission in solution. The fluorescent emission of formed BPBA-Zn2+ dropped with the addition of Hg2+. BPBA could be a good Zn2+ sensor candidate and BPBA-Zn2+ could be a good Hg2+ sensor candidate based on the mechanisms of the chelation-enhanced fluorescence effect and the replacement of central metal ion induced chelation-enhanced fluorescence quenching effect, respectively.     

Comparison of upper and lower rim-functionalized,di-ionizable calix[4]arene-crown-6 structural isomers in divalent metal ion extraction

Upper rim-functionalized, di-ionizable calix[4]arene-crown-6 ligands are synthesized and compared with structural isomers having the two acidic side arms attached to the lower rim. Solvent extractions of selected divalent metal cations (alkaline earth metal cations, Pb²⁺, and Hg²⁺) from aqueous solutions into chloroform by the upper and lower rim-functionalized, di-ionizable calix[4]arene-crown-6 isomers are utilized to assess the effects of this structural modification on metal ion complexation abilities of the ligands. The observed effects are compared with those reported for analogous di-ionizable calix[4]arene-crown-5 structural isomers.     

Fluorometric sensing of alkali metal and alkaline earth metal cations by novel photosensitive monoazacryptand derivatives in aqueous micellar solutions

Novel monoazacryptand-type fluorescent chemosensors, (derived from an 18-crown-6) and (derived from a 15-crown-5) both with a pyrene ring as their photoresponsive moiety, were synthesized. Their fluorescence properties for alkali metal and alkaline earth metal cations in water were then examined. The detection of metal cations was accomplished by a change in the fluorescence intensity of the host compounds, based on a photoinduced electron transfer (PET) mechanism. In aqueous solution, showed little fluorescence upon the addition of Ba2+ because of the very weak complexation with Ba2+, but the presence of micelles of polyoxyethylene(10) isooctylphenyl ether (Triton X-100) enabled to show highly sensitive and selective Ba2+ detection among alkali metal and alkaline earth metal cations. With respect to the selective fluorescent detection of important metal cations (Na+, K+, Mg2+, Ca2+) relevant to living organisms, was found to detect K+ with high selectivity in aqueous micellar solutions of polyoxyethylene(20) sorbitan monostearate (Tween-60). The selectivity for metal cations was mainly dependent on the goodness of fit of the host cavity and the metal cation size. In the presence of anionic surfactants, detected alkaline earth metal cations more effectively than alkali metal cations.     

Effects of Metal Ion Adduction on the Gas-Phase Conformations of Protein Ions

Changes in protein ion conformation as a result of nonspecific adduction of metal ions to the protein during electrospray ionization (ESI) from aqueous solutions were investigated using traveling wave ion mobility spectrometry (TWIMS). For all proteins examined, protein cations (and in most cases anions) with nonspecific metal ion adducts are more compact than the fully protonated (or deprotonated) ions with the same charge state. Compaction of protein cations upon nonspecific metal ion binding is most significant for intermediate charge state ions, and there is a greater reduction in collisional cross section with increasing number of metal ion adducts and increasing ion valency, consistent with an electrostatic interaction between the ions and the protein. Protein cations with the greatest number of adducted metal ions are no more compact than the lowest protonated ions formed from aqueous solutions. These results show that smaller collisional cross sections for metal-attached protein ions are not a good indicator of a specific metal–protein interaction in solution because nonspecific metal ion adduction also results in smaller gaseous protein cation cross sections. In contrast, the collisional cross section of α-lactalbumin, which specifically binds one Ca²⁺, is larger for the holo-form compared with the apo-form, in agreement with solution-phase measurements. Because compaction of protein cations occurs when metal ion adduction is nonspecific, elongation of a protein cation may be a more reliable indicator that a specific metal ion–protein interaction occurs in solution.      

溶液中选择识别Hg(Ⅱ)的基于罗丹明的荧光传感器

设计合成了一种可在含水体系中选择性识别Hg²⁺的荧光传感器(化合物1),该化合物中同时包含了作为信号输出基团的罗丹明6G和作为键合基团的2-取代吡啶。其结构得到了¹H NMR,ESI-HRMS和单晶X-ray衍射分析的确认。在混合的水体系中,该化合物对二价汞离子表现出高选择性和高灵敏度的荧光和显色传感,体系的发光伴随着汞离子的加入而得以增强,颜色由无色变成粉红色。荧光滴定、ESI-HRMS和Job曲线分析都显示该传感器分子和汞离子形成1∶1的配合物。     

Ester and Ketone Groups Substituted Mono- and Di- Azo-coupled Azocalix[4]arenes as Extractant for Hg+ and Hg2+, or Cr3+Cations

This article describes extraction properties of mono- (A1–A8) and di- (B1–B8) substituted azocalix[4]arene analogues. The ionophore solvent extractions of alkaline-earth (Sr²⁺), basic metal (Pb²⁺) and transition metal cations (Ag⁺, Hg⁺, Hg²⁺, Co²⁺, Ni²⁺, Cu²⁺, Cr³⁺) from aqueous phase to organic phase were carried out by azocalix[4]arene derivatives. It has been observed that they show a good extraction behavior toward selected heavy metal (Hg) and toxic metal (Cr), while A4 and B4 prefer Hg⁺, Hg²⁺ and Cr³⁺ among transition metal cations, respectively. The azocalix[4]arenes (A1–A8) and (B1–B8) are not efficient extractants for all of the selected metal cations, whereas A4 and B4 are selective only for Hg metal cation.     

噻二嗪衍生物的合成及Pb2+在水/1,2-二氯乙烷界面转移的电化学性质

The transfer of Pb2+ facilitated by interfacial complexation with 5-(4-phenoxyphenyl)-6H-1,3,4-thiadiazin-2-amine(PPTA) at the polarized water/1,2-dicholoroethane(1,2-DCE) interface was investigated by cyclic voltammetry.We synthesized the thiadiazine derivative,PPTA,firstly.The transfer was performed at different metal concentrations and scan rates,and the obtained voltammetric transfer peaks toward Pb2+ ion over other divalent cations(Zn2+,Co2+,Ni2+,Cd2+,Hg2+,and Cu2+) were reversible.The dependence of the half-wave potentials of the Pb2+ ion on the concentration of PPTA in the organic phase indicates that the ion transfer is facilitated by the formation of 1:2(metal:ligand) complex in the organic phase with the association constant(lgβ2) of(17.1±0.2).     

新型氮杂大环化合物的研究Ⅲ.取代不对称多齿氮杂大环化合物的合成、表征与配位性能

合成了四种以Nsp2 和Nsp3为配位原子的取代不对称多齿氮杂大环化合物 ,制备了它们与不同金属离子的配合物 ,通过元素分析和光谱表征 ,研究了配体的结构与其配位性能的关系 .以吡啶环为侧链功能基的配体L1和L2可根据其环大小选择性地识别Na+或K+离子 ,与过渡金属离子形成 1∶1型配合物 ,而与Hg2 +,Cd2 +等离子则形成1∶2型配合物 .大环配体L3与Co2 +和Na+离子形成的双核配合物中两个冠醚环和一个Na+离子形成夹心配位结构 .L5环中有两个配位中心 ,因而可同时与两个Ru2 +离子配位 .L1和L2 均表现出对不同金属离子良好的液膜传输性能和传输选择性     

Rigid versus flexible: how important is ligand "preorganization" for metal ion recognition by lower rim-functionalized calix[4]arenes?

For an assessment of the outcomes from use of an appropriately "preorganized" calixarene-based ionophore versus its conformationally mobile prototype, solvent extraction propensities of flexible calix[4]arene di-[N-(X-sulfonyl)carboxamides] for alkali, alkaline earth metal cations, Pb2+, Ag+ and Hg2+ are compared with those for seven new rigid analogs fixed in the cone, partial cone and 1,3-alternate conformations. For each of the metal ions, the preferred calix[4]arene conformation was determined from the NMR spectra for the metal salt of the flexible ligand. Except for Ag+, flexible calix[4]arene di-[N-(X-sulfonyl)carboxamides] were found to provide greater metal ion extraction efficiency and better selectivity than the corresponding "preorganized" ionophores.     

Molecular Design of Crown Ethers. 191. Synthesis of Novel Disulfide- and Diselenide-Bridged Bis (benzo-12-crown-4)s and their Ag+ Selective Electrode Properties

Crown ethers have enjoyed widespread use in various fields since the very firstpreparation of the ligand by Pedersen. One of the great applications of them is inanalytical chemistry. In particular, the ion-selective electrode is a most important targetin analytical applications"'. A wide variety of moncyclic crown ethers and bicycliccrown ethers have been employed in the studies of the ion-selective electrode in rece.ntyears'-'. Especially, bicyclic crown ethers have been extensively studied …     

Interaction of three pradimicin derivatives with divalent cations in aqueous solution

This study focused on further analysis of the aggregation behavior of pradimicin derivatives and their interaction with cations in aqueous solution. BMY was compared with two other pradimicin antibiotics (T2 and FB) with the same aglycone moiety but consisting of different substitute groups. The surface tension measurement showed a clear critical micelle concentration at 1-2 mM of the BMY aqueous solution. The role of Zn2+ in replacing the Ca2+ was examined using 1H nuclear magnetic resonance (NMR) method. From changes in the NMR spectrum and precipitability, it was concluded that zinc ion has lower affinity and higher precipitating ability to BMY than the divalent cations of alkaline earth metal. The aggregation behavior of T2 and FB in aqueous solution was also studied using NMR method. The results suggest that the supramolecular behavior of T2 is similar to BMY whether or not Ca2+ ions are present in solution and that there are two binding sites for calcium ions in a T2 molecule. Unlike BMY and T2, the NMR spectrum of FB does not show distinct change upon Ca2+ addition. The interaction of pradimicin antibiotics with divalent metal ions was thought to be related to ionic electronegativity and to the amphoteric property of the antibiotics.     

Heavy metal sorption in the lichen cationactive layer

Results of copper ion sorption in lichens owing to the ion exchange between the surroundings (aqueous solution) and the lichen cationactive layer have been presented. It indicates that the course of sorption of these ions, similarly as in the case of cations of other heavy metals, depends on the concentration and type of cations naturally found in lichen surroundings: H+, Na+, K+, Mg2+ and Ca2+. A determination method of heavy metal concentration in lichen surroundings has been proposed. It consists in exposure of transplanted lichens in the presence of salts that provide precisely determined, artificial salinity of precipitation with which the lichens are in contact. The studies were conducted on Hypogymnia physodes lichens.     

A rhodamine-based fluorescent and colorimetric chemodosimeter for the rapid detection of Hg2+ ions in aqueous media

A rhodamine-based fluorescent and colorimetric chemodosimeter for the rapid detection of Hg2+ ions in aqueous media was developed. The system, which utilizes an irreversible Hg2+-promoted oxadiazole forming reaction, responds instantaneously at room temperature in a 1:1 stoichiometric manner to the amount of Hg2+. The selectivity of this system for Hg2+ over other metal ions is remarkably high, and its sensitivity is below 2 ppb in aqueous solutions.     

A new calix[4]pyrrole derivative and its anion (fluoride)/cation (mercury and silver) recognition

A new calix[4]pyrrole-based macrocycle, meso-tetramethyl-tetrakis{4-[2-(ethylthio)ethoxy]phenyl}calix[4]pyrrole, 7, has been synthesized and fully characterized. Unlike other calixpyrrole derivatives that show selective interaction with anions, calixpyrrole 7 described in the present work forms stable complexes with both metal cations and anions. The thermodynamics of complexation of this ditopic calixpyrrole derivative with metal cations (Hg2+ and Ag+) and the fluoride anion in nonaqueous solutions have been determined by titration calorimetry, and the host-guest composition has been investigated by using conductance measurements at 298.15 K. 1H NMR studies provide clear evidence about the sites of complexation of 7 with the ionic species, which show that the NH groups are taking part in the complexation of this ligand with the fluoride anion while the sulfur donor atoms are responsible for the interaction with metal cations. Using the present data on 7 and structurally related analogues (1-6), the complexation behavior is discussed comparatively from the thermodynamic point of view. Possessing four sulfur-containing pendent arms, 7 displays an enhanced hosting ability for Hg2+ in acetonitrile. As compared with 1, the calixpyrrole derivative, 7, shows a unique interaction with fluoride among the anions investigated in acetonitrile and dimethyl sulfoxide. As far as the fluoride complex is concerned, the medium effect is assessed in terms of the thermodynamics of the transfer of reactants and product from acetonitrile (reference solvent) to dimethyl sulfoxide.