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The complexes of Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Hg(II) and Pt(II) were prepared from the complexation reaction between the new Schiff base ligand and selected metal ions. Ligand was derived from the condensation reaction of Oxo(4-(pyridin-2-yl)phenyl) methyline, 4-amino antipyrine, and (6- amino Penicillanic acid). The ligand and its complexes were characterized by C.H.N elemental analysis, Uv-Vis, FT-IR, and molar conductivity, Atomic absorption, magnetic moment measurements and mass spectra studies. The results of their studies show the coordination sites for the ligand with the metal ion were to be through oxygen, nitrogen atoms of 6-amino penicillic acid, and the nitrogen atom of 4-amino antipyrine. The complexes were found to have the general formula [(M)(L)2]Cl2 where M = Co(II), Ni(II), Cu(II), Zn(II), Hg(II), and Cd(II), except the [Pt(L)Cl]Cl. The electronic spectral and magnetic measurement data indicated that the complexes exhibited octahedral geometry, except the Pt(II) complex suggested a square planar geometry around the central metal ion. The ligand forms shape as natural tridentate manner. The biological activity results showed the inhibitory effect for platinum(II) the complex. In this study the cytotoxicity of Pt(II) complex on human colon cancer cell line LS 174 T CRC was investigated and African green monkey kidney cells normal cells were MTT assay. The metal complex showed selective cytotoxicity against colorectal, this metal Complex excelled in halting proliferation of LS 174 T CRC cancer cells line with median inhibitory concentration (IC50) values of Pt(II) complex. The results indicate undoubtedly the possibility of using them as antitumor drugs in the pharmacy colon field cancer. [ABSTRACT FROM AUTHOR]

The contamination of heavy metal ions in water resources poses a threat to both human health and the environment. Fluorescent sensing technologies based on rare earth elements can be widely applied for the accurate detection and quantitative analysis of metal ions. A fluorescent nanofiber membrane material with sensitivity to copper ions was developed. The Eu(TTA) 3 ·2H 2 O complex was formed through a complexation reaction between europium (Eu) and 2-thenoyltrifluoroacetone (TTA). This complex was then co-spuned with a solution of PEG-modified PET (GPET) using the centrifugal electrostatic spinning method to create a fluorescent PET fiber membrane (GPET@Eu-NFM). Results show that the fluorescence intensity of GPET@Eu-NFM is enhanced compared to the Eu(TTA) 3 ·2H 2 O complex. As the concentration of the copper ion solution increases, the fluorescence intensity of the film presents a linear decreasing trend, and it also has a linear relationship with pH. This indicates that the fluorescent polyester fiber membrane exhibits dual responsiveness to copper ions and pH. An effective, quick, and convenient method for the monitoring and analysis of copper ions can be proposed by utilizing the fluorescence quenching phenomenon observed when the super hydrophilic surface of functionalized GPET@Eu-NFM comes into contact with copper ions. ● Poly(ethylene terephthalate) was modified hydrophilically via copolymerization and endowed with fluorescence function. ● The rare earth organic complex was loaded onto PET by electrospinning. ● Fluorescent PET nanofiber membranes showed dual responsiveness to aqueous copper and pH. [ABSTRACT FROM AUTHOR]

This review summarizes the data on the synthesis of coordination compounds containing two or more different metal ions based on fluorinated β-diketonates. Heterometallic systems are of high interest in terms of their potential use in catalysis, medicine and diagnostics, as well as in the development of effective sensor devices and functional materials. Having a rich history in coordination chemistry, fluorinated β-diketones are well-known ligands generating a wide variety of heterometallic complexes. In this context, we focused on both the synthetic approaches to β-dicarbonyl ligands with additional coordination centers and their possible transformations in complexation reactions. The review describes bi- and polynuclear structures in which β-diketones are the key building blocks in the formation of a heterometallic framework, including the examples of both homo- and heteroleptic complexes. [ABSTRACT FROM AUTHOR]

The extraction of Nd(III), Eu(III), Am(III), and Cm(III), trivalent lanthanides and actinides in high level nuclear waste, by the extractant N,N-di(2-ethylhexyl)-thio-diglycolamic acid (HDEHSDGA, HA) is investigated via thermochemical and spectroscopic methods. In this study, HDEHSDGA behaves as a conventional mono-basic cation-exchanging ligand extracting Ln(III) and An(III) from nitrate solutions of pH region. The information obtained from the extraction experiments and the spectroscopic analyses indicate that the primary extracted complex species may be MA3 · 2H2O for these four cations and likely for the other trivalent f-elements. In the extracted complexes, the anionic monomer extractant A− coordinates to the metal ions presumably forming bidentate coordination via the carbonyl oxygen atom and one of the oxygen atoms of the carboxylate; it appears that the thio-ether does not directly participate in the complexation reaction. The results ultimately demonstrate that HDEHSDGA does not exhibit significant selectivity for An(III) over Ln(III), in contrast to results reported in a previous study conducted with unpurified extractant. [ABSTRACT FROM AUTHOR]

[Display omitted] • The hexamethyldipyrromethene is multifunctional chemosensor of Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+ ions. • The influence of the complexing ion on thermodynamic stability of the [ML 2 ] was analyzed. • The constant logarithm (lg K o) of processes of [ML 2 ] formation range from 4.72 to 11.08. • The maximum fluorescent response is observed for the reaction of dipyrromethene with Zn2+ ions. • The dipyrromethene-doped cellulose tablets for detecting Zn2+ and Cd2+ ions in water were developed. Multifunctional sensors are becoming increasingly important because a single such compound can be used to detect ions of two or more metals. We propose a 3,3′,4,4′,5,5′-hexamethyl-2,2′-dipyrromethene (HL) as multifunctional chemosensor for absorbance ratiometric detection of Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+ ions, and fluorescent detection of Zn2+, Cd2+ ions. The influence of the nature of complexing ion and medium on the thermodynamic stability of the [ML 2 ] complexes, chromophoric and fluorescent responses of complexation reactions was analyzed. The lg K o values of [ML 2 ] formation processes range from 4.72 to 11.08 and, regardless of the medium nature, increase in similar sequences of complexing agents: Cd2+, Ni2+, Hg2+, Co2+, Zn2+, Cu2+ – in the c -hexane/propanol-1 (30:1, v/v) and Cd2+, Hg2+, Co2+, Zn2+ – in DMF. The maximum fluorescent response (I / I o = 100–150) was observed for the reaction of dipyrromethene with Zn2+ ions. The reaction of HL with Cd(AcO) 2 is accompanied by a 10-fold increase in fluorescence. Depending on the nature of the metal ion being determined and the medium, the detection limit of M2+ ions reaches 5 × 10−9–5 × 10−8 mol/L. Test-systems as HL-doped cellulose tablets were developed for detecting trace amounts of Zn2+ and Cd2+ ions in aqueous solutions. The using 3,3′,4,4′,5,5′-hexamethyl-2,2′-dipyrromethene as a multifunctional chemosensor, both chromophore detection of Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+ ions and "turn-on" fluorescent sensing trace amounts of Zn2+ and Cd2+ ions can be performed. Considering the significant differences in the chromophore-fluorescent characteristics of ligands and metal complexes, dipyrromethenes have great prospects for use in cation recognition. [ABSTRACT FROM AUTHOR]

BACKGROUND At present, various kinds of hydrogel adsorbents are applied to the treatment of heavy metal ions in wastewater. In this work, we focused on the adsorption of cadmium [Cd(II)] and copper [Cu(II)] onto microspheres of a novel thermosensitive hydrogel (NH2‐SA/PNIPA, aminated sodium alginate/poly‐N‐isopropyl acrylamide), studied the effect of temperature on the phase transition of the hydrogel in detail, and discussed the influence on the adsorption behavior of metal ions in the hydrogel. RESULTS: The NH2‐SA/PNIPA exhibited a higher adsorption efficiency under the conditions of interfering monovalent cationic and neutral pH. The adsorption capacities based on the Langmuir model were 57.2 mg g–1 for Cu(II) and 100.5 mg g–1 for Cd(II) at 20 °C, respectively. Higher temperature facilitated the adsorption process and also led to the volume shrinkage and hydrophobicity of NH2‐SA/PNIPA. The metal ions had different hydration and hence different adsorption capacities, of 56.7 mg g–1 for Cu(II) and 88.6 mg g–1 for Cd(II) at 40 °C. The results of diffusion behavior analysis showed that the diffusion coefficients were ≈1 × 10−11 m2 s–1. The adsorption performance of NH2‐SA/PNIPA hardly decreased even after five cycles. In addition, the adsorption process was controlled mainly by the complexation reaction. CONCLUSION: The novel hydrogel microspheres overcame the deficiency of conventional adsorbents and possessed high diffusibility. This work provides a theoretical basis and empirical evidence for enhancement of adsorbents for removing heavy metals in wastewater. © 2021 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

[Display omitted] • BODIPYs are promising fluorophores in classical fluorescent probes in cation recognition. • Chromo-fluorogenic BODIPY probes have been developed for the detection of s , p -, d - or f -element ions. • The action of chemosensors was based on various mechanisms, such as PET, ICT, FRET and others. • The reaction of probe with metal ions results in fluorescent "Off-On" or "On-Off" responses. • Multianalyte BODIPY-probes for the detection of multiple metal ions are tested simultaneously. Content assessment of metal ions (analytes) in solutions, industrial waters and natural objects is one of the most important tasks in biochemistry, medicine, ecology and various industries. To solve this problem, new types of highly sensitive and selective analytical probes are being developed. The most promising areas of analytical control are based on the bright coloristic and fluorescent responses of the complexation reactions of the probe with the analyte. Various classes of fluorescent dyes have been successfully used to obtain such probes. Among them, BODIPY fluorophores are of particular interest due to the manifestation of intense spectral-luminescent and other practically significant properties. The review focuses on advances in the development of chromo-fluorogenic BODIPY probes containing various receptor fragments selective for cations of individual s- , p -, d - or f -elements. Probes work by various mechanisms, such as photo induced electron transfer (PET), internal charge transfer (ICT), fluorescence resonance energy transfer (FRET) and others. Ultimately, the reaction of the probe with the analyte results in significant fluorescent "Off-On" or "On-Off" responses. The review contains several sections in which fluorescent BODIPY probes were divided into groups of detectable s- , p -, d - and f -elements. The spectral properties of BODIPY probes, their chromo-fluorogenic, including ratiometric, responses when binding to the analyte being determined in solutions, the binding efficiency, as well as the selectivity of determining the analyte are discussed. In addition, in many cases the possibility of practical use of probes for the analysis of metal ions in aqueous, aqueous-organic media, and cells was shown. [ABSTRACT FROM AUTHOR]

Fluoroquinolone antibiotics (FQs) form complex pollutants when they coexist with metal ions or oxides in water. These complexes alter the physicochemical properties and ecotoxicological effects of all of these three components, posing significant challenges to water treatment processes and drinking water safety. Previous studies have primarily focused on individual pollutants with little research on complex pollutants as a whole. This study summarizes the research status of complex pollutants in water environments. First, the occurrence of complex pollutants in the water was recorded. Second, the interaction mechanisms between FQs and metal ions/oxides are summarized. Complex pollution by FQs and metal ions mainly occurs through chelation reactions, whereas FQs and metal oxides are prone to adsorption and oxidation reactions. In this regard, the functional groups of FQs influence the reaction by modifying the electron transfer ability and steric hindrance, altering the reaction intensity owing to the differences in electron affinity and steric hindrance effects. Metal oxides affect complex pollution formation through differences in adsorption and oxidation capabilities. Subsequently, the effect of complex pollutants on the removal of FQs, metal ions, and metal oxides was evaluated. In particular, complex pollution affects the oxidative removal of FQs by modifying the oxidation pathways and influencing the efficiency of oxidants. In addition, complex pollution affects the photodegradation of FQs by modifying FQs' activity, electron capture, and reaction activation energy. Finally, the toxicological effects of the complex pollution were assessed to provide valuable insights into the prevention and treatment of complex pollution processes. [Display omitted] • Complexes of FQs and metal oxides/metal ions were widely detected in water. • The reaction between FQs and metal ions was complexation reaction. • FQs and metal oxides were prone to adsorption and oxidation reactions. • Impact of complexes on the removal of FQs and metal oxides/metal ions were evaluated. [ABSTRACT FROM AUTHOR]

Phytoplankton growth in the open ocean is critical to carbon fixation and often limited by low iron concentrations. Owing to its low solubility, phytoplankton employ ligands for iron uptake; therefore, ligand binding characterization is important. Herein, a micro immiscible liquid/liquid interface was employed with four ligands through an electrochemically induced facilitated ion-transfer process. Ligands 1,10-phenathroline (phen), 1-nitroso-2-naphthol (N2N), 2-(2-thiazolylazo)-p-cresol (TAC), and salicylaldoxime (SAL), where tested using established facilitated ion-transfer thermodynamics combined with differential pulse voltammetry. Three metal ion/ligand binding stoichiometries were observed for Fe2+:phen, whereas only one was observed with Fe2+ with SAL, N2N, and TAC. Overall binding constants were calculated such that binding strengths can be ranked highest to lowest as phen>N2N>TAC>SAL. Additionally, the formal ion transfer for Fe2+ (0.66 V) for an aqueous/1,2-dichloroethane interface was also determined. [ABSTRACT FROM AUTHOR]

Transition metals such as Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Zn(II), Cd(II), and Hg(II) have been reacted with gibberellic acid (HGA) to give novel complexes, and those have been characterized by physical, spectral and analytical methods. The plant hormone gibberellate acts as a deprotonated bidentate ligand in the complexation reaction with central metal ions in the ratio 1 : 2 (Mn+ : GA). The complexes [M(GA)2(H2O)2], where [M = Mn(II), Co(II), and Ni(II)] form octahedral structures, while [M(GA)2] complexes [M = Zn(II), Cd(II), and Hg(II)] display four-coordination geometry. The octahedral structures of Cr(III) and Fe(III) complexes are characterized by the general formula [M(GA)2(H2O)(Cl)]. Computational study carried out has determined possible interactions of the complexes with COVID-19 (6LU7). [ABSTRACT FROM AUTHOR]

Monoiodo- and dibromsubstituted dipyrromethenes HL1 – HL3 were described as a highly sensitive and selective «Off-On» fluorescent chemosensor for Zn2+ based on the chelation-enhanced fluorescence (CHEF) effect. Сoordination reactions of HL1 – HL3 with Zn2+ cations are accompanied by a significant (124 to 215-fold) increase in fluorescence intensity against the background of other metal ions in the binary propanol-1/cyclohexane mixture (1:30). The fluorometric detection limit of Zn2+ ions using HL1 – HL3 sensors is from 3.0∙10−8 to 3.3·10−9 mol/L. The presence of Na+, K+, Ca2+, Mg2+, Mn2+, Ni2+, Co2+, Pb2+ cations does not interfere with the detection of Zn2+. Complexation reactions are accompanied by a visual change in the color of the solution from yellow-orange to pink-raspberry so that the HL1 – HL3 ligands can also be used as a «naked-eye» indicators of the presence of Zn2+ ions. [ABSTRACT FROM AUTHOR]

This paper investigates interaction processes of the Fe3+, Cu2+, Ni2+, and Co2+ cations with humic acids isolated from brown coals of Ekibastuz basin. It was demonstrated that the sorption of heavy metal ions by humic acids (HA) depends on the concentration and nature of cations and decreases in the order of Fe3+ > Cu2+ > Ni2+ > Co2+; while increase in the concentration of humic acids (HA) results in the higher yield of ions and metals. The occurrence of ion exchange and complexation reactions in metal-humic acid systems is confirmed by the appearance of new bands and the shift of the absorption bands corresponding to stretching and deformation vibrations of carboxylate ions, C = O and OH groups. The occurrence of these processes is also evidenced by spectrophotometric data, as well as a decrease in the pH of the solution due to deprotonation of humic acids during these reactions. Thus, based on the data on the degree of sorption of metal cations by humic acids, the results of infra-red spectroscopy and spectrophotometry, it can be concluded that the Fe3+, Ni2+, Co2+, Cu2+ cations interact with HA by the ionic mechanism and by the complexation mechanism with electron-donating functional groups. Electrochemical studies of the Cu2+ – humic acid system carried out by the method of cyclic voltammetry also indicate the occurrence of the interaction of humic acid with copper cations. Modification of humic acid with copper ions shows the electrochemical activity of copper immobilized on the surface of dispersed humic acid, which is important for the implementation of electrocatalytic reactions on modified glassy carbon-humic electrodes. [ABSTRACT FROM AUTHOR]

In this paper, we describe a very fast and efficient synthesis of series of new Schiff bases L1-L5 derived from benzimidazole. It was found that, these compounds react efficiently with mercury ions to afford the corresponding complexes COP1-COP5 in nearly quantitative yield. This reaction takes place in water and in most of the usual solvents. The study of the complexation reaction of L1 with other metal ions has been carried out and shown that L1 can efficiently coordinate with Cu2+ and Co2+. In addition, the reactivity of the benzimidazole Schiff bases has been compared with some reported pyridine analogues and checked with DFT calculations. It has been found that both experimental results and theoretical calculations confirm that the benzimidazole Schiff bases are clearly more reactive than their pyridine analogues. Image 1 • A new series of Schiff bases derived from benzimidazole has been synthesized. • Their coordination behavior toward mercury ions has been studied. • Molecular structure of the obtained mercury complexes has been established. • The complexation of the Schiff bases with other metal ions has been carried out. • A comparative study has been performed by means of DFT calculations. [ABSTRACT FROM AUTHOR]

A new metal organic framework UiO-66-RSA (UiO-66 with hydroxyl) was prepared by the post-modification of UiO-66-NH 2 (UiO-66 with amino) with resorcyl aldehyde and was employed for the efficient and selective separation and removal of Pb(II) in aqueous media. The maximum adsorption amount of UiO-66-RSA was 189.8 mg/g at an optimal pH of 4. The adsorption isotherm and kinetic were well described by Langmuir/Dubinin-Radushkevich and pseudo-second-order models respectively. Adsorption process was monolayer chemisorption. UiO-66-RSA was regenerated by thiourea/nitric acid and the removal rate was only decreased by 3.7% after five successive cycles. The analysis of X-ray photoelectron spectroscopy suggested the adsorption mechanism lay on the complexation reaction between hydroxyl/nitrogen-containing groups and Pb(II). The UiO-66-RSA bound Pb(II) by forming double/quadri coordinated complexes. Compared with a multitude of usual metal ions, viz., Zn(II), Co(IV), Ni(II), Mg(II), Cd(II), Cu(II) and Ca(II), the Pb(II) could be absorbed selectively by UiO-66-RSA. The results indicated that the UiO-66-RSA sorbent could be of great potential in the removal of Pb(II) from aqueous solutions. Image 1040734 • The Zr-based metal organic framework was post-modified with resorcyl aldehyde. • The UiO-66-RSA bound Pb(II) by forming double/quadri coordinate complexes. • The maximum adsorption amount of UiO-66-RSA was 189.8 mg/g. • The UiO-66-RSA had excellent reusability and selectivity. [ABSTRACT FROM AUTHOR]

Abstract Waste activated sludge (WAS) contains many anionic functional groups which can interact with heavy metal ions through electrostatic action and complexation reactions. The transition metals adsorbed in WAS can catalyze sludge pyrolysis in anaerobic conditions and improve structural properties of organic matter. In this work, a multistage WAS utilization process for preparing the carbon-based Fenton-like catalysis materials is proposed. More specifically, WAS is firstly used as an adsorbent for heavy metals (Cu and Ni) removal, and then complexes are converted into heterogeneous Fenton-like carbon-based catalysts through oxygen-free pyrolysis. The mechanisms of interactions between extracellular polymeric substances (EPS) and metals are investigated, and the physicochemical properties of sludge-based carbons (SBC) are comprehensively characterized using varies techniques. It is found that WAS is an excellent adsorbent for Cu and Ni removal, which is mainly due to the coordination and electrostatic interactions between EPS and heavy metals. Cu and Ni adsorbed in WAS significantly improved the porous structure of SBC. Both adsorption and catalytic oxidization of Cu/Ni-SBC contribute the removal of E2 in real wastewater. The E2 removal mechanism is explored by electron-spin resonance spectroscopy (ESR) analysis, and it is found that both of .O 2 − and .OH radicals are responsible for E2 degradation in Cu(II)-SBC-H 2 O 2 , while .O 2 − radicals contributes to E2 degradation in Ni(II)-SBC-H 2 O 2 system, so the former performed better than the latter in total removal of E2. Besides, Cu(II) and Cu(I) are both formed in Cu(II)-SBC during the oxidation process, while only Ni(II) is found in the Ni(II)-SBC-H 2 O 2 process, confirming that different catalytic oxidation reactions are occurred in the Cu(II)-SBC-H 2 O 2 and Ni(II)-SBC-H 2 O 2 processes. This study facilitates a great strategy to the sludge multi-stage circulating utilization and a better understanding about the role of the Cu/Ni existed in SBC during the estrogens removal process. Graphical abstract Image 1 Highlights • Proposed multistage WAS process to initiate carbon-based Fenton-like catalysis for the first time. • Cu(II)/Ni(II) adsorbed in sludge improved the porous structure of SBC materials. • The coordination interactions mechanisms between EPS and heavy metals were determined. • The combination of Cu(II)/Ni(II) and sludge carbon (SBC) enhanced E2 removal from wastewater. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Binding of group IA/IIA cations to N -phenylaza-15-crown-5 substituted Schiff bases. • Spontaneous complexation process in the gas phase for all metal cations. • Spontaneous complexation process for the smaller cations in acetonitrile. • More negative ΔG values for the complex formation with group IIA metal cations. Abstract N -Phenylaza-15-crown-5 containing Schiff bases act as excellent ligands for alkali and alkaline-earth metal ions. The complex formation ability of two differently N -phenylaza-15-crown-5 substituted Schiff bases has been investigated using density functional theory methods. The structures of the ligands and of the respective complexes with alkali and alkaline earth metal ions have been optimized and the thermodynamic parameters of the complex formation reactions have been determined. According to the obtained results there is a rough correlation between the metal cation radius and ΔG values in the gas phase and in acetonitrile solution: the smaller the cationic radius is, the more thermodynamically favorable is the complex formation. The results for the Gibbs free energy of the complex formation reaction of these ligands with seemingly ordinary structure with IA and IIA group metal ions indicate a spontaneous and energy-favorable process in the gas phase (for all metal cations) and in the acetonitrile environment (for the smaller ones). [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • MGO showed the best adsorption capacities for TC, Cd(II) and As(V) among three magnetic graphene nanomaterials. • Adsorption behaviors of MGO in three different types of binary systems were systematically studied. • Mutual effects of TC and Cd(II) in the simultaneously added system were negligible. • Adsorption of As(V) was significantly suppressed in the presence of TC. • Cd(II) and As(V) were co-adsorbed by MGO via electrostatic attraction and formation of type A ternary surface complexation. Abstract The adsorption of tetracycline (TC), cadmium [Cd(II)] and arsenate [As(V)] onto magnetic graphene oxide (MGO), magnetic chemically-reduced graphene (MCRG) and magnetic annealing-reduced graphene (MARG) was investigated to understand the adsorption properties and molecular mechanisms. The adsorption of three contaminants was pH-dependent and the adsorption capability followed the order of MGO > MCRG > MARG, and hence MGO was selected to systematically study the adsorption behaviors in three different types of binary systems. The maximum adsorption capacities of MGO were 252 mg/g for TC, 234 mg/g for Cd(II) and 14 mg/g for As(V). The superiority of MGO was mainly attributed to its high dispersibility, thin nanosheets and various O-containing functional groups. In addition to H-bonding and π–π interactions, the strong adsorption of TC onto MGO was mainly due to the n–π electron-donor–acceptor (EDA) effect, with the maximum adsorption around pKa of TC. The mutual effects of TC and Cd(II) in the simultaneously added system were negligible. Adsorption of As(V) was significantly suppressed in the presence of TC, whilst As(V) hardly affected TC adsorption. The adsorptions of Cd(II) and As(V) in the co-adsorption system were increased by 65% and 30%, respectively. This synergistic effect resulted from the electrostatic attraction and the formation of type A ternary surface complexation. These new insights were valuable for elucidating the interaction mechanisms and designing novel adsorbents for traditional and emerging pollutions in practical application. [ABSTRACT FROM AUTHOR]

Abstract Sulfonated poly(phenylene) (sPP) thermal stability, physical properties, and gas transport characteristics were evaluated as a function of ion-exchange capacity (x = IEC), and counter-ion type (M = H+, Cs+, Na+, Mg2+, and Al3+). Counter-ion substitution with its sulfonated groups produced Δv (SO 3 -) vibrational shifts that were related to ion type and valence observed using FTIR. Increasing IEC and counter ion complexation strength within sPP led to greater density and reduced fractional free volume (FFV). sPP x -M exhibited a single thermal degradation step greater than 550 °C that decreased with increasing IEC. Unsulfonated poly(phenylene) (PP) had a glass transition at 391 °C, which shifted to 420 °C upon sulfonation. Thermal stability and mechanical properties increased with counter-ion type in the following order: sPP2.5-Cs+ < sPP2.5-Na+ < sPP2.5-Mg2+. However, decreased thermal stability and physical properties were observed using Al3+ as a counter-ion (sPP2.5-Al3+). He, H 2 , CO 2 , N 2 , O 2 and CH 4 permeability decreased within sPP2.5-M based upon counter-ion type, size, and valence. Larger CO 2 and H 2 molecules were more permeable than He, which revealed a more complex transport process was occurring within sPP2.5. Metal-ion complexation with sPP2.5 significantly reduced CO 2 and H 2 permeability. PP possessed high CO 2 permeability (152 Barrers) with moderate CO 2 /CH 4 selectivity (12.6). sPP2.5-Na+ (IEC = 2.5 meq/g) had a CO 2 /CH 4 selectivity of 71.3, and counter-ion substitution to create sPP2.5-Cs+ increased CO 2 /CH 4 selectivity by 2 3%. Gas solubility and diffusivity decreased with increasing IEC and metal-ion complexation strength. sPP x -M had tunable ideal gas permselectivity that was largely a function of sulfonate group concentration and counter-ion type. Graphical abstract fx1 Highlights • Sulfonated poly(phenylene) (sPP) physical, thermal, and gas transport properties were dependent upon counter-ion size and type. • Sulfonate group Δv (SO 3 -) shifted to higher energy based upon ion size and valence. • sPP thermal (> 560 °C) stability increased using Cs+, Na+, and Mg2+. • sPP films underwent metal-ion complexation and ionic crosslinking observed with DMTA. • sPP complexed with Al3+ led to a simultaneous improvement in O 2 /N 2 selectivity and O 2 permeability. [ABSTRACT FROM AUTHOR]

Abstract A thymine moiety as ion binding accepter was introduced into asymmetric squaraine fluorophore by amide coupling reaction to develop a new thymine-squaraine based fluorescent chemosensor (SQ). Its detection ability towards heavy metal ions was investigated by UV–vis and fluorescent spectrometry. The results showed that the sensor had high selectivity towards Cd2+ over the other metal ions in aqueous media. Moreover, it was shown that the turn on fluorescence signal occurred in the present of high concentration of cationic surfactant hexadecyl trimethyl ammonium bromide (CTAB) solution which resulting in deaggregations of SQ. The stoichiometric ratio was determined by Job's plot analysis as 1:1 and the binding constant as 2.03 × 103 M−1 for the complex between Cd2+ and SQ was further calculated by the Benesi-Hilderbrand plot. The complexation mechanism was proposed according to ESI-MS and NMR results. The following DFT calculation fully supported that the detailed coordination mode of Cd2+ and SQ went through six-membered carbonyl oxygen and the C O group in the amide chain. Finally, the SQ sensor was successfully applied in waste water sample analysis. Graphical Abstract A new thymine-squaraine based turn on fluorescent probe has been developed for detecting Cd2+ ions on CTAB controlled squaraine aggregation. Unlabelled Image Highlights • A new near infrared thymine-squaraine based chemosensor SQ has been synthesized for Cd2+ detection. • 5-fold enhancements of turn on fluorescent signal for exclusive detection of Cd2+ can be observed. • The LOD was determined as 104 nM by tuning the surfactant controlled squaraine aggregation. • The chemosensor has proven to be applied in the industrial waste water analysis. [ABSTRACT FROM AUTHOR]

Abstract The development of predictive tools capable of simulating adsorption behavior on goethite (α-FeOOH) surfaces has evolved over the past several decades. Recent research has focused on capturing the variation of surface reactivity and adsorption behavior for different preparations of synthetic goethites. In this research, an approach to estimate modeling parameters based on the specific surface area (SSA) of goethites was established and combined with a Charge Distribution – Multi-site Complexation (CD-MUSIC) surface complexation model. It was assumed that differences in crystal face contributions (CFC), inner-Helmholtz capacitances (C 1), and protonation constants of surface oxygens (pK a 's) among different preparations of goethite contribute to the variation of surface reactivity. Thus, correlations of these modeling parameters with the SSA of a range of goethites were identified by comprehensively combining microscopic, macroscopic, and modeling data reported in literature along with adsorption data collected from macroscopic experiments conducted as part of this study. A CD-MUSIC model shown to be capable of accurately predicting adsorption for several metal ions and oxyanion selenite on a 62.9 m2/g SSA goethite served as the basis for the development of the adsorption modeling approach described in this paper. The predictive capability of the newly developed modeling approach was verified by comparing predictions of protons, SeO 3 2−, and Cd2+ adsorption with experimental data from goethites with SSAs ranging between 21.3 and 105 m2/g; in total, 40 adsorption data sets from 13 different goethites were used for model verification. The results from this study indicate that the variation of surface reactivity of goethites can be successfully simulated by changing CFC, C 1 , and pK 2,singly (i.e. second protonation constant of singly-coordinated oxygens on the goethite surface) based on the SSA, which implies that self-consistent adsorption parameters can be applied to predict adsorption behavior over a range of goethite preparations. [ABSTRACT FROM AUTHOR]

Abstract Novel pyrenocrown ethers having different ring sizes were synthesized, and change of fluorescence spectra was investigated upon addition of metal ions. By the addition of Li+ and Na+ ions to 10–2 M CH 3 CN solutions of pyreno-15-crown-5 ether (3), excimer/monomer ratio decreased with 3–4 nm longer wavelength shift. Upon addition of Mg2+ and Ba2+ ions to the solution of 3 , excimer emission increased with 11–25 nm longer wavelength shift. On the other hand, when these metal ions were added to pyreno-18-crown-6 ether (4), the excimer/monomer ratio monotonically decreased. Addition of Pb2+ ion to solutions of 3 and 4 caused dramatic decrease of both monomer and excimer fluorescence intensity. Inspection of these results indicates that 3 forms 1:1 and 2:1 complexes with respective monovalent and divalent metal ions, whereas 4 forms 1:1 complexes with both monovalent and divalent metal ions. The 1:1 complexes of 3 with monovalent and divalent metal ions emit respective excimer and monomer fluorescence, whereas the 2:1 complexes of 3 emit excimer fluorescence. Monotonical decrease of fluorescence intensity by the addition Pb2+ is attributed to heavy atom effect. Graphical abstract fx1 Highlights • Pyrenocrown ethers are synthesized. • Mg2+, Ca2+, Ba2+, and Pb2+ ions can be detected by fluorescence. • Complexation equilibrium and luminescence mechanism are discussed. [ABSTRACT FROM AUTHOR]

Abstract Manganese is a trace element in human nutrition. It is involved in many enzymes, proteins and biological activities. Mn(II) ion has the capable of binding to protein or peptides. Insulin is a blood glucose-lowering peptide hormone and it is secreted by the pancreatic β -cells. In this study, the binding capability of Mn(II) ions to insulin was studied using ESI-MS, nano-ESI-MS and MS/MS methods. The binding of Mn(II) ions to insulin molecule was studied by examining the effect of pH, the molar ratio of Mn(II) ions to insulin, the flow rate with nano-ESI system and MS/MS spectrometry. The ESI-MS measurements showed that the Mn(II)-insulin complexation mostly produces ML and M 2 L type complexes. The highest binding ratio was found at pH 7. The complex formation equilibrium constants of Mn(II)-insulin were calculated as K f1 : 1.03 ± 0.12 × 104 and K f2 : 1.93 ± 0.17 × 103. The nano-ESI-MS and MS/MS measurements exhibited strong and specific binding of Mn(II) ions to insulin molecule. It was concluded from all the ESI-MS measurements that Mn(II) ion has a high affinity to insulin molecule to form stable complexes. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

Abstract: Amino-functionalized SBA-15 (SBA-Pr-NH2) with a pore size of 6 nm has been used as a basic nanocatalyst in the domino one-pot synthesis of quinoxaline derivatives via the four-component reaction of ninhydrin, 1,2-aryl-diamines, malono derivatives, and α-methylenecarbonyl compound using microwave irradiation. The solid basic catalyst plays a significant role in catalysis, and enhancing the rate and yield of the reaction, it can be easily handled and removed from the reaction mixture by simple filtration and also reused several times without substantial loss of reactivity. Moreover, the complexation reaction between quinoxaline as a model ligand and some metal ions including Cd2+, Co2+, Cu2+, Fe3+, Hg2+, Ni2+, Pb2+, and Zn2+ ions was examined spectrophotometrically in DMF solution at 25 °C. The formation constants of the resulting complexes were calculated from the computer fitting of the molar absorbance measurements in different mole ratios. The obtained data indicated that the stability constant of the resulting complexes varied in the following order Pb2+> Hg2+> Cd2+> Ni2+> Cu2+> Fe3+> Zn2+> Co2+.Graphical Abstract: [ABSTRACT FROM AUTHOR]

Photocoloration and complexation reactions of pyridine-containing nitrosubstituted spiropyran with terbium, zinc, and lanthanum cations in acetonitrile have been studied using laser kinetic spectroscopy. The triplet state participates in the photocoloration reaction of spiropyran. The complexation reaction is accompanied by a hypsochromic shift of the absorption band and proceeds in the microsecond range with pseudo-first order rate constants of 1.4 × 106, 2.3 × 106, and 3.5 × 105 s-1 for lanthanum, zinc, and terbium cations, respectively. [ABSTRACT FROM AUTHOR]

Cu(II) ion was selected as an additive to improve the enantioseparation efficiency of three dihydroflavone enantiomers in high-speed counter-current chromatography (HSCCC), using hydroxypropyl-β-cyclodextrin (HP-β-CyD) as the chiral selector. The influences of important parameters, including the metal ion, the concentrations of HP-β-CyD and the Cu(II) ion, and the sample size were investigated. Under optimal conditions, three dihydroflavone enantiomers, including (±)-hesperetin, (±)-naringenin, and (±)-farrerol, were successfully enantioseparated. The chiral recognition mechanism was investigated. The enantioseparation was attributed to the different thermodynamic stabilities of the binary complexes of HP-β-CyD and (±)-hesperetin, and Cu(II) ion could enhance this difference by forming ternary complexes with the binary complexes. This Cu(II) ion-improved complexation HSCCC system exhibited improved performance for chiral separation, and therefore it has great application potential in the preparative enantioseparation of other compounds with similar skeletons. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel quinoline base NQQM Schiff base was synthesized successfully. • Both colorimetric and fluorescence sensing of Sn2+ studied. • Selective sensing of Sn2+ by NQQM achieved. • The limit of detection towards Sn2+ was 0.026 µM. • The ratio of stoichiometry of the complex is found to be 1:1. Current work dealing with novel fluorescent turn-on to Sn2+ metal ions with N-(quinolin.3-yl.)-1-(quinoline-4-yl) methenamine (NQQM) containing quinoline constituents with the other combining metal ions. A Schiff base (NQQM) with quinoline moieties was schemed and prepared by the basic condensation reaction process in a greener approach. Basic observation of both colorimetric and fluorometric techniques was done to detect Sn2+ ions rapidly. A definite color change from colorless to yellow was noted with the addition of the Sn2+ ion. A synthesized probe was characterized by FTIR, 1HNMR, 13CNMR and mass spectroscopic techniques. The study of fluorescent spectrum for the complex behavior of NQQM with several metal ions solution in methanol was done. NQQM remarkably possesses remarkable fluorescence enhancement at 461 nm with the mixing of Sn2+ because of the complexation between them. Under enhanced conditions, the LOD calculated is 0.026 μM. The complexation reaction increases the fluorescence intensities with an increase in the metal ion concentration. Further, the characterization of the complex material confirms the formation of 1:1 stoichiometric binding between the probe and the metal cation. [ABSTRACT FROM AUTHOR]

The behavior of a xanthene derivative with one bismuthane and one phosphane function, Xan(PPh2)(BiPh2), as a ligand toward group 11 metal cations was investigated. It was found that contact with [Cu(MeCN)4]OTf, AgOTf, [Au(PPh3)OTf], in all three cases leads to a transformation of Xan(PPh2)(BiPh2) into a tridentate PBiP system, where a BiPh unit connects two phosphinoxanthyl moieties. In the resulting compounds, [PhBi(Xan(PPh2))2Cu]OTf, 1, [PhBi(Xan(PPh2))2Ag]OTf, 2, and [PhBi(Xan(PPh2))2AuPPh3]OTf, 3, the metal cations are coordinated tetrahedrally by two phosphane donors, one bismuthane donor and a fourth ligand, corresponding to OTf- in case of 1 and 2, or PPh3 in the case of 3. DFT calculations in combination with NBO analysis showed that the bismuth atoms in these PBiP ligands act as σ-donors. 3 thus corresponds to the first known AuI ← BiIII complex. [ABSTRACT FROM AUTHOR]

Complexation TOPOS is a free software package to generate 3-D topographic surfaces ("topos") for metal-ligand complexometric titrations in aqueous media. It constructs surfaces by plotting computed equilibrium parameters above a composition grid with "volume of ligand added" as the x-axis and overall system dilution as the y-axis. The sample systems in this paper are restricted to EDTA as a ligand. Other chelating ligands that form exclusively 1:1 complexes could also be modeled with this software. The surfaces show the quality of the equivalence point break under various conditions. More importantly, they develop the phenomenon of metal ion buffering. They clearly distinguish the difference between "pseudo-buffering" and "true buffering". They introduce terminology for two different forms of metal ion buffering: (1) mass action metal ion buffering under excess ligand conditions and (2) precipitate metal ion buffering when hydroxide precipitates are present under excess metal ion conditions. Systems modeled are EDTA titrations of Cu2+ and Mg2+. Supporting Information for this paper includes the Complexation TOPOS software, an Excel workbook that generates topos in under 20 seconds. Required inputs are the following: (1) a stability constant for the metal-ligand complex, (2) acid dissociation constants for the ligand, (3) stability constants for hydroxy complexes of the metal, and (4) a Ksp value and stoichiometry for hydroxide precipitates. Many constants are tabulated in a workbook tab. Also included are a PowerPoint lecture and teaching materials (for lecture, homework, and prelaboratory activities) that are suitable in general chemistry courses or third-year and graduate courses in analytical chemistry, biochemistry, and geochemistry. [ABSTRACT FROM AUTHOR]

The influence of the metallic cation of the base (Li+, Na+or K+) was determined on the acid–base constants ofp-t-butylthiacalix[4]arene (TC4),p-t-butylcalix[4]arene (CA4) andp-t-butylcalix[6]arene (CA6) in ethanol/water in an large interval of pH values by potentiometry and spectrophotometry. The pKavalues determined by both methods correlate very well and these are characteristic for each macrocycle with influence of the cation of the base without a straight evidence of an effect by the size of the metallic cation. In the case ofTC4, pKa1and pKa2were lower to Li+and Na+than with K+. ForCA4, an effect of K+on the pKa2with respect to Li+was observed. A very different behaviour was observed forCA6with Li+and K+showing a lower pKa2and a higher pKa3than with Na+. These effects were interpreted on the basis of the interaction/complexation of each cation with each macrocycle. [ABSTRACT FROM PUBLISHER]

Ultrasound irradiation, cloud point and adsorption methods were coupled to develop a new technique for the simultaneous removal of Cd(II), Ni(II), Pb(II) and Cu(II) ions after their complexation with ( E )-4-((2-hydroxybenzylidene) amino) naphthalene-1-sulfonic acid (HBANSA). In order to reduce cost and improve practicability of process, chitosan gel (CSG) composited with bismuth(III) phosphate/iron(III) phosphate nanoparticles (CSG-BiPO 4 /FePO 4 ) were hydrothermally synthesized followed by their characterization using FE-SEM, EDS and XRD analysis. The operational parameters such as metal ions concentration, CSG-BiPO 4 /FePO 4 mass, sonication time and temperature were investigated and optimized using central composite design (CCD). In addition, the possible significant correlation between these variables and removal efficiency was studied from which the maximum efficiencies were obtained at 5.57 mg/L, 51.49 °C, 0.018 g and 10.73 min corresponding to metal ions concentration, temperature, CSG-BiPO 4 /FePO 4 and sonication time, respectively. Moreover, at these conditions, the removal percentages of the Cd(II), Ni(II), Pb(II) and Cu(II) ions were found to be 96.24, 93.73, 95.55 and 97.47, respectively. After applying various isotherms, the Langmuir isotherm model was found to be most appropriate model for describing and fitting the experimental equilibrium data and thus maximum mono-layer adsorption capacities of 8.61, 8.54, 8.65 and 8.62 mg g −1 were obtained for Cd(II), Pb(II), Cu(II) and Ni(II) ions, respectively. The study of kinetics showed well applicability of pseudo second order kinetic model with maximum mass transfer rate in adsorption process. [ABSTRACT FROM AUTHOR]

The isolation of reaction products of asparagine with reducing sugars at alkaline pH and high temperature has been probed by a combination of high performance liquid chromatography (HPLC) coupled with a Fraction Collector. The UV–vis and FTIR spectra of the isolated Maillard reaction products showed structure-sensitive changes as depicted by deamination events and formation of asparagine-saccharide conjugates. The initial reaction species of the Asn-Gluc reaction were also characterized by Density Functional Theory (DFT) methods. Evidence for Cu (II) metal ion complexation with the Maillard reaction products is supported by UV–vis and FTIR spectroscopy. [ABSTRACT FROM AUTHOR]

The colorimetric chemosensors for metal ion sensing containing azo group (–N N–) as a chromogenic signaling unit and 2-(2′-hydroxyphenyl)benzimidazole as binding unit are reported. Compound 2 and 3 were studied as metal ion chemosensors in the presence of Ni 2+ , Cu 2+ , Zn 2+ /Co 2+ in aqueous CH 3 CN solutions. Well-defined color change was observed upon addition of metal ions to aqueous CH 3 CN solutions of chemosensors 2 and 3 enabling “bare-eye” color change from colorless to yellow-gold upon Ni 2+ or Cu 2+ complexation. Furthermore, test strips containing the receptor molecule were easily fabricated and offered a practical, efficient and low-cost test kit for Ni 2+ ions. The present sensing system has been successfully applied for the detection of Ni 2+ ions in real samples. [ABSTRACT FROM AUTHOR]

The aim of this work was to study in-depth the acid dissociation constants of Ritodrine, phenylepherine and Midodrine using the potentiometric technique in an aqueous solution and three different mixtures of water and dioxane. Also, the dissociation constants of Ritodrine, phenylepherine and Midodrine have been calculated in an aqueous medium with an ionic strength of 0.15–0.30 mol L−1NaNO3. The dissociation constants (pKa) values for the ionisation in a water (1) + dioxane (2) mixture have been determined at different temperatures ranging from 298.15 to 328.15 K. Then, the thermodynamic parameters (have been examined and discussed. The ligation action of ligands was studied in order to get an idea about their potentiality towards some transition metalsin vitrosystems. The formation of binary complexes of [Cu+2, Co+2, Cd+2, Ni+2, Mn+2and Zn+2] with Ritodrine, phenylepherine and Midodrine has been studied by pH-metric titrations at 37.0 ± 0.1°C and with an ionic strength ofI = 0.15 mol L−1(NaNO3) in an aqueous solution. Along with their overall stability, constants were taken by the HYPERQUAD 2008 program from the potentiometric data. The thermodynamic parameters were determined and discussed for Cu+2–L (L: Ritodrine, phenylepherine and Midodrine). The formation in the binary and ternary complexes of the Cu+2, Co+2and Ni+2metal ion with aromatic acid (anthranilic acid and 5-sulfosalicylic acid and phenylepherine) was estimated by means of potentiometry and conductometry at 37°C and inI = 0.15 mol. Results showed that L−1NaNO3was with stoichiometric coefficients 1:1:1. The ternary system formation has been displayed in a stepwise mechanism. The stability constants of these ternary systems have been calculated and discussed. The concentration distributions of the various complex species in solution have been evaluated and discussed. [ABSTRACT FROM PUBLISHER]

Green composites based on montmorillonite (Mt) and cysteine, were prepared for heavy metal removal. A comparison between the adsorption properties of the resulting hybrid inorganic-organic materials and the pure montmorillonite was carried out for the following heavy metal cations Cd 2+ , Hg 2+ , Pb 2+ , Co 2+ and Zn 2+ . It appears that the adsorption capacity is higher on the composite. Moreover, in release experiments, the heavy metal cations are more strongly retained by the hybrid material. Interactions between the hybrid clay mineral and the inorganic hosts were studied by spectroscopic methods such as solid-state NMR (Nuclear Magnetic Resonance) and FTIR (Fourier Transform Infrared). The experimental data were in agreement with the theoretical periodic DFT (Density Functional Theory) calculations where a molecular picture of the adsorption complex is proposed. [ABSTRACT FROM AUTHOR]

Because highly saline groundwaters are found at potential repository sites for nuclear waste, geochemical models should predict the speciation of relevant radionuclides in brines, including their complexation with substances such as humic acids (HA). In this study, available experimental radionuclide-HA complexation data in high 1:1 background electrolyte solutions (0.01 < m NaCl / NO 3 / ClO 4 < 4 molal, m) are reviewed. Discrepancies in the amplitude of ionic strength effects on radionuclide-HA complexation are observed, which might depend on the nature of the interacting radionuclide or on the origin of HA. However, significant differences in the experimental conditions and calculations applied to determine conditional metal ion-HA complexation constants hamper direct comparison between these datasets. To clarify whether metal ion-HA binding in saline solutions can be described, two sophisticated humic-ion binding models (Model VII and NICA-Donnan) are presently used. This is the first time that Model VII and NICA-Donnan are applied to predict metal ion-HA binding at high ionic strength ( I > 1 m). The advantage of these models, compared to more simple ones (e.g., the polyelectrolyte or the charge neutralization models), is that both electrostatic and chemical contributions to the overall metal ion-HA binding are explicitly taken into account. Model VII and NICA-Donnan are shown to produce very similar results. Trends in conditional metal ion-HA binding constants and in the maximum metal ion uptake by HA (e.g., the loading capacity) with I agree with experiments. The present data evaluation suggests that most of the apparent discrepancies between various experimental datasets arise from differences in the experimental conditions. Both Model VII and NICA-Donnan predict that the specific ion interaction theory (SIT) parameters for metal ion-HA systems, which are required for high ionic strength with more simple models, vary with pH and metal loading. Overall, Model VII and NICA-Donnan are able to account for various mechanisms involved in metal ion-HA complexation, including the metal loading effects and cation competition, and might be helpful predictive tools for performance safety assessment up to highly saline conditions. [ABSTRACT FROM AUTHOR]

Phytochelatins or PCn, (γGlu-Cys) n -Gly, and their glutathione (GSH) precursor are thiol-rich peptides that play an important role in heavy metal detoxification in plants and microorganisms. Complex formation between Cd 2+ and Pb 2+ and GSH or PCn (n = 2, 4 and 6) are investigated by microcalorimetry, absorption spectrophotometry and T-jump kinetics. Complex formation with Pb 2+ or Cd 2+ is exothermic, and induces ligand metal charge transfer bands in UV absorption spectral range, which implies the formation of a coordination bond between the metal and the thiol groups of the phytochelatins. Absorption spectra and microcalorimetry experiments allow the determination of the affinity constants and the stoichiometry of the complexes. We show that the three PCn interact with Pb 2+ to form the 1:1 and 2:1 M:L complexes, with similar affinity constants (log K 11 Pb ∼4.6, log K 21 Pb ∼11.4). These affinities are independent of the number of thiols and are, moreover, lower than those determined for complex formation with Cd 2+ . On the other hand, with Cd 2+ , PC2-Cd, PC2-Cd 2 , (PC2) 3 -Cd 2 , PC4-Cd, PC4-Cd 2 , PC6-Cd, (PC6) 2 -Cd 3 and PC6-Cd 3 complexes are detected. Furthermore, for PC4-Cd, the 1:1 complex is the most stable: affinity constant (log K 11 Cd ∼7.5). Kinetic studies indicate that complex formation between Cd 2+ and GSH occurs in the ms range; direct rate constant k obs = (6.8 ± 0.3) 10 6 M −1 s −1 and reverse rate constant k − obs = 340 ± 210 s −1 . Thus, when encapsulated in a silica matrix, PCn can be good candidates for heavy metal detection. [ABSTRACT FROM AUTHOR]

In a Siberian river, the concentrations of chemical species vary with the hydrological regime. Dissolved Organic Matter (DOM) and aluminum ions show a parallel trend in the course of the hydrological year. However, the speciation of aluminum in this natural environment remains an open question. We propose here a combination of spectroscopic techniques to investigate the proximity between the aluminum atoms and DOM. First, one-dimensional (1D) solid-state Nuclear Magnetic Resonance (NMR), Electron Paramagnetic Resonance (EPR) and 1D and 2D solution NMR spectra were acquired, providing a clear overview of the DOM composition. Second, the sensitivity enhancement yielded by Dynamic Nuclear Polarization enabled the NMR detection of proximities between the 27 Al and 13 C nuclei. Hence, we show that 8.3 ± 1.3% of the carboxylate groups observed by NMR are connected to the Al 3 + ions in the DOM sample. We here demonstrate for the first time how advanced solid-state NMR methods can provide key information about the localization of aluminum in such complex natural materials. [ABSTRACT FROM AUTHOR]

This study examines the feasibility of coupling electrodialysis (ED) to an in-situ complexation reaction (CR) step (named as ED-CR process), to selectively recover and concentrate various metallic cations with different or similar valences hardly separable by conventional ED. In a first stage, the complexing behaviour of different chemical agents towards four metal ions (Ag, Zn, Cu and Cd) have been studied and modeled from ionic forms distribution calculations. EDTA was found to be the best agent which combines advantageous characteristics: the formation of thermodynamically stable negative charged complexes in a large range of metal ion concentration, a discriminant complexation ability, and the possibility of ligand displacement for the ultimate recovery of the released metal ion (and the complexing agent as well). In a second stage, electro-extraction performances have been investigated under various operating conditions: pH of the feed to be treated, solution flow rates and concentrations, electric voltage applied, concentration of electrolyte solutions used, continuous or batch mode applied. The results showed high electro-separation performances both for the Ag/Zn and Cu/Cd systems. Some limitations of the process have been identified and well-delimited operating conditions could be proposed to achieve both optimal extraction and selectivity. This original hybrid technology would extend the potentialities of ED for the treatment of added-value metal ion containing wastewaters. [ABSTRACT FROM AUTHOR]

Alternative solutions need to be developed to overcome the growing problem of multi-drug resistant bacteria. This study explored the possibility of creating complexes of antibiotics with metal ions, thereby increasing their activity. Analytical techniques such as isothermal titration calorimetry and nuclear magnetic resonance were used to examine the structure and interactions between Cu(II), Ag(I) or Zn(II) and β-lactam antibiotics. The metal-β-lactam complexes were also tested for antimicrobial activity, by micro-broth dilution and disk diffusion methods, showing a synergistic increase in the activity of the drugs, and enzymatic inhibition assays confirming inhibition of β-lactamases responsible for resistance. The metal-antibiotic complex concept was proven to be successful with the activity of the drugs enhanced against β-lactamase-producing bacteria. The highest synergistic effects were observed for complexes formed with Ag(I). [ABSTRACT FROM AUTHOR]

Metal cations complexation and proton binding by 13- and 16-membered diphenyl-azobenzocrowns and diphenyl-hydroxyazobenzocrowns were studied in acetonitrile using spectroscopic methods: UV–vis spectroscopy, spectrofluorimetry, and 1 H NMR spectroscopy. Phenyl moieties in benzene rings were found to affect binding strength alkali and alkaline earth metal cations and hydrogen ion, and affect tautomeric equilibrium of hydroxyazobenzocrowns. X-ray structure of 13-membered diphenyl-hydroxyazobenzocrown was solved showing the existence of this compound in quinone-hydrazone form in a solid state. The suitability of diphenyl-azobenzocrowns for potentiometric metal cation determination using miniature, planar, all-solid-state type electrodes was also tested. [ABSTRACT FROM AUTHOR]

The synthesis and electrochemical characterization of a new azulene-thiourea like complexing monomer namely, (2E)-2-(azulen-1-ylmethylidene) hydrazinecarbothioamide ( L) is reported. The electropolymerization of L in acetonitrile on glassy carbon electrodes, put in evidence by EQCM and ferrocene redox assay probe, led to the immobilization of the complexing monomer on the electrode surface. The poly L modified electrodes were electrochemically characterized and their morphology was evaluated using scanning electron microscopy. The complexing abilities of L and poly L towards heavy metal ions were highlighted. [ABSTRACT FROM AUTHOR]

We reported herein the studies on in situ metal-ion complexation and H 2 O 2 oxidation for a pyridine-2,6-dione based heterocyclic dye (C.I. Disperse Yellow 211) in the hydrazone-tautomeric form. Our results reveal that four kinds of compounds can be isolated successfully by treating this dye with Cu(OAc) 2 ·H 2 O and H 2 O 2 in the presence of NH 3 ·H 2 O and DMF, namely oxidation and complexation product 1 , oxidation product 2 , ring-degradation (ring-opening and oxidative cleavage) product 3 and complexation product 4 . In contrast, when copper(II) and nickel(II) ions were used under the similar reaction condition just in the absence of H 2 O 2 oxidant, only direct complexation products 4 and 5 could be obtained. It is noted that organic compounds 2 and 3 adopt the same hydrazone-tautomeric form as that in C.I. Disperse Yellow 211, but all three dye-metal complexes 1 and 4 – 5 exhibit the deprotonated azo form. A possible reaction mechanism is proposed for the formation of hydroxyl-addition and ring-degradation products 1 – 3 . Furthermore, we have provided an effective preparation method for new dyes with an additional ortho phenolic hydroxyl group by H 2 O 2 oxidation, metal-ion complexation and subsequent demetallization by Na 2 S. [ABSTRACT FROM AUTHOR]

In the present work new naphthalene appended calix[4]arene ( NAC4) i.e. 5,11,17,23-tetra-tert-butyl-25,27-di((2-amido(1-naphthlene)ethyl)-26,28-dihydroxy calix[4]arene ( 6) was designed and successfully synthesized. NAC4 was characterized by HNMR and FTIR. To explore the complexation behavior and fluorescence response of NAC4, UV-visible and fluorescence studies were carried out with series of metal ions and anions that include solvatochromic effect, ion-ligand response and interference on absorption and fluorescence spectra. Results show that the NAC4 is highly Cu and Iselective. The ligand ion interaction follow photoinduced electron transfer (PET) mechanism. The stiochiomatric ratio of ion-ligand was calculated as 1:1 by using Job's plot method and binding constant K values were calculated by using Benesi-Hildebrand equation as 1×10 and 8×10 M with detection limit of 1.05×10 and 4.0×10 M for Cu and I respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] • The FeS/PS system exhibited excellent removal for TTC-Cu at different pHs. • The Cu(II) increased TTC elimination via the complexation and redox process. • Structural Fe(Ⅱ) and Cu(Ⅰ) played important roles in the activation of PS under alkaline conditions. • SO 4 •− mainly contributed to TTC degradation. • Effect of different metal ions on the TTC removal by FeS/PS was studied. Herein, mackinawite (FeS) was employed for activation of persulfate (PS) to remove tetracycline (TTC). The effect of the coexistence of Cu(II) on TTC degradation was explored at different initial pHs. Nearly 100% removal in 5 min at an initial pH of 3 was achieved with/without Cu(II). No less than 90% of TTC removal was achieved in a 60 min reaction at initial pH of 5, 7 and 9 where the Fe(II) leaching was small. More surprisingly, compared to FeS/PS/TTC system, up to a three-fold increase in degradation rates of TTC was observed in the FeS/PS/TTC-Cu system at initial pH of 9. Cu(I) produced by TTC-Cu associated with PS activation at initial pH of 5, 7 and 9 was thought to result in the apparent increase in TTC degradation efficiency. By further comparing the TTC degradation processes involving oxidizing complexed Cu(II), oxidizing non-complexed Cr(VI), non-oxidizing complexed Zn(II) and Pb(II), respectively, we determined the contribution of the complexation and redox processes of metal ions to TTC degradation. In addition, free radicals were detected in the FeS/PS/TTC-Cu system, in which SO 4 •− played the dominant role in the TTC degradation. Meanwhile, the structural Fe(II) was presumed as the primary form of Fe(II) improving to the activation of PS under basic conditions based on the theoretical calculations. These findings emphasize the importance of the complexation and redox reaction of metals at basic pH in the FeS/PS system, which may broaden the application of FeS/PS system. [ABSTRACT FROM AUTHOR]

Among known molecular switches, spiropyrans attract considerable interest because of their reversible responsiveness to external stimuli and the deep conformational and electronic changes that characterize the switching process between the two isomeric forms [spiropyran (SP) and merocyanine (MC)]. Metal coordination is one of the most interesting aspects of spiropyrans for its potential in sensing, catalysis, and medicinal chemistry, but little is known about the details surrounding spiropyran-metal ion binding. We investigated the interplay between an N-modified 8-methoxy-6-nitrospiropyran (SP-E), designed to provide appropriate molecular flexibility and a range of competing/collaborative metal binding sites, with Mg2+, Cu2+ and Zn2+, which were chosen for their similar coordination geometry preferences while differing in their hard/soft character. The formed molecular complexes were studied by means of UV/Vis, fluorescence, and NMR spectroscopies and mass spectrometry, and the crystal structure of the SP-E-Cu complex was also obtained. The results indicate that the Mg2+, Zn2+ and Cu2+ complexes have identical coordination stoichiometry. Furthermore, the Mg2+ and Zn2+ complexes display fluorescence properties in solution and visible-light responsiveness. These results provide important spectroscopic and structural information that can serve as a foundation for rational design of spiropyran-based smart materials for metal sensing and scavenging applications. [ABSTRACT FROM AUTHOR]

We have reported the synthesis involving the condensation of pyridoxal with tris(2-aminoethyl)amine obtained a tripodal ligand, as well as its subsequent complexation with the manganese(II) and nickel(II) ions. The structural analysis revealed, in the case of complex 1 , the formation of a monomeric complex with Mn(II) species. In the complex 2 , with Ni(II) metal ion, we describe the probable mechanism for the formation of hemiacetal in these complexes. Only the complex 1 catalyze the dismutation of superoxide efficiently with IC 50 equal to 3.38 μM, evaluated through the nitro blue tetrazolium photoreduction inhibition superoxide dismutase assay, in aqueous solution of pH 7.8. Density functional theory calculations are done to characterize and compare the molecular frontier orbitals of the Mn(II) and Ni(II) complexes. [ABSTRACT FROM AUTHOR]

The Experimental thermodynamic equilibrium ( p K a values) and stability (log β ) constants of vanadium and platinum binary and mixed ligand complexes involving naringenin, ferulic acid, p-coumaric acid, caffeic acid, vanillic acid, sinapic acid, and gallic acid were determined at 310.15 K in 0.16 mol·dm −3 KCl aqueous solutions using pH-potentiometric technique and by means of two estimation models (HYPERQUAD 2008 and Bjerrum–Calvin). The theoretical calculations of overall protonation and stability constants of the metal complex species in solution were predicted as the free energy change associated with the ligand protonation, and metal ion–ligand complex formation equilibria (species solvation/de-solvation) using ab initio and density function theory (DFT) calculations. The usage of the experimental potentiometry technique and theoretical predictions provides a complete picture of the microscopic equilibria of the studied systems (vanadium/platinum–naringenin–phenolic acid). Specifically, this theoretically DFT predications would be useful to determine the most real protonation constants of the studied bioligands in which the binding sites changes due to the ligand protonation/deprotonation equilibria. Also, the complexing capacities of vanadium and platinum towards naringenin, ferulic acid, p-coumaric acid, caffeic acid, vanillic acid, sinapic acid, and gallic acid in solutions were evaluated and discussed. From the determined experimental stability constants of different metal complex species, the concentration distribution diagrams of the various metal ion complex species in solution was estimated using HySS 2009 software. [ABSTRACT FROM AUTHOR]

The adsorption of Cr(III) or Cr(VI) in the absence and presence of Cu(II) onto kaolin was investigated under pH 2.0–7.0. Results indicated that the adsorption rate was not necessarily proportional to the adsorption capacity. The solutions’ pH values played a key role in kaolin zeta potential (ζ), especially the hydrolysis behavior and saturation index of heavy metal ions. In the presence of Cu(II), qmixCr(III) reached the maximum adsorption capacity of 0.73 mg·g−1 at pH 6.0, while the maximum adsorption capacity for the mixed Cr(VI) and Cu(II) system (qmixCr(VI)) was observed at pH 2.0 (0.38 mg·g−1). Comparing the adsorption behaviors and mechanisms, we found that kaolin prefers to adsorb hydrolyzed products of Cr(III) instead of Cr3+ ion, while adsorption sites of kaolin surface were occupied primarily by Cu(II) through surface complexation, leading to Cu(II) inhibited Cr(VI) adsorption. Moreover, Cr(III) and Cr(VI) removal efficiency had a positive correlation with distribution coefficient Kd. Cr(III) and Cr(VI) removal efficiency had a positive correlation with distribution coefficient Kd and that of adsorption affinities of Cr(III) or Cr(VI) on kaolin was found to be Kd Cr(III) < Kd Cr(III)-Cu(II) and Kd Cr(VI) > Kd Cr(VI)-Cu(II). [ABSTRACT FROM AUTHOR]

Schiff base pyridin-2-ylimino methyl naphthanol (HL) was synthesized and characterized by spectroscopic (FTIR, ESIMS, and NMR) techniques. The ligand was reacted with perchlorate salts of Mn+2, Co+2, and Ni+2. ESIMS mass spectra indicate the formation of mononuclear complex ML2for all three complexes. CoL2crystallizes inP21/nspace group, adopting a distorted tetrahedral geometry where Co is in a N2O2donor environment. Structure of the Co complex was optimized by DFT calculation. Solution-phase complexation between the ligand and the three metals ions: Mn+2, Co+2, and Ni+2(pH 7.2 in tris buffer), in CH3CN–H2O was performed spectrophotometrically by UV–vis spectral study. Job’s plot from each titration suggests a 1 : 2 metal to ligand combination. The association constants for the formation of ML2are as follows: Mn (19.80 × 103 M−1), Co (14.54 × 103 M−1) and Ni (19.04 × 103 M−1). [ABSTRACT FROM AUTHOR]

A fundamental property of ions is their size, a known fact since before the acceptance of the modern atom model. The common way to describe the size of an ion is to determine its radius, defined as one of a pair of radii adding up to the bond distance between the centers of two nuclei. There are numerous factors that influence the ionic radius of a metal ion, where both valence and coordination number are essential when explaining reactivity, complexation, and chemical behavior. The similarity in ionic radii and chemical behavior between the elements in the lanthanoid and actinoid series is well-known and frequently used, making members of the former safe substitutes to avoid hazardous experiments with the radioactive actinoids. This review establishes reliable ionic radii for the nine-coordinate actinoid(III) ions, based on reported structural data, shedding light upon common misconceptions and clarifying the relationship between the ionic radii in the lantanoid and actinoid series. [ABSTRACT FROM AUTHOR]