An EPR study of Cu doped diaquabis(nicotinamide)bis(o-sulfobenzimidato-N)-cadmium(II) single crystals

The electron paramagnetic resonance spectra of Cu²⁺ doped diaquabis(nicotinamide)bis(o-sulfobenzimidato-N)-cadmium(II) (hereafter, CdNAS) single crystals which were taken at room temperature are discussed. It was found from the analysis of the EPR data that the Cu²⁺ ions substitute for magnetically inequivalent Cd²⁺ ions. Two magnetically inequivalent Cu²⁺sites were observed. The principal values of the g and the hyperfine tensors were determined. The ground state wave functions of the unpaired electron of Cu²⁺ ions in two sites were constructed and type of the distortion was determined.     

EPR study of Cu(2+)-doped tetraaqua-di(nicotinamide)Co(II) saccharinate single crystals

The electron paramagnetic resonance spectra of Cu(2+) impurities in [Co(nicotinamide)(2)(H(2)O)(4)](saccharinate)(2) single crystals have been studied at ambient temperature in three mutually perpendicular planes. The angular variation of the spectra shows that the Cu(2+) ion substitutes the Co(2+) site in the lattice. The EPR spectra of Cu(2+) ions are characteristic of tetragonally elongated octahedral site. The spin-Hamiltonien parameters were obtained from the single crystal EPR analysis. The ground-state wave function of Cu(2+) ion in the lattice has been constructed.     

A highly selective visual and fluorescent sensor for Pb2+ and Zn2+ and crystal structure of Cu2+ complex based-on a novel single-armed Salamo-type bisoxime

A novel single-armed Salamo-type bisoximes (H₄L) has been designed and synthesised. An obvious colour change from yellow (H₄L) to pale pink (HL-Pb²⁺) which can be visually observed by the naked eye in visible light. H₄L can act as a fluorescent sensor for ratiometric recognition of Zn²⁺ with high selectivity and sensitivity. Crystallographic data of the [Cu(HL)(μ-OAc)Cu] reveals that the two Cu²⁺ ions are both penta-coordinated with square pyramidal geometries, and forms a 2D supramolecular plane structure by hydrogen bonding interactions.     

Electron paramagnetic resonance studies of Cu2+ ion in tetraaqua-di(nicotinamide)Ni(II)-saccharinates single crystals

X-band (approximately 9.8 GHz) electron paramagnetic resonance (EPR) measurement at ambient temperature in three mutually perpendicular planes have been carried out on a single crystal of Cu2+ doped mixed ligand complex of Ni(II) with saccharin and nicotinamide [Ni(Nic)2(H2O)4](sac)2. The angular dependent spectra showed that the Cu2+ ion enters Ni2+ sites in the lattice and distorted local environment of Ni2+ site. The principal g and A values, covalency parameter (alpha'2), mixing coefficients (alpha and beta) and Fermi contact term (K) have been evaluated from the EPR analysis. The ground-state wave function of the Cu2+ ion has been constructed using the alpha'2, alpha and beta values. The nature of the distortion present in the lattice is obtained from the values of the mixing coefficients.     

Reduction of Cu2+ to Cu+ in Xerogels Prepared from (3-Aminopropyl)Trimethoxysilane

Silica gels doped with Cu²⁺ ions were prepared from the (3-aminopropyl) trimethoxysilane (APTMOS)/tetraethoxysilane (TEOS) systems. Sols showed a broad absorption peak at 640 nm, suggesting 3–5 coordination of the aminopropyl groups to Cu²⁺. For gels prepared from APTMOS and dried at room temperature, the 640 nm peak decreased and a red-shifted absorption appeared below 400 nm within a few months. The luminescence spectra of the xerogels showed emission bands at 430–470 and 510 nm. The former and latter bands are ascribed to Cu⁺ monomer and dimer emissions, respectively. These results indicate that Cu²⁺ ions are reduced to Cu⁺. When xerogels were prepared from APTMOS/TEOS = 1 (vol/vol), the color of xerogels was blue with an absorption peak at around 670 nm, indicating no reduction of Cu²⁺ ions.     

Novel naphthalene-based fluorescent chemosensors for Cu2+ and Fe3+ in aqueous media

Three novel compounds bearing 2,7-dihydroxylnaphthalene capable of detecting Cu²⁺ or Fe³⁺ have been synthesised based on photoinduced electron transfer. The ability of these compounds for complex transition metal ions has been studied, and complex stoichiometry for Cu²⁺ and Fe³⁺ complex has been determined in the Tris–HCl (0.01 M DMSO/H₂O (v/v) 1:1, buffer, pH 7.4) solution system by fluorescence titration experiments. These chemosensors form a 1:1 complex with Cu²⁺ or Fe³⁺ and show a fluorescent quenching with a binding constant of (4.46 ± 0.29) × 10³ and (8.04 ± 0.26) × 10⁴, respectively.     

Cu(II)-triggered release of paclitaxel from a supramolecular complex

The research on the stimuli-responsive property of biological or synthetic macromolecules in a wide range of scientific fields is a crucial subject for the achievements of the targeted drug release and the precise control of the functions of the supramolecules at a molecular level. We used an anthraquinone-functioned cyclodextrin (1) bridged by an aza-arm to solubilise paclitaxel (PTX) by forming a supramolecular complex (1/PTX). The possible inclusion mode was given based on the experimental results of ultraviolet–visible spectroscopy, Fourier transform infrared, X-ray diffraction, fluorescence spectra, nuclear magnetic resonance, transmission electron microscope, scanning electron microscope and dynamic light scattering characterisations. The controlled release of PTX can be achieved by adding Cu²⁺ to the solution. This study provides useful references in developing stimuli-responsive drug-carrying and drug-releasing materials.     

EPR parameters and local geometry for Cr3+ and V2+ ions in HfS2 crystals

From the high-order perturbation formulas of EPR parameters (zero-field splitting D, g factors gparallel, gperpendicular and hyperfine structure constants Aparallel, Aperpendicular) based on the two spin-orbit coupling parameter model for 3d3 ions in trigonal symmetry, the EPR parameters of Cr3+ and V2+ ions in HfS2 crystals are calculated. From the calculations, it is found that the local trigonal distortion angle theta of impurity center in HfS2:Cr3+ is smaller than that in HfS2:V2+. The dominant cause of the small zero-field splitting |D| and g-anisotropy |Deltag|=|gparallel-gperpendicular| in HfS2:Cr3+ (compound to HfS2:V2+) is due to the small local trigonal distortion angle theta rather than to the small impurity-ligand distance R in HfS2:Cr3+.     

A novel method for the simple and simultaneous preconcentration of Pb2+, Cu2+ and Zn2+ ions with aid of diethylenetriamine functionalized SBA-15 nanoporous silica compound

A rapid method for the extraction and monitoring of nanogram level of Pb²⁺, Cu²⁺ and Zn²⁺ ions using uniform silanized mesopor (SBA-15) functionalized with diethylenetriamine groups and flame atomic absorption spectrometry (FAAS) is presented. The preconcentration factor of the method is 100 and detection limit of the technique is 5.5?ng?mL^?1 and 1.4?ng?mL^?1 and 0.1?ng?mL^?1 for Pb²⁺, Cu²⁺ and Zn²⁺ respectively. The time and the optimum amount of the sorbent, pH and minimum amount of acid for stripping of ions from functionalized SBA-15 were tested. The maximum capacity the functionalized SBA-15 was found to be 183.0 (±1.9) µg, 156.0 (±1.5) µg and 80.0 (±1.6) µg of Pb²⁺, Cu²⁺ and Zn²⁺/mg functionalized SBA-15, respectively.     

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

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

A new lawsone azo-dye for optical sensing of Fe3+ and Cu2+ and their DFT study

A new lawsone-based azo-dye 2-hydroxy-3-((pyridin-2-ylmethyl)diazenyl)naphthalene-1,4-dione (1) was synthesized and applied for sensing of metal ions. Receptor 1 showed selective fluorescent and colorimetric response for the detection of Cu²⁺ and Fe³⁺ over other tested metal ions. The fluorescence intensity of 1 was significantly quenched allowing detection of Fe³⁺ and Cu²⁺ down to 0.61 and 6.06 μM, respectively. The binding has been established by fluorescence spectroscopic method. Receptor 1 provided a 1?:?1 binding scaffold for recognition of Fe³⁺ and Cu²⁺ ions with the association constant of 3.33 × 10⁶ and 3.33 × 10⁵ M^?1, respectively. The B3LYP/6-31G/LANL2DZ method was employed for the optimization of 1 and 1·Fe³⁺ and 1·Cu²⁺.     

多吡啶钴(Ⅲ)配合物与Zn2+形成的新型“关-开”荧光探针

近十几年来,对小分子过渡金属配合物与大分子DNA键合与识别机理的研究一直是国际上生物无机化学领域十分活跃的研究课题[1￣3],已发展了一系列具有特定功能的配合物,如DNA结构探针和DNA荧光探针等。与其他类型的金属配合物相比,八面体过渡金属多吡啶配合物具有丰富的光化学和光物理信息,当这些配合物与DNA相互作用时,由于结构匹配或微环境的差异,配合物的光谱特征会出现不同程度的改变,从而达到对DNA的检测。传统的DNA荧光探针有[Ru(bpy)2dppz]2 和[Ru(phen)2dppz]2 (bpy=2,2′-联吡啶,phen=1,10-菲咯啉,dppz=二吡啶[3,2-a∶2′,3′…     

A Conductometric Study of Complexation Reactions Between Dibenzo-18-Crown-6 (DB18C6) with Cu2+, Zn2+, Tl+ and Cd2+ Metal Cations in Dimethylsulfoxide–Ethylacetate Binary Mixtures

The complex formation between Cu²⁺, Zn²⁺, Tl⁺ and Cd²⁺ metal cations with macrocyclic ligand, dibenzo- 18-crown-6 (DB18C6) was studied in dimethylsulfoxide (DMSO)–ethylacetate (EtOAc) binary systems at different temperatures using conductometric method. In all cases, DB18C6 forms 1:1 complexes with these metal cations. The stability constants of the complexes were obtained from fitting of molar conductivity curves using a computer program, Genplot. The non-linear behaviour which was observed for variations of log K _f of the complexes versus the composition of the mixed solvent was discussed in terms of changing the chemical and physical properties of the constituent solvents when they mix with one another and, therefore, changing the solvation capacities of the metal cations, crown ether molecules and even the resulting complexes with changing the mixed solvent composition. The results show that the selectivity order of DB18C6 for the metal cations in pure ethylacetate and pure dimethylsulfoxide is: Tl⁺ > Cu²⁺ > Zn²⁺ > Cd²⁺ but the selectivity order is changed with the composition of the mixed solvents. The values of enthalpy changes (ΔH°_C) for complexation reactions were obtained from the slope of the van’t Hoff plots and the changes in standard enthalpy (ΔS°_C) were calculated from the relationship: ΔG°_C,298.15=ΔH°_C − 298.15 ΔS°_C. The obtained results show that in most cases, the complexes are enthalpy stabilized, but entropy destabilized and the values of ΔH°_C and ΔS°_C depend strongly on the nature of the medium.     

Epoxy-based oligomer containing dithia-aza-based naphthylazobenzene pendant: a chemosensor for Hg2+ and Cu2+ ions

A simple epoxy-based oligomer 1 containing naphthylazobenzene-appended dithia-aza moieties was prepared. In UV–vis measurements, the proposed oligomer showed the ion-sensing ability to Hg²⁺ and Cu²⁺ ions. The discrimination between two differently responding Hg²⁺ and Cu²⁺ ions was also realised from ‘ON–OFF’ type fluorescence responses of 1.     

Highly selective ratiometric fluorescent sensor for Cu(II) with two urea groups

A new Naphthalene derivative with two urea groups, 1,8-bis[N-(o-methoxyphenyl)ureido]naphthalene (BMPUN), was synthesized for detecting Cu(II) ratiometrically. Complexation between urea groups of BMPUN and Cu(II) with high selectivity gives rise to a great red-shift from 380 to 440 nm in the emission spectra. The introduction of electron donating groups is helpful to increase the electron density of the nitrogen atom of urea groups and then enhance the ability of complexation for Cu(II).     

A chemosensor showing discriminating fluorescent response for highly selective and nanomolar detection of Cu and Zn and its application in molecular logic gate

A fluorescent based receptor (4Z)-4-(4-diethylamino)-2-hydroxybenzylidene amino)-1,2dihydro-1,5-dimethyl-2-phenylpyrazol-3-one (receptor 3) was developed for the highly selective and sensitive detection of Cu²⁺ and Zn²⁺ in semi-aqueous system. The fluorescence of receptor 3 was enhanced and quenched, respectively, with the addition of Zn²⁺ and Cu²⁺ ions over other surveyed cations. The receptor formed host-guest complexes in 1:1 stoichiometry with the detection limit of 5 nM and 15 nM for Cu²⁺ and Zn²⁺ ions, respectively. Further, we have effectively utilized the two metal ions (Cu²⁺ and Zn²⁺) as chemical inputs for the manufacture of INHIBIT type logic gate at molecular level using the fluorescence responses of receptor 3 at 450 nm.     

Graphene quantum dots with Zn2+ and Ni2+ conjugates can cleave supercoiled DNA

Graphene quantum dots (GQDs), inheriting the superb property of graphene oxide, possess smaller lateral size and high biocompatibility, thus having potential in biomedical applications. We previously discovered that GQDs, combining with Cu²⁺ ions, could cleave DNA primarily through an oxidative pathway; yet, oxidative DNA cleavage is not practically preferred in biology. In this work, we explore the DNA cleavage ability of GQDs with Zn²⁺ and Ni²⁺. Zn²⁺ and Ni²⁺ alone are incapable of cleaving supercoiled DNA, but when combining with the GQDs, Zn²⁺ and Ni²⁺ exhibit DNA cleavage activity. However, the activity of these two systems is much lower than that of GQDs/Cu²⁺, and GQDs/Ni²⁺ is less active than GQDs/Zn²⁺. The functional mechanism of GQDs/Ni²⁺ and GQDs/Zn²⁺ is different from that of GQDs/Cu²⁺. The GQDs play a key role in the two systems; the redox inactive Zn²⁺ and Ni²⁺ ions assist to generate the oxidative species that eventually lead to the DNA cleavage. The current results together with our previous result indicate that GQDs together with metal ions can cleave supercoiled DNA, and their cleavage activities depend on the properties of metal ions: for redox active metal ions, metal ions play key roles, for redox inactive metal ions, GQDs are dominant.     

Concentration and Separation of Ni2+, Cu2+ and Co2+ by Back Extraction Chromatography Using Lix 64N and Cationic Resins

Abstract

This paper describes the method for the concentration of Cu²⁺ by liquid-liquid extraction using Lix 64N solutions in kerosene, followed by back extraction chromatography.

It consists of a pass of the organic phase through columns filled with cationic resins (H⁺) which contains only the water surrounding the grains.

The effect of the pH of the aqueous film surrounding the resin grains on the capacity of Vionit CS-3 (-SO₃H) and Vionit CM-14 (-SH) has been established.

The loading curves of these resins have been drawn, as the optimum pH of the aqueous film and the resin capacities shown to increase in the order -SH < -SO₃H.

The effect of the flow-rate on the loading and the optimum elution conditions have been also determined.

A mechanism for the ion-exchange process is proposed.     

A coumarin-based fluorescent probe for selective detection of Cu2+ in water

Fluorescent Red GK, a commercially available coumarin-based dye, was developed as a “turn-off” fluorescent probe for detection of Cu²⁺ in aqueous solution. It exhibited high selectivity and sensitivity at room temperature. Upon addition of Cu²⁺, the strong fluorescence of Fluorescent Red GK was severely quenched and its color changed from orange to colorless under illumination with a UV lamp; the color of the solution also changed from pink to colorless. So, it can be used as a specific colorimetric and fluorescent probe for Cu²⁺ with a detection limit as low as 0.0634?μM.     

Defect models of the three trigonal Ti3+ centers in LiF:Ti3+ and LiF:Ti3+:Mg2+ crystals

The EPR g factors of the trigonal Ti3+ center A in LiF:Ti3+ and two additional trigonal Ti3+ centers B and C in LiF:Ti3+:Mg2+ crystals are calculated from the third-order perturbation formulas based on the cluster approach. From the calculations and by considering the Ti3+ displacement along 111 axis obtained by ENDOR experiment, the defect models for the three Ti3+ centers are suggested. For center A, there are two possible models: (i) [Ti3+F3-O3(2-)] cluster and (ii) [Ti3+F6-] cluster with the Ti3+ off-center caused by a neighboring Li+ vacancy (VLi+) at <111> axis. The latter seems the more likely. The defect models of centers B and C are the [Ti3+F3-O(3)2-] clusters associated with a neighboring: Mg2+ ion at the Li+ site along 111 axis in the vicinity of three F- ions and three O2- ions, respectively. The reasonableness of these models is discussed.