Synthesis,characterization and properties of 3,3′-diethyl-1,1′-oxydiethylenedicarbonyl bis(thiourea)

In this paper, 3,3′-diethyl-1,1′-oxydiethylenedicarbonyl bis(thiourea) (DEOECTU), was synthesized by phase transfer catalysis and then characterized by UV, elemental analysis, infrared spectra, mass spectrum, ¹H NMR and TGA. DEOECTU properties, such as response to metal ions, adsorption on sulfide mineral surfaces, and hydrometallurgical performance as flotation collectors, were also investigated. The results indicated that DEOECTU reacted chemically with Cu²⁺ ions through its S and N atoms in the C(=S)–NH–C(=O) group to form a new chelate compound, but no reaction of DEOECTU with Zn²⁺, Pb²⁺, Fe³⁺ or Fe²⁺ ions was observed. The results of adsorption and flotation experiments demonstrated, that compared to pyrite, sphalerite and galena, DEOECTU exhibited a superior collecting power for chalcopyrite and might attach on chalcopyrite surface by chemisorption. The further theoretical analysis from Pearson’s HSAB view point briefly explained the experimental results of the selective response of DEOECTU to Cu²⁺ ions and chalcopyrite.     

A dual-function chemosensor based on coumarin for fluorescent turn-on recognition of Hg2+ and colorimetric detection of Cu2+ in aqueous media

A novel coumarin derivative CTT was synthesized via the condensation of 7-(N,N-diethylamino) coumarin-3-aldehyde with 5-amino-1,3,4-thiadiazole-2-thiol and its structure was characterized using infrared spectroscopy (IR), ¹H NMR, mass spectrometry (MS) techniques, and elemental analysis. The recognition properties of CTT with metal ions were investigated in CH₃CN–H₂O (v/v = 1/1) solution using UV–vis absorption and fluorescence emission spectrum method. The results showed that CTT could monitor Cu²⁺ and Hg²⁺ simultaneously as a dual-function chemosensor in CH₃CN–H₂O (v/v = 1/1). CTT could be used to detect Cu²⁺ colorimetrically; when using CTT, a color change from yellowish-brown to yellowish-green could be readily observed by the naked eye. CTT showed turn-on fluorescent recognition of Hg²⁺, the fluorescence enhancement was attributed to the inhibited C=N isomerization and the obstructed excited state intramolecular proton transfer (ESIPT) of CTT. The recognition mechanism of CTT for Cu²⁺ and Hg²⁺ was studied by experiments and theoretical calculations, respectively. Therefore, CTT has the ability to be a “single chemosensor for dual targets.”     

Synthesis and spectroscopic properties of new bis-tetrazoles

Syntheses of N,N′-phenyltetrazole podands link with aliphatic chains containing oxygen, nitrogen and sulphur atoms, are described. The complexing properties of these compounds towards metal cations (Fe²⁺, Cu²⁺, Zn²⁺, Co²⁺, Ni²⁺) were investigated by absorption and infrared spectroscopy. The UV–Vis titrations were performed to estimate the stability constant values of the respective complexes with Cu²⁺ ion. Changes in UV–Vis absorption spectra and IR spectra of compound 6 under various concentrations of Cu²⁺ ion in methanol suggest formation of very unstable complex. The structure of ligand 2 has been deduced by X-ray crystallography.     

Ferrocene containing N-tosyl hydrazones as optical and electrochemical sensors for Hg2+, Cu2+ and F− ions

Ferrocene containing N-tosyl hydrazones as selective and sensitive optical and electrochemical chemosensors were synthesized and characterized by ¹H NMR, ¹³C NMR, ESI-MS and X-ray analysis. The cation and anion binding studies were carried out using various techniques including electrochemistry, UV–vis and ¹H NMR spectroscopy. Chemosensors 2a and 2b have shown excellent selective recognition toward Hg²⁺, Cu²⁺ and F^? through optical and electrochemical signals. The color of 2a and 2b in solution changed visibly from pale yellow to red upon addition of Hg²⁺ion, while the color of solution changed from pale yellow to yellow green upon addition of Cu²⁺, which can be easily detected by the naked eye.     

Synthesis and characterization of novel silica gel supported N-pyrazole ligand for selective elimination of Hg(II)

The polar organic molecule N-(2-hydroxyethyl)-3,5-dimethylpyrazole reacted with a 3-glycidoxypropyltrimethoxysilane silylant agent, previously anchored on a silica surface in a heterogeneous way to yield the product SiPz. The epoxide group was opened yielding chelating pendant group bonded to the inorganic surface. The product was characterized through elemental analysis, infrared spectroscopy, ¹³C NMR, surface area and thermogravimetry. The binding and adsorption abilities of SiPz was investigated for Hg²⁺, Cd²⁺, Pb²⁺, Cu²⁺, Zn²⁺, K⁺, Na⁺ and Li⁺ cations and compared to results of classical liquid-liquid extraction with the unbound N-pyrazole compound. The grafting at the surface of silica does not affect complexing properties of the ligand and the SiPz exhibits a high selectivity toward Hg²⁺ ion with no complexation being observed towards Zinc and alkali metals. The extracted and the complexing cation percentage were determined by atomic absorption measurements.     

A Comparative Study of Stabilities and Coordination Modes of β-Alaninephosphonic Acid in Copper(II) Heteroligand Complexes with Ethylenediamine, Diethylenetriamine or N,N,N′,N′,N″-Pentamethyldiethylene Triamine in Aqueous Solution

Solution equilibrium studies on Cu²⁺?CL₁?CL₂ ternary systems have been performed by pH-potentiometry, UV?CVis spectrophotometry and EPR methods {where L₁ corresponds to a polyamine such as ethylenediamine (en), diethylenetriamine (dien), N,N,N??,N??,N??-pentamethyldiethylenetriamine (Me₅dien)} and L₂ denotes 2-aminoethylphosphonic acid (??-alaninephosphonic acid)}. The results suggest the formation of heteroligand complexes with [Cu(L₁)(??-Ala(P))] stoichiometry in all of the studied systems. Additionally, in the system with en, [Cu(en)(??-Ala(P))H_?1]^? is formed in basic solutions. Our spectroscopic results indicate tetragonal geometry for the [Cu(en)(??-Ala(P))] species, a geometry slightly deviated from square pyramidal for the [Cu(dien)(??-Ala(P))] complex, and somewhat stronger geometry distortion was present for the [Cu(Me₅dien)(??-Ala(P))] complex. The coordination modes in these heteroligand complexes are discussed.     

Anion-selective receptors based on dinuclear copper(II) and nickel(II) cage complexes of bis-salicylaldimines

The selectivity, anion uptake and exchangeability of anion-binding by metal salt extractants of the form [M₂ L ₂]⁴⁺ have been assessed by the method of anion exchange chromatography in biphasic systems. The order of sulfate-, nitrate-, and chloride-uptake into the solid copper(II) complex as of the dioxime pro-ligand N,N??-dimethyl-N,N??-hexamethylenedi(3-hydroxyiminomethyl-2-hydroxy-5-tert-butylbenzylamine (L ¹ ) is 56, 42, and 16%, respectively, consistent with the relative magnitudes of formation constants for the inclusion complexes, [A?Cu₂ L ¹ ₂] ⁿ⁺ where A = anion, found in UV?Cvis titration studies in a single phase. X-ray structural determination of the bis-benzylimine pro-ligand, N,N??-dimethyl-N,N??-hexamethylenedi-(3-benzyliminomehyl-2-hydroxy-5-tert-butylbenzylamine), nickel(II) sulfato complex [SO₄?Ni₂ L ² ₂]SO₄ reveals the nickel atoms to have a significant tetrahedral distortion, providing more favourable sulfate-alkylammonium interactions within the cage.     

p-tert-butylcalix[4]arenes containing azacrown ether substituents at the lower rim as potential polytopic receptors

A series of disubstituted p-tert-butylcalix[4]arenes with N-methoxycarbonylmonoazacrown ether and N-ethoxymonoazacrown ether residues at the lower rim has been prepared via the reaction of di(carboxymethoxy)-p-tert-butylcalix[4]arene with azacrown ethers and subsequent reduction of the resulting amide derivatives. Using UV titration and ¹H NMR spectroscopy we have demonstrated the ability of the calixarene with two N-carbonylmonoaza-18-crown-6-ether substituents to form the 1:3 complexes with K⁺ and Na⁺ and the 1:2 complexes with Cs⁺, Sr²⁺, Cu²⁺, and Zn²⁺. The calixarene with two fragments of N-ethoxymonoazo-18-crown ether has formed binuclear complexes with alkali metals cations and mononuclear complexes with transition metals cations.     

A direct fluorescence-on chemo-sensor for selective recognition of Zn(II) by a lower rim 1,3-di-derivative of calix[4]arene possessing bis-{N-(2-hydroxynaphthyl-1-methylimine)} pendants

The bis-{N-(2-hydroxynaphthyl-1-methylimine)} anchored 1,3-di-derivative of lower rim p-tert-butyl-calix[4]arene possessing a N₂O₂, N₂O₄ or N₂O₆ binding core was found to be selective for Zn(II) ions even at ?60 ppb by eliciting fluorescence-on behaviour while the other ions, viz., Ti⁴⁺, VO²⁺, Cr³⁺, Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Mg²⁺, Cd²⁺ and Hg²⁺ caused no change in the fluorescence. The reaction between 1 and Zn²⁺ was found to be stoichiometric with the formation of a 1:1 complex; while H⁺ quenched the fluorescence of the complex, OH⁻ restored it. The studies of the 1:1 isolated complexes of Zn²⁺, Ni²⁺ and Cu²⁺ augmented the results.     

The effect of ligand donor atoms on ternary complex stability

Formation constants of mixed ligand complexes of Cu²⁺, Zn²⁺, Ni²⁺, Co²⁺, and Mn²⁺,with cyadine-5′-monophosphoric acid (CMP) and various primary ligands such as 1,10-phenanthroline(phen), glycylglycine(glygly) and salicylic acid (sal) have been determined in aqueous solution at 35°C and 0.1 M (KNO₃) by potentiomeric measurements. The acid dissociation constants of all the above mentioned ligands together with their 1 : 1 binary metal complex formation constants were also measured at 35°C. In general all the 1 : 1 binary complexes follow the Irving-Williams order of stability. Further the binary metal complexes of primary ligands are more stable than their ternary complexes with CMP. For ternary complexes, Δ(log K) values seem to change from positive to highly negative as the coordinating atoms of the primary ligands were varied from N,N to N,O^? to O^?O^?. The higher stability of ternary complexes involving phen is due to its Π-bonding interaction with the above metal ions and the relative decrease in the stability of other ternary systems is due to the coulombic repulsion of donor oxygen atoms of primary and secondary ligands. Thus for ternary complexes the stabilities follow a decreasing order of M-phen-CMP > M-glygly-CMP > M-sal-CMP.     

Coordination complexes of rare earth metals with hydrazine and isomeric acetamidobenzoates as ligands– spectral,thermal and kinetic studies

The isomeric acetamido benzoic acids (abbreviated as acambH) on reaction with hydrazine hydrate and lanthanides, La³⁺, Ce³⁺, Pr³⁺, Nd³⁺, Sm³⁺ and Gd³⁺ form complexes of formulae, [Ln{x-C₆H₄(CH₃CONH)}₃(N₂H₄)] where x = 2 (or) 3 (or) 4, at pH 3–4.5 in (1:1) aqueous ethanolic medium, which are insoluble in water and organic solvents. They are characterized by using elemental analysis, IR, UV, ¹³C, ¹H NMR and mass spectroscopic, XRD, SEM-EDAX, thermal and conductance studies. The difference between IR bands of v_{C=O asym} (acid) and v_{C=O sym}(acid) range, 122–166 cm^?1 supports the bidental coordination of carboxylate ions to metal. v_N-N values of 955 to 980 cm^?1, substantiate bridging bidentate coordination of hydrazine to metal. v_C=O of amide group 1632 to1709 cm^?1 indicates its non-coordination with metal. The thermal studies reveal that complexes undergo dehydrazination between 52 and 180 °C and exothermic degradation into phthalate intermediate between 172 and 496 °C and further degradation to form microsized metal oxide around 600 °C. The magnetic susceptibility measurements indicated that the presence of metals in the same electronic state and electronic spectral assignments suggested that the coordination number is eight for the complexes. The conductance measurement results in DMSO medium indicated that the complexes are neutral. The ¹³C – NMR, ¹H- NMR and the LC-Mass techniques substantiated the composition of the complexes.     

Spectroscopy and stereochemistry of the optically active copper(II), cobalt(II) and nickel(II) complexes with Schiff bases N,N′-(1R,2R)-(−)-1,2-cyclohexylenebis(3-methylbenzylideneiminato) and N,N′-(1R,2R)-(−)-1,2-cyclohexylenebis(5-methylbenzylideneiminato)

Schiff bases obtained from N,N′-(1R,2R)-1,2-cyclohexanediamine and 2-hydroxy-3-methylbenzaldehyde, 2-hydroxy-5-methylbenzaldehyde, have been used as ligands for copper(II), cobalt(II) and nickel(II). The complexes were characterized with UV–Vis, circular dichroism (CD), infrared, diamagnetic and paramagnetic ¹H NMR spectroscopy. CD spectra revealed exciton coupled π→π* transitions. Assignments of LMCT and d–d transitions in CD spectra of Ni(II), Co(II) and Cu(II) complexes is proposed. CD data are characteristic for central ion tetrahedral distortion from the planarity and λ conformation of the cyclohexane ring. ¹H NMR of Ni(II) complexes exhibited significant coordination shifts of CHN and ring protons which are in the closest proximity to Ni(II). The ¹H NMR paramagnetic spectra of Co(II) complexes revealed the most upfield shifted resonance at −60 ppm assigned to CHN and −28 ppm to hydrogen atom at C(5′) of the phenyl ring. Results of spectral analyses suggest central ions in a distorted square-planar geometry with N₂O₂ chromofore group.     

First generation poly(propyleneimine) dendrimers functionalised with 1,8-naphthalimide units as fluorescence sensors for metal cations and protons

The synthesis of two new green fluorescent poly(propyleneimine) dendrimers from first generation has been described. The new materials are comprised of a 1,8-naphthalimide fluorophore having a substituent at C-4 position. The substituent in the first case is a N,N-dimethylaminoethylamino group while in the second one it is N-methylpiperazine. The spectroscopic and photophysical characteristics of the new dendrimers determined in organic solvent of different polarity have been presented. Both dendrimers show substantial increases in their fluorescence intensity in the presence of metal cations (Zn²⁺, Co²⁺, Ni²⁺, Pb²⁺, Mn²⁺, Cu²⁺, Fe³⁺ and Ag⁺) and protons. The influence of the photoinduced electron transfer on their sensing properties has been discussed.     

Synthesis,characterization and applications of schiff base chemosensor for determination of Cu2+ ions

A novel thiazole-based Schiffbase chemosensor SB1 with N- and O- donor atoms was synthesized and characterized by different techniques (UV–vis, ¹³C NMR, ¹H NMR, and FT-IR analysis). The chemosensor SB1 was used for the determination of Cu²⁺ ions in various samples. The significant spectral changes in absorption spectra of chemosensor SB1 at 220 and 416 nm and the color change from light yellow to yellowish-brown indicate high selectivity and sensitivity towards Cu²⁺ ions as compared to other cations (Na⁺, K⁺, Ag⁺, Zn²⁺, Ni²⁺, Pb²⁺, Mn²⁺, Mg²⁺, Co²⁺, Cd²⁺, Sn²⁺, Hg²⁺, Cr³⁺, Fe^3+, and Al³⁺). The sensing mechanism of SB1 was investigated through various techniques such as FT-IR, UV–vis and ¹H NMR titration experiment and further confirmed by DFT computational studies. The 2:1 binding mode between SB1 and Cu²⁺ ions was confirmed by Job‘s plot using UV–vis spectrophotometry. The limit of detection (LOD) and limit of quantification (LOQ) were found to be 0.015 and 0.0471 µg mL^?1, respectively. The percent recovery of Cu²⁺ from various environmental samples was found to be 95.00–103.33% at various levels. These obtained results demonstrate that chemosensor SB1 is a cost-effective, facile, selective, sensitive, and colorimetric sensing platform to detect trace amounts of Cu²⁺ ions in variousenvironmental and agricultural samples.     

Coumarin salen-based zinc complex for solvent-free ring opening polymerization of ε-caprolactone

A new zinc complex based on a tetradentate N,N,O,O-type coumarin salen ligand (H₂L) was prepared and characterized by elemental analysis, thermogravimetric analysis (TGA), and FT-IR, UV–vis and ¹H NMR spectroscopy. The complex [Zn(L)(H₂O)]·H₂O was active in the ring opening polymerization (ROP) of ε-caprolactone under solvent-free conditions, producing polycaprolactone (PCL) with a molecular weight up to 17,700 g mol^?1 and a narrow molecular weight distribution. ¹H NMR analysis showed that the PCL obtained was mainly linear, having hydroxymethylene groups in the chain ends. Differential scanning calorimetry (DSC) showed that the polymer had high crystallinity (61%) and that TGA had a decomposition temperature above 300 °C.     

2，2′-(1，2-亚乙基双氮次甲基)二喹啉及其Cu2+、 Zn2+、Ni2+、 Mn2+配合物的合成与表征

本文报道2,2′-(1,2-亚乙基双氮次甲基)二喹啉及其与Cu²⁺、 Zn²⁺、 Ni²⁺、 Mn²⁺配合物的合成,并通过元素分析、红外光谱、紫外光谱、X-射线粉末衍射、热分析及核磁共振等手段对配体和配合物进行了表征。配合物的化学组成为M.L.(ClO₄)₂·H₂O(M=Cu²⁺、 Zn²⁺、 Ni²⁺、 Mn²⁺离子;L=C₂₂H₁₈N₄)。     

Design and synthesis of two armed molecular receptor for recognition of Gd3+ metal ion and its computational study

New receptor P henylene‐ B is‐ M ethylfuran‐yl‐2‐ M ethyele A cetohydrazide ( PBMMA ) has been synthesized by condensation of hydrazide and 5‐methyl furfural. Synthesized receptor has been fully characterized by IR, ¹H NMR, ¹³C NMR, mass spectroscopic and thermo gravimetric analysis. The receptor PBMMA shows selective recognition potential towards Gd³⁺ ion when tested with several metal ions such as Na⁺, K⁺, Mg²⁺, Cu²⁺, Cd²⁺, Hg²⁺, Y³⁺, La³⁺, Eu³⁺, Sm³⁺, Gd³⁺, Re⁶⁺ and Th⁴⁺ ion as their sulfates by UV–visible and fluorescence spectroscopic studies. Binding nature of PBMMA with Gd³⁺ ion was further studied by mass spectroscopic and cyclic voltammetric studies. The stoichiometry of PBMMA‐ Gd³⁺ ion has been established, 1:1 by Benesi‐Hildebrand plot method and method of continuous variation (Job's plot) with association affinity K = 6.491 × 10⁴ M^?1. In addition to these, molecular docking, molecular dynamic stimulation and binding energy of complex; through Density Function theory ?595.66 kcal/mol has also indication of strong binding. The electron transfer energy of Higher occupied molecular orbital (HOMO) to Lower unoccupied molecular orbital (LUMO) is about 4.186 eV and 295 nm for PBMMA‐Gd³⁺ Complex.     

New Mononuclear and Binuclear Cu(II), Co(II), Ni(II), and Zn(II) Thiosemicarbazone Complexes with Potential Biological Activity: Antimicrobial and Molecular Docking Study

Herein, we report the synthesis of eight new mononuclear and binuclear Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺ methoxy thiosemicarbazone (MTSC) complexes aiming at obtaining thiosemicarbazone complex with potent biological activity. The structure of the MTSC ligand and its metal complexes was fully characterized by elemental analysis, spectroscopic techniques (NMR, FTIR, UV-Vis), molar conductivity, thermogravimetric analysis (TG), and thermal differential analysis (DrTGA). The spectral and analytical data revealed that the obtained thiosemicarbazone-metal complexes have octahedral geometry around the metal center, except for the Zn²⁺-thiosemicarbazone complexes, which showed a tetrahedral geometry. The antibacterial and antifungal activities of the MTSC ligand and its (Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺) metal complexes were also investigated. Interestingly, the antibacterial activity of MTSC- metal complexes against examined bacteria was higher than that of the MTSC alone, which indicates that metal complexation improved the antibacterial activity of the parent ligand. Among different metal complexes, the MTSC- mono- and binuclear Cu²⁺ complexes showed significant antibacterial activity against Bacillus subtilis and Proteus vulgaris, better than that of the standard gentamycin drug. The in silico molecular docking study has revealed that the MTSC ligand could be a potential inhibitor for the oxidoreductase protein.     

Host-guest chemistry of copper(II)-histidine complexes encaged in zeolite Y

Structural analysis has been carried out on copper(II )–histidine (Cu²⁺/His) complexes after immobilization in the pore system of the zeolites NaY and de‐aluminated NaY (DAY). The aim of this study was to determine the geometrical structure of Cu²⁺/His complexes after encaging, to obtain insight into both the effect of the zeolite matrix on the molecular structure and redox properties of the immobilized complexes. In addition to N₂ physisorption and X‐ray fluorescence (XRF) analyses, a combination of UV/Vis/NIR, ESR, X‐ray absorption (EXAFS and XANES), IR, and Raman spectroscopy was used to obtain complementary information on both the first coordination shell of the copper ion and the orientation of the coordinating His ligands. It was demonstrated that two complexes ( A and B ) are formed, of which the absolute and relative abundance depends on the Cu²⁺/His concentration in the ion‐exchange solution and on the Si/Al ratio of the zeolite material. In complex A , one His ligand coordinates in a tridentate facial‐like manner through N_am, N_im, and O_c, a fourth position being occupied by an oxygen atom from a zeolite Brønsted site. In complex B , two His ligands coordinate as bidentate ligands; one histamine‐like (N_am, N_im) and the other one glycine‐like (N_am, O_c). In particular the geometrical structure of complex A differs from the preferred structure of Cu²⁺/His complexes in aqueous solutions; this fact implies that the zeolite host material actively participates in the coordination and orientation of the guest molecules. The tendency for complex A to undergo reduction in inert atmosphere to Cu¹⁺ (as revealed by dynamic XANES studies) suggests activation of complex A by the interaction with the zeolite material. EXAFS analysis confirms the formation of a distorted four coordinate geometry of complex A , suggesting that the combination of zeolite and one His ligand force the Cu²⁺ complex into an activated, entactic state.     

Selective Alcohol Oxidation by a Copper TEMPO Catalyst: Mechanistic Insights by Simultaneously Coupled Operando EPR/UV‐Vis/ATR‐IR Spectroscopy

The first coupled operando EPR/UV‐Vis/ATR‐IR spectroscopy setup for mechanistic studies of gas‐liquid phase reactions is presented and exemplarily applied to the well‐known copper/TEMPO‐catalyzed (TEMPO=(2,2,6,6‐tetramethylpiperidin‐1‐yl)oxyl) oxidation of benzyl alcohol. In contrast to previous proposals, no direct redox reaction between TEMPO and Cu^I/Cu^II has been detected. Instead, the role of TEMPO is postulated to be the stabilization of a (bpy)(NMI)Cu^II‐O₂^??‐TEMPO (bpy=2,2′‐bipyridine, NMI=N‐methylimidazole) intermediate formed by electron transfer from Cu^I to molecular O₂.