The use of ultrasonic treatment for improvement of metrological performance of sorption atomic absorption determination of lead(II) and cadmium(II) traces

The optimal parameters for ultrasonic treatment (frequency 200–300 kHz, intensity 2–4 W cm^?2) were obtained to intensify Pb(II) and Cd(II) sorption concentration by carbon sorbent from apricot pit. The combined action of ultrasonic frequency of 18 kHz and 1 MHz on concentrate slurry increases its sedimentation stability from 3 to 180 minutes and decreases S_r value up to 7% at Pb(II), Cd(II) hybrid sorption atomic absorption determination in natural waters, brines, common salt.      

Experimental and computational investigations of a cadmium(II) mononuclear complex with 2,6-Bis(3,5-dimethyl-N-pyrazolyl)pyridine (bdmpp) and selenocyanate as ligands

A new cadmium (II) complex, [Cd(bdmpp)(SeCN)₂(H₂O)] (1) (where bdmpp = 2,6-bis(3,5-dimethyl-N-pyrazolyl)pyridine), has been synthesized and characterized by elemental and spectral (IR, ¹H-NMR and ¹³C-NMR, UV-Vis) analyses, differential scanning calorimetry, and single crystal X-ray diffraction studies. X-ray analysis showed that the structure was crystallized in the monoclinic space group Cc with a = 9.031(2), b = 13.884(3), c = 16.910(3) Å, and Z = 4. The geometry around the cadmium atom is distorted octahedral with a CdN₃Se₂O setup. The N atoms of the SeCN are engaged in two strong intermolecular H-bonding interactions forming a 3D supramolecular polymeric network. The geometry and vibrational frequencies of complex 1 computed with the DFT methods (BLYP, B3LYP, B3PW91, MPW1PW91) are in better agreement with experiment than those obtained with the ab-initio method except for the bond angles. The molecular orbital diagram has been also calculated and visualized at the B3LYP/LanL2DZ level of theory.      

New 5-bromo-2-hydroxybenzaldehyde S-ethylisothiosemicarbazone and its mixed-ligand Cu(II) complex with imidazole: synthesis, characterization and DFT calculation

A new Schiff base ligand of 5-bromo-2-hydroxybenzaldehyde S-ethyl-isothiosemicarbazone (H₂L) was synthesized and its mixed-ligand Cu(II) complex was also prepared by reaction of Cu(NO₃)₂·3H₂O with H₂L and imidazole. Their structures were fully characterized by elemental analysis, FT-IR, molar conductivity and UV-Vis methods. The analytical data suggest that the metal, H₂L and imidazole ratios in the Schiff base complex are 1:1:1. Single crystal diffraction was also used to better understand the molecular structure of the Cu(II) complex. The results of physico-chemical analyses of the Schiff base complex reveal the coordination geometry around the central atom is square planar. The H₂L ligand (NNO donor) is coordinated to the metal center as a tridentate bionegatively agent. Another position of the square planar geometry is occupied by the imidazole ligand. Furthermore, computational studies of the new complex were performed by carrying out DFT calculations. Geometry optimization and natural band analysis of the complex is discussed in further detail.      

Cytostatic and cytotoxic properties of monensic acid and its biometal(II) complexes against human tumor / non-tumor cell lines

The anticancer activity of monensic acid (MonH) and its biometal(II) complexes [M(Mon)₂(H₂O)₂](M = Mg, Ca, Mn, Co, Ni, Zn) was evaluated against cultured human permanent cell lines established from glioblastoma multiforme (8MGBA) and cancers of the lung (A549), breast (MCF-7), uterine cervix (HeLa) and liver (HepG2). The viability and proliferation of the non-tumor human embryonic cell line Lep3 was also tested. The investigations were carried out using a thiazolyl blue tetrazolium bromide test, neutral red uptake cytotoxicity assay, crystal violet staining, colony forming method and double staining with acridin orange and propidium iodide. The results obtained reveal that the compounds applied at concentrations of 0.5–25 μg mL⁻¹ for 24–72 h decrease the viability and proliferation of the treated cells in a time- and concentration-dependent manner. The metal(II) complexes studied (especially those of Co(II), Ni(II) and Zn(II)) have been found to express stronger cytotoxic and cytostatic activities than the non-coordinated monensic acid. The non-tumor human cell line showed strong chemosensitivity towards compounds tested comparable to that of cultured human tumor cell lines.      

The synthesis, structure and physical properties of lanthanide(III) complexes with nicotinic acid

This article reports the synthesis of novel, rare-earth coordination complexes with nicotinic acid. Three compounds with the general formula Ln₂[(C₅H₄NCOO)₆(H₂O)₄] (Ln = Yb, 1; Ln = Gd, 2; Ln = Nd, 3) were prepared from relatively cheap and readily available reactants. Their compositions and structure were characterized by IR spectroscopy and single-crystal X-ray diffraction. The magnetic and thermogravimetric properties were also studied. The complexes consist of centrosymetric, dimeric molecules having all six nicotinato ligands coordinated with the central atom in the bidentate mode. The coordination environment of the Ln³⁺ for all three compounds is 8. Here we describe the crystal structure of Yb and Gd complexes with nicotinic acid.      

Phenylcopper(I) clusters in the gas phase obtained by laser desorption/ionization from bis(dibenzoylmethane)copper(II)

It has been demonstrated that phenylcopper(I)-containing clusters are generated in the gas phase from bis(dibenzoylmethane) copper(II) (Cu(dbm)₂) by laser desorption/ ionization (LDI) method. For example, the [Cu₅dbm₂(C₆H₅)₂]⁺ ion can be considered as consisting of two Cudbm molecules, two CuC₆H₅ molecules and a Cu⁺ cation. The [Cu₅(C₆H₅)₄]⁺ ion can be considered as phenylcopper(I) cluster (consisting of four phenylcopper molecules) ionized by additional Cu⁺ cation. Results from MS/MS (tandem mass spectrometry) experiments have confirmed the presence of phenylcopper molecules in the analyzed clusters. Ease of preparation of dibenzoylmethane-metal complexes and straightforward method to obtain LDI mass spectra offer a wide range of possibilities to study similar organometallic clusters in the gas phase.      

A novel triply bridged dinuclear four-coordinate copper(I) complex with sterically bulky bis(dicyclohexylphosphino)methane ligand

A novel triply bridged dinuclear copper(I) complex: Cu₂(μ-paa)(μ-dcpm)₂(BF₄)₂·2CH₂Cl₂ [ paa = pyridine-2-carbaldehyde azine (C₁₂H₁₀N₄) and dcpm = bis(dicyclohexylphosphino)methane(C₂₅H₄₆P₂) ] has been synthesized and structurally characterized. Crystallographic studies of the complex showed that two copper(I) ions were bridged by one paa ligand and two dcpm ligands. The paa ligand adopted the Z configuration at the partially double N-N bond and the two copper ions have distorted tetrahedral coordination geometry. Because of the steric effect of dcpm, the pyridine rings of the paa ligand are obviously not on the same plane (the dihedral angle is 43.61⁰). The interaction between neighboring ligands results in a N-N bond length (1.374(7) Å) contraction. The UV-vis spectra of the complex exhibited intense high-energy absorptions at λ_max < 340 nm and broad visible bands in a range of 380?550 nm, ascribed to intraligand (IL π-π*) transitions and metal-to-ligand charge-transfer (MLCT) transitions, respectively. Interestingly, the absorbtion peaks varied regularly with the solvent polarity. Although the complex has a rigid structure with the copper ions held firmly by triply bridged ligands, the emission and excitation spectra revealed that the complex exhibits weak fluorescence.

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Spectral properties and photophysical behaviour of water soluble cationic Mg(II) and Al(III) phthalocyanines

Peripherally and non-peripherally tetrasubstituted-[(N-methyl-2-pyridylthio)]phthalocyaninato magnesium (II) (5 and 6) and chloro aluminium (III) (7 and 8) tetraiodide have been synthesized and characterized. The photophysical properties of the complexes in dimethyl sulfoxide (DMSO) and aqueous medium in the presence and absence of cremophore EL have been studied. These complexes show high solubility in aqueous medium though they were aggregated. The triplet state quantum yields (F_T) and the triplet lifetimes (t_T) were found to be higher in DMSO with Φ_T ranging from 0.32 to 0.51, while t_T ranged from 282 to 622 ms in DMSO, compared to aqueous medium (pH 7.4 buffer) where Φ_T ranged from 0.15 to 0.19 and t_T from 26 to 35 ms. Addition of cremophore EL in aqueous solution resulted in partial disaggregation and increased photoactivity. The fluorescence lifetimes of the complexes showed strong dependence on their immediate environment. The ionic magnesium(II) and aluminium(III) phthalocyanines strongly bind to bovine serum albumin (BSA).      

Synthesis, characterization and antitumor activity of Cu(II), Co(II), Zn(II) and Mn(II) complex compounds with aminothiazole acetate derivative

This paper presents the synthesis of complex compounds of type [M(L1)₂], where M(II)= Cu (1), Co (2), Zn (3), L1=2-aminothiazole-4-acetate and [Mn(L1)₂(H₂O)] (4) using ethyl 2-(2-aminothiazole-4-yl) acetate (L), and characterization by elemental analysis, magnetic susceptibilities, IR, 1H-NMR, UV-Vis spectroscopy and for [Mn(L1)₂(H₂O)] also by X-ray diffraction. In vitro cytotoxicity studies were performed on human cervix adenocarcinoma, HeLa cells. The antitumor selectivity was assessed using normal human peripheral blood mononuclear cells, PBMC as control.      

The crystal structure of Ho<Subscript>4</Subscript>Ni<Subscript>11</Subscript>In<Subscript>20</Subscript>

The polycrystalline Ho₄Ni₁₁In₂₀ was obtained by arc-melting of the elements. The subsequent high temperature procedure was used for single crystal growth. Crystal structure of the compound was investigated by X-ray single crystal method: U₄Ni₁₁Ga₂₀ type, C 2/m, a = 22.4528(17), b = 4.2947(3), c = 16.5587(13) Å, β = 124.591(5)°, R1 = 0.0276, wR2 = 0.0493 for 1989 independent reflections with [I>2σ(I)].The structure is composed of three-dimensional network from Ni and In atoms in which Ho atoms fill distorted pentagonal channels. Open image in new window     

Spectroscopic study of associated systems formed between water-soluble cationic porphyrins or their copper (II) complexes and nucleic building blocks

The association process between two water soluble cationic porphyrins, 5,10,15,20-tetrakis[4-(trimethyl-ammonio)phenyl]-21H,23H-porphine tetra-p-tosylate (H₂TTMePP) and 5,10,15,20-tetrakis(1-methyl-4-pyridyl)-21H,23H-porphine tetra-p-tosylate (H₂TMePyP), as well as their Cu (II) complexes, with five series of nucleic agents has been studied using UV-VIS spectroscopy in aqueous solutions. During the titration with nucleic compounds the bathochromic effect of porphyrins absorption spectra can be observed as well as the hypochromicity of the Soret maximum. The association constants were calculated using a curve-fitting procedure (K_AC of the order of magnitude of 10³–10⁵ mol^?1). It has been shown that the interactions of H₂TTMePP with nucleic agents are much stronger than interactions of H₂TMePyP, which is most likely related to the kind and the size of the porphyrin substituent groups partaking in the process of stacking. The strength of the observed associated systems increases generally in a series: nucleic base < nucleoside < nucleotide.      

Complexation of nickel (II) ion with B3 vitamin in aqueous dimethyl sulfoxide

The stability change of nickel(II) ion complexes including one and two nicotinamide (B₃ vitamin) molecules in aqueous dimethyl sulfoxide (X_DMSO = 0–0.85 m.f.) was studied at 298.2±0.1 K and 0.25 ionic strength value (NaClO₄) using the potentiometric method. The first stage constant of complexation increased until organic solvent concentration was 0.5 m.f. and reduced at higher DMSO content. The difference between complex and central ions solvation is a dominating contribution into the Gibbs energy change of mononicotinamide complex formation reaction. When the second ligand molecule was bonded into the coordination compound, the nicotinamide contribution to Δ_trG_r rose and became prevailing at X_DMSO = 0.7–0.85. The ligand was found to replace a water molecule in the coordination sphere of the cation according to spectrophotometric study results.      

Solvent extraction with organophosphorus extractants in environmental samples: determination of cadmium(II) in natural water

In this work, Cd(II) extraction in natural waters by organophosphorus extractants as organic phase, as well as its back-extraction in an acidic media, has been studied. Cadmium extraction behavior at natural waters’ pH conditions (values in the range 7–8) was studied with two different extractants and co-ions, obtaining the highest extraction efficiency when using 0.1M Cyanex 272 in kerosene as organic phase and 0.1 M NO₃ ^? as co-ion. Once they were selected, the effect on the extraction efficiency of sample pH, buffer concentration, extraction time, Cyanex 272 concentration as well as back-extractant concentration, was studied. The presence of the main inorganic and organic ligands in the sample was also studied, observing that extraction efficiency was affected most significantly when chlorides were present, with a decrease of about 14%, proving negligible for the others. Under the selected conditions, spiked real samples were successfully analyzed.      

Fullerene-based anodic stripping voltammetry for simultaneous determination of Hg(II), Cu(II), Pb(II) and Cd(II) in foodstuff

Various carbon nanomaterials for use in anodic stripping voltammetric analysis of Hg(II), Cu(II), Pb(II) and Cd(II) are screened. Graphene, carbon nanotubes, carbon nanofibers and fullerene (C₆₀), dispersed in chitosan (Chit) aqueous solution, are used to modify a glassy carbon electrode (GCE). The fullerene-chitosan modified GCE (C₆₀-Chit/GCE) displays superior performance in terms of simultaneous determination of the above ions. The electrodes and materials are characterized by electrochemical impedance spectroscopy, cyclic voltammetry, scanning electron microscopy, Raman spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The excellent performance of C₆₀-Chit/GCE is attributed to the good electrical conductivity, large surface area, strong adsorption affinity and unique crystalline structure of C₆₀. Using differential pulse anodic stripping voltammetry, the assay has the following features for Hg(II), Cu(II), Pb(II) and Cd(II), respectively: (a) Peak voltages of +0.14, ?0.11, ?0.58 and???0.82 V (vs SCE); (b) linear ranges extending from 0.01–6.0 μM, 0.05–6.0 μM, 0.005–6.0 μM and 0.5–9.0 μM; and (c), detection limits (3σ method) of 3 nM (0.6 ppb), 14 nM (0.9 ppb), 1 nM (0.2 ppb) and 21 nM (2.4 ppb). Moreover, the modified GCE is well reproducible and suitable for long-term usage. The method was successfully applied to the simultaneous determination of these ions in spiked foodstuff.

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Graphical abstract Compared with graphene, carbon nanotubes and carbon nanofibers, an electrode modified with fullerene in chitosan electrode displays superior performance for the simultaneous anodic stripping voltammetric detection of Hg(II), Cu(II), Pb(II) and Cd(II).

     

Synthesis,spectroscopic characterization,crystal structure and antifungal activity of thiourea derivatives containing a thiazole moiety

Four novel thiourea derivatives containing a thiazole moiety were synthesized and characterized by IR, ¹H and ¹³C NMR, mass spectrometry and elemental analysis. The crystal structure of 1a was determined from single crystal X-ray diffraction data. It crystallizes in monoclinic space group P2₁/n with unit cell dimensions a = 11.7752(6) Å, b= 3.8677(2) Å, c= 27.4126(13) Å and β = 92.734(5) Å. There is a strong intramolecular hydrogen bond of the type N-H?O, with H?O distance of 2.5869(19) Å. The mass fragmentation pattern has also been discussed. The antifungal activity of the synthesized compounds was studied by broth micro-dilution method and poisoned food technique. The compounds 1b and 1c possessed a broad spectrum of antifungal activity.

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Organoruthenium(II) thiosemicarbazone complexes: synthesis, spectral characterization, DNA binding and DNA cleavage studies

A series of new ruthenium(II) complexes were synthesized with Schiff bases derived from salicylaldehyde / o-hydroxyacetophenone/ o-vanillin / 2-hydroxy-1-naphthaldehyde with thiosemicarbazide and acetyl furan. They are characterized by elemental analysis, IR, electronic, ¹H NMR, ¹³C NMR and mass spectral studies. The elemental analysis suggests the stoichiometry to be 1:1 (metal:ligand). Four of these complexes were tested for its binding with CT-DNA using absorption spectroscopic studies and two of these complexes exhibit efficient DNA cleavage activity.      

Lead and cadmium atomic absorption determination in solid carbonized food samples using flame-furnace atomizer

Direct atomic absorption solid sampling analysis using flame-furnace atomizer enables a significant decrease in the analysis duration, to avoid sample pollution and to exclude toxic reagents. The selection of the chemical modifiers decreasing the detection limit and improving the results repeatability is based on the analyte’s free atoms formation mechanism. The developed kinetic approach has allowed to determine pre-exponential factors k₀ and apparent activation energies E_a of atomization processes for Pb(II) and Cd(II) compounds and to propose effective chemical modifiers sodium N,N-diethyldithiocarbamate and urea for food samples. The express and precision technique for lead and cadmium determination in food, using proposed chemical modifiers and carbonization techniques was developed.      

Synthesis and spectroscopic characterization of Zn(II), Cd(II), and Hg(II) ciprofloxacin complexes

Ciprofloxacin metal co mplexes with general for mula [M(CPF)₂]X₂·nH₂O [M = Zn(II), Cd(II), and Hg(II)] have been synthesised and characterized using elemental analysis (CHN), spectroscopic (UV-Vis, IR, MS, and ¹H NMR) and ther mogravimetric (TG and DTA) data. Using the Coats-Redfern and Horowitz-Metzeger methods, kinetic analysis of the thermogravimetric data had been performed.     

Studies on complex formation between curcumin and Hg(II) ion by spectrophotometric method: A new approach to overcome peak overlap

Complex formation between curcumin and Hg(II) ion MeOH/H₂O (1: 1 v/v) was investigated and monitored by the spectrophotometric method. The absorption peak of unreacted curcumin which was close and overlapped with that of the complex, was removed by calculation using Microsoft Excel, thereby, allowing determination of the stoichiometry of the complex by the mole-ratio and the Job’s continuous variation methods. Both methods indicated that a 1:1 complex of curcumin and Hg(II) was formed in solution. The formation constant of the 1:1 Hg(II) complex was obtained from two methods, the equilibrium concentration calculation and the linear plot of Benesi-Hildebrand equation, as log K = 4.44 ± 0.16 and 4.83 ± 0.02, respectively. The structure is proposed as a tetrahedral complex of Hg(II) with one curcumin and two chloride ions as ligands. Electronic Supplementary Material  Supplementary material is available for this article at and is accessible for authorized users.     

Molecular structures of metalmacrocyclic chelates of 3d-elements formed at template synthesis in the ion M(II)- thiooxamide-guanidine-formaldehyde quaternary systems

Using density functional theory (DFT) at the OPBE/TZP level, the calculation of the geometric parameters of the molecular structures of M(II) (5456)macrotetracyclic complexes with a tetradentate macrocyclic ligand with (NNNN)-coordination of donor centers, resulting from template reactions in M(II)- thiooxamide- guanidine-formaldehyde quaternary systems, where M= Mn, Fe, Co, Ni, Cu, Zn was performed. The calculation of the molecular structure of this “template” ligand itself was also carried out. The values of the bond lengths, bond and torsion angles in the resulting complexes are presented. The values of the standard enthalpy, entropy and Gibbs free energy of formation of these compounds were also calculated.