Hg Complexes Research Articles

Retention and transformation of exogenous Hg in acidic paddy soil under alternating anoxic and oxic conditions: Kinetic and mechanistic insights

To estimate the risks and developing remediation strategies for the mercury (Hg)-contaminated soils, it is crucial to understand the mechanisms of Hg transformation and migration in the redox-changing paddy fields. In present study, a Hg-spiked acidic paddy soil (pH 4.52) was incubated under anoxic conditions for 40 d and then under oxic conditions for 20 d. During anoxic incubation, the water-soluble, exchangeable, specifically adsorbed, and fulvic acid-complexed Hg decreased sharply, whereas the humic acid-complexed Hg, organic, and sulfide-bound Hg gradually increased, which were mainly ascribed to the enhanced adsorption on the surface of soil minerals with an increase in soil pH, complexation by organic matters, precipitation as HgS, and absorption by soil colloids triggered by reductive dissolution of Fe(III) oxides. By contrast, after oxygen was introduced into the system, a gradual increase in available Hg occurred with decreasing soil pH, decomposition of organic matters and formation of Fe(III) oxides. A kinetic model was established based on the key elementary reactions to quantitatively estimate transformation processes of Hg fractions. The model matched well with the modified Tessier sequential extraction data, and suggested that large molecular organic matter and humic acid dominated Hg complexation and immobilization in acidic paddy soils. The content of methylmercury increased and reached its peak on anoxic 20 d. Sulfate-reducing bacteria Desulfovibrio and Desulfomicrobium were the major Hg methylating bacteria in the anoxic stage whereas demethylating microorganisms Clostridium_sensu_stricto_1 and Clostridium_sensu_stricto_12 began to grow after oxygen was introduced. These new dynamic results provided new insights into the exogenous Hg transformation processes and the model could be used to predict Hg availability in periodically flooded acidic paddy fields.

Solidification/stabilization of mercury contaminated soil by geopolymer/MoS2 composites

The present study is aimed to solidify and stabilize mercury contaminated soil (MCS) by molybdenum disulfide nanosheets (MoS2)/geopolymer composite, which is a novel and efficient treatment for MCS. Therefore, fly ash and blast furnace slag were used to prepare geopolymer, and MoS2 was synthesized via the hydrothermal method. Firstly, MSC was pre-adsorbed by MoS2 and the adsorption mechanism was investigated through the structure characterization and adsorption kinetics test. The results indicated that the MoS2 has outstanding Hg adsorption due to the complexation of Hg with intrinsic S on MoS2 surfaces, and the electrostatic interaction between MoS2 and Hg2+. Then geopolymer was used to solidify and stabilize MCS pre-adsorbed by MoS2. The compressive strength and leaching toxicity test demonstrated that the MCS/geopolymer/MoS2 composite could effectively solidify and stabilize Hg. The excellent Hg immobilization property of MCS/geopolymer/MoS2 was mainly attributed to the synergy effect between geopolymer and MoS2. Dispersed Hg was concentrated on MoS2 and then was encapsulated by geopolymer. Meanwhile, the MoS2 could accelerate the hydration process and decrease the porosity of geopolymer, which further strengthening Hg immobilization. The findings will provide a new strategy for immobile heavy metal pollution using two-dimensional nanosheet composites.

Mn (II), Cu(II), Zn(II), Cd(II) and Hg(II) complexes with new tetra dentate Schiff base ligand type N4 : synthesis and characterization

A new complexes of Mn(II), Cu(II), Zn(II), Cd(II) and Hg(II) have been synthesized by reaction of the divalent metal salts with a new tetra dentate Schiff base ligand type N4 as donor atoms derivative from 2,4-diketopentane, 1,2-diamino benzene and aniline, (C28H30N4) N,N'-Bis-(1-methyl-3-phenylimino-butylidene)-benzene-1,2-diamine. All these complexes were characterized by the spectroscopic methods (FT.IR, UV-Vis, and Atomic Absorption) and H1NMR for the free ligand and, along with the magnetic susceptibility, melting point and molar conductivity. From all above measurements data, we suggested the tetrahedral geometry around the central metal ions for the all neutral complexes.

Synthesis, Physicochemical Studies and Powder X‐Ray Diffraction Analyses for New Niclosamide Metal Complexes with Significant Bioactive Behavior

AbstractThis work underlines some important features for the research on metal complexes of Niclosamide as antioxidants and antimicrobial evaluation of some of these compounds as possible therapeutic agents. Niclosamide metal complexes show a significant leap in the study of antibiotic resistance bacteria including Methicillin Resistant S.aureus (MRSA). The synthesized metal complexes of niclosamide in our current innovation are highly effective at eliminating this destructive sort of bacteria. Niclosamide metal complexes were synthesized then characterized by elemental analysis, Infra‐Red, electronic spectra, magnetic susceptibility, Mass spectra and ESR spectra of Cu (II) complex to know their geometries and mode of bonding, with stoichiometry, 1 : 1 (M : L). All the Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II) metal ions complexes were proposed to be with distorted octahedral geometry. Powder X‐Ray Diffraction technique is being utilized to further investigation of synthesized Niclosamide metal complexes. Expo2014 software was also employed to solve the structure of these novel complexes which proven the distortion of crystal structure. The TGA and DTA curves were employed to derive the kinetic thermodynamic parameters. The thermal decomposition of the complexes ended with the formation of divalent metal oxide, MO or trivalent, M2O3 as a final product except in case of Hg complex. The results of the antimicrobial activity of tested new metal complexes compounds exhibited potent antibacterial and antifungal activities in comparison to the Niclosamide ligand as reference. Quantum chemical parameters were estimated and provided noticeable values which completely matched with antimicrobial results that [Mn(NIC)(Cl2)(H2O)2] ⋅ 0.4H2O has higher biological activity than ligand and other novel complexes. low concentration value of MIC results by 125 μg/ml for both niclosamide (NIC) complexes [Ni(NIC)(Cl2)(H2O)2] and [Cu(NIC)(Cl2)(H2O)2] ⋅ 2.5H2O with Methicillin Resistant S.aureus (MRSA) genus maybe a valuable data used to produce novel therapeutic agent. Depending on their structure and on the source of the oxidative stress, metal complexes of Niclosamide might act as antioxidants or pro‐oxidants.

Moxifloxacin Metal Complexes: Synthesis, Characterisation, Antimicrobial and Antidiabetic Activities with Docking Studies

Six new metal complexes of Fe(III), Cu(II), and Hg(II) were synthesised, i.e., three (2, 4, and 5) with moxifloxacin (mono-ligand) and the other three (1, 3 and 6) with moxifloxacin and hydrazine (biligand). These were characterised through UV-Vis, FT-IR, elemental analysis (CHN), atomic absorption spectroscopy, TGA, scanning electron microscopy (SEM), and powder XRD studies. Further, all of these compounds were screened for their antimicrobial, cytotoxic, and antidiabetic potential. The study revealed that the synthesised metal complexes possess an excellent ability to become antifungal agents compared to moxifloxacin. Additionally, the cytotoxicity of compounds 1, 3, and 4 was in the acceptable range with much better antidiabetic potential as compared to the ligand moxifloxacin. Interestingly, the α-amylase inhibition activity of complexes 1 and 3 was found very close to the standard drug acarbose. Furthermore, the computational studies also authenticate the results of the antidiabetic potential of complexes 1, 3, and 4 by presenting the necessary interactions of these compounds with their respective binding sites. The overall results indicate that the antifungal and antidiabetic ability of moxifloxacin is enhanced significantly by complexation with the given metals and the secondary ligand, thereby making it a suitable lead compound for yet another avenue of an antifungal and antidiabetic agent in the field of drug discovery and development.

Preparation and Characterization of some Bivalent Metal Complexes with bis[2-(2ethyledenebenzimidazolyl)thiocarbohydrazide] and Studies of their Antiamoebic and Antihelminthic Activities

Manifestation of various medicinal potentiality and pharmacological activities associated in a pretty large number of Benzemidazole derivatives is due to presence of imidazole nuclei present in benzimidazole nuclei, which is essential constituent of Haemoglobin, Vitamin B-12, Adenine, Guanine (present in DNA). In present investigation we had prepared and characterized the complexes of some bivalent nontransition metal like Zn(II), Cd(II), Pb(II), Hg(II) and Sn(II) complexes with quadridentate ligand of benzimidazole derivative bis[2-(2ethyledenebenzimidazole) thiocarbohydrazide] (H2bisbtch) from studies of Elemental analysis, Electrical conductance data, Infrared and H-NMR spectral data. The complexes have general composition [M(bisbtch)] and almost insoluble in aqueous medium and fairly soluble in dimethyl formamide and polar organic solvent. The antiamoebic properties of ligand and its Zn(II) complexes were investigated in detail both ligand and Zn(II) complexs showed appreciable antiamoebic and antihelminthic activities similar to albendazole and Thiobendazole

Influence of non-covalent interactions on the coordination geometry of Ni(ii) in Ni(ii)–M(ii) complexes (M = Zn and Hg) with a salen-type N2O2 Schiff base ligand and thiocyanate ion as the coligand

The effect of non-covalent interactions on the coordination geometry of Ni(ii) in a Ni(ii)–Zn(ii) and a Ni(ii)–Hg(ii) complexes has been studied using DFT calculations.

Spectroscopic, computational, anti-bacterial studies of bivalent metal complexes of N-picolyl-amine dithiocarbamate

This study reports the synthesis of seven picolylamine dithiocarbamate complexes of M(II) {M =CoII (1), NiII (2), CuII (3), PdII (4), ZnII (5), CdII (6) and HgII (7)}. CHN analysis, conductivity measurements, magnetic susceptibility measurement, FT-IR, 1H and 13C-NMR, SEM, and XRD were used to investigate the structural geometries of the complexes. The dithiocarbamate ligand coordinates to the M(II) ion in a bidentate mode through sulfur atoms forming a square planar or tetrahedral geometry. Moreover, the surface structural analysis revealed nano-pattern properties. For instance, complexes of Cd(II) and Hg(II) showed a nano-flower pattern, averaging 2–5 µm. Furthermore, the obtained complexes exhibited biological activity properties. The results showed that the new metal (II) compounds possessed remarkable antibacterial inhibition activity against both Gram-positive and Gram-negative bacteria. Additionally, the complexes [Ni(PA-dtc)2], [Cu(PA-dtc)2], and [Pd(PA-dtc)2] were theoretically studied and their quantum parameters were evaluated using Gaussian 09 program at B3LYP/SDD level of theory. The optimized structures of all of the three complexes showed square planar geometry. The calculated bond lengths showed close values, specifically for CSS and CN group, which suggests a partially double bond character. Other quantum parameters have evaluated and showed similar properties such as the total energy, HOMO-LUMO energy gap, Affinity, Hardness, and dipole moment.

Synthesis, Characterization and Biological Studies of Bimetallic Complexes Containing Co(II), Cd(II) and Hg(II) and {N, N’,-Bis (Benzylidene)-1,3,-Diamine} Schiff Base in 1:2 Ratio

A new series of bimetallic complexes of Co(II), Cd(II) and Hg(II) with Schiff base ligand (N,N',-Bis(Benzylidene)-1,3-Phenylenediamine, {BENDAMB (1,3)} have been synthesized and characterized by elemental analysis, molar conductance, magnetic moment measurements, IR, Electronic and 1H NMR spectral studies. The softness parameter TEn of complexes have also been calculated to derive the binding side of the thiocyanate ligand. The spectral data shows that the Schiff base ligand is linked with comparatively harder metal Co2+ whereas SCN present as terminal. Magnetic susceptibility measurements indicate tetrahedral geometry around Cobalt ion. The softness parameter, suggest cationic-anionic structure for these complexes. Newly synthesized bimetallic complexes have been screened, for their antimicrobial and antifungal activities and was compared with solvent and Schiff base, screening results indicates that, the metal complexes are moderately active compared with those of pure Schiff base, BENDAMB (1,3).

Mercury (II) complex based on quinoxaline–aminoantipyrine: Synthesis, crystal structure, computational studies and anticancer activities evaluation

A new complex of a heterocyclic Schiff base derived from 4-aminoantipyrine and 2-carboxaldehyde quinoxaline ((4E)-4-((quinoxalin-3-yl) methylene amino)-1, 2-dihydro-1, 5-dimethyl-2-phenylpyrazol-3-one) (L) with Hg(II) iodide, [Hg(L)I2], was synthesized and characterized using elemental analysis, FT-IR, 13CNMR and 1H NMR spectra methods. Stoichiometry of the complex was determined as 1: 1. The structure of the ligand and its mercury iodide complex was investigated using single-crystal X-ray diffraction method, which revealed that the complex had a distorted square-pyramidal geometry. In the molecular structure of the complex, the ligand coordinated to the central metal in a tridentate form (one oxygen and two nitrogen atoms as donors). The mercury atom also had a five-coordinate geometry with τ5 of 0.044. The optimization geometry, charge distribution pattern, HOMO and LUMO energy, and quantum chemical parameters for the ligand and its complex were confirmed by Density Functional Theory (DFT) calculations and NBO analysis. The synthesized compounds were tested against MCF-7 and HT-29 cancer cell lines using MTT cell viability assay. A comparative study of the IC50 values indicated that the Hg(II) complex exhibited a higher activity compared to the related free ligand against MCF-7 and HT-29 cell lines after 48 h.

Fabrication of novel Fe (III), Co (II), Hg (II), and Pd (II) complexes based on water‐soluble ligand (NaH2PH): structural characterization, cyclic voltammetric, powder X‐ray diffraction, zeta potential, and biological studies

Sodium4‐hydroxy‐3‐([2‐picolinoylhydrazineylidene]methyl)benzenesulfonate (NaH2PH) was synthesized as a novel water‐soluble ligand, by the condensation of picolinohydrazide with sodium 3‐formyl‐4‐hydroxybenzenesulfonate. The (NaH2PH) ligand and its isolated Co (II), Fe (III), Hg (II), and Pd (II) complexes were analyzed by elemental analysis and characterized by spectroscopic (Fourier transform infrared spectroscopy, UV–visible, powder XRD, 1H NMR,13C NMR, MS) and magnetic measurements. By comparing IR spectra of both ligand and the metal complexes, one can assume that the (NaH2PH) ligand behaves as a bi‐negative tetradentate (ONNO) in [Co (NaPH)(H2O)2].3H2O, and a mono‐negative tridentate (ONO) in [Fe (NaPH)Cl2(H2O)] complex, whereas in [Hg2(NaPH)Cl2(H2O)] complex, (NaH2PH) coordinates as a bi‐negative pentadentate (ONNNO) ligand via deprotonated OH group of phenolic ring (C=N)Py and (C=N*) coordinated to one of Hg (II) ion and the oxygen atom of enolic group and (C=N)az group with the another Hg (II) ion. Moreover, (NaH2PH) acts as bi‐negative tridentate (ONO) ligand in [Pd (NaPH)(H2O)].2H2O complex. The geometries of complexes were suggested based on the UV–visible spectra, magnetic measurements and confirmed by applying discrete Fourier transform (DFT) optimization studies. The thermal fragmentation of both [Pd (NaPH)(H2O)].2H2O and [Co (NaPH)(H2O)2].3H2O complexes was performed, and the kinetic and thermodynamic parameters were computed using the Coats–Redfern and Horowitz–Metzger methods. The redox behavior of divalent ions of cobalt and mercury were discussed by the cyclic voltammetry technique in the presence and absence of (NaH2PH) ligand. Biological potencies of the ligand and its metal complexes were evaluated as antioxidants (ABTS and DPPH), anticancer, DNA, and antimicrobial (Staphylococcus aureus and Bacillus subtilis as Gram (+) bacteria, Escherichia coli and Pseudomonas aeruginosa as Gram (−) bacteria, and Candida albicans as fungi).

Fully bio-based supramolecular gel based on cellulose nanowhisker gallate by cyclodextrin host-guest chemistry

Nowadays, supramolecular hydrogels have gained special importance and development of versatile approaches for their preparation as well as their new facile characterization strategies has elicited tremendous scientific interest. Herein, we demonstrate that modified cellulose nanowhisker with gallic acid pendant groups (CNW-GA) could effectively bind with CNW grafted with β-Cyclodextrin (CNW-g-β-CD) through HG interaction to form fully biocompatible and low-cost supramolecular hydrogel. Also, we reported an easy and efficient colorimetric characterization method for confirming HG complexation using naked eye. The possibility of this characterization strategy evaluated both experimentally and theoretically using DFT method. Also, phenolphthalein (PP) was used for visual detection of HG complexation. Interestingly, PP undergoes a rearrangement in its structure in presence of CNW-g-β-CD because of HG complexation that turns the purple molecule into a colorless compound in alkaline condition. Addition of CNW-GA to the resulting colorless solution turned the color to purple again which easily confirmed HG formation.

Characterization and antioxidant activity of newly synthesized N1-(2-chlorophenyl)-N2-phenyl-1,2-hydrazinedicarbothioamide and its Cu(II), Zn(II), ZrO(II), Hg(II) and UO2(II) metal complexes

Thiourea derivatives are well known class of organic compounds having diverse application in the field of medicine, agriculture, coordination, and analytical chemistry. This study reports novel N1-(2-chlorophenyl)-N2-phenyl-1,2-hydrazinedicarbothioamide and its Mn (II),Co(II), Ni(II),Cu(II), metal complexes. These synthesized compounds were characterized by H1NMR, UV-Vis, IR spectroscopy and elemental (CHN/S) analysis. Moreover, antioxidant activity was screened for synthesized compounds. All the compounds showed significant antioxidant potential with IC50 values ranges from 23.81± 1.57µM - 58.32± 1.23µM. It was revealed that synthesized compounds displayed better antioxidant activity with IC50 values between 127.10-271.41 µM to256.42 ± 0.34 µM. The ligand (IC50 =33.41 ± 1.32µM)as well as metal complex Cu(L)2 (IC50 = 28.10± 1.05µM ), Zn(L)2 (IC50 = 24.53± 1.12µM), ZrO(L)2 (IC50 = 58.32± 1.23µM), Hg(L)2 (IC50 = 23.81± 1.57µM ), UO2(L)2 (IC50 =52.14± 1.45µM) showed far better activity than the standard (IC50 = 44.7± 1.21). Among these metal complexes, Hg complex (IC50 = 23.81 ± 1.57) showed highest antioxidant activity, while Zn complex (IC50= 24.53 ± 1.12), Cu complex (28.10 ± 1.05) and Co complex (IC50= 29.76 ± 1.21), The metal complexes UO2(L)2, ZrO(L)2 showed moderate anti-oxidant activity. These compounds were found be less active than other metal complexes as well as standard. The antioxidant activity pattern of these compounds is Hg(L)2 > Zn(L)2 > Cu(L)2 > UO2(L) > ZrO(L)2. These metal complexes showed remarkable antioxidant activity which may find their importance in avoiding or reducing the development of both heart disease and some forms of cancer.

Template synthesis, characterization and antibacterial activity of d10 (Zn2+, Cd2+, Hg2+) Schiff base complexes: A novel supramolecular Cd2+ complex with two 1D helical chains, and its Hirshfeld surface analysis

Three new macroacyclic Schiff base complexes were prepared via condensation of N,N,N',N'-tetrakis(2-aminoethyl) ethylenediamine hydrobromide with 5-bromo salicylaldehyde in the presence of metal ions (Zn2+, Cd2+, Hg2+) as template agents. The compounds were studied with elemental analysis, FT-IR, and 1H, 13C NMR spectroscopy. The structure of the Cd(II) complex, [Cd(H2L)] .2H2O (1), (H4L = N,N,N',N'-tetrakis(5-bromo salicylidene) N,N,N',N'-tetrakis(2-aminoethyl) ethylenediamine), was determined by single crystal X-ray crystallography. The X-ray diffraction analysis revealed that 1 crystallizes in monoclinic space group P21/c. Intermolecular O–H⋯O and C–H⋯Br hydrogen bonds linked [Cd(H2L)] monomers to a 2D network structure along the ac plane. The Br⋯Br halogen bonding interactions further expand the structure and construct a 3D supramolecular network with 1D right-handed and left-handed helical chains along the b axis in a 1:1 ratio. Furthermore, 1 is self-assembled through hydrogen bonding between the lattice water molecules with the phenolic oxygen atoms and phenolato oxygen atoms to form a 1D helical chain perpendicular to bc plane. The impact of the intermolecular contacts on the crystal packing of 1 has been further studied using Hirshfeld surface analysis and corresponding 2D fingerprint plots. Antibacterial activities of the compounds were screened by the disc diffusion method against three Gram-positive bacteria (Staphylococcus aureus ATCC 25923, Enterococcus faecalis ATCC 23212 and S. epidermidis ATCC 34384), and three Gram-negative bacteria (Eschericha coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853 and Klebsiella pneumonia ATCC 70063). All compounds demonstrated good antibacterial activities, and in three cases, the antibacterial activity of the Hg(II) complex exceeded the one of sulfisoxazole used as a standard.

Preparation and Characterization of New (Halogenated Azo-Schiff) Ligands with Some of their Transition Metal Ions Complexes

Two new halogenated azo-Schiff ligands were prepared in two steps. The first step included a condensation between 4-amino acetophenone and 2-fluoro-4-bromo aniline to give the corresponding Schiff base. In the second step, the diazonium salt of this Schiff base reacted with 2-naphthol and 4,5-diphenylimidazole to form two new azo-Schiff base derivatives as ligands; (3-((E)-(4-((E)-1-((4-bromo-2-fluorophenyl) imino)ethyl) phenyl) diazenyl) naphthalen-2-ol (HSBAN) (L1) and ((E)-N-(4-bromo-2-fluorophenyl)-1-(4-((E)-(4,5-diphenyl-1H-imidazol-2-yl)diazenyl) phenyl) ethan-1-imine) (HSBAI) (L2), respectively. These new ligands were characterized by mass spectrometry, FT-IR, 1H NMR, UV-Visible spectroscopy and elemental microanalysis (CHN). Five divalent transition metal ion complexes (Co, Ni, Cu, Cd, and Hg) were prepared and characterized, beyond the determination of the optimal condition (concentration, pH value, and the mole ratio M:L) using UV-visible studies. Additionally, complementary techniques, such as atomic absorption, electrical conductivity and magnetic susceptibility, were performed to deduce their geometries. The comprehensive study suggested an octahedral geometry for all complexes except Cd and Hg complexes of the first ligand.

Synthesis and Biological Study of Novel Schiff Base (1-(3-(4-fluorophenyl)-1-isopropyl-1H-indol-2-yl) methylene) hydrazine) Ligand and Metal Complexes

Background and objectivesHydrazone ligands along with their metal complexes exhibit important biological potential. Our objective was to synthesize new Schiff base ligands and their metal complexes which can act as vital drugs. Metal complexes of Zn(II), Ni(II), Cu(II), Mn(II), Co(II), Hg(II), Cd(II), Sn(II), Zr(II), and Fe(II) were synthesized from a novel Schiff base (1-((3-(4-fluorophenyl)-1-isopropyl-1H-indol-2-yl)methylene) hydrazine) ligand. The synthesized metal complexes were studied for antimicrobial, antimalarial, and anti-tubercular activity.

Experimental and computational studies on transition metals interaction with Leucine and Isoleucine

In this study, we reported the leucine and isoleucine based metal complexes with Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II). The complexes were synthesized in an aqueous medium followed by characterization with various experimental techniques. Besides experimental investigation, the density functional theory (DFT) calculation is performed which confirms a square planar structure for the Co, Ni and Cu complexes whereas Zn, Cd and Hg complexes adopt the distorted tetrahedral structure. The stability of the complexes is ensured by some calculated thermodynamic parameters. In addition, the elemental and thermos-gravimetric study are also conducted. Metal chelating affects the frontier molecular orbital energies of the ligand and reduces the HOMO-LUMO gap. The complexes are more reactive than the parent ligand. The FT-IR, UV-Visible and NMR spectral analysis of the complexes are reported. The experimental FT-IR and the electronic absorption properties agree with the calculated values. The presence of the characteristic metal-ligand charge transfer and d-d transitions in the complexes is confirmed through photo-excitation study. The UV-Visible reflectance spectral analysis indicates good conducting behavior of the complexes. The differential scanning calorimetry (DSC) analysis shows that the complexes undergo endothermic phase transition. The magnetic moment value agrees with the paramagnetic behavior of Co, Ni and Cu complexes but diamagnetic behavior of Zn, Cd and Hg complexes.

Anion Binding Based on Hg3 Anticrowns as Multidentate Lewis Acidic Hosts.

We present herein a combined structural and computational analysis of the anion binding capabilities of perfluorinated polymercuramacrocycles. The Cambridge Structural Database (CSD) has been explored to find the coordination preference of these cyclic systems toward specific Lewis bases, both anionic and neutral. Interaction energies with different electron-rich species have been computed and further decomposed into chemically meaningful terms by means of energy decomposition analysis. Furthermore, we have investigated, by means of the natural resonance theory and natural bond orbital analyses how the orbitals involved in the interaction are key in determining the final geometry of the adduct. Finally, a generalization of the findings in terms of the molecular orbital theory has allowed us to understand the formation of the pseudo-octahedral second coordination sphere in linear Hg(II) complexes.

Synthesis and Characterization of a New Azo Ligand Derivative from 4,5-BIS(4-Methoxyphenyl) Imidazol and its Metal Complexes and Biological Activity Study of its PD(II) Complex

In the current work, the azo ligand and its Pd (Ⅱ), Cd (Ⅱ), Zn (Ⅱ) and Hg (Ⅱ) complexes were synthesized, characterized and their spectroscopic characteristics were studied. The new ligand was synthesized from the coupling reaction between 4,5-bis(4-methoxy phenyl)imidazole and the diazonium salt of 4-Amino benzoic acid in an alkaline medium at 0-5 ᵒC. the new azo metal complexes were prepared by the reaction between the ligand and metals chlorides. All the synthesized compounds were characterized by FT-IR, 1H-NMR, Mass spectral analysis, UV-Vis spectrophotometric, molar conductivity, and magnetic sensitivity. The biological activity of the azo ligand and its Pd (Ⅱ) complex was also studied. keywords: Azo compound, 4,5-di (4-methoxy phenyl) imidazole, azo metal complexes

Effect of Pretreatments on bioremoval of metals and subsequent exposure to simulated gastrointestinal conditions

Water contamination with heavy metals is increased due to environmental contaminants. Arsenic, cadmium, mercury, and lead are well-known toxic heavy metals for humans. Lactobacillus acidophilus is an ideal absorbent for the removal of metals from drinking water. In this study, the ability of treated and untreated L. acidophilus ATCC 4356 to remove four heavy metals, simultaneously, from multi-metallic contaminated water in 24 h was investigated. In addition, the stability of the bacteria–metal complexes was evaluated in simulated gastrointestinal tract conditions. According to the results, untreated L. acidophilus could remove 99.01% and 92.35% of mercury and lead in water, respectively (initial concentration of 700 µg.L−1; inoculum size of 2.6×1012 CFU.mL−1; pH 4; 37°C; 24 h), whereas removal of arsenic and cadmium, under the same conditions, was 91.28% and 61.91% by heat and NaOH treated cells, respectively. In the digest condition, the complexes of bacteria-metal were reversible and the bond stability of untreated bacteria–Hg complexes was stronger than other complexes. The results suggest that treated or untreated L. acidophilus ATCC 4356 cells have the potential to adsorb heavy metals in contaminated water.