Complexes NiL2 Research Articles

Structural and computational analysis of a nickel(II) complex with S-benzyldithiocarbazate Schiff base ligand: Synthesis, X-ray crystallography, MEP, HOMO-LUMO, Hirshfeld surface analysis, and molecular docking

A new compound, benzyl N-[1-(thiophen-2-yl)propylidene]hydrazinecarbodithioate (LH), and its nickel(II) complex (NiL2), were synthesized and structurally identified. Single crystal X-ray diffraction analyses determined that both the LH ligand and the NiL2 complex crystallized in the monoclinic system, with space group P21/c and Z = 4. The LH ligand exhibited lattice parameters of a = 9.661(2)Å, b = 8.995(2)Å, c = 18.939(4)Å, β = 102.677(4)°, V = 1605.7(7)Å3, whereas, NiL2 exhibited a = 17.805(7)Å, b = 10.548(4)Å, c = 18.100(7)Å, β = 108.279(6)°, V = 3228(2)Å3. The NiL2 complex was found to possess a slightly distorted square planar geometry with the LH deprotonated ligand acting as a monoanionic bidentate by coordinating through the azomethine nitrogen and thiolate sulfur atoms. It was observed that the HOMO-LUMO energy gap of the NiL2 complex (0.3654 eV) was lower than that of the LH ligand (2.4425 eV), indicating that NiL2 possesses a higher reactivity than the LH ligand. Intermolecular hydrogen bonding interactions were examined by Hirshfeld surface and 2D fingerprint analysis, which showed predominant H…H interactions for both the LH ligand and the NiL2 complex. A molecular docking simulation study with the dopamine D4 receptor (DRD4) and farnesyltransferase (FTase) revealed that NiL2 was able to interact with 13 residues in FTase, as compared to the farnesyl-Cys drug interacted with 11 residues.

Advancing photopolymerization and 3D printing: High-Performance NiII complexes bearing N2O2 Schiff-base ligands as photocatalysts

New high-performance photocatalysts based on metal structures are being developed for polymerization. However, using low-cost metals while ensuring effectiveness is challenging. In this study, two NiII complexes NiL1 and NiL2 were synthesized using N2O2 Schiff-base ligands bearing π-extended rings (naphthaldehyde (H2L1) and phenylsalicylaldehyde (H2L2) groups), respectively. These complexes were characterized by FTIR, UV–Vis and 1H NMR spectroscopy, elemental analysis, cyclic voltammetry, and MALDI-TOF mass spectrometry. NiL1 and NiL2 were evaluated in photoinitiating system as new photocatalysts for the Free Radical Photopolymerization of Ethoxylated (3) Trimethylolpropane Triacrylate (TMPETA) for violet and green light. Three-component systems were employed in the presence of Di-tert-butyl-diphenyl iodonium hexafluorophosphate (Iod) and ethyl dimethylaminobenzoate (EDB). The absorption, luminescence, and redox properties of nickel complexes and ligands were explored and compared for a better understanding of their structure/reactivity relationship. The designed nickel complexes showed good photoinitiation abilities. NiL2 exhibited the highest monomer conversion, and it was investigated in the on–off process under green light irradiation, demonstrating the efficiency of the system in reactivating the polymerization process. An oxidative pathway mechanism was proposed based on free energy, steady state photolysis and electron spin resonance spin trapping experiments. The best system was successfully applied in cationic photopolymerization and 3D printing.

Synthesis, characterization, molecular modeling studies, and biological evaluation of metal piroxicam complexes (M = Ni(II), Pt(IV), Pd(II), Ag(I)) as antibacterial and anticancer agents.

Four piroxicam metal complexes; NiL2 , PtL2 , PdL2 , and AgL were synthesized and characterized by different techniques with enhanced antibacterial and anticancer activity. Regarding in vitro antimicrobial activity, complex NiL2 displayed potent antibacterial effect against Escherichia coli and Pseudomonas aeruginosa that was 1.9-folds higher than piroxicam (minimum inhibitory concentration [MIC] = 31.85, 65.32 µM), respectively. In case of G+ve bacteria, complex PtL2 had potent activity on Staphylococcus aureus which was 2.1-folds higher than piroxicam (MIC = 43.12 µM), while activity of complex AgL against Enterococcus faecalis was threefolds higher than piroxicam (MIC = 74.57 µM. Complexes PtL2 and PdL2 exhibited higher inhibition of DNA gyrase than piroxicam (IC50 = 6.21 µM) in the range of 1.9-1.7-folds. The in vitro antiproliferative activity depicted that all investigated complexes showed better cytotoxic effect than piroxicam, specifically Pt and Pd complexes which had lower IC50 values than piroxicam on human liver cancer cell line HepG2 by 1.8 and 1.7-folds, respectively. While Pd and Ag complexes showed 2 and 1.6-folds better effect on human colon cancer cell line HT-29 compared with piroxicam. Molecular modeling studies including docking on Stranded DNA Duplex (1juu) and DNA gyrase enzyme (1kzn) that gave good insight about interaction of complexes with target molecules, calculation of electrostatic potential map and global reactivity descriptors were performed.

Amphiphilic mercapto-1,2,4-triazole Schiff bases as novel efficient extracting ligands for recovery of nickel(II) from highly saline chloride media in chloroform-water mixture

This work dealt with the extractive performance and behaviors of new three Schiff base amphiphiles ligands derived from 3-mercapto-1,2,4-triazole and different alkyl chains for recovery of nickel(II) from concentrated saline chloride medium (1 M ± 0.01) at 30 ± 1 °C. The chloroform has been used as solvent for research purposes only. The effects of the main experimental parameters such as extraction time, pH, extractant concentration and ionic strength of the aqueous medium on the extraction process of nickel(II) with amphiphilic Schiff bases (ASBn) were studied and compared. The analysis of extraction data revealed that the synthesized Schiff bases exhibit a better and faster extractability than many extractants reported in the literature. The extraction constants, log K ex, of these chelating extractants increased with an increase in the alkyl chain. A good recovery (E = 75–100%± 0.05) of nickel was obtained with amphiphilic Schiff bases. The hydrophobic Schiff base amphiphile (ASB18) was the most effective extractant for nickel ions from chloride solutions in the acidic pH range (2.41 − 2.90 ± 0.02). Ni(II) was readily extracted by ASB18 in 5 min. Extracted complexes NiL2 into chloroform phase were ascertained by slope analysis method for all extractants. The extraction mechanism of nickel(II) have been finally suggested. The results obtained are promising and can find practical applications such as for recovering of Ni(II) from Ni-MH battery wastes and electroplating industries effluents. However, in view of the acute toxicity of the solvent chloroform, implementation of this process in large-scale nickel processing strategies needs to be thoroughly evaluated from an environmental perspective.

A dithiocarbazate N,S Schiff base ligand with a long alkyl chain: Synthesis, characterization, DFT study and antimicrobial activity of its Ni(II) complex

The N,S bidentate ligand S-hexyl-β-N-(4-nitrobenzylidene)dithiocarbazate (HL), obtained by condensation of S-hexyldithiocarbazate with 4-nitrobenzaldehyde, has been used to synthesize the nickel(II) complex, NiL2. The ligand and complex were characterized by physicochemical techniques and the nickel species also by single crystal X-ray diffraction. The metal is four-coordinated with trans configuration of the Schiff bases that chelate the metal in the deprotonated monoanionic form. When compared to the free ligand, the metal complex exhibits a considerable increase in fluorescence intensity. Hirshfeld surface analysis and quantum chemical density functional theory (DFT) calculations were conducted to evaluate the non-covalent interactions of the complex NiL2. The antibacterial activity of free ligand HL and the complex was evaluated in vitro against pathogenic gram-negative bacteria, Escherichia coli and Klebsiella pneumonia. The test showed that neither the HL alone nor the complex were found to exhibit any activity against the tested organisms.

Nickel (II) chloride schiff base complex: Synthesis, characterization, toxicity, antibacterial and leishmanicidal activity

The use of schiff base complex against microbial agentes a has recently received more attention as a strategy to combat infections caused by multidrug-resistant bacteria and leishmania. This study aimed to evaluate the toxicity, antibacterial and leishmanicidal activities of the nickel (II) chloride schiff base complex ([Ni(L2)] against Leishmania amazonensis promastigote, multi-resistant bacterial strains and evaluate to modulate antibiotic activity against multi-resistant bacterial. The schiff base complex was characterized by the techniques of elemental analysis, Fourier transform infrared spectroscopy (FTIR), UV–vis absorption spectroscopy and thermal analysis (TGA/DTG/DSC). The [Ni(L2)] complex presented moderate toxicity in saline artemia (LC50 = 150.8 μg/mL). In leishmanicidal assay, the NiL2 complex showed values of IC50 of (6.079 μg/mL ± 0.05656 at the 24 h), (0.854 μg/mL ± 0.02474, 48 h) and (1.076 μg/mL ± 0.04039, 72 h). In antibacterial assay, the [Ni(L2)] complex presented significant inhibited the bacterial growth of P. aeruginosa (MIC = 256 μg/mL). However, [Ni(L2)] complex did not present clinically relevant minimum inhibitory concentration (MIC ≥1024 μg/mL) against S. aureus and E. coli. The combination of [Ni(L2)] complex and antibacterial drugs resulted in the increased antibiotic activity of gentamicin and amikacin against S. aureus and E.coli multi-resistant strains. Thus, our results showed that [Ni(L2)] complex is a promising molecule for the development of new therapies associated with aminoglycoside antibiotics and in disease control related to resistant bacteria and leishmaniasis.

Synthesis, characterization, electrochemical behavior, molecular simulation studies and in vitro toxicity assessment of new metal Schiff base complexes derived from 3‑methoxy-2‑hydroxy-benzaldehyde and allylamine

In this research, a series of new Schiff base complexes of CoL3 (1) and NiL2 (2) were derived from 3‑methoxy-2‑hydroxy-benzaldehyde with 3-amino‑prop-1-ene (allylamine). The functional groups were elaborately demonstrated using elemental analyses, Mass spectra, Fourier transform infrared (FT-IR), UV–Vis spectroscopy and single-crystal X-ray diffraction technique. X-ray diffraction results revealed that both complexes crystallized in the triclinic system with a space group of P1¯. The structural studies exhibited octahedral and square planar geometry for (1) and (2) around the central metal ion. Moreover, the redox behavior of the complexes was evaluated in methanol by cyclic voltammetry (CV) technique. The electrochemical behavior of the complexes showed the electronic effects of the groups on redox potential for both complexes. The synthesized allyl-based metal complexes were tested for anticancer activity in the human colorectal (SW-480) cancer cell line. In vitro cell proliferation was studied by microculture tetrazolium technique (MTT colorimetric assay) which indicated that all treatment groups are capable of decreasing the proliferation rate of SW-480 cells. The cytotoxic measurements showed strong inhibitory activity against cancer cells for all ligands and complexes in a concentration-dependent manner. Pharmacophore of novel colorectal cancer compounds was also explored. Molecular docking studies of our Schiff bases complexes was carried out to bind to B-DNA .

Synthesis, X-Ray Structure, Hirshfeld Surface Analysis, DFT Calculations, and Molecular Docking Studies of Nickel(II) Complex with Thiosemicarbazone Derivative.

This article presents both experimental and computational study of a new Ni(II) complex, namely, bis{2-(2-trifluoromethylbenzylidene)hydrazine-1-carbothioamido-κ2N2, S}nickel(II) (abbreviate as NiL2). The complex was synthesized and well characterized using various spectroscopic methods. The single X-ray crystallographic study revealed a distorted square planar geometry around Ni(II) metal ion centre in which the angles deviated from ideal 90° with a maximum value of 6.57° occupied by nitrogen and sulphur donor atoms. The theoretical bond lengths and angles for the NiL2 complex were obtained by using the B3LYP level of density function theory (DFT) with LANL2DZ/6-311G (d, p) basis sets. These results showed very good agreement with the experimental X-ray values. The electrophilicity index (ω = 50.233 eV) shows that the NiL2 complex is a very strong electrophile. In addition, strong F⋯H/H⋯F interactions with 28.5% of the total Hirshfeld surface analyses in NiL2 were obtained indicating that the complex could bind with protein effectively. Furthermore, the new NiL2 complex was docked with plasma retinol-binding protein 4 (RBP4) (PDB id: 5NU7), which implied that the NiL2 complex bound to Tyrosine 133 and Aspartate 102 amino acids via N-H intermolecular hydrogen bonds.

Ni(II) complex containing a thiosemicarbazone ligand: Synthesis, spectroscopy, single-crystal X-ray crystallographic and conductivity studies

In this study, 4-(diphenylamino)benzaldehyde-4-(2-fluorophenyl)thiosemicarbazone (LH) ligand was synthesized from the reaction of 4-diphenylaminobenzaldehyde and 2-fluorophenyl thiosemicarbazide. The NiL2 complex containing LH ligand were synthesized and characterized using elemental analysis, infrared spectroscopy, magnetic susceptibility, molar conductivity and UV-Vis spectroscopy. X-ray structure was determined for both the LH ligand and the NiL2 complex. LH ligand was also characterised via1H NMR and 13C NMR spectroscopy. FTIR data determined the coordination mode of the ligand with Ni(II) metal ion. The FTIR spectra shows that the LH ligand behave as mononegative bidentate through azomethine (N=C) and (C-S) groups with Ni(II) metal ion. The electronic spectra and magnetic measurements agreed well with a square planar geometry for NiL2 complex with the value of 0.00 B.M. Further confirmation of NiL2 complex was determined through single X-ray Crystallography which indicated a distorted square planar geometry which the angles deviated from 90° with a maximum value of 7°. In addition, the structure of LH ligand presented a thione form and the molecule has crystallized in triclinic crystal system with Pī space group. Conductivity studies of polymer electrolyte (PE) films composed of carboxymethyl cellulose (CMC) polymer, propylene carbonate as a plasticizer and LH/NiL2 compound as a dopant were prepared by a solution casting technique. The conductivity of the prepared PE films was studied using Electrochemical Impedance Spectroscopy (EIS). The conductivity was observed for LH ligand and NiL2 complex at 3.73 × 10−9 Scm−1 and 9.81 ×10−9Scm−1, respectively.

Synthesis, DFT calculation, DNA-binding, antimicrobial, cytotoxic and molecular docking studies on new complexes VO(II), Fe(III), Co(II), Ni(II) and Cu(II) of pyridine Schiff base ligand

A new H2L ligand (6, 6′-(pyridine-2, 6-diylbis(azan-1-yl-1-ylidene))bis(methan-1-yl-1-ylidene)bis(2-ethoxyphenol) was obtained from the reaction of 2, 6- diamino pyridine and 3- ethoxy salicyaldehyde in 1:2 molar ratio and fully characterized using elemental analyses and spectroscopic tools. The reaction of a ligand with the different metal salts yields five new complexes CuL, CoL, NiL, FeL, and VOL. The new complexes were identified according to the results of elemental analyses, IR and UV–vis spectra, magnetic moment, molar conductance and thermal analyses (TGA). From the conductivity data, it is deduced that all complexes are non-electrolytes. FT-IR spectra displayed that the Schiff base ligand coordinated to the metal ions in a manner with ONNO donor sites, the nitrogen atom of the pyridine ring, the nitrogen of one azomethine group and two oxygen atoms of the two phenolic OH groups. The results of electronic spectra and magnetic susceptibility confirmed octahedral geometry of FeL complex and square pyramidal geometry for CoL, CuL and VOL and square planar for NiL. The electronic structure of H2L ligand and its complexes were investigated theoretically at the DFT-B3LYP-311 G** level of the theory. FT-IR spectra established the involvement of pyridine nitrogen in the coordination process. The presence of coordinated water molecules inside the coordination sphere of the complexes CoL, CuL and FeL are supported by TGA studies. The antimicrobial activities of the ligand and its complexes were determined against two Gram-positive bacteria (B. subtitles and S. aureus) and two Gram-negative (E. coli and P. vulgaris) and two fungus (Candida albicans and Aspergilla’s fumigates). The results showed that the complexes behaved as better antimicrobial agents than the ligand, VOL complex shows exceptional antimicrobial efficacy. The order of increasing the antibacterial and antifungal potency is H2L < NiL < CuL < CoL < FeL < VOL. The binding of the complexes with CT-DNA was followed using electronic absorption, viscosity and gel-electrophoresis measurements. These studies confirmed that the complexes bind to CT-DNA through a groove binding mode with certain affinities (Kb = 6.25 × 105, 5.50 × 105, 3.20 × 105, 2.50 × 105 and 1.52 × 105 for CuL, FeL, VOL, NiL, and CoL respectively). Moreover, cytotoxic effect against hepatocellular carcinoma cell line (HEP-G2) was screened. The IC50 values of the ligand and complexes suggest that the compounds possess very good cytotoxic activity and follow the order: CuL >FeL>VOL>NiL>CoL > H2L. These results strongly agree with results of binding constant of CT-DNA with different metal complexes.

Nickel(II) Complexes with Mono(imino)pyrrole Ligands: Preparation, Structure, and MMA Polymerization Behavior

A simplified synthetic method was initiated to prepare the corresponding nickel complexes NiL2 (I–III) with direct condensation of mono(imino)pyrroles (L1–L3) and nickel dichloride, the structures and methyl methacrylate (MMA) catalytic polymerization behavior of this series of mono(imino)pyrrole nickel complexes were presented. The mono(imine)pyrrole ligands and the corresponding nickel complexes were determined by 1H NMR, 13C NMR, IR and MS, etc. Complexes I and III were further characterized by X-ray crystal diffraction (CIF files CCDC nos. 1890965 (I), 1890964 (III)). Both of the structures showed that the ligand chelated to nickel with 2 : 1 molar ratio. The systematic studies were focused on the relationship between the catalytic behavior of these complexes for MMA polymerization and catalyst structure, reaction time, reaction temperature, and ratio of monomer with catalyst. The optimum reaction conditions of the molar ratio of monomer to catalyst is of 1200 : 1, the polymerization temperature of 100°C, time of 10 h, the nickel complex with two bulky substituents on the o-position of phenyl ring linked with imine showed excellent catalytic activities for MMA polymerization (4.791 × 104 g mol–1 h–1), high molecular weight (Mn = 65.873 × 103 g mol–1), and narrow molecular mass distribution (polymer dispersity index = 3.9877), and azodiisobutyronitrile acted as co-catalyst during MMA polymerization.

Synthesis and Crystal Structure of Nikel(II) and Zinc(II) Complexes with Benzoylacetic Aldehyde Derivatives

Ni(II) and Zn(II) complexes of composition MLn ⋅ NH3 (n = 1–3) are synthesized based on condensation products of benzoylacetic aldehyde with aromatic acid hydrazides (H2L1–H2L3). The resulting complexes are studied by elemental analysis, as well as IR and NMR spectroscopy. The structure of complex NiL2 ⋅ Py is determined by the method of the XRD analysis (CIF file CCDC no. 1508698).

Tuning Semiconductor Performance of Nickel Complexes through Crystal Transformation.

Crystal transformation between two polymorphs (green, 1-G, and red, 1-R) of the square-planar nickel complex NiL2 (L = 2-ethoxy-6-( N-methyliminomethyl)phenolate) and their tuning effect to semiconductor properties were studied both experimentally and theoretically. When 1-G is heated to 413 K, it converts to 1-R, whereas soaking 1-R in several kinds of solvents causes it to revert to 1-G. Crystallographic and PXRD studies reveal the dramatic changes in crystal dimensions due to the changes of packing models. Heating device made from 1-G (D-1-G(298)) at 413 K significantly increases the electrical conductivity from 6.55 × 10-4 S cm-1 for D-1-G(298) to 1.11 × 10-3 S cm-1 for D-1-G(413), showing significant crystal form dependence. Heat-treating D-1-G and D-1-R devices at different temperatures clearly reveals the reason for the conductivity tuning. Thus, the conductivity of NiL2-based devices could be well tuned through crystal transformation by heating or by soaking in solvent. Theoretical calculations clearly revealed the reason for such conductivity changes and also predicted that both polymorphs are good p-type semiconductors with hole mobilities of 1.63 × 10-2 (1-G) and 2.11 × 10-1 cm2 V-1 s-1 (1-R).

Syntheses, Crystal Structures, and Fluorescence Properties of 3d–4f Coordination Polymers LnNi (Ln = Er, Eu)

Two novel 3d–4f coordination polymers [Ln(NiL)(Nipt)(C2O4)0.5 · H2O] · H2O (Ln = Er (I), Eu (II) (H2L = 2,3-dioxo-5,6,14,15-dibenzo-1,4,8,12-tetraazacyclopentadeca-7,13-dien; H2Nip = 5-nit-roisophthalic acid) were obtained by using 5-nitroisophthalate and mononuclear macrocyclic oxamide complex NiL as co-ligand to react with Ln(NO3)3 ⋅ 6H2O (Ln = Er, Eu) under solvothermal condition, and characterized by single crystal X-ray diffraction (CIF files CCDC nos. 1587618 (I) and 1587619 (II)). Two complexes are isostructural structure and exhibit a two-dimensional network architecture formed by [Ln(III)Ni(II)] units via the oxamide, 5-nitroisophthalate and oxalate bridges, and adjacent 2D structures are linked together with C–H⋅⋅⋅O and O–H⋅⋅⋅O intermolecular hydrogen bonds to form a 3D superamolecular architectures. The fluorescence properties of I and II are also characterized.

Quantum-Chemical Simulation of Tetra-, Penta-, and Hexacoordinated Stereoisomers of Bis-Ligand Ni(II) Complexes based on Polydentate Heterocyclic Derivatives of Azomethines

Molecular structures and relative energies of tetra-, penta-, and hexacoordinated stereoisomers of bis-ligand Ni(II) complexes based on polydentate heterocyclic derivatives of azomethines [coordination nodes of isomers NiN2O2, NiN2O2Y, NiN2O2Y2 (Y = S, Se)] were calculated using density functional theory. Within the framework of the proposed quantum chemical model of the mechanism of formation of NiL2 complexes (taking into account the possibility of subsequent stereoisomerization) the most probable product of complex formation was found to be the isomer with pentacoordinated central metal atom and nonequivalent ligands, tridentate and bidentate.

The crystal structure of bis-[(E)-4-bromo-2-({[2-(pyridin-2-yl)eth-yl]imino}-meth-yl)phenol]nickel(II) bis-[(E)-4-bromo-2-({[2-(pyridin-2-yl)eth-yl]imino}-meth-yl)phenolato]nickel(II) bis(perchlorate) methanol monosolvate, a structure containing strong inter-species hydrogen bonds.

The title compound, [Ni(C14H12BrN2O)2][Ni(C14H13BrN2O)2](ClO4)2·CH3OH consists of two mononuclear ([Ni(HL)2]2+ and [NiL2]) complex mol-ecules linked by strong hydrogen bonding [O⋯O separations of only 2.430 (5) Å], which is the shortest reported to date for such species. In one of the complexes, both the coordinated phen-oxy groups retain their protons and thus this is the cationic equivalent species of the other complex where both coordinated phen-oxy groups are deprotonated. In addition, perchlorate anions are present for charge balance, as well as methanol solvate mol-ecules. For the neutral NiL2 complex, each 2-ethyl-amine-pyridine arm is disordered over two equivalent conformations with occupancies of 0.750 (8):0.250 (8). The perchlorate anion is disordered over two equivalent conformations with occupancies of 0.602 (8):0.398 (8). The perchlorate ions also link to the H atoms on the methanol methyl and hydroxyl groups. These inter-actions link the moieties into a complex three-dimensional array. The crystal studied was refined as a two-component twin.

Identification of four isomers of Dihydroxynaphthalene by using a Briggs-Rauscher oscillating system

A novel method for identification of four isomers of dihydroxynaphthalene (DHN) was reported by their different perturbation effects on a Briggs-Rauscher (BR) oscillating system. In the system, macrocyclic nickel (II) complex NiL(ClO4)2 is used as the catalyst, where the ligand L in the complex is 5,7,7,12,14,14‑hexemethyl‑1,4,8,11‑tetraazacyclotetradeca‑4,11‑diene. By putting equal amount of the same concentrations of four isomers (1,4‑dihydroxynaphthalene (1,4-DHN), 1,5‑dihydroxynaphthalene (1,5-DHN), 2,3‑dihydroxynaphthalene (2,3-DHN) and 2,7‑dihydroxynaphthalene (2,7-DHN)) into BR system, the system could or couldn't be perturbed, being reflected in quite different oscillating behaviors after addition of isomers. These four isomers were identified in their concentration range of 5.0 × 10−6 to 2.5 × 10−4 mol/L. An explanation of such perturbation mechanism is that, 1,4-DHN couldn't be oxidized by BR matrix, but 1,5-DHN, 2,3-DHN and 2,7-DHN could be oxidized by HOO to yield 5‑Hydrox‑1,4‑naphthoquinone, phthalic acid and 6,7‑dihydroxyperylene‑1,12‑quinone (DHPQ), respectively.

Comparative study of bis-chelate M(II) complexes (M = Ni, Cu, Zn) as new heterogeneous photocatalysts for degradation of methylene blue under visible light

Three tetrahedral coordination compounds formed from Ni(II), Cu(II), and Zn(II) transition-metal ions with ON-donor, (2-aminophenol) ligand (L), were synthesized and characterized by Fourier-transform infrared (FTIR) spectroscopy, ultraviolet–visible (UV–Vis) absorption spectroscopy, elemental analysis, and magnetic susceptibility measurements. The magnetic properties revealed that the NiL2 and CuL2 complexes were paramagnetic while the ZnL2 complex was diamagnetic. Also, photodegradation of methylene blue as model organic pollutant by the synthesized complexes was studied based on an oxidation process under visible-light irradiation. The results showed that the photocatalytic activity of the Cu complex was greater compared with the Ni and Zn complexes, with degradation efficiency of 100, 85, and 60 %, respectively, after 30 min of irradiation in this condition. Thus, the Cu (bis-chelate) complex is more efficient, produces higher yield, is easily produced, and represents a more stable heterogeneous photocatalyst for degradation of organic dyes such as methylene blue.

Thermodynamic Characteristics of Reactions of the Formation of Complexes between Triglycine and Ni2+ Ions in Aqueous Solution

Thermal effects of reactions of the formation of complexes between Ni(II) and triglycine are determined via direct calorimetry in aqueous solutions at 298.15 K and ionic strengths of 0.2, 0.5, and 1.0 (KNO3). Standard thermodynamic characteristics (ΔrH°, ΔrG°, ΔrS°) of complexing processes in the investigated systems are calculated. The structures of triglycinate complexes NiL+, NiH−1L, NiL2, NiH−2L2−2, NiL-3, and NiH−3L4−3 are introduced to compare the obtained values and data on the thermodynamics of triglycinate complexes of Ni(II).

Copper(II), nickel(II), zinc(II) and vanadium(IV) Schiff base complexes: Synthesis, characterization, crystal structure determination, and thermal studies

Four new bis-chelate ML2 complexes (M = Cu2+, Ni2+, Zn2+, VO2+ and L = 1-[Furan-2-ylmethylimino)methyl]naphthalene-2-olate) with bidentate NO Schiff base ligand were synthesized and characterized by spectral and analytical techniques. The crystal structures of CuL2, NiL2, and VOL2 were determined by single crystal X-ray analysis. These complexes crystalized in the monoclinic system with the space groups of P21/n, P21/n, and C2/c, respectively. The Schiff base ligand acts as bidentate ligand and coordinates to the metal center via N and O atoms. The NiL2 and CuL2 complexes exhibit a distorted square planar coordination geometry while in the case of VOL2 the geometry is distorted square-pyramidal. In all cases, two Schiff base ligands bind to the metal centers in the trans O–M–N manner. Thermal analysis and thermal decomposition of the titled complexes were investigated. The data of TGA, XRD and SEM analyses revealed that they were converted to corresponding metal oxides in a form of nanoparticles (NiO, CuO, ZnO and V2O5).