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There are six different linearized models of the pseudo-second-order kinetic model found in the literature. The pseudo-second-order kinetic model's linearized model count was expanded to eight in this study by deriving two newly linearized models. This study used experimental data from the literature for creating plots of these two new models. In the type 7 model, the slope of the line obtained by plotting 1/(qe - qt) vs. t graph gives 1/k2, and its shift gives [-1/k2qe]. In the type 8 model, the slope of the line obtained by plotting t vs. t/qt graph gives qe, and its shift gives [-1/k2qe]. Regression analysis was performed based on R² values, which revealed that the concordance of the kinetic data's degree was type 3 = type 4 < type 2 = type 5 < type 1 = type 7 < type 6 = type 8. It was discovered that the regression coefficients of type 6 and newly derived type 8 models are equal and have the highest value. It was determined that the highest qe value belonged to type 6 with 12.594 mg·g-1, and the highest k2 value belongs to type 2 as 0.0175 g·mg-1·min-1. It was also understood that the k2 and qe constants are close in the six models. On the other hand, the constants of types 1 and 7 are almost half the value of the constants in other models. Different constants offer alternatives in adsorption affinity, uptake in equilibrium, and degree of coherence. Since the k2 constants are also used in the Arrhenius equation, it is understood that different k2 constants will provide a wide range of alternatives for calculating the activation energy. [ABSTRACT FROM AUTHOR]

Over the preceding years, nickel (Ni) and its compounds have been increasingly employed in various aspects of human social life, metallurgical/industrial manufactures, healthcare and chemical processes. Although Ni is considered as an essential trace element in biological system, excessive intake or metabolic deficiency of Ni2+ ions may cause detrimental health effects to the living organisms. Therefore, a facile and accurate detection of Ni2+, especially in environment and biological settings, is of huge significance. As an efficient detection method, assaying Ni2+ using optical (colorimetric and/or fluorogenic) sensors has experienced quite a vigorous growth period with large number of excellent researches. Nanomaterial-based optical sensors including metal nanoparticles (MNPs), quantum dots (QDs), and carbon dots (CDs) offer distinct advantages over conventional small-molecule organic and inorganic sensors. This study mainly provides an overview of the recent advancements and challenges related to the design strategies of various optical nanosensors to selectively detect Ni2+ ion. Emphasis has also been placed on comparing the sensing performance of various nanosensors along with exploring future perspectives. [Display omitted] • This study covers nanomaterials based sensors for optical detection of Ni(II) ion. • Various metal-based nanoparticles (MNPs) and quantum dots (QDs) have been exloited. • Recent developments and challenges in the design and fabrication of nanosensors are emphasized. [ABSTRACT FROM AUTHOR]

The target of this research was to scrutinize a creeper plant, that is, Combretum indicum as a novel, eco-friendly, easily attainable and low cost biosorbent for the targeted metal ions’ removal. Ni(II) and Cu(II) ions were withdrawn from their aqueous solution by using the biosorbent. The said biomass was studied and characterized in detail via multiple analyzing techniques including scanning electron microscopy-energy-dispersive X-ray analysis, thermogravimetry, Brunauer– Emmett–Teller surface analysis and Fourier-transform infrared spectroscopy. After the thorough analysis the optimum dosage of C.I. was found to be 0.5 g for both adsorbates. The optimum time of contact for C.I. was 25 min for Cu(II) and 30 min for Ni(II) metal ions. Optimum pH was found to be acidic. The maximum adsorption capacities for Ni(II) and Cu(II) were found to be 27.8 and 12.1 mg/g, respectively. Equilibrium modeling revealed that experimental data fits best in Freundlich’s isotherm for both metals. The thermodynamic research depicted the process as spontaneously occurring and endothermic. The biosorption of the metal ions was in accordance with the pseudo-second-order kinetic model. [ABSTRACT FROM AUTHOR]

[Display omitted] New six-coordinated N -propargylimidazole complexes with cobalt(II), nickel(II) and copper(II) chlorides, [M(N -propargylimidazole) 4 Cl 2 ], were obtained in good yields by the reaction of N -propargylimidazole with corresponding metal chlorides. Molecular and crystal structures of compounds 1 – 3 were studied by X-ray analysis. Numerous non-covalent interactions including halogen bonds and π-stacking forms in the crystal were analyzed in the framework of quantum theory Atom in molecules. An evaluation of the antimicrobial activity of N -propargylimidazole complexes with Co(II), Ni(II) and Cu(II) chlorides in relation to E. durans , B. subtilis and E. coli showed that the complexes of nickel exhibit antimicrobial activity comparable to gentamicin in relation to E. coli. To explore the inhibitory activity mechanism the molecular docking was carry out. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synthesis of two distinct mononuclear metallocyclams, each adorned with the benzoate ligands. • Characterization of the synthesized compounds through spectral and thermal characterization employing various techniques. • Determination of structural aspects and bulk purity via diffraction studies. • Assessment of non-covenant interactions using Hirshfeld surface area analysis. • Catalytic efficiency and antibacterial activity of compounds have been investigated. Two mononuclear compounds, cis -[Co(cyclam)(Bz) 2 ](Bz)·H 2 O (1) , and trans - [Ni(cyclam)(H 2 O) 2 ](MOBA) 2 ·4H 2 O (2) (where Bz = benzoate and MOBA = o -methoxy benzoate) have been synthesized and characterized by elemental analyses, spectroscopy, X-ray diffraction, and thermogravimetric techniques. Compounds 1 and 2 crystallize in a monoclinic crystal system with P 2 1 / c and P 2 1 / n space groups, respectively. The carboxylate ligand in compound 1 enables the cyclam ligand to adopt a cis -V conformation, while in compound 2 , cyclam adopts a stable trans- III conformation. Hirshfeld surface analyses were carried out to elucidate the intricate intermolecular forces shaping the crystal structure. The ability of compounds 1 and 2 to imitate the activities of the catechol oxidase enzyme was evaluated using 3,5-di- tert -butyl catechol (3,5-DTBC) as the model substrate. The antibacterial activity was investigated using the Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli bacterial strains. Interestingly, compound 1 exhibited higher catecholase-like activity than compound 2 and enhanced antibacterial activity. [ABSTRACT FROM AUTHOR]

In the realm of biomass valorization, catalysts play a pivotal role, and UiO-66(Zr), a type of metal organic framework (MOF), emerges as a promising heterogeneous catalyst. This study focuses on incorporating Ni2+ into UiO-66(Zr) for application in catalytic transfer hydrogenation (CTH) of bio-derived α-angelica lactone (a-AL) to ɣ-valerolactone (GVL). The synthesis of UiO-66(Zr) occurs through a solvothermal process at 120 °C for 24 h. Ni(II) modification, achieved through wet impregnation with loadings of 2.5 and 5.0 wt%, results in no observable diffraction peaks associated with Ni particles in XRD analysis. FTIR analysis indicates significant shifts, suggesting deprotonation of the carboxylic moiety from the ligand and coordination with Zr4+ metal ion. Nitrogen sorption isotherms show a reduction in surface area and pore volume upon Ni(II) incorporation. FESEM analysis reveals particle agglomeration and increased size with Ni(II) introduction. EDX and HRTEM confirm the presence of 0.9 and 1.8 wt% Ni(II) on UiO-66(Zr). TG/DTA analysis affirms that Ni(II) does not affect the thermal stability of UiO-66(Zr). Ultimately, the introduction of Ni(II) enhances the catalytic performance of UiO-66(Zr), increasing the conversion and selectivity towards ɣ-valerolactone from 67 to 83.3 % and 71.6 % to 97.4 %, respectively, under mild reaction conditions. [Display omitted] • UiO-66(Zr) MOF was successfully synthesized and decorated with Ni(II). • The Ni(II)/UiO-66(Zr) is highly active and selective to catalyze transfer hydrogenation of α-AL to GVL under mild conditions. • The catalytic performance of 5%Ni(II)/UiO-66(Zr) achieved 83 % a-AL conversion with 97 % selectivity towards GVL. [ABSTRACT FROM AUTHOR]

Base metal hydrometallurgy in a chloride medium has considerable advantages, as metals can be recovered by solvent extraction through a neutral complex mechanism without extra reagent addition, leading to ready lixiviant recycling and significantly reduced wastewater discharge. However, the recovery of Ni(II) using this hydrometallurgical method is challenging because of the unavailability of appropriate extraction reagents. In this study, a new reagent, N-2-ethylhexylpyridine-3-formamide (MEH3), was used to efficiently extract Ni(II) from weakly acidic (pH > 2.5) or neutral chloride solutions in the form of neutral complexes without pH adjustment. Some other metal ions can also be extracted; the selectivity of the reagent for each metal decreased in the following order: Cu(II) > Zn(II) > Ni(II) > Fe(III) > Co(II) > Mn(II). The reagent had weak ability to extract other metal ions such as Ca, Al, Cr(III), Mg, and Li. The extraction of Ni(II) was positively correlated with the Cl− concentration in the aqueous solution, indicating that Cl− is a driving force for Ni(II) extraction. The Ni(II) loaded organic phase was stripped with water, and approximately 50 g/L of Ni(II) in the loaded strip liquor was obtained at an O/A ratio of 15:1. The Ni(II) extraction mechanism was further studied using crystal structure analysis, FT-IR spectroscopy, and the maximum loading capacity. The results showed that a Ni(MEH3) 2 Cl 2 complex was formed via Ni(II) extraction. In conclusion, the MEH3 system can selectively extract Ni(II) from a chloride solution without consuming alkaline reagents, and no new substances are produced, which is beneficial for the realization of mother liquor recycling and has a positive impact on clean hydrometallurgy. • The reagent N-2-ethylhexylpyridine-3-formamide was prepared as a new extractant for metal ions. • Ni(II) can be extracted by MEH3 in the form of neutral complexes in weakly acidic (pH > 2.5) chloride solutions. • A complex of Ni(MEH3) 2 Cl 2 was formed via Ni(II) extraction. [ABSTRACT FROM AUTHOR]

Palladium and nickel complexes featuring thiosemicarbazones derived from chalcones and benzalketone were synthesized and fully characterized. Palladium compounds demonstrated remarkable antitumor efficacy against prostate (DU-145), breast (MCF-7), and non-tumor prostate (PNT2) cell lines. In contrast, the Ni(II) compound was inactive. Highlight the role of the metallic center for anticancer activity. Notably, these compounds did not interact significantly with DNA and Topoisomerase. [Display omitted] In this study, we report the synthesis and characterization of eight new palladium complexes and a nickel complex containing thiosemicarbazone ligands derived from chalcones and benzalketones. The techniques of Infrared and UV–visible spectroscopy, Nuclear Magnetic Resonance, Mass Spectrometry, and Elemental Analysis fully characterized the compounds. Crystallography was successful for five complexes and two ligands, allowing for X-ray Diffraction analysis. Molecular docking studies and assays involving DNA interaction via agarose gel electrophoresis and UV–Vis titration revealed no DNA interaction or inhibition of topoisomerase IIα enzyme activity. However, these compounds demonstrated potent cytotoxic effects (IC 50) against breast tumor (MCF-7) and prostate (DU-145) cell lines, as well as non-tumor prostate (PNT2) cell lines. These findings highlight the relevance of structural variations and the metallic center's nature in achieving cytotoxic effects, offering insights into the development of bioactive compounds. [ABSTRACT FROM AUTHOR]

• Two new nickel (II) Schiff base complexes were synthesized and characterized. • Complexes 1-2 form monoclinic systems in space group P 2 1 /c. • X-ray crystallography data indicate that complex 1 has a distorted square planar geometry while 2 has distorted octahedral geometry. • Supramolecular chains in 1 through Br...Br and π...π interactions and in 2 via C–Br...π intermolecular interactions have been observed. • For both compounds 1-2 , electrostatic and polarization energies have less influence than dispersion energies. Two new mononuclear Nickel(II) Schiff base complexes [Ni L 2 ] (1) and [Ni L 2 (D M S O) 2 ] (2) where HL is 2,4-dibromo-6-[(E)-{[2-(thiophen-2-yl)ethyl]imino}methyl]phenol, a bidentate Schiff base prepared from the condensation reaction of 2-thiopheneethylamine and 3,5dibromosalicylaldehyde, have been made. Complexes 1-2 are characterized by FTIR, UV-Vis. absorption spectra, TGA analysis (for 2) , and single-crystal X-ray diffraction studies. Complexes 1-2 crystallize in a similar space group P 2 1 /c as a monoclinic system. X-ray crystallography data indicate that complex 1 has a distorted square planar geometry whereas 2 has distorted octahedral geometry. Using the crystallographic data, the Hirshfeld surface (HS) analysis was also carried out to examine the nature and quantitative contribution of all potential non-covalent intermolecular interactions inside the crystal lattice. Supramolecular chains in 1 through Br∙∙∙Br and π∙∙∙π interactions and in 2 via C‒Br∙∙∙π intermolecular interactions have been observed. The interaction energies between molecules within the crystals were computed to get idea about molecular packing stabilization. [Display omitted] [ABSTRACT FROM AUTHOR]

Three Ni(II) complexes of thiosemicarbazone, two mononuclear and one dinuclear, has been synthesized and X-ray crystallographically characterized. Each of the metal centers in 1 and 2 are found to have square planar geometries. 3 adopts octahedral geometry at its Ni(II) center. All the complexes show anti-cancer and anti-angiogenic activities. According to Chorio-Allantoic Membrane (CAM) assay, all the Ni(II) complexes are found to promote blood capillary growth by 18.18%, −10.7% and –22.7%, respectively in 24h. In aortic arch assay, complexes show the inhibitory effect of samples on the proliferation and migration of constituent cells namely endothelial cell, fibroblast and smooth muscle cell of the aortae. [Display omitted] Synthesis and X-ray structural characterization of three Ni(II) complexes of thiosemicarbazone ligand [Ni(L1) 2 ] (1), [Ni(L2)] 2 (2) and [Ni(L3) 2 ] (3) [L1 = 2-ethoxybenzaldehyde-N(4)-diethyl-3-thiosemicarbazone, L2 = o -vanillin-N(4)-diethyl-3-thiosemicarbazone and L3 = 2-benzoylpyridine-N(4)-diethyl-3-thiosemicarbazone] are reported. From the structural characterization data, the metal centers in 1 and 2 are found to have distorted square planar geometries but in 3 , the Ni(II) center adopts distorted octahedral geometry. The metal complexes (1 , 2 and 3) show anti-cancer and anti-angiogenic activities. The complexes act in dual mode by both inhibiting the growth of the cancer cells directly through inducing intracellular Reactive Oxygen Species (ROS) level and inhibiting the growth of blood vessels which can indirectly retard and inhibit tumor growth and progression. Angiogenesis assay performed in in vivo Chorio-Allantoic Membrane (CAM) assay indicated that the complexes significantly inhibited the blood capillary growth within 24 h. The anti-angiogenic effect was observed to be effective against all the key cells involved in angiogenesis namely endothelial cell, fibroblast and smooth muscle cell of the blood vessel as observed in aortic arch assay where the complexes exhibited inhibitory effect on aortic capillary sprouting. [ABSTRACT FROM AUTHOR]

Two new Ni(II) coordination polymers (CPs) [Ni(TP)(L1)(H 2 O)] n (1) and [Ni(TP)(L2)] n (2), were synthesized via hydrothermal reaction (H 2 TP = terephthalic acid, L1 = 1,6-bis(2-methylbenzimidazol-1-yl)hexane, L2 = 1,6-bis(5,6-dimethylbenzimidazol-1-yl)hexane, and structurally characterized by X-ray single crystal diffraction analysis, elemental analyses, thermogravimetric analysis, X-ray powder diffraction and IR spectra. CP 1 exhibits a 2D hcb layer, which is further extended into 3D supramolecular architecture by classical O–H⋯O hydrogen-bonding interactions. CP 2 possesses a 3D 4-connected sra framework. Both CPs possess high thermal stability and promising photocatalytic activities for the degradation of methylene blue (MB) under UV irradiation. The photocatalytic mechanism was investigated by introducing benzoquinone (BQ), the ammonium oxalate (AO), and tert -butyl alcohol (TBA) as superoxide radical (·O 2 −), hole (h+), and hydroxyl radical (·OH) scavengers, respectively. Two Ni(II)-based coordination polymers(CPs) have been synthesized. CP 1 exhibits an uninodal 3-connected hcb network with the point symbol {63} and extended to a 3D supramolecular framework by the classical O–H⋯O hydrogen-bonding interactions. CP 2 possesses a 3D sra network. They display high photocatalytic capacities for degrading the methylene blue (MB) solution. Image 1 • Two Ni(II)-based coordination polymers have been synthesized and characterized. • CP 1 displays a 2D hcb layer which further extend into a 3D supramolecular framework. • CP 2 possesses a 3D 4-connected network with SrAl 2 topology. • Both CPs show high photocatalytic efficiency for MB degradation. • The photocatalytic mechanisms of two CPs were investigated in detail. [ABSTRACT FROM AUTHOR]

In this study, the significant role of carbinol in the construction of a tetranickel(II) cluster, [Ni 4 II(μ- OHCH 3) 2 (L) 2 (CH 3 OH) 2 ] · 2CH 3 OH (1) with a compartmental Schiff base, [H 3 L = N,N′ -bis(3-methoxysalicylidene)-1,3-diamino-2-propanol] is reported and emphasized. The tetranickel cluster crystallizes in a monoclinic system with P 2 1 /n space group. The tetranickel(II) core exists in a dicubane structure adopting octahedral geometry for each nickel(II) centres. In forming tetrametallic core, carbinol as solvent molecules exhibit its uniqueness through versatile coordination motifs (bridging-, terminal- and solvent of crystallization) in assembling four nickel(II) ion with two Schiff base units. Hirshfeld analysis for 1 defines pivotal role of MeOH in construction of long range crystalline architecture. Examination of its ability towards cleavage of phosphoesterase bonds using 4-nitrophenylphosphate (PNPP) in carbinol authenticates its excellent cleavage efficiency with rate constant 1.61 × 10−4 min−1. Presence of coordinated methanol molecules at Ni(II) centre as well as multiple reaction centres in tetra-nickel(II) core remain the driving force for the phosphatase activity. Outcomes from extensive density functional theory (DFT) justify well the experimental observations. This paper highlights the significant role of carbinol in the construction of a tetranickel(II) cluster, [Ni 4 II(μ- OHCH 3) 2 (L) 2 (CH 3 OH) 2 ] · 2CH 3 OH (1) with a compartmental Schiff base, and its cleavage efficiency towards phosphatase activity. Image 1 • Synthesis and X-ray structure of a tetranuclear nickel(II) cluster. • Carbinol exhibits its uniqueness through versatile coordination motifs in this structure. • The nickel(II) complex efficiently cleave PNPP with rate constant 1.61 × 10−4 min−1. • Presence of coordinated methanol molecules at Ni(II) centre remains the driving force for this phosphatase activity. [ABSTRACT FROM AUTHOR]

A new heteroleptic octahedral [NiL(H 2 O) 3 ](NO 3) 2 ·1/2H 2 O complex with the tridentate pincer type ligand L; 2,4-bis(3,5-dimethyl- 1H -pyrazol-1-yl)-6-methoxy-1,3,5-triazine, was synthesized and characterized using self assembly and single crystal X-ray diffraction, respectively. The Ni(II) ion is coordinated with one organic ligand unit (L) as NNN -chelate and three water molecules in the inner sphere while the outer sphere contains two nitrate anions and half crystal water molecule. The nitrate ions and the crystal water molecule connected the complex cation units via O–H⋯O hydrogen bonding interactions. Also, the nitrate ions are effectively interacting with the coordinated organic ligand via anion-π stacking interactions. The percentages of the O⋯H contacts range from 34.5 to 37.7% using Hirshfeld analysis. As a result of the interaction between the Ni(II) and ligand groups, its charge and spin densities were reduced to 0.86 and 1.68 e, respectively instead of 2.00 e. The nature and strength of the Ni–O and Ni–N coordination interactions were discussed using atoms in molecules theory. The Ni–N(triazine) and the equatorial Ni–O bonds showed the highest interaction energies among the Ni–N and Ni–O bonds, respectively. Antimicrobial studies on selected Ni(II) pincer complexes of L indicated high selectivity against the Gram positive bacteria with very close actions to the positive control Gentamycin. The organic ligand showed no antimicrobial action at the applicable concentration. Image 1 • A new Ni(II) s -triazine pincer complex was synthesized and well characterized. • The antimicrobial activities of three Ni(II) s -triazine complexes were assessed. • All have selectivity against Gram positive bacteria while the ligand is inactive. • The strength and nature of Ni–N and Ni–O coordination interactions were discussed. [ABSTRACT FROM AUTHOR]

The oligo-oxamates oxamide- N,N′- bis(o-phenylene oxamic acid ethyl ester (= L1H 4 Et 2 , 5), oxamide- N,N′- bis(4,5-dimethyl-o-phenylene oxamic acid ethyl ester (= L2H 4 Et 2 Me 4 , 6) and oxamide- N,N′ -bis(o-phenylene- N 1 -methyloxalamide (= L3H 6 Me 2 , 7) were used as precursor for the synthesis of the binuclear complexes [ n Bu 4 N] 2 [Cu 2 (L1)] (8), [ n Bu 4 N] 2 [Cu 2 (L2Me 4)] (9), [ n Bu 4 N] 2 [Cu 2 (L3Me 2)] (10), [ n Bu 4 N] 2 [Ni 2 (L1)] (11) and [ n Bu 4 N] 2 [Ni 2 (L3Me 2)] (12), the trinuclear complexes [Cu 3 (L1)(pmdta)] (13) and [Cu 3 (L2Me 4)(pmdta)] (14) as well as the tetranuclear complexes [Cu 4 (L1)(pmdta) 2 ](NO 3) 2 ] (15), [Cu 4 (L2Me 4)(pmdta) 2 ](NO 3) 2 ] (16) and [Cu 4 (L3Me 2)(pmdta) 2 ](NO 3) 2 ] (17), (pmdta = N,N,N′,N′′,N′′- pentamethyldiethylenetriamine). The redox properties of the multinuclear complexes 8 ‒ 17 were studied by cyclic voltammetry and compared comprehensively to the ones of related mononuclear bis(oxamato), (oxamato)(oxamidato) and bis(oxamidato) complexes. The studies established further the crucial relationship between the molecular structure and the reversibility of individual redox processes and prove that unlike NiII-containing multinuclear complexes CuII ions can be reversibly oxidized when delivered in CuN 3 O and CuN 4 coordination units. On the other hand, all here reported binuclear NiII-complexes can be reversibly reduced. Furthermore, reversible electrochemical reduction of the terminal {Cu(pmdta)}2+ fragments within 13 ‒ 17 and of [Cu(pmdta)(NO 3) 2 ] is demonstrated, providing means as new reducing agents or electron storage material. [ABSTRACT FROM AUTHOR]

This paper presents sustainable hydrometallurgical recovery of Co(II) from wastewater, achieved by application of two ionic liquids (Cyphos IL 101 or 104) and an acidic extractant (Cyanex 272). The separation of Co(II) is carried out from model aqueous chloride and sulfate solutions, as well as from a real waste sulfate solution containing also Ni(II). The extractants were investigated both as single carriers and as synergic mixtures, the latter giving no positive synergistic effect. Cyanex 272 does not allow Co(II) to be transferred from chloride solutions effectively, while extraction from sulfate mixtures reaches totally up to 100% after two stages. Cyphos IL 101 does not give satisfactory results of Co(II) recovery from sulfate solutions, while both Co(II) and Ni(II) are transferred efficiently from chloride ones. Stripping of Co(II) from the loaded organic phases with 1 M H 2 SO 4 is very efficient (95–100%), regardless of the type of extractant (Cyanex 272 or Cyphos IL 104) and its concentration. Application of 1 M H 2 SO 4 allows Co(II) to be recovered from the loaded organic phase (up to 100%) in one stage of stripping and to be enriched even three-to fivefold relative to that in the feed. It also allows the organic phase to be reused for further extractions. Theoretical considerations of economic feasibility of the process proposed indicated that the value of cobalt in solutions after proposed steps increases from 0.32 USD/dm3 (after two stages of extraction) to 1.42 USD/dm3 after stripping. The major novelty of this work is the design of hydrometallurgical recovery of Co(II) from real sulfate wastewater in the presence of Ni(II), which permits sustainable processing of waste, recycling and recovery of critical element and also regeneration and reuse of organic chemicals applied for extraction. Image 1 • Sustainable hydrometallurgical recovery of Co(II) from wastewater is proposed. • Cyphos IL 101 or 104 and an acidic Cyanex 272 are applied as Co(II) extractants. • Flow sheet for Co(II) separation from real waste sulfate solution is proposed. • Process includes: 2 steps of extraction, stripping, 3 steps of organic phase scrubbing. • After stripping Co(II) is separated from Ni(II), concentrated and ready for electrowinning. [ABSTRACT FROM AUTHOR]

A Nickel(II) complex, catena -poly[bis(N -methylthiourea)bis(thiocyanato- κN)nickel(II)], [Ni(Metu) 2 (NCS) 2 ] n (1) was prepared and its structure was determined by single crystal X-ray analysis. In 1 , the nickel(II) ion is bound to four sulfur atoms of bridging Metu ligands and two nitrogen atoms of thiocyanate adopting a distorted octahedral environment. The crystal structure is stabilized by both intra and intermolecular hydrogen bonding interactions. The complex was also characterized by IR spectroscopy and the spectroscopic data is discussed in terms of the nature of bonding. The structures of [Ni(Metu) 2 (NCS) 2 ] n (1) and its analogous thiourea (Tu) complex, [Ni(Tu) 2 (NCS) 2 ] n (2) were predicted by DFT calculations. The IR frequency calculations were performed using DFT/B3LYP-D3 methodology. The atomic charges and spin densities were calculated using natural bond orbital (NBO) analysis for complexes 1 and 2. Image 1 (1). •Crystal structure of a new nickel(II) N -methylthiourea complex, [Ni(Metu) 2 (NCS) 2 ] n • DFT calculations validate the experimental structure. • The IR spectra of 1 and [Ni(Thiourea) 2 (NCS) 2 ] n (2) were reliably interpreted. • The atomic charges and spin densities were calculated using natural bond orbital (NBO) analysis for complexes 1 and 2. [ABSTRACT FROM AUTHOR]

Abstract Two new heteroleptic Ni(II) pincer complexes of s -triazine core ligand (L) were synthesized and characterized. The two complexes [NiL(H 2 O) 2 Cl]Cl; (1) and [NiL(H 2 O) 3 ](ClO 4) 2.H 2 O; (2) showed a slightly distorted octahedral configuration around Ni(II), and L acts as a tridentate N -chelate with Ni N bonds are generally shorter in 2 than 1. Using atoms in molecules (AIM) theory, the net interaction energies between Ni(II) and L are higher in 2 (96.75 kcal/mol) than in 1 (90.32 kcal/mol). The packing is dominated by O⋯H (45.0%) and Cl⋯H (16.0%) hydrogen bonds, respectively. Both complexes showed different extents of C H⋯O and anion-π stacking interactions. The MPW1PW91/TZVP method was used to predict the electronic properties of complexes 1 and 2. As a result of the interactions between the Ni(II) ion and ligand groups, the charge densities of nickel ion are reduced to 0.76–0.86 e in 1 and 0.87–0.98 e in 2. Also, its spin density is reduced to ∼1.73 e instead of 2.00 e in both complexes. Thermogravimetric analysis showed that 2 exploded at 281 °C in a fashion like the popcorn. Graphical abstract Image 1 Highlights • [NiL(H 2 O) 2 Cl]Cl (1) and [NiL(H 2 O) 3 ](ClO 4) 2.H 2 O (2) were synthesized. • Both have slightly distorted octahedral coordination environment. • Cl⋯H in 1 and O⋯H in 2 are the most important intermolecular interactions. • AIM topological parameters correlated inversely with the Ni N/Ni O distances. • Complex 2 thermally exploded at 281 °C. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • High Nickel(II) extraction was obtained in combination with a novel synergist. • With competitive extraction, Cu(II) has the highest extraction followed by Ni(II). • Kinetic studies shows that after at most 4 h, extraction equilibrium is established. Abstract This work consists of the synthesis of seven pyridine based ligands, 2-(3-butyl-1 H -pyrazol-5-yl)-pyridine (1), 2-[3-(tert -butyl)-1 H -pyrazol-5-yl]-pyridine (2), 2-(3-octyl-1 H -pyrazol-5-yl)-pyridine (3), 2-(1-octyl-1 H -imidazol-2-yl)pyridine (4), 2-[(1 H -pyrazol-1-yl)methyl]pyridine (5), 2-[(3,5-dimethyl-1 H -pyrazol-1-yl)methyl]pyridine (6) and 2-[(3-methyl-1 H -pyrazol-1-yl)methyl]pyridine (7) which have been made before. We modified some routes and obtained improved yields in most cases. The ligands were fully characterised using 1H and 13C NMR, infrared (IR) spectroscopy, mass spectrometry (ms), elemental analysis (EA) and melting point where appropriate. We managed to grow single crystals of the 2-[(1 H -pyrazol-1-yl)methyl]pyridine copper(II) perchlorate complex and solved the structure using single crystal X-ray diffraction. Coordination around the copper(II) centre is pseudo square planar, having two ligands coordinated to the metal ion. Indications are that the extraction stoichiometry using this ligand for copper(II) is also 2:1, L:M. This indicates how these ligands are capable of coordinating to metal ions. All the ligands were then used for the extraction of Ni(II) with and without a synergist, viz., sodium p-dodecylbenzenesulfonate (SDBS). The solvent extraction of only Ni(II) in the absence of synergist produced values from 3% to 15% and values between 69% and 79% with synergist. The competitive extraction of metal ions from a base metal ion mix (Co2+, Ni2+, Zn2+, Cu2+, Pb2+ and Cd2+) produced extraction values of 15%−87% extraction of different metal ions with synergist. Finally, time dependent extraction studies with Ni(II) showed that after 4 h equilibrium was established and in some cases even after 1 h equilibrium had been reached. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The structures of five nickel(II) tris-imidazolylphosphine complexes are reported. • The nickel complexes can be interconverted by altering the solvent or reagents. • The electronic structures of these complexes have been characterized by DFT. Abstract In this work we report the synthesis of five new nickel(II) complexes all coordinated to the tripodal ligand tris(1-ethyl-4- i Pr-imidazolyl)phosphine (T1Et4iPrIP). They are [Ni(T1Et4iPrIP)(CH 3 CN) 2 (OTf)](OTf) (1), [Ni(T1Et4iPrIP)(OTf) 2 ] (2), [Ni(T1Et4iPrIP)(H 2 O)(OTf)](OTf) (3), [Ni(T1Et4iPrIP)Cl](OTf) (4), and [Ni(T1Et4iPrIP)Cl 2 ] (5). The complexes serve as bioinorganic structural model complexes for histidine-coordinated nickel proteins. The X-ray structures have been determine for all complexes which feature coordination numbers 4–6. We investigated the spectroscopic interconversions for these compound in dichloromethane solution and demonstrate interconversion between 1 and 3 via 2 and conversion of 2 to 4. Complex 5 can be spectroscopically converted to the cation of 4 by dissolving it in dichloromethane. Fits of variable temperature magnetic susceptibility data yielded the following parameters: g = 1.944, D = −0.327 cm−1, E / D = 3.706 for 1 ; g = 2.280, D = −0.365 cm−1, E / D = 22.178 for 2 ; g = 2.000, D = −7.402 cm−1, E / D = −0.272 for 3 ; g = 2.176, D = −0.128 cm−1, E / D = −0.783 for 4 ; g = 2.258, D = 14.288 cm−1, E / D = 0.095 for 5. DFT structure optimizations afforded HOMO and LUMO energies indicating that complex 1 is the most stable. [ABSTRACT FROM AUTHOR]

Graphical abstract Two nano-sized Ni(II) coordination polymers (CPs) were synthesized under hydrothermal and Sonochemical condition, 1 exhibits a 3D architecture with CdSO 4 topology, while 2 displays 2D network with hcb layery. Nano-sized 1 displays higher photocatalytic activities than nano-sized 2. Abstract Two new Ni(II) coordination polymers (CPs), [Ni(L1)(IPA)] n (1) and [Ni(L2)(IPA)·H 2 O] n (2) (L1 = 1,6-bis(benzimidazol-1-yl)hexane, L2 = 1,6-bis(5,6-dimethylbenzimidazol-1-yl)hexane, H 2 IPA = isophthalic acid) were synthesized by hydrothermal and sonochemical process. X-ray crystal structure analysis revealed that 1 possesses a 4-connected 3D architecture with a 65. 8 CdSO 4 topology, while 2 exhibits a 2D layer, which can be classified as a honeycomb 63- hcb network. The results indicate that Ni(II) mixed CPs structurally modulated by the flexible bis(benzimidazole)-involved co-ligands. The role of ultrasound irradiation power, reaction time and reaction temperature on the size and morphology of the nano-sized 1 and 2 were investigated in detail. Further, fluorescence and photocatalytic activities of nano-sized CPs for degradation of methylene blue (MB) are presented. [ABSTRACT FROM AUTHOR]

• Crystal structure of the [Ni(neoc) 2 (NO 3)]+ with three different anions including TCNQ. • New Ni(II) complex with two NO 3 − groups coordinated in two different ways. • Influence of NO 3 − group on the crystal structure of [M(neoc)(NO 3) 2 (H 2 O)]. • Application of several crystallization methods. • Detailed structural analysis with emphasis on inter/intramolecular interactions. The cationic complex [Ni(neoc) 2 (NO 3)]+ with NO 3 − (1), TCNQ− (3), or (TCNQ-TCNQ)2− (4) as counterions, and the neutral complex [Ni(neoc)([NO 3 ]−- κ1O)([NO 3 ]−- κ2O,O´)(H 2 O)] (2) can be obtained from different reactions involving Ni(II), neoc , NO 3 − and TCNQ. The molecular and extended crystal structure of compound 2 , which displays two different coordination modes for NO 3 −, are compared to those of the analogous Mn, Fe and Co compounds, revealing a correlation between the coordination geometry of the nominally monodentate nitrato ligand and the covalent radius of the central metal atom. Despite the differences in molecular geometry, the extended structures of the Ni (2) and Mn compounds are similar to each other but different from those of the Fe and Co complexes, which are similar to each other. Complex 1 was further used in the preparation of a new heterospin compound [Ni(neoc) 2 (NO 3)](TCNQ) (3), having an ionic structure with the same complex cation present in 1 , accompanied by centrosymmetric anion-radicals (ARs) TCNQ•−. Through a different preparation process, complex 4 , with the formula [Ni(neoc) 2 (NO 3)] 2 (TCNQ-TCNQ), containing the same complex cation as in complexes 1 and 3 , but now with the centrosymmetric σ-dimerized dianion (TCNQ-TCNQ)2− has been obtained. The influence of NO 3 −, TCNQ•− and TCNQ-TCNQ2− anions on the crystal structure of the cation [Ni(neoc) 2 (NO 3)]+ in the compounds has been studied. All of the complexes reported here have supramolecular structures governed by hydrogen bonding systems, adding to their stability. [Display omitted] [ABSTRACT FROM AUTHOR]

A new Ni(II) complex was prepared and used as a luminescent molecular thermometer. Fluorescence intensity and 13C NMR chemical shift results showed excellent linear correlations with temperature from 10 to 60 °C in acetonitrile solutions. [Display omitted] A new luminescent molecular thermometer (LMT) was prepared, characterized, and investigated. The sensor works based on the temperature effect on the spin-crossover equilibrium between two spin states of a nickel-cyclen derivative (cyclen = 1,4,7,10-tetraazacyclododecane) containing a naphthalene fragment as the emitting unit. DFT and TD– DFT calculations revealed that photoelectron transfer (PET) can partially quenches the fluorescence of the naphthalene fragment to varying degrees in both high- and low-spin states of the sensor. UV–visible spectra in coordinating solvents such as acetonitrile revealed that 80% of the predominant species adopt five-coordination in the triplet state ([Ni(cycna)(CH 3 CN)]2+) at 20 °C, while 20 % of the molecules are square planar in the singlet spin state. The fluorescence spectra showed excellent correlation of luminescence intensity with temperature (R2 = 1.00) from 10 to 70 °C, proving that the coordination compound can function as LMT. [ABSTRACT FROM AUTHOR]

Graphical abstract New heteronuclear Fe–Ni carboxylate complexes with 1,10-phen and 2,2-bpy with different metal core ({Fe 2 Ni} or {Fe 2 Ni 2 }) were synthesized and characterized by single crystal X-ray analysis, Mossbauer spectroscopy, magnetic measurements and thermal analysis. Exchange coupling between Fe(III) ions was described according to magnetic data simulation and quantum-chemical calculations. Abstract The reactions of complex [Fe 2 Ni(O)(Piv) 6 (Et 2 O)(H 2 O) 2 ] (1) with 1,10-phenanthroline (phen) and 2,2′-bipyridine (bpy) gave the following new coordination compounds: the trinuclear complex [Fe 2 Ni(O)(Piv) 6 (phen)H 2 O]·(C 2 H 5) 2 O (2), the tetranuclear ones [Fe 2 Ni 2 (OH) 2 (Piv) 8 (phen) 2 ] (3) and [Fe 2 Ni 2 (OH) 2 (Piv) 8 (bpy) 2 ] (4), depending on the crystallization conditions. According to single crystal X-ray diffraction data, all the compounds have molecular structures. The Mössbauer spectra of 1 – 3 correspond to high-spin Fe3+ ions in an octahedral environment consisting of oxygen atoms. The DC magnetic susceptibility studies and quantum-chemical analysis of intra- and intermolecular J pathways using broken-symmetry density functional theory (DFT) showed that all exchange interactions in tri- (1 , 2) and tetranuclear (3) complexes are antiferromagnetic. The exchange coupling is weaker in 3 due to the lower ability of the bridging OH-groups to mediate superexchange. Thermal destruction processes have been studied for 2 and 3. The final products of thermolysis are the mixed oxide NiFe 2 O 4. [ABSTRACT FROM AUTHOR]

Abstract The aim of this study was to examine the effect of chromium(III), iron(III), molybdenum(III) and nickel(II) and their combinations on pro- and antioxidant activity in mouse embryo fibroblasts and liver cancer cells. The present study shows that chromium(III), iron(III), nickel(II) and molybdenum(III) induce oxidative stress. In the case of chromium(III), nickel(II) and molybdenum(III) the intracellular ROS were dominant. However, in the case of iron(III) MDA was dominant - the end product of lipid peroxidation. Antioxidant activity of superoxide dismutase and catalase increased in low concentration of chromium(III); however, they decreased in higher concentrations. The same enzymes decreased after iron(III), nickel(II) and molybdenum(III) treatment in dose dependent manner. The activity of glutathione peroxidise decreased in dose dependent manner in all used microelements. Additions of Cr(III) at 200 μM plus Fe(III) at 1000 μM showed synergistic effect in ROS production and in lowering antioxidant activity. The same type of interaction in pairs Cr(III) at 1000 μM plus Fe(III) or Ni(II) or Mo(III) at concentration of 200 μM was observed. The protective effects of Cr(III) in antioxidant activity and in lowering intracellular ROS production in pairs of Cr(III) at 200 μM and Ni(II) or Mo(III) at concentration of 1000 μM were observed. Highlights • Cr(III), Fe(III), Ni(II) and Mo(III) induce oxidative stress in normal and cancer cell lines. • Cr(III), Fe (III), Ni(II) and Mo(III) impaired antioxidant activity in normal and cancer cells. • Antioxidant activity plays a crucial role in interactions between Cr(III) and Fe(III) or Ni(II) or Mo(III). [ABSTRACT FROM AUTHOR]

Graphical abstract Highly active homoleptic nickel(II) bis-N-heterocyclic carbene catalyst for Suzuki–Miyaura and Heck cross-coupling reactions are reported. Abstract New homoleptic nickel(II) biscarbene complex was synthesized and structurally characterized. The complex depicted the excellent catalytic activities with only 3 mol% catalyst loading along with wide substrate scope for the Suzuki–Miyaura cross-coupling reactions (twenty six examples) and Heck coupling reactions (eighteen examples). [ABSTRACT FROM AUTHOR]

Abstract A tridentate Schiff base ligand (5-methyl-2-hydroxy-acetophenone- S -methyl-thiosemicarbazone, H 2 L) and its mononuclear nickel complex, [Ni L (PPh 3)], were obtained and characterized by spectroscopic techniques. Structural analysis of the compounds was supported by complementing crystallographic studies. The X-ray data related to molecular geometries was used in the DFT/B3LYP calculations with 6-311G (d, p) and LANL2DZ (for nickel atom) basis sets. Atomic charge distribution data indicated that the negative charges of free thiosemicarbazidato ligand were transferred to nickel (II) by the formation of the metal complex. To understand the nucleophilic or electrophilic reaction capabilities the ligand and nickel complex, the molecular electrostatic potential (MEP) and electrostatic potential (ESP) analyses have performed. Graphical abstract Image Highlights • Nickel (II) complex of 5-methyl-2-hydroxy-acetophenone- S -methyl-thiosemicarbazone. • X-ray structures of the ligand and nickel (II) complex containing PPh 3. • The electronic properties were determined by quantum-mechanical calculations. • Theoretical datas of the compounds compared with the experimental ones. [ABSTRACT FROM AUTHOR]

Graphical abstract A nickel(II) guanidinate compound [((Me) 2 NC(i PrN) 2) 2 Ni] has been synthesized and characterized by 1H NMR, elemental analysis and X-ray diffraction. Its thermal properties, including volatility, stability, and transport behavior, were studied by thermogravimetric analysis (TGA). Moreover, deposition test was conducted in a hot-wall CVD reactor to verify its potential as a CVD precursor. Abstract In this study, a nickel(II) compound with guanidinate ligand of the general form [((Me) 2 NC(i PrN) 2) 2 Ni] has been synthesized and isolated from the reaction of NiCl 2 with the corresponding lithium salt of guanidinate ligand [(Me) 2 NC(i PrN) 2 Li] at 70 °C. Its structure was determined by 1H NMR, elemental analysis, and single crystal X-ray diffraction. Thermogravimetric analysis (TGA) was employed to study the thermal properties (including thermal stability, volatility, vapor pressure and transport behavior) of compound. Furthermore, a deposition experiment was made to examine the compound's potential as CVD precursor, and a Ni metal film was successfully deposited. These preliminary results illustrate the potential of this compound to act as CVD precursor. [ABSTRACT FROM AUTHOR]

The biosorption of nickel(II) ions from aqueous solution by non-living strain Streptomyces roseorubens SY was thoroughly investigated as a function of pH, nickel(II) concentration, dosage, temperature, agitation speed and contact time. This versatile strain Streptomyces roseorubens SY was proved to be a highly efficient biosorbent for the removal of nickel(II) from aqueous solution. The optimum adsorption condition was occurred at a pH of 5.0, an initial nickel (II) concentration of 100 mg/L, a biomass of 1.0 g/L, an agitation speed of 150 rpm with a contact time of 60 min. The adsorption behavior of nickel(II) on strain Streptomyces roseorubens SY was evaluated by both Langmuir and Freundlich isotherms, resulting in R 2 of 0.9584 and 0.9166, respectively. The biosorption data showed an excellent fit to Langmuir isotherm and the maximum adsorption capacity of nickel(II) by strain Streptomyces roseorubens SY was found to be 208.39 mg/g at 313 K. The pseudo-second-order model (R 2  = 0.9998) provides the best fit for biosorption data than did pseudo-first-order model (R 2  = 0.8988). Results from thermodynamic analysis indicated that the nickel(II) biosorption by strain Streptomyces roseorubens SY was endothermic and spontaneous. The biosorption mechanism was mainly ascribed to the contributions from functional groups of OH, C O, C O, N H, etc . Our findings suggest that strain Streptomyces roseorubens SY is a promising, cost-effective and environment-friendly biosorbent for the treatment of industrial wastewater containing nickel(II) ions. [ABSTRACT FROM AUTHOR]

The aim of this study was to examine the effect of chromium(III) and iron(III) and molybdenum(III) and nickel(II) and their combinations on cyto-, genotoxicity and mutagenicity in BALB/3T3 and HepG2 cells. The results obtained from cytotoxicity assays indicate that there are differences between BALB/3T3 and HepG2 cell lines in their sensitivity to chromium chloride, iron chloride, molybdenum trioxide and nickel chloride. The statistically significant increase of DNA damage of all used microelements in both cell lines was observed. The micronucleus assay performed with the use of all concentrations shows statistically significant induction of chromosomal aberrations in all tested microelements in both cell lines. Moreover, treated cells display characteristic apoptosis in comparison to control cells. In all tested microelements, the increase of number of reverse mutations was observed with and without metabolic activation. Additions of Cr(III) at 200 μM plus Fe(III) at 1000 μM showed synergistic effect in decrease of cell viability and increase of comets, micronuclei and number of revertants in both cell lines. In case of Cr(III) at 200 μM plus Mo(III) at 1000 μM, a protective effect of chromium against molybdenum at 1000 μM toxicity in both cell lines (assessed by MTT, LDH and NRU, comet, micronucleus and Ames assays) was observed. The protective effect of Cr(III) in decrease of cell viability was observed in pair of Cr(III) at 200 μM and Ni(II) at 1000 μM in BALB/3T3 and HepG2 cell lines assessed by MTT, LDH and NRU, comet, micronucleus and Ames assays. [ABSTRACT FROM AUTHOR]

The new tetrakis[methyl(diphenylphosphorylated)] cyclen derivative DOTMPPh 2 was synthesized and its complexation with cobalt(II), nickel(II), copper(II), and zinc(II) perchlorates was studied. According to the X-ray diffraction data, isostructural compounds [Zn(DOTMPPh 2 )](ClO 4 ) 2 ·2.66CH 3 CN·0.34H 2 O and [Co(DOTMPPh 2 )](ClO 4 ) 2 ·2.72CH 3 CN·0.28H 2 O provide the first examples of octacoordinate Zn 2+ and Co 2+ complexes with cyclen molecules. The coordination polyhedra of M 2+ atoms are distorted Archimedean antiprisms formed by four cyclen N atoms and four phosphoryl O atoms. In [Cu(DOTMPPh 2 )](ClO 4 ) 2 the polyhedron of the copper atom is a slightly distorted tetragonal pyramid with four nitrogen atoms at the base and the O atom of a phosphoryl group at the apical vertex. The IR spectral data suggest that in the solid state Ni 2+ complex with DOTMPPh 2 has an octahedral structure, and it was confirmed by the high-spin magnetic moment of the complex. According to the UV–vis data, the structures of Cu 2+ , Ni 2+ , and Co 2+ complexes in solution are close to those in the solid state. The stability constants of Cu 2+ , Ni 2+ , and Co 2+ complexes with DOTMPPh 2 in ethanol and acetonitrile have been estimated from UV–vis spectrophotometric data. The log K values for the M 2+  + L = M 2+ L reaction in acetonitrile increase in the Co 2+ L < Ni 2+ L < Cu 2+ L order (4.56, 5.10, and 5.85, respectively). The stability of complexes in MeCN is slightly higher than in EtOH. In MeCN solution, complex Cu 2+ 2 L is found along with Cu 2+ L. [ABSTRACT FROM AUTHOR]

The equilibrium constants, spectral characteristics of complexes, formation thermodynamic parameters and constants of the chemical exchange reactions in the nickel(II) – l / d / dl -histidine (HisH) – l / d / dl -methionine (MetH) systems (25 °C, 1.0 mol dm −3 KNO 3 ) over wide ranges of pH and ligands to metal ratio were calculated from the pH-potentiometry, multi-wavelength electronic spectroscopy, calorimetry and NMR relaxation data. Based on the DFT computation the structures of some complexes have been proposed. Significant enantioselective effects are exhibited in the formation constants and in some electronic spectra and NMR relaxation parameters of a number of complexes with the meso -forms domination. For the Ni(His) 2 complex the process of alkaline catalysis of proton exchange with the short-time N-H proton removal from the coordinated imidazole fragment was characterized. It was shown that in the ligand exchange reaction between Ni(His) 2 and His − the Ni(His) 3 − complex participates as an intermediate. It was found that the Met − thiomethyl group is not bounded in the Ni(Met) + and Ni(Met) 2 complexes but coordinated in the Ni(His)(Met) form. Main factors determining stereoselectivity in the complex formation processes and ligand exchange reactions in the systems studied were identified as trans effect, solvation effect and a new type of interligand thiomethyl group–imidazole ring weak interaction. [ABSTRACT FROM AUTHOR]

X-ray crystal structures of multinuclear Cu(II) and Ni(II) complexes with 6+6 macrocyclic amine show variable coordination numbers of metal ions and various conformations adopted by the ligand. In Cu(II) complexes the macrocycle provides N3 donor set for each metal ion, while in the Ni(II) complex alternating N3 and N4 environments of the metal ions are observed. [Display omitted] An extended macrocyclic amine L derived from the [6+6] condensation of trans-1,2- diaminocyclohexane and 2,6-diformylpyridine contains 18 nitrogen atoms in its main cycle. All of these atoms can be engaged in the formation of polynuclear complexes with transition metal ions and the macrocycle L is able to bind six Cu(II), Ni(II) or Zn(II) ions within its interior. X-ray crystal structures of these complexes indicate variable coordination numbers of metal ions as well as various conformations adopted by the macrocyclic ligand. In the hexanuclear Cu(II) complex with coordinated nitrate anions Cu(II) ions are hexacoordinate and exhibit highly distorted octahedral geometry, while in analogous complexes with coordinated sulphate anions Cu(II) ions are pentacoordinate of distorted square pyramid geometry. Both complexes are relatively symmetric having (approximate) S 6 axis and adopt a circular doughnut shape with a central void not occupied by metal ions. The NMR spectrum of the zinc(II) derivative also reflects the symmetrical coordination. In contrast, the macrocycle L is squeezed and less symmetric in the octanuclear chloride derivative where two additional Cu(II) ions are linked to a hexanuclear macrocyclic unit via chloride bridges. The macrocycle is also squeezed in the hexanuclear Ni(II) complex containing metal ions of approximate octahedral geometry. In all three Cu(II) complexes the macrocycle provides N 3 donor set for each metal ion, while in the Ni(II) complex alternating N 3 and N 4 environments of the metal ions are observed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Phenanthroline-mono- N -oxides form stable complexes with copper(II) and nickel(II) ions. • The introduction of hydrophobic methyl substituents leads to selective metal binding. • The structures of the complexes were thoroughly characterized. Thorough equilibrium and spectroscopic studies are reported on the complexes formed between copper(II) or nickel(II) and derivatives of phenanthroline-mono- N -oxides (1,10-phenanthroline-1- N -oxide (phenO), 2,9-dimethyl-1,10-phenanthroline-1- N -oxide (DMPO) and 3,4,7,8-tetramethyl-1,10-phenanthroline-1- N -oxide (TMPO)). PhenO exhibits excellent metal binding ability, both copper(II) and nickel(II) form bis complexes in which the ligands coordinate to the metal ions via the (N,O) donor set. In the case of copper(II), a square-pyramidal complex forms, where the phenO-s coordinate at the corners of the square and the remaining site is occupied by the water molecule. The bis complex formed between nickel(II) and phenO possesses square-planar geometry in solution, however, the Ni(II) ion exhibits a distorted octahedral geometry in solid phase. DMPO forms relatively stable complexes with copper(II), but the coordination of this ligand to nickel(II) could not be confirmed. Because of precipitate formation in the entire studied pH range (pH = 2.0 – 11.0), well defined complexes could not be identified in the copper(II) – TMPO system. In contrast, this ligand forms stable water soluble nickel(II) complexes. The noted selectivity of these ligands in complex formation reactions is explained by considering the plasticity of copper(II), the rigid, square-planar geometry of nickel(II) and the enhanced steric repulsion of the methyl substituents of DMPO. [ABSTRACT FROM AUTHOR]

• Three new Ni(II)/Zn(II)-based complexes synthesized using mixed ligand strategy. • The complexes were characterized using different physico-chemical techniques. • The complexes were used as photocatalyst for photodegradation of methyl violet dye. • The Ni(II) complex displayed best photocatalytic activity for the degradation of MV. Three new complexes comprising Ni(II) and Zn(II) metal centers having compositions [Zn 2 (HL) 2 (bpy) 2 (H 2 O) 2 ] (1), [Ni(H 2 L)(bpy)(H 2 O) 2 (OH)] (2) and [Ni(H 2 L) 2 (bpy) 2 ] (3) have been synthesized by adopting mixed ligand strategy using 4′-(3,4- dicarboxylphenyloxy) -4-biphenylcarboxylic acid (H 3 L) as main ligand and 2,2′-bipyridine (bpy) as co-ligand. These complexes have been characterized by microanalyses, FTIR and single crystal X-ray diffraction technique. The single crystal X-ray analyses reveal that all the three complexes have 2D supramolecular network constructed by hydrogen bonding interactions. These complexes have been employed as photocatalysts for the photodegradation of methyl violet (MV) dye. The photocatalytic experiments reveal that amongst all three complexes, the complex 2 exhibits best photocatalytic performance and degrades 92.8% of MV in time span of 100 min. The plausible photocatalytic degradation mechanism have been proposed with the help of trapping experiments and density of states calculations. Three new Ni(II)/Zn(II)-based complexes with tricarboxylate ligand and bipyridine co-ligand synthesized and used as photocatalyst against methyl violet. [Display omitted] [ABSTRACT FROM AUTHOR]

Three new trinuclear hetero-metallic Ni II 2 M II complexes with M II  = Mn, Fe and Co have been synthesized using a [NiL R ] “metalloligand”, where H 2 L R  = N,N′-bis(2-hydroxybenzyl)-1,3-propanediamine. All complexes have been characterized by elemental analysis, spectroscopic methods, single crystal XRD and magnetic and electrochemical studies. In the three complexes, in addition to the double phenoxido bridges, the two terminal Ni II atoms are linked to the central M II [M = Mn( 1 ), Fe( 2 ) and Co( 3 )] ion by means of a bridging carboxylato co-anion, giving rise to a linear Ni II -M II -Ni II structure. Variable temperature magnetic susceptibility measurements show the presence of weak ferromagnetic and antiferromagnetic exchange interactions mediated through the double phenoxido bridges with J values of +8.5 and −3.0 cm −1 for complexes 1 and 2 , respectively. Compound 3 shows the presence of antiferromagnetic interactions. Cyclic voltammetry shows a common quasi-reversible one electron oxidation corresponding to the Ni(II)/Ni(III) process in 1 – 3 and an irreversible M(II)/M(III) oxidation for Mn( 1 ) and Fe( 2 ). [ABSTRACT FROM AUTHOR]

In this paper, citronellal, vanillin and pyridoxal thiosemicarbazones were modified with polar substituents, namely ethylmorpholine and glucose, to increase their polarity and compare the effects of these moieties on their biological activity. Altogether, nine ligands were synthesized and for each of them also their copper(II) and nickel(II) complexes were prepared and used for the biological tests. Eventually, assays on proliferation inhibition were conducted using leukemic cell line U937, already used as a model for previous citronellal thiosemicarbazone tests. Biological tests were also performed on solid tumor cell line HT29. From the first screenings, two of the metal complexes showed remarkable interesting properties, and, therefore, were also tested for histosensitivity. [ABSTRACT FROM AUTHOR]

A series of isomorphous random bimetallic Ni II -Mn II compounds with N -methylpyridinium-4-carboxylate (4-mpc) and azide, have been synthesized and characterized. They are of formula [Ni II x Mn II 1−x (N 3 ) 2 (4-mpc)] ( 1 − 6 ), ( x = 1 ( 1 ), 0.86 ( 2 ), 0.83 ( 3 ), 0.71 ( 4 ), 0.56 ( 5 ), 0.47 ( 6 )). Compounds 1 – 6 consist of one-dimensional uniform chains with [( μ -EO-N 3 ) 2 ( μ -COO)] triple bridges (EO = end-on). Magnetic measurements reveal that compounds 1 – 6 behave as antiferromagnets with a gradual ferromagnetic-to-antiferromagnetic evolution by the incorporating of isotropic Mn II ions into Ni II chain. The Ni II -rich compounds 1 – 3 exhibit field-induced metamagnetism. And the T N of the heterometallic compounds exhibit a composition-dependence of the content of Ni II . [ABSTRACT FROM AUTHOR]

Three new trinuclear hetero-metallic complexes, [(NiL R ) 2 Fe(N 3 ) 3 ] ( 1 ), [(NiL R (H 2 O)) 2 Fe(C 6 H 5 CH 2 CO 2 ) 2 ]·(HSO 4 ) ( 2 ) and [(NiL R (H 2 O)) 2 Fe(C 6 H 5 CO 2 ) 2 ]·(HSO 4 )·(H 2 O)·(CH 2 Cl 2 ) ( 3 ) have been synthesized using [NiL R ] as a “metalloligand” (where H 2 L R = N,N′-bis(2-hydroxybenzyl)-1,3-propanediamine). All complexes have been characterized by elemental analysis, spectroscopic methods, single crystal XRD and magnetic study. In the angular trinuclear units of 1 , the two terminals [NiL R ] coordinate through double phenoxido bridges to the central Fe III ion which is penta-coordinated having terminally coordinated azide ion. The two terminal Ni II centers are connected to each other and also to neighbouring units through μ 1,3 -azido bridges to form an alternating chain. On the other hand, complexes, 2 and 3 are linear discrete trinuclear species [Ni II –Fe III –Ni II ] in which two terminal octahedral [NiL R ] units coordinate to the central octahedral Fe III ion, located on a crystallographic centre of symmetry, through a μ 2 -phenoxido oxygen atom and a bridging carboxylato ion. Variable temperature magnetic susceptibility measurements show the presence of antiferromagnetic exchange interactions in 1 mediated through the phenoxido bridges ( J 1 = −33.2 cm −1 ,) and μ 1,3 -N 3 single bridges ( J 2 = −19.9 cm −1 and J 3 = −16.7 cm −1 ). On the other hand, compounds 2 and 3 show ferromagnetic coupling interactions mediated through the double phenoxido bridges with J values of +4.9 and +3.0 cm −1 for 2 and 3 , respectively. [ABSTRACT FROM AUTHOR]

Several high spin ground-state compounds based upon ferromagnetic coupling between a metal ion and the chelating 3,5-di- tert -butyl-1,2-semiquinonate radical anion, [DTBSQ] − , as they possess unpaired electron spins in orthogonal d x 2 −y 2 /d z 2 and π ∗ orbitals, are described. [Cu II (DPyA)(DTBSQ)](ClO 4 ) (DPyA = 2,2′-dipyridylamine) was reinvestigated and its singlet excited state is 282 cm −1 [0.035 eV; J / k B = 406 K ( H = − J S a ·S b )] above the triplet ground state. [Cu II (bipy)(DBCat)(MeOH)] (bipy = 2,2-bipyridine; DBCat = 3,5-di- tert -butylcatecholate), [Cu II (bipy)(DTBSQ)](BF 4 ), [Cu II (DPyA)(DTBSQ)-(THF) 2 ](BF 4 ) and [Ni II (DPyA)(DTBSQ)(THF) 2 ](BF 4 ) have been structurally characterized and have high spin ground states whose low spin excited states lie 28 cm −1 (0.0034 eV), 382 cm −1 (0.047 eV), 335 cm −1 (0.042 eV), and 108 cm −1 (0.013 eV) higher, respectively. The triplet-singlet separation is 18% greater for [Cu II (DPyA)(DTBSQ)(THF) 2 ] + than [Cu II (DPyA)(DTBSQ)] + and is ascribed to greater orthogonality of the Cu II d x 2 −y 2 /d z 2 and [DTBSQ] − π ∗ orbitals for octahedral [Cu(DPyA)(DTBSQ)(THF) 2 ] + with respect to distorted square pyramidal structure of [Cu(DPyA)(DTBSQ)] + . This greater energy of the excited state correlates with the shorter than average M-O DTBSQ distance, i.e. [Cu(bipy)(DTBSQ)] + > [Cu II (DPyA)(DTBSQ)(THF) 2 ] + > [Ni(DPyA)(DTBSQ)(THF) 2 ] + . The order of magnitude lower value for [Cu II (bipy)(DBCat)(MeOH)] arises from a weak intradimer S = 1/2 Cu(II) interaction, not via ferromagnetic coupling between the S = 1/2 Cu(II) and [DTBSQ] − sites. [ABSTRACT FROM AUTHOR]

A new 3-acetylcoumarin thiosemicarbazone (AcTsc) and its copper(II) ( 1 ), nickel(II) ( 2 ) and zinc(II) ( 3 ) complexes were synthesized and characterized by elemental analysis, UV–Vis, FT-IR, 1 H and 13 C NMR/EPR and mass spectroscopic techniques. The molecular structure of AcTsc, and the complexes 1 and 3 was confirmed by single crystal X-ray crystallography. The interaction of the complexes ( 1 – 3 ) with calf thymus DNA (CT-DNA) and bovine serum albumin (BSA) was explored using absorption and emission spectral methods, and viscosity measurement. The spectroscopic results clearly suggested that the complexes ( 1 – 3 ) interacted with CT-DNA through intercalative binding mode. In addition, all the complexes were subjected to cytotoxic studies against human liver carcinoma (HepG-2), lung carcinoma (A549), human leukemic monocyte lymphoma (U937) and lymphoblastoid multiple myeloma cells (IM-9). Complex 3 showed significant cytotoxicity against human liver carcinoma (HepG-2) and lymphoblastoid multiple myeloma (IM-9) cell lines with the IC 50 value of 25 μg/mL. [ABSTRACT FROM AUTHOR]

In this paper the efficiency of cloud point microextraction method has been confirmed by the preconcentration and spectrophotometric determination of nickel(II) ions with a new organic reagent 1-[(5-benzyl-1,3-thiazol-2-yl)diazenyl]naphthalene-2-ol. The influence of several factors (the acidity of the media, the time of the reaction and heating, the type of extraction solvent used) on the interactions between Ni(II) and the azo dye was checked. Optimal conditions for carrying out the complexation reaction between the reagent and Ni(II) were established (absorbance maximum wavelength λ max = 605 nm, time of heating the solution t heat. = 10 min, the acidity pH opt. = 5.5). Qualitative characteristics of the formed complex were calculated (ε 610 = 1.56 × 10 4 L mol − 1 cm − 1 , lgβ = 6.18). Two spectrophotometric methods of nickel(II) determination with the application of conventional liquid-liquid extraction and cloud-point microextraction were developed, and their main analytical characteristics were compared. The elaborated extraction technique with the application of cloud-point extraction and liquid-liquid microextraction provides significantly better performance characteristics for nickel determination (LOD = 3.9 μg L − 1 , LOQ = 11.8 μg L − 1 ), and instead of 25 mL of toxic toluene, only 200 μL of ethylene glycol was used. The new method of Ni(II) determination was tested on model solutions and real samples. [ABSTRACT FROM AUTHOR]

Several high spin ground-state compounds based upon ferromagnetic coupling between a metal ion and the chelating 3,5-di- tert -butyl-1,2-semiquinonate radical anion, [DTBSQ] − , as they possess unpaired electron spins in orthogonal d x 2 −y 2 /d z 2 and π ∗ orbitals, are described. [Cu II (DPyA)(DTBSQ)](ClO 4 ) (DPyA = 2,2′-dipyridylamine) was reinvestigated and its singlet excited state is 282 cm −1 [0.035 eV; J / k B = 406 K ( H = − J S a ·S b )] above the triplet ground state. [Cu II (bipy)(DBCat)(MeOH)] (bipy = 2,2-bipyridine; DBCat = 3,5-di- tert -butylcatecholate), [Cu II (bipy)(DTBSQ)](BF 4 ), [Cu II (DPyA)(DTBSQ)-(THF) 2 ](BF 4 ) and [Ni II (DPyA)(DTBSQ)(THF) 2 ](BF 4 ) have been structurally characterized and have high spin ground states whose low spin excited states lie 28 cm −1 (0.0034 eV), 382 cm −1 (0.047 eV), 335 cm −1 (0.042 eV), and 108 cm −1 (0.013 eV) higher, respectively. The triplet-singlet separation is 18% greater for [Cu II (DPyA)(DTBSQ)(THF) 2 ] + than [Cu II (DPyA)(DTBSQ)] + and is ascribed to greater orthogonality of the Cu II d x 2 −y 2 /d z 2 and [DTBSQ] − π ∗ orbitals for octahedral [Cu(DPyA)(DTBSQ)(THF) 2 ] + with respect to distorted square pyramidal structure of [Cu(DPyA)(DTBSQ)] + . This greater energy of the excited state correlates with the shorter than average M-O DTBSQ distance, i.e. [Cu(bipy)(DTBSQ)] + > [Cu II (DPyA)(DTBSQ)(THF) 2 ] + > [Ni(DPyA)(DTBSQ)(THF) 2 ] + . The order of magnitude lower value for [Cu II (bipy)(DBCat)(MeOH)] arises from a weak intradimer S = 1/2 Cu(II) interaction, not via ferromagnetic coupling between the S = 1/2 Cu(II) and [DTBSQ] − sites. [ABSTRACT FROM AUTHOR]

Nickel(II), zinc(II) and cadmium(II) complexes of two hexapeptides ADAAAC-NH 2 and AADAAC-NH 2 containing terminal amino, separate aspartyl carboxylate and cysteinyl thiolate donor functions have been studied by potentiometric and spectroscopic techniques. For nickel(II), the amino terminus and the aspartyl residues are the primary metal binding sites. At high pH values, thiolate groups can also coordinate to nickel(II) and this interaction results in the co-existence of various coordination isomers. In the case of AADAAC-NH 2 , even dinuclear complexes can be formed with separate (NH 2 , N − , N − , COO − ) and (S − , 3N − ) binding modes. On the contrary, the thiolate functions are the primary binding site for zinc(II) and especially cadmium(II) ions. The formation of macrochelate complexes is the most characteristic with these metal ions including the terminal amino, the internal carboxylate and thiolate donor functions. None of the side chain donors can, however, induce the deprotonation and zinc(II) or cadmium(II) coordination of the amide functions of these peptides. [ABSTRACT FROM AUTHOR]

The preparation and structure of cis -1 RS ,8 RS -[(5,7,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradec-4,11-diene)(pentan-2,4-dionato)nickel(II)] perchlorate 0.167 water are reported. This compound is the first reported example of this macrocycle in folded coordination to triplet ground state octahedrally coordinated nickel(II). [ABSTRACT FROM AUTHOR]

Structure and properties of a rare metal complex of the chiral Schiff base ligand derived from ortho -vanillin and L -tyrosine are presented. This study is a continuation of research on ligands containing biologically compatible moieties. The ligand is also fully characterized in form of a sodium salt, in particular in solution, for the first time. The metal complex contains a unique bowl-shaped [Ni 4 ] core. Its structure is investigated both in solution (ESI-MS, NMR) and in solid state (X-ray diffraction studies). Under certain conditions the complex can be isolated as crystalline DMF solvate which is studied in solid state. [ABSTRACT FROM AUTHOR]