Is Ni Research Articles

Binuclear Malonohydrazide Dithiocarbamate Complexes of Ni(II), Pd(II) and Pt(II): Synthesis, Characterization, Antimicrobial Activity, and SEM Studies

Binuclear complexes have been prepared with formula [M2L2], where L is potassium 2,2'-malonylbis(hydrazine-1-carbodithioate), M is Ni(II), Pd(II), and Pt(II). Each complex has been characterized by elemental analysis (CHNS), UV-Visible, FT-IR spectra, proton and carbon nuclear magnetic resonance (1H NMR and 13C NMR) spectra, magnetic susceptibility, scanning electron microscopy (SEM), and molar conductivity.

Low-temperature controlled synthesis of Ni3S4/NiS2 composite powder in deep eutectic solvent

Ni3S4/NiS2 composite powder with controllable morphology and proportion is synthesized without using any surfactant in choline chloride-ethylene glycol (ChCl-EG) deep eutectic solvent (DES) at 120 °C. The products are characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) to reveal the effects of reaction time, and reactant concentration on their composition and structure. The reaction mechanism for synthesizing Ni3S4/NiS2 in ChCl-EG DES is also elaborated. The results show that different proportions of wrinkled, lamellar and layer-rolled Ni3S4/NiS2 can be obtained by controlling the concentration of NiCl2·6H2O and Na2S2O3·5H2O. The analysis found that the reaction mechanism of Ni3S4/NiS2 is Ni(II) reacting with S2O32− and H2O to form Ni3S4, NiS2, SO42−, and H+. The NMR hydrogen spectrum (1H NMR), NMR carbon spectrum (13C NMR) and FT-IR tests of ChCl-EG indicate that it is structurally stable, and acted as a solvent and template during the reaction process.

Adsorption of Cu(II) in aqueous solution by sodium dodecyl benzene sulfonate‐modified montmorillonite

AbstractThe pristine montmorillonite (P‐Mt) was modified with sodium dodecyl benzene sulfonate (SDBS) to form SDBS montmorillonite (SDBS‐Mt) for the purpose of enhancing the removal performance of Cu(II) from aqueous solution. The materials were characterized by means of XRD, SEM‐EDS, BET, and FTIR to analyze the surface morphology and structure. SDBS‐Mt displayed a higher adsorption capacity than P‐Mt. The adsorption kinetic model and the adsorption isotherm model are depicted by the pseudo‐second‐order kinetic equation and the Langmuir equation, respectively. The adsorption of Cu(II) on SDBS‐Mt is a spontaneous and endothermic process. The order of influence of coexisting cations on the adsorption of Cu(II) is Ni(II) > Co(II) > Zn(II). In addition, the adsorbent has great regeneration performance after five cycles of regeneration. The main mechanisms of Cu(II) adsorption by SDBS‐Mt may include electrostatic attraction, ion exchange, and complexation of sulfonate groups. In brief, SDBS‐Mt may be a promising, simple, and low‐cost adsorbent for the treatment of Cu(II) in aqueoussolutions.

Synthesis, DFT Calculations, DNA Interaction, and Antimicrobial Studies of Some Mixed Ligand Complexes of Oxalic Acid and Schiff Base Trimethoprim with Various Metal Ions

Mixed ligand metal complexes are synthesized from oxalic acid with Schiff base, and the Schiff base was obtained from trimethoprim and acetylacetone. The synthesized complexes were of the type [M(L1)(L2)], where the metal, M, is Ni(II), Cu(II), Cr(III), and Zn(II), L1 corresponds to the trimethoprim ((Z)-4-((4-amino-5-(3,4,5-trimethoxybenzyl)pyrimidine-2-yl)imino)pentane-2-one) as the first ligand and L2 represent the oxalate anion ( ) as a second ligand. Characterization of the prepared compounds was performed by elemental analysis, molar conductivity, magnetic measurements, 1H-NMR, 13C-NMR, FT-IR, and Ultraviolet-visible (UV-Vis) spectral studies. The recorded infrared data is reinforced with density functional theory (DFT) calculations. Also, the recorded and calculated IR spectra of the complexes suggested that the coordination of Schiff base is a bidentate ligand with Cu and Ni complexes and a tridentate ligand with Co, Cr, and Zn complexes. The electronic structures of the complexes were investigated by DFT calculations, showing several degrees of HOMO-LUMO energy gaps between complexes. The complexes were studied for their DNA interaction activities. The synthesized ligand and its metal complexes were evaluated for antimicrobial properties against bacterial strains of Bacillus subtilis (G+), Enterobacter cloacae (G-), and Staphylococcus aureus (G+). These complexes considered in this study showed good antimicrobial activity.

Synthesis, Characterization and Bioactivity Study of Few Metal Complexes of Curcumin with 2-(1H-Benzimidazol-2-yl) Aniline

We have synthesized many metal (II) complexes using curcumin L1 as the major ligand and 2-(1H-Benzimidazol-2-yl) aniline L2 as a supporting ligand. The complexes were characterized by spectroscopy methods such as; molar conductivity, elements microanalysis, Fourier-transform spectroscopy (FT-IR), UV-vis, and mass spectroscopy. Both curcumin ligands and L2 were found to be capable of binding to M(II) and metal ions via their two N atoms, according to the data. The formula for the complexes is the same. [M (L1)(L2)H2OCl], where M is Ni(II), Co(II), Cu(II), Cd(II), and Hg(II) (II). Octahedral complexes are proposed for the prepared compounds. The bio-actives suggested that the complexes are effective against bacteria and fungus on a mild to moderate level.

SYNTHESIS AND SPECTRAL CHARACTERISTICS OF Cu(II), Ni(II) AND Fe(III) NANOSIZED COM­PLEXES ON THE SURFACE OF CARBON QUANTUM DOT

Processes of interaction between carbon quantum dots (CQDs) and solutions of Cu(II) Ni(II) and Fe(III) chlorides in the surface layer have been investigated by electron and IR spectroscopy.
 When hydrochloric acid is added to the aqueous suspension of CQDs, there is a signi­ficant batochromic shift of the average absorption band (AB) by 1285 cm-1 with a decrease in its intensity to ε = 23.39. The presence of copper in the suspension of CQDs at room temperature leads to a decrease in the intensity of this AB (ε = 21.80), which indicates the interaction of CQDs with metal ions.
 After heating the suspension for 1 and 3 hours, the gypsochromic shift of this ABs (by 335 cm-1) to 27790 cm-1 with a decrease in intensity depending on the heating time was recorded. Such changes in the UV–Vis Spectrum are due to the redistribution of the electron density of electron transitions n → π *due to the coordination of functional groups with metal ions and the appearance of transitions with charge transfer from ligand to metal (CQD→Cu2+).
 When heating the suspensions significantly increases the absorption intensity of the AB at 22070 cm-1: from ε = 4.59 to ε = 6.75, which indicates the formation of transitions with charge transfer from ligand to metal (ChTLM) due to the coordination of copper ions with CQD.
 In the absorption spectra of CQD suspensions with NiCl2 before heating, a hypsochromic shift of AB at 27305 cm-1 by 150 cm-1 and an increase in the intensity of its to ε = 4.95 were registered. That is, Ni(II) ions also form coordination bonds with functional groups on the periphery of the CQD.
 After heating hydrochloric acid suspensions of CQD with FeCl3, in contrast to the chlorides of previous metals, in the UV-region registered shoulder-shaped AB at 31545 cm-1, the intensity of which increases with heating time (from ε = 9.59 to ε = 12.10), and in the visible region, a weakly intense shoulder-shaped AB at 19345 cm-1 (ε = 3.71 and 4.58), associated with the presence of dd-electron transitions in the metal ion.
 Such changes in the absorption spectra are explained by the fact that iron may interact with CQD in different ways (in addition to coordination with functional donor groups, the formation of coordination bonds with the π-electron system of conjugated CQDs bonds), which leads to additional weak shoulder-like AB at 31545 cm-1.
 The IR-spectra data of CQDs showed the presence of a number of characteristic ABs for functionalized CQDs: ν(N–H) at 3260 сm1, (C=O) at 1830, 1840 and 1850 сm1, –С=O(NH) at 1770 сm1, ν(C=N) at 1680 and δ(N–H) at 1640 сm1 and 320-360 см-1 СП ν(Cu–Cl, Ni–Cl, Fe–Cl), which confirms the coordination of metals on the surface of CQDs.

Simple, green organic acid-based hydrometallurgy for waste-to-energy storage devices: Recovery of NiMnCoC2O4 as an electrode material for pseudocapacitor from spent LiNiMnCoO2 batteries

A simple, green approach to recover NiMnCoC2O4 as an electrode material for high-performance pseudocapacitors from spent LiNiMnCoO2 (NMC) batteries is proposed. Four strategic metals (Li, Ni, Co, and Mn) were leached from spent NMC batteries using several organic acids as model green leachants. Among the various candidates of green leaching agents, 2 M citric acid and 5 wt% glucose were selected as the leachant and reductant, respectively. Microwave irradiation was conducted during the leaching step to maximize the performance of the leaching rate and efficiency. The leaching efficiencies within 0.5 h for Ni(II), Li(I), Mn(II), and Co(II) were 90.7 ± 1.6%, 98.3 ± 2.4%, 94.9 ± 4.3%, and 95.6 ± 1.4%, respectively, and were thus as efficient as using aqua regia leaching. After the leaching process, divalent metal ions, that is, Ni(II), Co(II), and Mn(II), were immediately separated at room temperature using oxalic acid. The recovered samples were not further treated and used directly for energy storage applications. The recovered NiMnCoC2O4⋅nH2O has been demonstrated as a promising electrode for pseudocapacitors, providing a specific capacitance of 1641 F/g, good rate-retention capability (80% of low-current capacitance), and good cycle stability over 4000 charge–discharge cycles.

Analytical and Spectral Study of Furan Ring Containing Organic Ligands

The reaction of Ethyl 5-(piperidin-1-yl-methyl)furan-2-carboxylate with 4-amino salicylic acid afford a 4-(5-((diphenylamino)methyl)furan-2-carboxamido)-2-hydroxybenzoic acid (PFSA). The transition metal complexes of Cu²⁺, Co²⁺, Ni²⁺, Mn²⁺ and Zn²⁺ of PFSA have been prepared. The objective of the research work is synthesis, characterization and chelating properties of furan ring containing organic ligands. To monitor its antimicrobial activity. PFSA and all the metal complexes were characterized by elemental analyses, spectral studies, magnetic moment determination, molar conductivity measurement. The free ligand and it’s complexes have been tested for their antibacterial activities against two types of human pathogenic bacteria the first group is gram positive while the second group is gram negative (by using agar well diffusion method). Finally, it was found that compounds show different activity of inhibition on growth of the bacteria. The conclusion is Ni (II) Cu (II), Co (II) and Mn (II) complexes possess octahedral geometry around the central metal ion.

Pd-Ni nanoparticles supported on titanium oxide as effective catalysts for Suzuki-Miyaura coupling reactions

We have successfully prepared a series of Pd-Ni/TiO2 catalysts by a one-step impregnation-reduction method. Among these catalysts with different compositions of Ni and Pd, the one with the Ni:Pd ratio of 2.95 showed the best activity. Small monodispersed Pd-Ni bimetallic nanoparticles were loaded on the surface of titanium oxide nanopowder as confirmed with TEM and EDS mapping. The XPS analysis demonstrated that Pd exists as 31% Pd(II) species and 69% Pd(0) species and all nickel is Ni(II). The prepared Pd-Ni/TiO2 exhibited enhanced catalytic activity compared to an equal amount of Pd/TiO2 for Suzuki-Miyaura reactions together with excellent applicability and reusability.

Process optimization for Ni(II) removal from wastewater by calcined oyster shell powders using Taguchi method

Waste oyster shells cause great environmental concerns and nickel is a harmful heavy metal. Therefore, we applied the Taguchi method to take care of both issues by optimizing the controllable factors for Ni(II) removal by calcined oyster shell powders (OSP), including the pH (P), OSP calcined temperature (T), Ni(II) concentration (C), OSP dose (D), and contact time (t). The results show that their percentage contribution in descending order is P (64.3%) > T (18.9%) > C (8.8%) > D (5.1%) > t (1.7%). The optimum condition is pH of 10 and OSP calcined temperature of 900 °C. Under the optimum condition, the Ni(II) can be removed almost completely; the higher the pH, the more the precipitation; the higher the calcined temperature, the more the adsorption. The latter is due to the large number of porosities created at the calcination temperature of 900 °C. The porosities generate a large amount of cavities which significantly increase the surface area for adsorption. A multiple linear regression equation obtained to correlate Ni(II) removal with the controllable factors is: Ni(II) removal(%) = 10.35 × P + 0.045 × T − 1.29 × C + 19.33 × D + 0.09 × t − 59.83. This equation predicts Ni(II) removal well and can be used for estimating Ni(II) removal during the design stage of Ni(II) removal by calcined OSP. Thus, OSP can be used to remove nickel effectively and the formula for removal prediction is developed for practical applications.

Syntheses, spectral characterization, thermal properties and DNA cleavage studies of a series of Co(II), Ni(II) and Cu(II) polypyridine complexes with some new imidazole derivatives of 1,10-phenanthroline

In the present study three new imidazole derivatives of phen, 2-(4-hydroxy-3,5-diiodophenyl) imidazo[4,5-f][1,10]phenanthroline L1, 2-(2-hydroxy-3,5-diiodophenyl)imidazo[4,5-f][1,10]phenanthroline L2, 2-(4-hydroxy-5-iodo-3-methoxyphenyl)imidazo[4,5-f][1,10]phenanthroline L3 and their nine new polypyridine complexes[M(N–N)2(L1–3)](OAc)2·(nH2O) where M is Ni(II), Co(II) and Cu(II) and where (N–N)2 is 2,2′-bipyridine (bpy)2 or 1,10-phenanthroline (phen)2 have been synthesized from the reaction of the metal precursor complexes [M(phen)2(OAc)2]·(nH2O) and [M(bpy)2(OAc)2]·(nH2O) with the respective ligands in ethanol and water. The structures of the compounds were determined with the aid of elemental analysis and FT-IR, UV–Vis, 1H NMR, ESR spectroscopic methods, magnetic measurements and conductance measurements, further analyzed by powder XRD and thermal studies. Elemental analysis data suggested that the complexes have a 1:2:1 molar ratio among the metal and phen or bpy and L1/L2 or L3 ligands. The spectral data show that all the complexes were six coordinated and possess octahedral geometry around the metal ions. The X-band ESR spectrum of the Cu(II) in DMSO solution at room temperature was recorded and observed anisotropic g values indicate the presence of metal ion in an octahedral environment. The powder XRD patterns of complexes recorded in the range (2θ=0–80°) and average crystallite size (dXRD) was calculated using Scherrer’s formula. Thermal decomposition profiles of complexes show high decompound temperatures indicating a good thermal stability. Binding of the complexes with calf thymus DNA (CT DNA) has been investigated by gel electrophoresis. The experimental results indicate that the complexes bind to DNA by intercalation mode and found to promote cleavage of plasmid pBR 322 DNA from the supercoiled form I to the open circular form II upon irradiation.

Stability Constants of Mixed Ligand Complexes of Nickel(II) with Adenine and Some Amino Acids.

Nickel is one of the essential trace elements found in biological systems. It is mostly found in nickel-based enzymes as an essential cofactor. It forms coordination complexes with amino acids within enzymes. Nickel is also present in nucleic acids, though its function in DNA or RNA is still not clearly understood. In this study, complex formation tendencies of Ni(II) with adenine and certain L-amino acids such as aspartic acid, glutamic acid, asparagine, leucine, phenylalanine, and tryptophan were investigated in an aqueous medium. Potentiometric equilibrium measurements showed that both binary and ternary complexes of Ni(II) form with adenine and the above-mentioned L-amino acids. Ternary complexes of Ni(II)-adenine-L-amino acids are formed by stepwise mechanisms. Relative stabilities of the ternary complexes are compared with those of the corresponding binary complexes in terms of Δlog10⁡K, log10⁡X, and % RS values. It was shown that the most stable ternary complex is Ni(II):Ade:L-Asn while the weakest one is Ni(II):Ade:L-Phe in aqueous solution used in this research. In addition, results of this research clearly show that various binary and ternary type Ni(II) complexes are formed in different concentrations as a function of pH in aqueous solution.

Syntheses, crystal structures, spectroscopic and thermal analyses of 3- and 4-aminomethylpyridinium tetracyanometallate(II) complexes

In this study, six new complexes (3ampyH)2[Ni(CN)4] (1), (3ampyH)2[Pd(CN)4] (2), (3ampyH)2[Pt(CN)4] (3), (4ampyH)2[Ni(CN)4] (4), (4ampyH)2[Pd(CN)4] (5) and (4ampyH)2[Pt(CN)4] (6) (3ampy=3-aminomethylpyridine and 4ampy=4-aminomethylpyridine) have been synthesized and characterized by spectroscopic, elemental and thermal analyses, and single crystal X-ray diffraction techniques. Complexes 1, 2 and 3 crystallize in the monoclinic system, space groups P21/c, C2 and C2, respectively, whereas complexes 4, 5 and 6 crystallize in the triclinic system, space groups P1¯. The asymmetric units contain one halves of the [M(CN)4]2− anions and the 3ampyH or the 4ampyH cations, where M is Ni(II), Pd(II) or Pt(II), respectively. The metal atoms are located on inversion centres and each metal atom is coordinated in a distorted square planar geometry by the four symmetry related C atoms from four cyano ligands.

Gas-phase noncovalent functionalization of carbon nanotubes with a Ni(II) tetraaza[14]annulene complex

The noncovalent functionalization of carbon nanotubes (CNTs) with aromatic polyazamacrocyclic compounds, based on π–π-interactions, keeps the intrinsic electronic structure of CNTs totally intact and allows for combining unique properties of the two interacting components. In addition to porphyrins and phthalocyanines, there are other, simpler compounds exhibiting similar properties, potentially useful for photovoltaic, catalytic and electrochemical applications: for example, tetraaza[14]annulenes. Many of them are highly thermally stable, which makes it possible to employ physical vapor deposition for the preparation of macrocycle–nanotube hybrids. One of such compounds is Ni(II) complex of 5,7,12,14-tetramethyldibenzo-1,4,8,11-tetraazacyclotetradeca-3,5,7,10,12,14-hexaene (also called Ni(II)-tetramethyldibenzotetraaza[14]annulene, or NiTMTAA for simplicity). In the present work, we attempted the noncovalent functionalization of both single-walled and multi-walled CNTs with NiTMTAA in the gas phase at two selected temperatures of 220 and 270°C, which does not require the use of organic solvents and therefore can be considered as ecologically friendly. The nanohybrids obtained were characterized by means of scanning and transmission electron microscopy, energy dispersive X-ray, Fourier-transform infrared and Raman spectroscopy, as well as thermogravimetric analysis. An additional insight into the structure of adsorption complexes of NiTMTAA on CNTs was provided from density functional theory and molecular mechanics calculations.

Synthesis, characterization and analytical applications of chelating resin containing orcinol

Synthesis, characterization and analytical applications of chelating resin containing orcinol A chelating resin based on Salicylic acid-Formaldehyde copolymer, containing Orcinol (SFO), has been synthesized and characterized on the basis of Elemental Analysis, Particle Size Distribution, FT-IR Analysis, XRD, SEM and Optical Photographs. The Physico-Chemical properties have been studied. This resin is highly stable in acidic and alkaline solutions and has been studied as a chelating sorbent for heavy metal ions and transition metal ions. The Exchange capacity order is Ni(II) > Cu(II) > Zn(II) > Cd(II) > Pb(II). The effect of nature and concentration of different electrolytes on distribution coefficient (Kd) for metal ions have been investigated. Separation of synthetic mixtures containing Cu(II)-Pb(II), Ni(II)-Cd(II) and Brass constituents has been carried out using a column prepared from the synthesized chelating resin. The developed procedure was also tested for the removal of Cd(II) and Pb(II) from natural water of Purna River near by Navsari, Gujarat, India.

REMOVAL OF METAL IONS FROM AQUEOUS SOLUTIONS USING CROSSLINKED POLYETHYLENE -GTMFJ-POLYSTYRENE SULFONIC ACID ADSORBENT PREPARED BY RADIATION GRAFTING

Crosslinked polyethylene-graft-polystyrene sulfonic acid (PE-g-PSSA) adsorbent prepared by simultaneous radiation induced grafting of styrene/divinyl benzene (DVB) mixture onto low density polyethylene (PE) film followed by sulfonation was investigated for the adsorption of Co(II), Cu(II), Ni(II), Pb(II) and Ag(I) ions from aqueous solutions on batch process basis. The effects of treatment parameters such as contact time, initial metal ion concentration, pH and temperature of the solution, on the adsorption capacity of the membrane were studied. The adsorption capacity of metal ions were found to be strongly dependent on the initial metal ion concentration and pH of adsorption medium and increased in the order of Ni(II)>Co(II)>Cu(II)>Pb(II)>Ag(I). Langmuir isotherm model was found to be more fitting to the adsorption equilibrium data of all metal ions than Freundlich isotherm model. The adsorption kinetics of all tested metal ions was found to follow the pseudo-first order kinetic model. The membrane showed an interesting stability represented by five repeated adsorption/desorption cycles of heavy metal ions without any significant loss in its adsorption capacity. It can be suggested that crosslinked PE-g-PSSA membrane obtained in this work can be effectively used for the adsorption of heavy metal ions from aqueous solutions and the preference order is Ni(II)> Co(II)>Cu(II)>Pb(II)> Ag(I).

Synthesis and characterization of novel Cd(II), Zn(II) and Ni(II) complexes with 2-quinolinecarboxaldehyde selenosemicarbazone. Crystal structure of bis(2-quinolinecarboxaldehyde selenosemicarbazonato)nickel(II)

New complexes of Cd(II), Zn(II) and Ni(II) with 2-quinolinecarboxaldehyde selenosemicarbazone (Hqasesc) were synthesized and structurally characterized. The structure of the ligand, Cd(II) and Zn(II) complexes was determined by NMR and IR spectroscopy, elemental microanalysis and molar conductivity measurements. Both complexes occur in solution in two forms, the major tetrahedral and minor octahedral. In the major Cd(II) complex one qasesc − ligand is coordinated as a tridentate, the fourth coordination site being occupied by acetate, while in the major Zn(II) complex two qasesc − ligands are coordinated as bidentates. In both minor complexes two qasesc − ligands are coordinated as tridentates forming the octahedral geometry around the central metal ion. The only paramagnetic complex in the series is Ni(II) complex for which X-ray structure analysis was performed. The complex has the angularly distorted octahedral geometry with two qasesc − ligands coordinated as tridentates, in a similar way as in the minor complexes of Cd(II) and Zn(II).

Synthesis of [(4,10-diaza-4,10-Ditosylbenzo-12-Crown-4)-4″-Yl] Salicylaldimine and its Metal Complexes

The synthesis of a new Schiff base ligand (HL) formed by the condensation of salicylaldehyde with 4′-amino-4,10-diaza-4,10-ditosylbenzo-12-crown-4 is described. The complexation of this ligand with Ni(II), Cd(II), Cu(II), Co(II) and UO2(VI) was investigated by potentiometric titration. The results indicate that Cu(II), Ni(II), Co(II). Cd(II), UO2(VI) give complexes with the metal-ligand ratio of 1:1. The order of the formation constants of the mononuclear complexes is Ni(II) > Cd(II) > Cu(II) > Co(II) > UO2(VI). Referee I: R. A. Bartsch Referee II: K. Moedritzer

Interactions of sulfates of divalent metals in nickel‐sulfate‐sensitive patients

70 nickel-sensitive subjects who previously gave positive patch test response to 10 microliters of nickel sulfate 0.1 M, were patch tested to 10 microliters of mixed aqueous solutions containing nickel sulfate 0.1 M+magnesium sulfate 0.3 M, nickel sulfate 0.1 M+zinc sulfate, 0.3 and 0.5 M, respectively, nickel sulfate 0.1 M+ manganese sulphate 0.3 and 0.5 M, respectively nickel sulphate 0.1 M+ cadmium sulfate 0.1 and 0.3 M, respectively, nickel sulfate 0.1 M+iron sulfate (III) 0.1 and 0.3 M, respectively, and to 10 microliters of aq. cadmium sulfate 0.1 M, aq. cadmium sulfate 0.3 M, aq. iron sulfate 0.1 M, aq. iron sulfate 0.3 M. The results showed that, whilst sulfates of divalent metals with similar size and redox properties (Mg, Zn and Mn) were able to reduce or to suppress, in a dose-dependent way, the majority (75%) of nickel reactions, those with large radius and different oxidation state(Fe III), generally gave an increase in the reactions. In about 15% of the tested subjects, an increase in all the positive reactions to the mixed solutions was found. The findings seem to demonstrate that in only a majority but not all of nickel sulfate allergic reactions, is Ni(II) able to substitute for divalent ions with similar properties at the ion sites of some proteins. This tendency reproduces the results of experimental systems, in which nickel toxicity and cancerogenity are considered responsible. In contrast, in about 15% of the tested subjects, there was a general enhancement of the reactions. In these cases, either the occurrence of a "hyper-irritable" skin caused by the adopted test system or, more likely, the formation of Ni complexes with different geometries, is hypothesized.

The spectroscopic study of cationic complexes of dithiomalonamide with Ni(II), Pd(II) and Pt(II)

In acid medium dithiomalonamide forms stable, cationic complexes of general formula: M(H 2A) 2X 2 (M is Ni(II), Pd(II), Pt(II); H 2A is H 2NCSCH 2CSNH 2; X is Cl, Br, I, ClO 4). A full vibrational analysis (infrared and Raman spectroscopy) is presented and the influence of the central metal ion and the counterion is investigated. Furthermore some solid state exchange reactions are studied and the thermal behaviour of the complexes is described. Finally the compounds are compared with analogous complexes of dithiooxamide. It seems that the presence of the methylene function between the thioamide groups in dithiomalonamide creates a series of interesting features.