Transition Metal Ion Complexes Research Articles

Synthesis, spectroscopic studies, and antibacterial activities of 14-membered tetraazamacrocyclic complexes of divalent transition metal ions

A new series of macrocyclic complexes, [M(C48H32N4)X2], where M = Co(II), Ni(II), Cu(II), and Zn(II); X = Cl−, NO3 −, CH3COO−, have been synthesized by condensation of 1,8-diaminonaphthalene and benzil, in the presence of divalent metal salts in methanolic medium. The complexes have been characterized by elemental analyses, conductance measurements, magnetic measurements, and electronic, NMR, IR, and MS spectral studies. The low value of molar conductance indicates the presence of non-electrolytes. A distorted octahedral geometry is proposed for the complexes. The metal complexes were also tested for their in vitro antibacterial activities against some bacterial strains and compared with the standard antibiotic Ciprofloxacin. Some tested complexes show good antibacterial activities against some bacterial strains.

Synthesis, Characterization and Spectral Studies of Noble Heterobinuclear Complexes of Transition Metal Ions and their Biological Activity

Some noble heterobinuclear complexes of transition metal ions with bis(salicylaldehyde)malonyl‐dihydrazone in the presence of 5‐nitroindazole Cu(II) / Ni(II)‐ chloride of the type [ML1M‘L2Cl2] or [ML1FeL2Cl2]Cl, where M = Ni(II), Cu(II) and M′ = Mn(II), Co(II), have been prepared. All the complexes have been characterized by IR, UV vis and EPR spectroscopy, elemental analysis, magnetic moment and molar conductance measurement. Spectral studies and magnetic moment measurement in DMF suggest the covalent nature of the complexes, except the [ML1FeL2Cl2]Cl complex which is 1:1 electrolyte. An octahedral geometry is proposed for M‘ and square planer for M for the heterobinuclear complexes. The low value of magnetic moment and overlapping EPR signals are due to spin crossover since both of the metals have unpaired electrons with same molecular symmetry. The lowering of the magnetic moment has been discussed. The biological activity (antifungal and antibacterial) of the represented compounds has been studied.

Potentiometric Study on Complexation of Divalent Transition Metal Ions with Amino Acids and Adenosine 5′-Triphosphate

Potentiometric equilibrium measurements have been performed at 25 °C and in an I = 0.10 M KCl ionic medium for the interaction of nickel(II), copper(II), and zinc(II) with adenosine 5′-triphosphate (ATP) and dicarboxylic amino acids (aa): aspartic acid (Asp) and glutamic acid (Glu). The formation of 1:1 and 1:2 binary and 1:1:1 ternary complexes was inferred from the potentiometric titration curves. It was deduced that adenosine 5′-triphosphate acts as a primary ligand in the ternary complexes involving the dicarboxylic amino acids. The complexation model for systems of adenosine 5′-triphosphate (ATP) and the dicarboxylic amino acids with nickel(II), copper(II), and zinc(II) have been established by the “BEST” software from the potentiometric data. Values of Δ log K (log βMAB − (log βMA + log βMB)) showed that the ternary complexes are less stable than the binary ones, suggesting that no interaction occurred between the ligands in the ternary complexes. The order of the values of the stability constants of all the ternary complexes was M(II)ATP(Asp) > M(II)ATP(Glu), and the same sequence was found in the binary complexes of metal ions with the amino acids. With respect to the metal ions, the stability constants of binary and ternary complexes decrease in the following order: copper(II) > nickel(II) > zinc(II).

Macrocyclic complexes of divalent transition metal ions derived from succinyldihydrazide and diacetyl with their antibacterial studies

Condensation of succinyldihydrazide with diacetyl in the presence of divalent metal ions in the molar ratio of 1 : 1 : 1 resulted in the formation of [M(C8H12N4O2)X2], where M = Co(II), Ni(II), Cu(II), Zn(II), and X = Cl−, , CH3COO−. The complexes have been characterized with the aid of various physicochemical techniques, such as elemental analyses, conductance measurements, electronic, NMR, EPR, and IR spectral studies. On the basis of these studies, a distorted octahedral geometry in which two nitrogens and two carbonyl oxygens were coordinated have been proposed for all the complexes. The complexes were also tested for their in vitro antibacterial activities against some bacterial strains and compared with standard antibiotic Ciprofloxacin. Some of the complexes showed good antibacterial activities against selected bacterial strains.

Stability Constants of Mixed Ligand Complexes of Transition Metal(II) Ions with N‐(2‐Hydroxy‐1‐naphthylidene)‐2,6‐diisopropylaniline as Primary Ligand and N‐(2‐Hydroxybenzylidene)‐2,3‐dimethylaniline as Secondary Ligand

Binary and ternary complexes of the type M‐Y and M‐X‐Y [M = Co(II), Ni(II), Cu(II) and Zn(II); X = N‐(2‐hydroxy‐1‐naphthylidene)‐2,6‐diisopropylaniline and Y = N‐(2‐hydroxybenzylidene)‐2,3‐dimethylaniline] have been examined pH‐metrically at 27±0.5 °C and µ = 0.1 M in 75: 25% (v/v) 1,4‐dioxne‐water medium. The logarithms of the values of stability constants for binary (M‐Y) and for ternary (M‐X‐Y) systems were calculated.

Synthesis, Characterization, and Antimicrobial Activities of Macrocyclic Complexes of Divalent Transition Metal Ions

A novel series of complexes of the type [M(C 36 H 22 N 6 )X 2 ]; where M = Co(II), Ni(II), Cu(II) and Zn(II); X = Cl−, NO3 −, CH3COO−has been synthesized by template condensation of 1,8-diaminonaphthalene and Isatin in the presence of divalent metal salts in methanolic medium. The complexes have been characterized by elemental analyses, conductance and magnetic measurements, UV/Vis, NMR, IR and MS spectroscopy. On the basis of these spectral data, a distorted octahedral geometry may be proposed for all of these complexes. All synthesized macrocyclic complexes were tested for in vitro antimicrobial activities against some pathogenic bacterial and fungal strains.

Low Molecular Weight Compounds with Transition Metals as Free Radical Scavengers and Novel Therapeutic Agents

Molecules able to modulate the levels of endogenous free radicals, such as reactive oxygen species (ROS) and nitric oxide (NO), are of pivotal interest for pharmacological and pharmaceutical sciences because of their potential therapeutic relevance. In fact, ROS and NO, which are normal products of cell metabolism, may play a dual beneficial/deleterious role, depending on local concentration and mode of generation. As such, they have been identified as key pathogenic factors for many inflammatory, vascular dysfunctional and degenerative disorders, including atherosclerosis, hypertension, cardiovascular and neurodegenerative diseases, cancer, diabetes mellitus, and ageing. Therefore, the identification and characterization of novel antioxidant/free radical scavenger molecules may expand the current therapeutic implements for the treatment and prevention of the above diseases. In this perspective, low molecular weight complexes of transition metals with organic scaffolds are viewed and investigated as promising pharmaceutical agents. These complexes take advantage of the known principles of inorganic chemistry, i.e. the ability of transition metals, Fe(II), Co(II), Mn(II) and Ru(II), to bind to and react with NO and/or ROS, to counterbalance excessive endogenous free radical generation in biological systems. Among NO scavengers, representative examples are iron complexes with dithiocarbamates or ruthenium compounds with polyamine-polycarboxylate scaffolds; on the other hand, manganese-based molecules appear effective as ROS scavengers. Of note, Mn(II)-containing molecules, currently under study as ROS scavengers, have major functional similarities to Mn-superoxide dismutase (SOD), a Mn-containing enzyme acting as potent endogenous anti-oxidant. In this article, we briefly summarize the state-of-the-art concerning the chemical and biological properties of transition metal ion complexes with low molecular weight synthetic ligands as ROS/NO scavengers provided with therapeutic effectiveness in animal models of free radical-induced diseases. A proper design of the organic scaffolds may yield metal complexes which are stable in aqueous solution in a wide range of physical and chemical conditions, thus preventing release of the metal and the related toxicity. These metal-based compounds may be viewed as a novel class of drugs helpful to reduce vascular dysfunction and oxidative tissue injury due to derangements of the endogenous generation/catabolism of NO and ROS.

Engineering selectivity into polymer-supported reagents for transition metal ion complex formation

Polymer-supported reagents are widely employed in the complexation of metal ions for applications in separations science, organic reactions (as catalysts) and in analytical chemistry (for processes requiring metal ion enrichment, detection and quantification). Various strategies for the continued development and optimization of polymer-supported reagents have evolved. This review cites ways in which polymer-supported reagents can be designed to achieve improved metal ion selectivities from the viewpoint of the mechanisms involved in the complexation of transition metal ions from aqueous solutions.

Synthesis and spectral study of biologically active macrocyclic complexes of divalent transition metal ions

The condensation reaction of succinyldihydrazide with glyoxal in the presence of divalent metal ions (1: 1: 1) results in the formation of the complexes of type [M(C6H8N4O2)X2], where M = Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and X = Cl−, NO 3 − , CH3COO−. The complexes have been characterized with the aid of elemental analyses, conductance measurements and electronic, NMR, infrared spectral studies. On the basis of these studies, a six-coordinated distorted octahedral geometry in which two nitrogen and two carbonyl oxygen atoms are suitably placed for coordination toward metal ion, has been proposed for all the complexes. The complexes were tested for their in vitro antibacterial activity. Some of the complexes showed remarkable antibacterial activities against some selected bacterial strains.

Potentiometric and conductometric studies of malonyl bis(salicyloylhydrazone) and divalent metal complexes

A series of complexes of divalent transition metal ions with malonyl bis(salicyloylhydrazone) (H4MSH) have been prepared and characterized with the help of conductometric, potentiometric methods. The proton–ligand and metal–ligand stability constants were obtained pH-metrically. The electrical conductivity of solid complexes was measured at 289K. The low molar conductance values observed for these complexes indicate that, they are non-electrolytes. They are soluble to a limited extent in DMF and DMSO. The elemental analyses of the complexes indicate that the complexes have 1:1 and 2:1 (M:L) stoichiometry with the existence of water, chloride, acetone molecules inside the coordination sphere as evidence from the IR spectral studies. Further, the complexes have been formulated by comparing C, H, N & metal analysis data, and UV–visible spectra of the complexes have been discussed. The protonation constants of the ligand and the stability constants of their metal complexes will be evaluated potentiometrically. The stoichiometric ratios of the complexes formed in solution will be evaluated applying the molar ratio (spectrophotometric) method and confirmed conductometrically.

A Novel Tetra(tetrathiafulvalene-Thiacrown Ether)-Substituted Porphyrazine: Synthesis, Electrochemical, and Control Aggregation in Solution by Complexation of Transition-Metal Ions

Synthesis of a novel magnesium porphyrazine 6, peripherally substituted with S 4 crown ether-TTF macrocycles was described. Molecular structure has been fully characterized by 1 H-NMR, IR, MS, and elemental analysis. Crystal structure of the precursor was determined by X-ray crystallography. Their solution electrochemical data showed two reductive and three oxidative processes within a -1.3 V to -1.5 V potential window. UV/Vis spectroscopy and electron paramagnetic resonance (EPR) measurements revealed the formation of a charge-transfer complex between porphyrazine 6 with F 4 TCNQ. UV/vis spectroscopy showed that addition of the transition-metal ions led to dimerization of the porphyrazine complexes.

Antibacterial and antifungal studies of macrocyclic complexes of trivalent transition metal ions with their spectroscopic approach

A new series of complexes of the type [M(C24H16N4)X]X2, where M = Cr(III), Fe(III), and Mn(III), X = Cl−, NO3−, and CH3COO−, has been synthesized by template condensation of 1,8-diaminonaphthalene and glyoxal in the presence of trivalent metal salts in methanolic medium. The complexes have been characterized with the help of elemental analysis, conductance measurements, magnetic measurements, and electronic, NMR, IR, and mass spectral studies. On the basis of these studies, a five-coordinate square pyramidal geometry for all of these complexes has been proposed. All the synthesized metal complexes were also tested for their in vitro antimicrobial activities against some bacterial strains, viz. Bacillus subtilis, Bacillus stearothermophilus (gram-positive bacteria), Escherichia coli, and Pseudomonas putida (gram-negative bacteria), and some fungal strains, viz. Aspergillus flavus and Aspergillus niger. The results obtained were compared with standard antibiotics: chloramphenicol, streptomycin, and the antifungal drug cyclohexamide. Some of the tested complexes showed remarkable antimicrobial activities.

New 14-membered octaazamacrocyclic complexes of divalent transition metal ions with their antimicrobial and spectral studies

A novel series of macrocyclic complexes of the type [M(C(18)H(14)N(10)S(2))X(2)]; where M=Co(II), Ni(II), Cu(II), Zn(II) and Cd(II); X=Cl(-), NO(3)(-), CH(3)COO(-) has been synthesized by [2+2] condensation of thiocarbohydrazide and isatin in the presence of divalent metal salts in methanolic medium. The complexes have been characterized with the help of elemental analyses, conductance measurements, magnetic measurements, electronic, NMR and infrared spectral studies. The low value of molar conductance indicates them to be non-electrolytes. On the basis of various studies a distorted octahedral geometry may be proposed for all of these complexes. These metal complexes were also tested for their in vitro antimicrobial activities against some Gram-positive bacteria viz. Staphylococcus aureus, Bacillus subtilis, and some Gram-negative bacteria Escherichia coli, Pseudomonas aeruginosa and some fungal strains Aspergillus niger, Aspergillus flavus (molds), Candida albicans, Saccharomyces cerevisiae (yeasts). The results obtained were compared with standard antibiotic: Ciprofloxacin and the standard antifungal drug: Amphotericin-B.

A Macrocyclic Bistriazene and its Complexes with Divalent Metal Ions

AbstractThe diazotisation of 2,2′‐diaminotolane with one equivalent of HNO2 yields the macrocyclic bis(tolanetriazene) (tolaneN3H)2 in moderate yield. As shown by the crystal structure determination, the molecule is essentially planar. After deprotonation, the central cavity is suitable for complexation of transition metal ions. In pyridine solution, the anion (tolaneN3)22– is formed, which reacts with the acetates of Co2+ and Ni2+ to the dark red coloured complexes [M((tolaneN3)2)(py)2]. The metal ions are located in the centre of the macrocycles, coordinated by four N atoms of the two triazenide groups. Two pyridine ligands occupy the axial positions, giving the central atoms a distorted octahedral coordination environment. In the temperature range between 30 and 300 K, both complexes show the expected magnetic properties of magnetically isolated ions with nearly fulfilled Curie behaviour and μeff = 3.40 for NiII and 5.19 for CoII, which is in the high spin state.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

A light-emitting memristor

A light-emitting memristor (LEM) is reported based on a metal/mixed conductor/metal structure, where the mixed conductor is the ionic transition metal complex ruthenium(II) tris(bipyridine) with hexafluorophosphate counter ions. The device shows memory effects upon the application of an ac bias, in both current and electroluminescence intensity. The observation of memory in light emission offers the potential for optical read-out of the state of memristive devices.

Potentiometric Investigation on Complexation of Divalent Transition Metal Ions with Some Zwitterionic Buffers and Triazoles

The interaction between the zwitterionic buffers N-(2-acetamido)iminodiacetic acid (ADA), N-[tris(hydroxymethyl)methyl]glycine (tricine), and N,N-bis(2-hydroxyethyl)glycine (bicine) and 1,2,4-triazole (TRZ), 3-mercapto-1,2,4-triazole (TRZSH), and 3-amino-1,2,4-triazole (TRZAM) with the divalent transition metal ions, Cu2+, Ni2+, Zn2+, and Co2+, was investigated in aqueous media at 25 °C and ionic strength I = 0.1 mol·dm−3 NaNO3 using the potentiometric technique. The acid−base properties of the ligands were investigated and discussed. The acidity constants of the ligands were determined and used for determining the stability constants of the different complexes formed in solution. The formation of the different 1:1 and 1:2 binary complexes and 1:1:1 ternary complexes is inferred from the corresponding titration curves. The ternary complex formation was found to occur in a stepwise manner. The order of stability of the complexes formed in solution was investigated in terms of the nature of the zwitterionic buffer, triazole, and metal ion used. The values of Δlog K, percentage of relative stabilization (% R.S.), and log X for the mixed-ligand complexes studied have been evaluated and discussed. The concentration distribution of the various species formed in solution was evaluated. The ionization processes of ADA and TRZAM and their interaction with Cu2+, Ni2+, and Co2+ were studied at different temperatures [(15, 25, 35, and 45) °C], and the corresponding thermodynamic parameters have been evaluated and discussed. In addition, the dissociation constants of ADA and TRZAM and stability constants of their 1:1 binary and 1:1:1 ternary complexes with Ni2+ in various water + dioxane mixtures at 25 °C were determined and discussed.

Mn(II), Co(II), Zn(II), Fe(III) and U (VI) complexes of 2-acetylpyridine 4N-(2-pyridyl) thiosemicarbazone (HAPT); structural, spectroscopic and biological studies

The present work carried out a study on transition metal ion complexes which have been synthesized from 2-acetylpyridine 4 N-(2-pyridyl) thiosemicarbazone (HAPT) 1. These complexes namely [Zn(HAPT)Cl 2] 2, [Mn (HAPT)Cl 2] 3, [Co (HAPT)Cl 2] 4, [Fe(APT)Cl 2(H 2O)] 5 and [UO 2(HAPT)(OAc) 2] 6, were characterized by elemental analysis, spectral (IR, 1H NMR and UV–vis) and magnetic moment measurements. Thermal properties and decomposition kinetics of all compounds are investigated. The interpretation, mathematical analysis and evaluation of kinetic parameters ( E, A, Δ H, Δ S and Δ G) of all thermal decomposition stages have been evaluated using Coats–Redfern equation. The biochemical studies showed that, complexes 3 and 6 have powerful and complete degradation effect on the both DNA and protein. The SOD-like activity exhibited that complex 3 has a strong antioxidative properties. The antibacterial screening demonstrated that, the free ligand (HAPT), complexes 2, 3 and 6 have the maximum and broad activities against Gram-positive and Gram-negative bacterial strains.

4,5-Bis(diphenylphosphinoyl)-1,2,3-triazole ligand: Studies on metal complex formations in liquid–liquid distribution systems

The formation reactions of hydrophobic metal complexes of divalent typical element and transition metal ions with a novel chelating ligand containing N and O donor atoms, 4,5-bis(diphenylphosphinoyl)-1,2,3-triazole (L TH), were investigated by the liquid–liquid distribution method carried out on metal ions between chloroform and aqueous solutions. The liquid–liquid distribution reaction formulae of metal ions via the formation of hydrophobic metal complexes were revealed, along with their equilibrium constants. Three types of hydrophobic mononuclear and binuclear metal complexes distributed into chloroform solutions were found, namely, ML 2 (M = Mg 2+, Zn 2+, Pb 2+; L = L T−), ML 2(HL) (M = Cd 2+, Mn 2+), and M 2L 3(OH) (M = Co 2+, Ni 2+, Cu 2+). Linear free energy relationships were found between the equilibrium constants of the liquid–liquid distribution reactions and the stability constants of 1:1 complexes consisting of a divalent metal ion and a glycinate. These relationships suggest the chelate formation of N,O-coordination with a heterocyclic five-membered ring in the metal complexes with L TH.

Complexation of late transition metal(II) ions (M = Co, Ni, Cu, and Zn) by a macrocyclic thiacrown ether studied by means of electrospray ionization mass spectrometry

Electrospray ionization mass spectrometry (ESI-MS) is used to probe the metal-binding selectivity of a macrocyclic thiacrown ether (C(44)H(32)S(20)) towards Co(II), Ni(II), Cu(II), and Zn(II). In homogeneous 1:1 v/v methanol/dichloromethane solutions, it is found that the thia ligand very selectively binds traces of copper even in the presence of an excess of the other metal ions. The large selectivity is ascribed to the redox-active nature of copper which enables a reduction from Cu(II) to Cu(I), occurring upon ESI-MS, whereas Co(II), Ni(II) and Zn(II) cannot undergo similar redox reactions.

New Approach Toward Fast Response Light‐Emitting Electrochemical Cells Based on Neutral Iridium Complexes via Cation Transport

AbstractHere, a new method is presented to increase the turn‐on time and stability of light‐emitting electrochemical cells (LECs). To this end, a neutral iridium complex (5) containing a pendant Na+ ion that is generally known to have a faster mobility in the solid film than bulky anions is introduced, instead of the classic ionic transition metal complex (iTMC) with counter anion (7). Synthesis, photophysical and electrochemical studies of these complexes are reported. In the device configuration of ITO/5 or 7+PEO (polyethylene oxide) (100–110 nm)/Au, as the voltage increases, complex 5 emits red light at −3.6 V while complex 7 appears at –5.6 V, although their electrochemical and photophysical gap are similar. Furthermore, at constant voltage, –3 V, the turn‐on time of complex 5 was less than 0.5 min, which is a 60‐fold faster turn‐on time compared to the iTMC (7) with PF6−. These results are presumably due to the faster delivery of the Na+ ions to the electrode compared to PF6− ions. Also, the device lifetime of complex 5 exhibits a six‐fold increase in stability and a three‐fold shorter time to reach maximum brightness at constant bias compared to the device made with complex 7.