Spectral, magnetic, thermal, antimicrobial, and eukaryotic DNA studies on acetone [N-(3-hydroxy-2-naphthoyl)]hydrazone complexes

Abstract  

Acetone [N-(3-hydroxy-2-naphthoyl)] hydrazone (H₂AHNH) has been prepared and its structure confirmed by elemental analysis and ¹H NMR spectroscopy. It has been used to produce diverse complexes with Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and U(VI)O₂ ions. The complexes obtained have been investigated by thermal analysis, spectral studies (¹H NMR, IR, UV–visible, ESR), and magnetic measurements. IR spectra suggest that H₂AHNH acts as a bidentate ligand. The electronic spectra of the complexes and their magnetic moments provide information about geometries. The ESR spectra give evidence for the proposed structure and the bonding for some Cu(II) complexes. Thermal decomposition of the Ni(II) and Cu(II) complexes afforded metal oxides as final products. Kinetic data were obtained for each stage of thermal degradation of some of the complexes using the Coats–Redfern method. The formation of complexes in solution was studied pH-metrically and the order of their stability constants (log K) was found to be U(VI)O₂ > Cu(II) > Zn(II) > Ni(II) > Cd(II) > Co(II). Antimicrobial and eukaryotic DNA studies were carried out.     

Synthesis, characterization, and crystal structure of two zinc(II) halide complexes with the symmetrical bidentate Schiff-base ligand (3,4-MeO-ba)2en

Abstract  

In this study two zinc(II) halide complexes with the Schiff-base ligand (3,4-MeO-ba)₂en [N,N′-bis(3,4-dimethoxybenzylidene)ethane-1,2-diamine] have been synthesized and characterized by elemental analyses (CHN), single-crystal X-ray diffraction, Fourier-transform infrared (FT-IR), and ¹H nuclear magnetic resonance (NMR) spectroscopy. The metal-to-ligand ratio was found to be 1:1 within the formula ZnX₂((3,4-MeO-ba)₂en) (X = Br, I). Crystal structure analysis reveals that the coordination geometry around the zinc(II) ions in the two isotypic complexes is distorted tetrahedral. The Schiff-base ligand (3,4-MeO-ba)₂en acts as a chelating ligand and coordinates via two N atoms to the metal center and adopts an (E,E) conformation. The coordination spheres of the metal atoms are completed by the two halide atoms, which are also involved in weak non-classical hydrogen-bonding interactions of the type C–H···X–Zn.     

Manganese(II), cobalts(II) and nickel(II) complexes of tris(2-pyridyl)phosphine and their catalytic activity toward oxidation of tetralin

Abstract  

Monomeric Mn²⁺, Co²⁺ and Ni²⁺ complexes of tris(2-pyridyl)phosphine (P(2-py)₃ were synthesized through the reaction of the hydrated metal(II) chlorides with P(2-py)₃ in near-quantitative yields. The solid-state structure of the Mn complex was determined by single-crystal X-ray diffraction. All three complexes were tested as homogeneous catalysts for the oxidation of tetralin to α-tetralone with tert-butyl hydroperoxide (TBHP) as oxidant. The influences of temperature, solvent, catalyst molar ratio and time of the reaction on the catalyzed reactions were investigated.     

Synthesis,spectral and structural studies of oxovanadium(IV/V) complexes derived from 2-hydroxyacetophenone-3-hydroxy-2-naphthoylhydrazone: polymorphs of oxovanadium(V) complex [VOL(OCH<Subscript>3</Subscript>)]

Abstract  

Oxovanadium(IV/V) complexes of 2-hydroxyacetophenone-3-hydroxy-2-naphthoylhydrazone (H₂L) have been synthesized and characterized. The complexes were characterized by elemental analyses, IR, electronic and EPR spectra. The oxovanadium(V) complex [VOL(OCH₃)] is crystallized in two polymorphic forms, denoted by 1a and 1b, with space groups Pn2₁a and P_[`1] P_{{\bar{1}}} , respectively. Both have distorted square pyramidal structures.     

Two new nickel(II) carboxylates with 3- and 4-aminopyridine: syntheses,structures, and magnetic properties

Abstract  

The synthesis and characterization of two new nickel(II) coordination compounds with 3- and 4-aminopyridine are reported. They were obtained after dissolving Ni(CH₃COO)₂·4H₂O in different solutions of 3- and 4-aminopyridine. The products were characterized magnetically, structurally by single-crystal X-ray diffraction analysis, and spectrally by FT-IR spectroscopy. Dark green crystals of the polymeric coordination complex {[Ni(O₂CCH₃)₂(3-apy)₂]·H₂O} _n were synthesized by the reaction of Ni(CH₃COO)₂·4H₂O and 3-aminopyridine (3-apy). The molecular structure of this complex consists of a zigzag chain in which nickel(II) ions are connected by bridging 3-aminopyridine ligands. The Ni(II) ion is six-coordinated by three oxygen atoms from two acetate ligands, one chelating and one monodenate, and by three nitrogen atoms from three 3-aminopyridine ligands, one terminal and two bridging ones. The blue crystals obtained by the reaction of Ni(CH₃COO)₂·4H₂O with 4-aminopyridine (4-apy) consist of the monomeric complex [Ni(O₂CCH₃)₂(4-apy)₂(H₂O)₂], in which the ligands possess trans geometry around the Ni(II) ion. The interactions including intra- and intermolecular hydrogen bonds in the crystal structures of both complexes are discussed. Magnetic properties of both compounds were studied between 2 and 300 K giving the result of μ _eff = 3.1 BM in the paramagnetic region.     

Interaction of 2-aminopyrimidine with dichloro-[1-alkyl-2-(naphthylazo) imidazole]palladium(II) complexes : Kinetic and mechanistic studies

Background  

The anticancer properties of cisplatin and palladium(II) complexes stem from the ability of the cis-MCl₂ fragment to bind to DNA bases. However, cisplatin also interacts with non-cancer cells, mainly through bonding molecules containing -SH groups, resulting in nephrotoxicity. This has aroused interest in the design of palladium(II) complexes of improved activity and lower toxicity. The reaction of DNA bases with palladium(II) complexes with chelating N,N^/donors of the cis-MCl₂ configuration constitutes a model system that may help explore the mechanism of cisplatin's anticancer activity. Heterocyclic compounds are found widely in nature and are essential to many biochemical processes. Amongst these naturally occurring compounds, the most thoroughly studied is that of pyrimidine. This was one of the factors that encouraged this study into the kinetics and mechanism of the interaction of 2-aminopyrimidine (2-NH₂-Pym) with dichloro-{1-alkyl-2-(α-naphthylazo)imidazole}palladium(II) [Pd(α-NaiR)Cl₂, 1] and dichloro-{1-alkyl-2-(β-naphthylazo)imidazole}palladium(II) [Pd(β-NaiR)Cl₂, 2] complexes where the alkyl R = Me (a), Et (b), or Bz (c).     

Manganese(II), cobalt(II) and nickel(II) complexes with 2-phenyl-3-(benzylamino)-1,2-dihydroquinazolin-4(3H)-one,pseudohalides and some bidentate N-donor ligands

Some mixed ligand complexes of the type [M(L)(en or phen)(X)₂]; where M = Mn(II), Co(II) or Ni(II); L = 2-phenyl-3-(benzylamino)-1,2-dihydroquinazolin-4(3H)-one; en = ethylenediamine, phen = 1,10-phenanthroline; X = N₃ ⁻ or NCS⁻ have been prepared. All the complexes were characterized by physico-chemical, spectroscopic and thermal studies. On the basis of electronic spectra and magnetic susceptibility measurements, an octahedral geometry has been proposed for all the complexes. The phen complexes are thermally more stable than the en complexes. The electrochemical behavior of the Ni(II) complexes showed that the complexes of phen are reduced at more positive potential compared to the corresponding en complexes.     

Dioxygen affinities of Schiff base cobalt(II) complexes with aza-crown or morpholino pendants

Abstract  

Schiff base Co(II) complexes, CoL₂¹–CoL₂⁶ with aza-crown or morpholino pendants were synthesized. The oxygenation constants (KO₂) of these complexes in MeOCH₂CH₂OMe solution were measured over the range of −5 to 25 °C, and the thermodynamic parameters (∆H ⁰, ∆S ⁰) for oxygenation were calculated based on these KO₂ values. The effects of different substituents on the Schiff base ligand with respect to the modulation of O₂-binding capability were explored. The results indicate that the dioxygen affinities of the Co(II) complexes are much more enhanced by aza-crown pendants than that by morpholino pendants, and the O₂-binding capabilities of the aza-crown pendants complexes can also be enhanced by adding Na⁺ cations.     

Copper(II) and nickel(II) complexes of 2-formylpyridine 3-piperidinyl-, 3-hexamethyleneiminyl- and 3-azabicyclo[3.2.2]nonylthiosemicarbazones

Summary Copper(II) and nickel(II) complexes of 2-formylpyridine 3-piperidinyl-, 3-hexamethyleneiminyl- and 3-azabicyclo-[3.2.2]nonylthiosemicarbazones were prepared and characterized spectroscopically. ¹H and ¹³C n.m.r. spectra of the thiosemicarbazones and a diamagnetic nickel(II) complex are reported, together with i.r., electronic and e.s.r. spectra of the metal complexes. The thiosemicarbazones and their copper(II) and nickel(II) complexes exhibit considerable growth inhibitory activity against Paecilomyces variotii, but show minimal activity against Aspergillus niger.     

Synthesis,characterization, and biological activity of some transition metal complexes with Schiff base ligands derived from 4-amino-5-phenyl-4<Emphasis Type="Italic">H</Emphasis>-1,2,4-triazole-3-thiol and salicaldehyde

Abstract  

The coordination behaviour of a Schiff base with SNO donation sites, derived from condensation of 4-amino-5-phenyl-4H-1,2,4-triazole-3-thiol and salicaldehyde, towards some bi- and trivalent metal ions, namely Cr(III), Mn(II), Fe(III), Co(II) (Cl, ClO₄), Ni(II) (Cl, ClO₄), Cu(II), and Zn(II), is reported. The metal complexes were characterized on the basis of elemental analysis, IR, ¹H NMR, solid reflectance, magnetic moment, molar conductance, and thermal analyses (TG, DTG, and DTA). The ionization constant of the Schiff base under investigation and the stability constants of its metal chelates were calculated pH-metrically at 25 °C and ionic strength μ = 0.1 M in 50% (v/v) ethanol–water mixture. The chelates were found to have octahedral (Mn(II)), trigonal bipyramidal (Co(II), Ni(II), Zn(II)), and tetrahedral (Cr(III), Fe(III), and Cu(II)) structures. The ligand and its binary chelates were subjected to thermal analyses and the different thermodynamic activation parameters were calculated from their corresponding DTG curves to throw more light on the nature of changes accompanying the thermal decomposition process of these compounds. The free Schiff base ligand and its metal complexes were tested in vitro against Aspergillus flavus, Candida albicans, C. tropicalis, and A. niger fungi and Bacillus subtilis and Escherichia coli bacteria in order to assess their antimicrobial potential. The results indicate that the ligand and its metal complexes possess antimicrobial properties.     

Equilibrium studies on complex formation reactions of dichlorido[(R,R)-trans-1,2-diaminocyclohexane]platinum(II) complex with ligands of biological significance

Abstract  

The hydrolysis and complex formation equilibria of [Pt(dach)(H₂O)₂]²⁺, where dach is (R,R)-trans-1,2-diaminocyclohexane, with some sulfur- and nitrogen-bonding ligands, such as l-methionine, glutathione, inosine, inosine-5′-monophosphate, and guanosine-5′-monophosphate, were studied in aqueous 0.10 M NaClO₄ solution at 298 K by potentiometric titrations. The experimentally determined pK _a values for the studied diaqua complex were 6.00 and 10.03, respectively. The acid dissociation constants of the ligands were also determined. The stoichiometry and stability constants of the formed complexes are reported, as well as the concentration distribution of the various complex species evaluated as a function of pH. In all studied systems, species with one coordinated molecule of ligand were detected. However, only in systems with l-methionine and inosine, complexes with two molecules of ligand directly coordinated to the Pt(II) ion were found. The results also show that glutathione formed the most stable complexes. These results could contribute to better understanding of the interactions between Pt(II) complexes and biologically significant molecules.     

Synthesis,spectral, thermal,solid state d.c. electrical conductivity and biological studies of Co(II), Ni(II) and Cu(II) complexes with 3-substituted-4-amino (indole-3-aldehydo)-5-mercapto-1,2,4-triazole Schiff bases

A series of cobalt(II), nickel(II) and copper(II) complexes have been synthesized with Schiff bases derived from 3-substituted-4-amino-5-mercapto-1,2,4-triazole and indole-3-aldehyde in ethanol. These complexes have been characterized by elemental analyses, magnetic, spectroscopic (IR, UV-Vis, H-NMR, ESR, FAB-mass), thermal, electrochemical (CV) and solid state d.c. electrical conductivity studies. The elemental analyses confirm 1 : 2 stoichiometry of the type ML₂·2H₂O (M = Co/Ni) and ML₂ (M=Cu). The complexes are colored solids and non-electrolytes in DMF and DMSO. Magnetic and spectral data suggest octahedral geometry for Co(II) and Ni(II) complexes and square-planar geometry for Cu(II) complexes. The presence of coordinated water in Co(II) and Ni(II) complexes was confirmed by thermal and IR data of the complexes. The complexes are insoluble in water and common organic solvents and decompose at higher temperature. All these ligands and their complexes have also been screened for antibacterial (Bacillus cereus, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa) and antifungal activities (Aspergillus niger and Aspergillus fumigates) by the cup plate method.     

Synthesis,spectral characterization,and antimicrobial activity of copper(II), cobalt(II), and nickel(II) complexes of 3-formylchromoniminopropylsilatrane

A new series of Cu(II), Ni(II), and Co(II) complexes have been synthesized from 3-formylchromoniminopropylsilatrane (C₁₉H₂₄O₅N₂Si) (2) and 3-formylchromoniminopropyltriethoxysilane (1). Silatrane ligand (C₁₉H₂₄O₅N₂Si) (2) has been synthesized by the reaction between 3-aminopropyltriethoxysilane and 3-formylchromone followed by a treatment with triethanolamine. The nature of bonding and the geometry of the complexes have been deduced from elemental analyses, magnetic susceptibility, infrared, electronic, ¹H NMR, ¹³C NMR, and ESR spectral studies. The electronic absorption spectra and magnetic susceptibility measurements of the complexes indicate square planar geometry for Cu(II) and Ni(II) and tetrahedral geometry for Co(II). The redox behavior of copper complexes was studied by cyclic voltammetry. The biological activity of the ligand and metal complexes has been studied on Klebsiella pneumoniae, Staphylococcus aureus, Escherichia Coli, and Bacillus subtilis by the well diffusion method using acetonitrile as solvent. The zone of inhibition values were measured at 37°C for 24 h. Antimicrobial screening tests show better results for the metal complexes than the ligand.     

Synthesis,crystal structures,and biological activities of silver(I) and cobalt(II) complexes with an azole derivative ligand

Abstract  Two new complexes, [Ag(L)₂](NO₃) · (H₂O) (1) and [Co(L)₂Cl₂] (2) [L = 1-(imidazol-1-yl-methyl)-benzotriazole], have been synthesized and structurally characterized by X-ray diffraction techniques. In complex (1), the Ag(I) atom adopts a linear coordination geometry involving the imidazole nitrogens of two ligands. The [Ag(L)₂] units are developed into a three-dimensional structure by intermolecular hydrogen bonds, π–π interactions, and Ag···O interactions. In complex (2), the Co(II) atom is in a distorted tetrahedral environment with two imidazole nitrogens and two chloride ligands. The [Co(L)₂Cl₂] units are assembled into a three-dimensional structure by intermolecular hydrogen bonds and π–π interactions. The bioactivities of both complexes have been studied, and the results indicate that complex (1) exhibits excellent radical-scavenging (RS) and fungicidal (FG) activities while complex (2) only has weak fungicidal activity. Graphical abstracts   Synthesis, crystal structures and biological activities of silver(I) and cobalt(II) complexes with an azole derivative ligand. Chang-Xue An, Xin-Li Han, Peng-Bang Wang, Zhi-Hui Zhang*, Hai-Ke Zhang and Zhi-Jin Fan Two novel complexes, [Ag(L)₂](NO₃) · (H₂O) (1) and [Co(L)₂Cl₂] (2) [L = 1-(imidazol-1-yl-methyl)-benzotriazole] have been synthesized and structurally characterized. The molecules of complexes (1) and (2) are extended to 2-D and 3-D structures by the non-coordinated bonds. The ligand and complex (1) exhibit excellent radical-scavenging and fungicidal activities. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Copper(II) complexes with N-(2-hydroxyethyl)-2-iminodiacetic acid and imidazoles: crystal structure,spectroscopic studies and superoxide dismutase activity

Abstract  

Two new copper(II) complexes, [Cu(Hhida)(BenzImH)]·H₂O (1) and [Cu(Hhida)(EtImH)]·2H₂O (2) have been synthesized by the interaction of basic copper carbonate with N-(2-hydroxyethyl)-2-aminodiacetic acid (Hhida²⁻) and benzimidazole (BenzImH) or (2-ethylimidazole (EtImH)). The structures of both complexes were studied by single crystal X-ray diffraction. The geometry around the copper(II) atom can be best described as distorted square pyramidal as indicated by the value of the trigonal index τ = 0.32 for (1) and 0.21 for (2). Spectroscopic and electrochemical studies were performed in order to correlate structural features of the complexes with their superoxide scavenger activity. The ability of the complexes to scavenge superoxide anions was also evaluated.     

Synthesis,characterization and biological activity studies of octahedral nickel(II) complexes

Abstract  

Three nickel(II) complexes, namely [Ni(BH)₃](H₂O)(NO₃)(ClO₄) 1, [Ni(BH)₂(NO₃)₂] 2 and [Ni(BH)(Tren)](ClO₄)₂ 3 (BH = Benzoylhydrazine, Tren = Tris(2-aminoethyl)amine) have been synthesized and characterized by physico-chemical techniques. X-ray crystallographic analysis shows the nickel to be six-coordinated in these complexes. The complexes are efficient catalysts for the dismutation of superoxide in alkaline DMSO-NBT assays. The IC₅₀ values are 74,108 and 105 μM for 1, 2 and 3, respectively.     

Red electrophosphorescent platinum(II) quinolinolate complexes

Abstract  

Luminescent organoplatinum complexes featuring 8-quinolinolates as chelating ligands have been synthesized and characterized. Substitution of the quinolinolate ligand has been achieved in the 5 position, where benzoyl substituents were introduced by reacting 8-hydroxyquinoline and the corresponding benzoyl chloride in a Friedel–Crafts acylation. The resulting complexes, κ²(N,C²)-(2-(4-tert-butylphenyl)pyridine)-κ²(N,O)-(5-(4-tert-butylphenyl)(8-quinolinolato-5-yl)methanone)platinum(II) and κ²(N,C²)-(3-hexyloxy-2-phenylpyridine)-κ²(N,O)-((8-quinolinolato-5-yl)phenylmethanone)platinum(II), have been investigated by nuclear magnetic resonance and infrared spectroscopy, matrix-assisted laser desorption ionization time-of-flight mass spectrometry, X-ray analysis, thermal analysis, cyclic voltammetry, UV–vis absorption spectroscopy, and luminescence measurements in solution and in the solid state. The solid-state structures of the complexes were found to be dominated by π–π intermolecular interactions. Organic light-emitting devices based on the complexes and a matching host material gave red to near-infrared electroluminescence with low-onset voltages (4–5 V) and continuous wave luminance intensities exceeding 500 cd/m².     

Spectral,magnetic, thermal,antimicrobial, and eukaryotic DNA studies on acetone [<Emphasis Type="Italic">N</Emphasis>-(3-hydroxy-2-naphthoyl)]hydrazone complexes

Abstract  Acetone [N-(3-hydroxy-2-naphthoyl)] hydrazone (H₂AHNH) has been prepared and its structure confirmed by elemental analysis and ¹H NMR spectroscopy. It has been used to produce diverse complexes with Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and U(VI)O₂ ions. The complexes obtained have been investigated by thermal analysis, spectral studies (¹H NMR, IR, UV–visible, ESR), and magnetic measurements. IR spectra suggest that H₂AHNH acts as a bidentate ligand. The electronic spectra of the complexes and their magnetic moments provide information about geometries. The ESR spectra give evidence for the proposed structure and the bonding for some Cu(II) complexes. Thermal decomposition of the Ni(II) and Cu(II) complexes afforded metal oxides as final products. Kinetic data were obtained for each stage of thermal degradation of some of the complexes using the Coats–Redfern method. The formation of complexes in solution was studied pH-metrically and the order of their stability constants (log K) was found to be U(VI)O₂ > Cu(II) > Zn(II) > Ni(II) > Cd(II) > Co(II). Antimicrobial and eukaryotic DNA studies were carried out. Graphical abstract        

Synthesis, characterization and thermal properties of cobalt(II), nickel(II) and copper(II) complexes of 2,6-bis(3,4,5-trimethyl-N-pyrazolyl)pyridine): the crystal structure of [Co(btmpp)(H2O)2(NO3)]NO3

Co(II), Ni(II) and Cu(II) nitrate complexes with btmpp, namely ([Co(btmpp)(H₂O)₂(NO₃)]NO₃ (1), [Ni(btmpp)(H₂O)(NO₃)]NO₃ (2) and [Cu(btmpp)(MeOH)(NO₃)]NO₃ (3), where btmpp = 2,6-bis(3,4,5-trimethyl-N-pyrazolyl)pyridine), have been synthesized and characterized by physicochemical and spectroscopic methods. The crystal structure of complex 1 has been determined by single crystal diffraction at 100K. In all the complexes, btmpp is coordinated in a tridentate mode through its nitrogen atoms. One of the nitrates in complex 1 is terminally bonded to the metal center through the oxygen atom, whereas the other one is out of the coordination sphere. The Co(II) atom in complex 1 is hexa-coordinated with a CoN₃O₃ distorted octahedral environment. Decomposition of three complexes was analyzed thermogravimetrically. All three complexes decompose similar to explosive material.     

Synthesis,crystal structures and yeast RNA-binding properties of copper(II) and nickel(II) complexes with a bidentate Schiff base

Abstract  

Trans-CuL₂ and cis-NiL₂ (L = 1-((furan-2-yl)methylene)-4-phenylthiosemicarbazide) were synthesized and characterized by physico-chemical and spectroscopic methods. Their X-ray crystal structures were determined. The complexes contain the same bidentate Schiff base ligand, but with different cis-NiN₂S₂ and trans-CuN₂S₂ square-planar coordination geometries. Three-dimensional supramolecular networks were formed through “face to face” π–π conjugated systems between phenyl and furan rings. The interactions with yeast RNA (yRNA) were investigated by UV spectra and electrochemical methods, which showed that the complexes intercalated into yRNA. The bonding of trans-CuL₂ to yRNA is the stronger of the two, suggesting that the trans geometry is more favorable for interaction with RNA.