Palladium(II) Complexes of N-(2-Thienylmethylidene)aniline Derivatives

Coordination reactions of N-(2-thienylmethylidene)aniline derivatives, L, with PdCl₂ or [PdCl₄]^2? in ethanol yield stable complexes of the type trans-(L)₂PdCl₂ with the azomethine nitrogen atoms as σ donors. These are not readily convertible to othor-palladated complexes. An X-ray crystallographic study of the complex (L₂)₂PdCl₂ reveals a centrosymmetric geometry. The structure is in the triclinic space group $ {\rm P}\bar 1 $ with a = 8.633(2) Å, b = 12.759(3) Å, c = 8.398(2) Å, α = 96.65(5)°, β = 111.47(5)*, γ= 101.28(6)°, and Z = 1. The final R factor is 0.043 (Rw = 0.044) for 2396 observed reflections. There is no real bonding between a thiophene sulfur atom and a central palladium ion. However, a long distance interaction between S and Pd does exist.     

Synthesis,spectroscopic, biological,and theoretical studies of new complexes from (E)-3-(2-(5, 6- diphenyl-1,2,4- triazin-3- yl)hydrazono)butan-2- one oxime

New mononuclear Fe (III), Cu (II), Ag (I), ZrO ( IV) and UO₂(VI) complexes were synthesized by the reaction of metal ions with (E)-3-(2-(5, 6- diphenyl-1,2,4- triazin-3- yl)hydrazono)butan-2- one oxime. The structures of the metal complexes were characterized using analytical, spectral (infrared, electronic, ¹H NMR, electron spin resonance (ESR), and mass), magnetic moment, molar conductance, thermal gravimetric analysis, and powder X-ray diffraction (XRD) measurements. All complexes have octahedral geometries except the Cu (II) complex, which has square planar geometry, and the UO₂(VI) complex, in which the coordination number is seven. The ligand acts as a (neutral, monoanionic or dianionic) tridentate with N₂O coordinating sites: N-azomethine, N-triazine, and O-oxime. Fluorescence spectral studies were carried out in solid state and in dimethylformamide (DMF). The kinetic parameters of the thermal decomposition stages were calculated using Coats–Redfern equations. The morphological structures of the ligand and some complexes were determined using XRD. The molecular orbital calculations were carried out for the ligand and metal complexes using the Hyperchem 7.52 program on the basis of the PM3 level. The antimicrobial activities of the ligand and its complexes were investigated towards the microorganisms S. aureus and B. subtilis as Gram-positive bacteria, S. typhimurium and E. coli as Gram-negative bacteria, C. albicans, and A. fumigatus. The ligand and its complexes showed antitumor activity against Hep G-2 cell lines, where Cu (II) and Ag (I) complexes seem to be promising as they showed IC₅₀ values that are lower than and comparable to that of the antitumor drug doxorubicin.     

Dicoordinate copper(I) silanechalcogenolates

The copper silanechalcogenolates tBu3PCuESiPh3 (1, E = O; 2, E = S; 3, E = Se) were prepared from the reaction of [tBu3PCu(CH3CN)3]BF4 with [Ph3SiELi(THF)2]2 in acetonitrile. The compounds were obtained as colorless, crystalline, but thermally labile solids. X-ray crystallography shows that complexes 1-3 are monomeric in the solid state with no Cu...Cu interactions. The Cu atoms have either a linear or a near-linear coordination geometry in all three complexes. Interestingly, the O atom in complex 1 is also linear, which is in contrast to the highly bent S (2) and Se analogues (3). Density functional theory calculations suggest that both the linear geometry of 1 and an associated extremely short Cu-O distance [1.769(4) A] are not the result of pi delocalization but are the result of a fine balance of electrostatic interaction and Pauli repulsion.     

Synthesis,structure and antimicrobial study of two new copper(II) complexes derived from N-(3-aminopropyl) benzylamine ligand (apba) and N-salicylidene-apba

Two new copper(II) complexes were synthesized by reaction of N-(3-aminopropyl)benzylamine (L1: apba, for complex 1) and N-salicylidene-apba (L2: for complex 2) with Cu²⁺. Crystals of complex 1 were orthorhombic, space group pccn, with a?=?15.2149(10), b?=?25.0071(16), c?=?7.6280(5)?Å and α?=?β?=?γ?=?90°. Complex 2 crystals were monoclinic, space group P2₁/c, with a?=?8.688(6), b?=?12.812(9), c?=?16.022(11)?Å and β?=?99.241(10)°. Structures of the two complexes were centro-symmetric and both Cu(II) atoms were four coordinate with a distorted square-planar geometry. The toxicity of the complexes was evaluated by testing antimicrobial activity against bacterial strands.     

Spectral and Thermal Studies of Some New Metal Complexes Derived from N-[(Phenylamino)Thioxomethyl] Hydrazinocarbonyl Methyl Pyridinium Chloride (PTHMPC)

New metal complexes derived from the reaction of N-[(phenylamino)thioxomethyl] hydrazino carbonyl methyl pyridinium chloride (H₂L; PTHMPC) with some metal salts of the general formula MX₂ [(X = Cl^? and/or CH₃COO^?; M = Cd(II), UO₂(II), Mn(II) and Zr(IV)] were synthesized and characterized by elemental analyses, spectral analyses (IR, UV-vis., ¹H NMR), thermal analyses (TGA, DTG), and conductance and magnetic measurements. The results showed that the ligand exists in metal complexes either in the keto form or in the enol form. Moreover, the IR spectral data suggest that the acetate ion behaves in a monodentate manner. Semi-empirical calculations ZINDO/1, PM3, and AM1 have been used to study the molecular geometry and the harmonic vibrational spectra of the ligand and its metal complexes with the purpose of assisting the experimental assignment of the complexes. Generally, there is an agreement between the observed and the calculated spectra. Finally, the thermodynamic parameters (ΔE*, ΔH, ΔG, and ΔS) have been calculated from the data of thermal analyses (TGA and DTG).

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

Synthesis and structure of dithizonato complexes of antimony(III), copper(II) and tin(IV)

In view of the important role of dithizone in trace metal analyses, new structural aspects and approaches used to probe metal complexes of dithizone are of interest. Three X-ray diffraction structures are reported, dichloridobis(dithizonato)tin(IV), dichlorido(dithizonato)antimony(III), and bis(dithizonato)copper(II). During synthesis of the tin complex, auto-oxidation of Sn^IICl₂ to Sn^IV occurred without chloride liberation. The Sb^III complex revealed a unique distorted see-saw geometry which is, as for the other complexes, predicted by DFT molecular orbital calculations. The computed products of the lowest energy reactions are in agreement with experimentally obtained reaction products, which, together with molecular orbital renderings serve as a tool toward prediction of modes of coordination in these complexes. The S–M–N bond angle in the five-membered coordination ring shows a linear relationship with the corresponding metal ionic radii.     

Synthesis, structure, and spatial arrangement of Si-substituted N-(dimethylsilylmethyl)imides

The synthesis of N-(chlorodimethylsilylmethyl)succinimide and N-(chlorodimethylsilylmethyl)-glutarimide by the reaction of the corresponding N-trimethylsilylimides with chlorodimethylsilane and by the reaction of unsubstituted imides with a mixture of hexamethyldisilazane with dimethylchloromethylchlorosilane is described. The formation of N-(chlorodimethylsilylmethyl)succinimide is followed by substitution by the silicon atom, which, depending on the reagent ratio, provides N-(dimethylsuccinimidomethyl)succinimide as the major or minor product. ¹H, ¹³C, and ²⁹Si NMR spectroscopy and X-ray diffraction analysis showed that the silicon atom in N-(chlorodimethylsilylmethyl)glutarimide is five-coordinate. By contrast, in N-(chlorodimethylsilylmethyl)succinimide and N-(dimethylsuccinimidomethyl)succinimide, according to NMR and X-ray diffraction data, the silicon atom is four-coordinate. Quantumchemical calculations by the AM1 method show that the molecular conformations of N-(chlorodimethylsilylmethyl)imides containing an intramolecular OSi bond are not energetically most favorable in the gas phase.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 10, 2004, pp. 1617–1623.Original Russian Text Copyright © 2004 by Pogozhikh, Ovchinnikov, Kramarova, Negrebetskii, Shipov, Albanov, Voronkov, Pestunovich, Baukov.This revised version was published online in April 2005 with a corrected cover date.     

An IR Study of the Structure of New Thiocarboxylic Acid N-(1-Arenesulfonamido-2-phenyl-2,2-dichloroethyl- and -2,2,2-trichloroethyl)amides

An IR study of thiocarboxylic acid N-(1-arenesulfonamido-2-phenyl-2,2-dichloroethyl- and -2,2,2-trichloroethyl)amides revealed intramolecular hydrogen bonds whose formation is accompanied by electron density delocalization and stabilization of conformations with quasiaromatic rings. Formation of chelate species was confirmed by AM1 calculations.     

Synthesis,characterization, DFT calculations and antimicrobial activity of pentagonal-bipyramidal Zn(II) and Cd(II) complexes with 2,6-diacetylpyridine-bis(trimethylammoniumacetohydrazone)

Isothiocyanate complexes of Zn(II) and Cd(II) with the condensation product of 2,6-diacetylpyridine and trimethylammoniumacetohydrazide (Girard’s T reagent) were synthesized, characterized, and their antimicrobial activities were evaluated. The structures of the complexes were determined by elemental analysis, IR, and NMR spectroscopy. The crystal structure of the Zn(II) complex was also determined. Quantum-chemical calculations of the geometry and total energy of isomers of 2,6-diacetylpyridine-bis(trimethylammoniumacetohydrazone) were performed in vacuum and methanol solution, with the aim to explain conformational behavior and E/Z isomerism of this compound. DFT calculations of the molecular structures and the relative stabilities of linkage isomers of the Cd(II) complex showed that the isomer with N–Cd–N coordination of SCN^? is the most stable. Complexes of Zn(II) and Cd(II) exhibited low to moderate activity against the tested microbial strains.     

Electrochemical Properties of Crown-Containing N-(Thio)phosphoryl(thio)ureas and Their Complexes with 3d Transition Metals

The electrochemical behavior of crown-containing N-(thio)phosphoryl(thio)ureas and their complexes with 3d transition metals was studied by dc voltammetry on a graphite electrode in acetone. Crown-containing N-(thio)phosphoryl(thio)ureas are not reduced but are oxidized on solid electrodes in the examined range of potentials; the electrons are transferred via the (thio)urea group. Electrooxidation of macrocyclic Co(II), Ni(II), and Cu(II) complexes probably occurs via formation of M(III) complex species. Electroreduction of these metal complexes involves stepwise electron transfer, with the oxidation state of the metal atom decreasing to 0, followed by dissociation of the electrochemical reaction products.     

Bis -(3,5-dimethyl-pyrazolyl-1-methyl)-(3-phosphanyl-propyl)-amine complexes of copper(II), nickel(II), and cobalt(II)

A series of Cu(II), Co(II), and Ni(II) complexes of bis-(3,5-dimethyl-pyrazolyl-1-methyl)-(3-phosphanyl-propyl)-amine C₁₅H₂₆N₅P (1), prepared from 3-aminopropylphosphine and 1-hydroxymethyl-3,5-dimethylpyrazole were characterized. The nature of bonding and the geometry of the complexes have been deduced from elemental analysis, infrared, electronic, ¹H NMR, ³¹P NMR spectra, magnetic susceptibility, and conductivity measurements. The studies indicate octahedral geometry for nickel complex and square pyramidal geometry for copper and cobalt complexes. The EPR spectra of copper complex in acetonitrile at 300 K and 77 K were recorded. Biological activities of the ligand and metal complexes have been studied on Staphylococcus aureus, Escherichia coli, Aspergillus niger, and Aspergillus flavus by well-diffusion method. The zone of inhibition values were measured at 37°C for a period of 24 h. The electrochemical behavior of copper complexes was studied by cyclic voltammetry. Catalytic study indicates the copper complex has efficient catalytic activity in oxidation of amitriptyline.     

DNA-binding and cleavage studies of chiral Mn(III) salen complexes

Chiral bridge-substituted manganese(III) complexes of N,N′-bis-(2-hydroxynaphthalene-1-carbaldehyde)-(1R,2R)-(−)-diaminocyclohexane and N,N′-bis-(2-hydroxynaphthalene-1-carbaldehyde)-(1S,2S)-(+)-diaminocyclohexane have been synthesized. The interaction of these complexes with calf thymus DNA(CT-DNA) was investigated by spectroscopic, thermal denaturation studies, circular dichroism (CD), and viscosity measurements. Results of spectroscopic and viscosity measurements suggest that the two complexes bind to DNA via an intercalative mode and display enantioselectivity. These Mn(III) complexes have been found to promote the cleavage of plasmid DNA pBR322 in the presence of H₂O₂.     

A Schiff base N-(2-hydroxylacetophenone)-3-oxapentane-1,5-diamine and its copper(II) coordination polymer: synthesis,crystal structure,antioxidation, and DNA-binding properties

A Schiff base, N-(2-hydroxylacetophenone)-3-oxapentane-1,5-diamine (HL) and its Cu(II) coordination polymer, [Cu(L)(NO₃)] _n , have been synthesized and characterized. [Cu(L)(NO₃)] _n is a 1?:?1 (Cu?:?L) polymer, in which copper is six-coordinate with distorted octahedral geometry. The polymer has a 1-D infinite chain structure in which coppers are bridged by a single nitrate. The interaction of HL and complex with calf thymus DNA (CT-DNA) has been investigated; the linear Stern–Volmer quenching constants (K _SV) suggest that the two compounds bind to DNA via intercalation. The binding affinity of complex was higher than HL. Antioxidant assay in vitro shows that the Cu(II) complex possesses significant antioxidant activities.     

Stereoisomerism of N-(1-Propenyl)thiobenzamide

A prototropic rearrangement of N-prop-2-enylbenzocarbothioamide afforded two stereoisomeric N-prop-1-enylbenzocarbothioamides (IIa, b) isolated as individual compounds. The stereoisomerism is due to hindered rotation around thioamide bond C(S)-N and also to -diastereoisomerism. The configuration of the isolated isomers was investigated by IR spectroscopy, AM1 and PM3 methods. In the molecules occurs the p,-conjugation with participation of nitrogen atom and multiple bonds resulting in formation of a united delocalized MO in the planar fragment C(S)-NC = C.     

Coordination modes of two flexidentate salicylaldimine ligands derived from N-(3-aminopropyl)morpholine toward zinc and copper

Two flexidentate Schiff-base ligands condensed from salicylaldehyde or 5-chlorosalicylaldehyde with N-(3-aminopropyl)morpholine were prepared in situ and reacted with Zn(II) and Cu(II) salts. Upon complexation, the Schiff bases underwent deprotonation at hydroxyl to act as mono-anionic ligands. When a ligand?:?metal ratio of 2?:?1 was applied, the deprotonated Schiff bases coordinated metal ions through phenolate and imine in a square-planar or tetrahedral geometry. In contrast, 5-chlorosalicylaldimine reacted with the metal ions in a 1?:?1 ratio to form complexes wherein morpholine nitrogen also participates in an N,N,O-tridentate coordination mode. The structures of the complexes were characterized by spectroscopic methods and single-crystal X-ray diffraction.     

Molecular Structure of Complexes with Bifurcated Hydrogen Bond: I. N-(4-Methyl-2-nitrophenyl)acetamide

According to the results of HF/6-31G* and B3LYP/6-31G* nonempirical calculations, N-(4-methyl- 2-nitrophenyl)acetamide in the synperiplanar and antiperiplanar conformations gives stable complexes with protophilic solvents, which are stabilized by bifurcated (three-center) hydrogen bond. The complexes are characterized by (1) opposite variations of the interatomic distances and angles corresponding to intra- and intermolecular components of the bifurcated hydrogen bond, (2) extension of the intramolecular component and a more pronounced shortening of the intermolecular component with increase in the strength of the three-center H-complex, and (3) nonlinear and nonmonotonic relation between the NH stretching vibration frequency and the energy of complex formation.     

A new pyrimidine-derived ligand,N-pyrimidine oxalamic acid,and its Cu(II), Co(II), Mn(II), Ni(II), Zn(II), Cd(II), and Pd(II) complexes: synthesis,characterization, electrochemical properties,and biological activity

A new heterocyclic compound N-(5-benzoyl-2-oxo-4-phenyl-2H-pyrimidin-1-yl)-oxalamic acid has been synthesized from N-amino pyrimidine-2-one and oxalylchloride. Bis-chelate complexes of the ligand were prepared from acetate/chloride salts of Cu(II), Co(II), Mn(II), Ni(II), Zn(II), Cd(II), and Pd(II) in methanol. The structures of the ligand and its metal complexes were characterized by microanalyses, IR, AAS, NMR, API-ES, UV-Vis spectroscopy, magnetic susceptibility, and thermogravimetric analyses. An octahedral geometry has been suggested for all the complexes, except for Pd(II) complex, in which the metal center is square planar. Each ligand binds using C(2)=O, HN, and carboxylate. The cyclic voltammograms of the ligand and the complexes are also discussed. The new synthesized compounds were evaluated for antimicrobial activities against Gram-positive, Gram-negative bacteria and fungi using the microdilution procedure. The Cu(II) complex displayed selective and effective antibacterial activity against one Gram-positive spore-forming bacterium (Bacillus cereus ATCC 7064), two Gram-positive bacteria (Staphylococcus aureus ATCC 6538 and S. aureus ATCC 25923) at 40–80 µg mL^?1, but poor activity against Candida species. The Cu(II) complex might be a new antibacterial agent against Gram-positive bacteria.     

Synthesis and complex formation of 2-ammoethylthioacet(N-2-pyridylmethyl)amide

Summary A new ligand, 2-aminoethylthioacet(N-2-pyridylmethyl)amide was synthesized. The complex formation of the ligand with Cu^II, Co^II and Co^III ions and that of the carbobenzoxy derivative of the ligand with Cu^II ions has been investigated. Structures are proposed for all complexes isolated and the factors influencing metal-sulphur bond formation in the complexes discussed.     

Molecular structures of antitumor active Pd(II) and Pt(II) complexes of N,N-donor benzimidazole methyl ester

[MLCl₂]?·?zH₂O?·?C₂H₅OH (L?=?2-[(1H-benzimidazol-2-ylmethyl)-amino]-benzoic acid methyl ester; M?=?Pd, z?=?2; M?=?Pt, z?=?0) complexes were synthesized as potential antitumor compounds and their structures were elucidated by elemental analysis and spectroscopic data. Theoretical molecular structures were investigated by the DFT/B3LYP method using the LANL2DZ basis set. The calculated molecular parameters, bond distances, and angles, revealed a square-planar geometry around the metal through pyridine-type nitrogen (N_py) of benzimidazole and the secondary amino group (NH_sec). The lone pair interaction LP(2)O48 of ethanol with anti-bonding σ*(C(16)–H(29)) is an evidence for charge transfer from ethanol to platinum. The electronic movement and assignment of electronic spectra were carried out by TD-DFT calculations. The ligand in comparison to its metal complexes was screened for antibacterial activity and cytotoxicity.     

Effect of Diamine Bridge on Reactivity of Tetradentate ONNO Nickel(II) Complexes

Two new square planar ONNO nickel(II) complexes C2_core and C3_core have been synthesized and characterized by single crystal X-ray diffraction, NMR spectroscopy, thermogravimetry, and DFT calculations. The experimental results revealed the effect of the length of diamine bridge in the ligand on the behavior of the studied complexes in the reaction with N-heterocyclic aromatic amines, while DFT calculations provided a basis for the rationalization of this observation. The complex with propylenediamine bridge ( C3_core ) readily reacts with pyridine and its derivatives to form high-spin (paramagnetic) complexes with octahedral geometry as characterized by X-ray diffraction; electron-donating substituents on the pyridine ring facilitate the coordination of axial ligands. In contrast, the complex with ethylenediamine bridge ( C2_core) does not undergo such a reaction because of the high deformation energy of the core required for the formation of C2_Py complex.