Determination of the solution structures of melamine-based bis- and tris-macrocyclic ligand copper(II) complexes

A combination of molecular mechanics (MM), electron paramagnetic resonance spectroscopy (EPR), and spectra simulation (MM-EPR) has been used to determine the solution structures of di- and trinuclear copper(II) complexes of melamine-based oligomacrocyclic ligands. The spin Hamiltonian parameters of the mononuclear, melamine-appended macrocyclic ligand copper(II) complex have been determined by EPR spectroscopy and were also studied with DFT methods. These spin Hamiltonian parameters, together with the structural parameters obtained from models optimized with MM, have been used for the simulation of the EPR spectra of the di- and trinuclear complexes. For the dinuclear complex, the syn isomer is preferred over the anti, for which an X-ray structure exists; for the trinuclear complex, the syn,syn isomer is preferred over the syn,anti form. Additional support for these assignments comes from DFT calculations, and this demonstrates that the MM-DFT-EPR method is a reliable approach for the determination of solution structures and for the analysis of spin Hamiltonian parameters of dipolar, coupled transition metal complexes (g and A tensors and J values).     

Reactions of 2-pyridylphenylacetonitrile with copper(II) chloride,copper(II) bromide,cobalt(II) chloride and cobalt(II) bromide

Reaction of 2-pyridylphenylacetonitrile with copper(II) chloride and copper(II) bromide in dry ethanol gives the hitherto unreported compound 1,2-di(cyano,phenyl,2′-pyridyl)ethane. The cobalt halides react with 2-pyridylphenylacetonitrile to form 1:1 complexes containing O-ethyl-2-phenyl-2-(2′-pyridyl)acetimidate as ligand. Removal of the ligand by the action of dry liquid ammonia on the complexes provides a better route to the pure imidate than the well known Pinner method.     

A new branched phenanthroline derivative ligand: synthesis, solution chemistry, and crystal structures of copper(II) and zinc(II) complexes

The synthesis and characterization of the new ligand 2,9-bis[N,N-bis(2-aminoethyl)aminomethyl]-1,10-phenanthroline (L) are reported. L contains two diethylenetriamine units connected on the central nitrogen atom by a 1,10-phenanthroline group forming a symmetrical branched ligand. The basicity and binding properties of L toward Cu(II) and Zn(II) in aqueous solution were determined by means of potentiometric, UV-vis, fluorescence, and 1H and 13C NMR techniques. L behaves as pentaprotic base under the experimental conditions used; from HL+ to H4L4+ species it is the secondary amine functions that are protonated while in the H5L5+ species also the phenanthroline is involved in protonation. L does not show fluorescence properties in the range of pH (0-14) investigated. It forms both mono- and dinuclear stable species where the phenanthroline is directly involved with both nitrogens in the coordination of the first metal which is coordinated in a pentacoordination environment also by one dien unit. The other dien unit undergoes easy protonation in the mononuclear complex while it binds the second metal in the dinuclear species. For this reason, L, in providing two different binding areas for metal coordination, behaves as an unsymmetrical compartmental ligand; one area is formed by one dien unit and by the phenanthroline, and the other by the remaining dien unit. This produces unsymmetrical metal complexes both for the mono- and dinuclear species; however, the role of the binding areas is fast exchanging in aqueous solution, at least on the NMR time scale. Solution studies and the three crystal structures of the [Zn(H2L)]4+, [[Cu(H2L)](ClO4)]3+, and [[Cu2LCl2](ClO4)]+ species highlight the unsymmetrical compartmental behavior of L as well as the host properties of the complexes in adding exogenous ligands such as hydroxide, pherchlorate, and chloride anions.     

Synthesis of new mixed ligand complexes of copper(II) dithiocarbamates

New mixed ligand complexes of copper(II) dithiocarbamates of the general formula, [CuCl(R₂dtc)L] or [CuCi(R′ dtc)L] (RCH₃ or C₂H₅, R′ = (CH₂)₅, dtc =-NCSS^? and L = Pyridine, 3-picoline or 4-picoline), have been prepared by the reaction of bis(dithiocarbamato)di-μ-chloro-dicopper(II) complexes with pyridine or picolines. The complexes are found to be non-electrolytes in nitrobenzene. Magnetic susceptibilities, i.r. and electronic spectra of the complexes are reported. A psuedo-tetrahedral structure is suggested for these complexes.     

Electrochemical behaviour of the complexes of copper(II) with a Schiff base compartmental ligand

Summary The ethylenediamine Schiff base derivative ofo-acetoacetylphenol, H₄aapen, is a ligand able to form both mononuclear and dinuclear complexes with copper(II) ion. Mononuclear positional isomers can be obtained, having the copper in the O₂O₂ site and in the N₂O₂ site. The electrochemistry of these copper(II) complexes in dimethylsulfoxide shows that the two positional isomers are reduced at different potentials through an e.c.e. mechanism, in which a chemical reaction is coupled between two one-electron transfers, the N₂O₂ isomer being the less reducible. They also undergo complicated oxidation processes at high potentials, less significant in distinguishing the two isomers. The electrochemical behaviour of the dinuclear copper(II) complex parallels that of the two mononuclear isomers.     

Three copper(II) complexes constructed from a new 1,3,5-triazine derivative ligand

Three new complexes {[Cu(dpdapt)(Hhbd)] · 6H₂O}_n (1) (dpdapt = N,N′-di(2-pyridyl)-2,4-diamino-6-phenyl-1,3,5-triazine, Hhbd = 2-hydroxybutanedioicate dianion), [Cu(dpdapt)(SO₄)] · 2H₂O (2) and [Cu(dpdapt)(oxa)] · H₂O (3) (oxa = oxalate dianion) have been synthesized and structurally characterized. The non-covalent interactions of π–π stacking and hydrogen bonding extend complexes 1–3 into supramolecular architectures, where 1 self-assembles into a 1D polymeric chain by dicarboxylate bridges and exhibits a 3D framework with 1D open channels, while complexes 2 and 3 display 2D wavelike networks. Interestingly, in 1, the host framework encapsulates hexameric water clusters that are connected into 1D arrays by supramolecular association along the 1D open channels. The UV/vis, IR spectra, fluorescence and TG analysis for complexes 1, 2 and 3 are also discussed.     

Synthesis and spectra of copper(II) chloride and copper(II) bromide complexes of bispidines. Molecular and crystal structure of copper chloride complexes of 1,5-diphenyl-3,7-di(2-cyanoethyl)-9-bispidone and copper bromide complexes of 1,5-diphenyl-3,7-diallyl-9-bispidone

By reaction of copper(II) chloride and bromide with the 1,5-diphenyl-3,7-dialkyl-9-bispidone series, we have synthesized a number of new complex compounds. In the IR spectra of the complexes, the absorption band for the carbonyl group is shifted toward longer wavelengths compared with the original ligands. This shift can be a criterion indicating formation of complexes of the given composition and structure. We have determined the crystal structure of two new complexes. We show that for complexes with alkylmethyl substituents at the nitrogen atoms, significant distortion of the coordination environment of the metal compared with the methyl analog is typical; this distortion is connected with the interaction between the substituents and the halogen atoms. We hypothesize that this type of interaction affects the structure and spectral properties of the complexes is solution.Communication 3 in the series Complexing properties of 3,7-diazabicyclo[3.3.1]nonanes. For Communication 2, see [1].Chemistry Department, M. V. Lomonosov Moscow State University. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 356–366, March, 1997.     

Synthesis and crystal structures of copper(II) and silver(I) complexes of a biphenyl-bridged bipyrazolyl ligand

A semirigid bipyrazolyl ligand, 4,4??-bis[(3??,5??-diethyl-1H-pyrazol-4??-yl)methylene)]-1,1??-biphenyl (H₂L), and four of its Ag(I) and Cu(II) complexes have been prepared and structurally characterized. X-ray analysis demonstrates that the Ag(I) complexes are dinuclear molecular rectangle, while the Cu(II) complexes display a twisted rectangular structure. Two different conformations, namely cis and trans, have been observed for this bipyrazolyl ligand.     

Mixed ligand complexes of copper(II) iminodiacetate with di- and tripeptides in solution

Calorimetric, potentiometric, and spectrophotometric studies on mixed ligand complexes of copper(II) iminodiacetate and simple di- and tripeptides (GlyGly, αAlaαAla, αAlaβAla, βAlaβAla, αAlaAsn, GlyGlyGly, AlaGlyGly) have been carried out in aqueous solution at 298.15 K and ionic strength of I = 0.5 (KNO₃). The thermodynamic parameters of formation of various mixed complexes have been determined. The probable coordination modes of the complex and peptide molecules in the mixed ligand complexes are discussed.     

Synthesis and crystal structures of copper(II) and silver(I) complexes of a semi-rigid bipyrazolyl ligand

A semi-rigid bipyrazolyl ligand, namely 5-tert-butyl-1,3-bis[(3′,5′-diethyl-1H-pyrazol-4′-yl) methylene]benzene, and its Ag(I) and Cu(II) complexes have been prepared and structurally characterized. X-ray analysis demonstrates that the Ag(I) complex is based on a dinuclear molecular rectangle, while the Cu(II) complex displays a mono-strand helical structure. Two different conformations, namely cis,cis and cis,trans have been observed for this bipyrazolyl ligand.     

Distorted pentacoordinate copper(II) complexes containing a tridentate ligand

Summary Copper(II) complexes with a tridentate chelating ligand within the general 2N, X (X = O or S) donor class, containing abis(benzimidazolyl) donor set, were prepared and characterized. X-band e.p.r. spectra of the complexes indicateg >g and the largeg and lowA have been interpreted in terms of a distorted basal plane. Superimposed on theg component are five SHF lines withA _N = 16±2G, supporting the interaction of two nitrogen atoms with the copper nucleus. Thus, the basal plane of the complex comprises 2N atoms, with the ligand hetero atom being axially coordinated.     

Thermal behaviour of hydrated copper(II) complexes

Dehydration steps of aquacopper(II) complexes with homogeneous and heterogeneous coordination sphere are investigated from the view point of structural changes taking place under their heating to the decomposition temperature and during the dehydration. The role of loosening of intra-and intermolecular hydrogen bonds in the decomposition reaction for the structure changes of the remainder, the structural presumptions of the reactants for lower hydrates formation are discussed. Activation parameters of dehydration were found to be the lower, the smaller are the structure differences between the reactants and products. They do not reflect the bond length central atomvolatile ligand, much more the overall structure differences between the starting and resulting compounds. From all data on crystal and molecular structures of dehydrated compounds is the reaction pathway best indicated by anisotropic temperature parameters of donor atoms corrected for the thermal movement of the central atom: the higher these values in the bond direction are, the lower the values of activation energies of dehydration are.     

Synthesis, characterization and structural analysis of new copper(II) complexes incorporating a pyridoxal-semicarbazone ligand

The reaction between 3-hydroxy-5-hydroxymethyl-2-methyl-4-pyridinecarboxaldehyde semicarbazone (pyridoxal-semicarbazone or PLSC) and appropriate chloride, sulfate, nitrate or thiocyanate Cu(II) salts in water/alcohol mixtures resulted in the formation of new copper(II) complexes: [Cu(PLSC)Cl₂] (1), [Cu(PLSC)(H₂O)(SO₄)]₂·3H₂O (2), [Cu₂(PLSC)₂(NCS)₂](NCS)₂ (3), [Cu(PLSC)(NO₃)₂(CH₃OH)] (4) and [Cu(PLSC-2H]NH₃·H₂O (5). The complexes were characterized by elemental analysis, conductometric measurements and IR spectroscopy, while complexes 1, 2, 3 and 4 were further characterized by single crystal X-ray diffraction.     

Synthesis,characterization, antifungal and antibacterial activities evaluation of copper (II), zinc (II) and cadmium (II) chloride and bromide complexes with new (E)-1-(3,4-dimethoxybenzylidene)-4-methylthiosemicarbazone ligand

The reactions of Cu (II), Zn (II) and Cd (II) chloride or bromide with (E)-1-(3,4-dimethoxybenzylidene)-4-methylthiosemicarbazone (MTSVT) lead to the formation of new complexes. They were characterized by spectroscopic studies: IR, ¹H and ¹³C NMR. The crystal structures of the compounds [MTSVT] ( L ), [ZnBr₂(MTSVT)₂] ( 2 ), [CdCl₂(MTSVT)₂] ( 3 ) and [CdBr₂(MTSVT)₂^.H₂O] ( 4 ) were determined by X-ray diffraction. For complexes 2 – 4 , the ion is coordinated through the sulfur atom. All compounds were tested for their antifungal activity against human pathogenic fungi Candida albicans and Aspergillus fumigatus, and for their antibacterial activity against Gram (+) Bacillus subtilis and Enterococcus faecalis as well as against Gram (−) bacteria such as Paracoccus yeei and Acinetobacter baumanii. The results indicated that the metal complexes exhibited a marked enhancement in antibacterial activity compared with the parent Schiff base.     

Dinuclear copper(II) complexes of a polybenzimidazole ligand: their structures and inductive roles in DNA condensation

The structures of two dinuclear Cu(II) complexes of dtpb were determined. They are shown to be capable of inducing DNA condensation into nanometer- and micrometer-scale particles under neutral conditions.     

Polymeric copper(II) and nickel(II) complexes of a tetraoxime containing a binucleating macrocycle ligand

Polymeric copper(II) and nickel(II) complexes of a binucleating tetraoxime macrocycle, 6,6-methylene-bis[1,12-di(hydroximino)- 2,3;9,10-dibenzo-1,11-diaza-4,8-dithiacyclotridecane] (H4L), have been prepared and characterised by elemental analysis, magnetic moments, i.r., uv/vis., and e.p.r. spectral studies. I.r. spectra show that the ligand acts in a tetradentate manner and coordinates via N, S and O donor atoms. The geometry of the resulting metal chelates is discussed with the help of magnetic and spectroscopic measurements. The elemental analyses, stoichiometry and the spectroscopic data of the complexes indicate that the copper(II) and nickel(II) ions are coordinated by the coordination environment of the ligand. The spectral data suggest a distorted tetragonal geometry for polymeric copper(II), and nickel(II) ions in the complexes. The stoichiometry of the metal-to- H4L ratio of complexes (2) and (3), prepared from CuCl2 and NiCl2 respectively, was 3:1, suggesting the formation of polymeric species.