Investigation of specific interaction between olefins and cyano-silica modified with copper(II) complexes

Summary Silica gel packings containing copper salt bonded to cyano functional groups on the surface of silica particles were synthesized. It was found that such packings are capable of specific interactions with olefins. The interactions were diversified enough to allow the separation of geometrical isomers. Moreover, it was found that, because of the character of the cyano group, the differences between the packing with free –CN groups and the packing containing –CN groups bonded into a complex with Cu(II) were less marked than in the case of diphenylphosphine and thiol groups investigated earlier.Part V of a series on transition metal complexes in GC Part IV see ref. [1]     

Iminoimidazole‐based Co(II) and Fe(II) complexes: Syntheses,characterization, and catalytic behaviors for isoprene polymerization

A stereoselectivity switchable polymerization of isoprene has been developed, which is catalyzed by iminoimidazole‐Co(II) and ‐Fe(II) complexes. The influence of substituents ranging from electron donating to the electron withdrawing on the iminoimidazole‐Co(II) and ‐Fe(II) catalysts is investigated for isoprene polymerization. Two sets of iminoimidazole‐Co(II) and ‐Fe(II) complexes have been prepared and fully characterized. X‐ray crystallography analysis reveals that the complexes Co1 and Fe1 adopt distorted tetrahedral geometries. In the presence of AlEt₂Cl as co‐catalyst, all the Co(II) complexes are active and the catalytic activity is highly dependent on the molar ratio of Al/Co. All the Co(II) complexes exhibit higher activities at low Al/Co ratio. Compared with the Co(II) complexes, the Fe(II) complexes are essentially inactive under the identical condition. However, on activation with combination of AlEtCl₂ and [Ph₃C][B(C₆F₅)₄], both Co(II) and Fe(II) complexes display high activities with good conversions of isoprene (up to >99%). Additionally, low molecular weight and high trans‐1,4‐unit (>96%) selectivity are characteristics of the resultant polyisoprene. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 767–775     

Complex formation of polyethyleneimine with copper(II), nickel(II), and cobalt(II) ions

An influence of the structure of a globule of polyethyleneimine on the complex formation of one with the copper(II), nickel(II), and cobalt(II) ions is described. A change of the coordination number from the pH of solution for complexes of ethylenediamine, diethylenetriamine, and polyethyleneimine with metal ions was found. The fraction of monomer links, bound with metal ions, depends on the volume of the globule of macromolecule as well as the condition of the proceeding reaction. The reaction of complex formation is controlled by the diffusion of metal ions into the polymer globule in solution. The effective equilibrium constants of complex formation were found. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 914–922, 2002; DOI 10.1002/pola.10157     

Metal derivatives of azoles,part VII. Pyrazolato-bridged dinuclear complexes containing either cyclopalladated or -platinated trimesitylphosphine or -arsine

Summary The halogen bridges of the dimeric, cyclometallated trimesityl-arsine and -phosphine complexes of palladium(II) and platinum(II), where M=Pd or Pt and E=P or As have been replaced with pyrazolate groups to give the corresponding and less symmetric pyrazolato-bridged complexes, where M=Pd or Pt, E=P or As, Pz=pyrazolato anion, and M=Pd, E=As, Pz=3,5-dimethylpyrazolato anion. In the case of the palladium complexes,¹H. n.m.r. clearly indicates the presence of only one isomer which is most likely to have thetrans configuration while the platinum complexes are mixtures of bothcis andtrans forms.Part VI, ref. 3c     

Synthesis and reactivity of allyl nickel(II) N‐heterocyclic carbene enolate complexes

Two new N‐heterocyclic carbene enolate nickel(II) allyl complexes have been prepared and their activity towards ethylene polymerization was investigated. It was found that in the presence of diethyl zinc, the carbene enolate complex bearing a nitro substituent produces highly linear polyethylene of modest molecular weight and high polydispersity. The influence of the reaction parameters on catalytic activity and the characteristics of the resulting polymer were investigated through systematic variation of the time, temperature, and diethyl zinc concentration. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45:3637–3647, 2007     

Pretreatment studies with biological and environmental materials

Summary In various biological and environmental materials the pressure pattern in closed teflon crucibles was followed after addition of nitric acid and heating. Hereby a significant influence of the matrix, of the temperature program and of the acid amount added on the pressure pattern was observed. The carbon balance, determined with the aid of gas-chromatography in several selected materials showed in no case a complete ashing and a very strong dependence of the decomposition rate on the kind of the investigated material.Part I: Fresenius Z. Anal. Chem. 291, 116 (1978); Part II: Fresenius Z. Anal. Chem. 293, 127 (1978)     

Synthesis, characterization and biological activity of bis(phenylimine) Schiff base ligands and their metal complexes

Metal complexes derived from 2,6-pyridinedicarboxaldehydebis(p-hydroxyphenylimine); L1, 2,6-pyridinedicarboxaldehydebis (o-hydroxyphenylimine); L2, are reported and characterized based on elemental analyses, IR, solid reflectance, magnetic moment, molar conductance and thermal analysis (TGA). The complexes are found to have the formulae [MX2(L1 or L2)] x nH2O, where M=Fe(II), Co(II), Ni(II), Cu(II) and Zn(II), X=Cl in case of Fe(II), Co(II), Ni(II), Cu(II) complexes and Br in case of Zn(II) complexes and n=0-2.5. The molar conductance data reveal that the chelates are non-electrolytes. IR spectra show that the Schiff bases are coordinated to the metal ions in a terdentate manner with NNN donor sites of the pyridine-N and two azomethine-N. From the magnetic and solid reflectance spectra, it is found that the geometrical structure of these complexes are trigonal bipyramidal (in case of Co(II), Ni(II), Cu(II) and Zn(II) complexes) and octahedral (in case of Fe(II) complexes). The thermal behaviour of these chelates shows that the hydrated complexes losses water molecules of hydration in the first step followed immediately by decomposition of the coordinated water, anions and ligands (L1 and L2) in the subsequent steps. The activation thermodynamic parameters, such as, E*, DeltaH*, DeltaS* and DeltaG* are calculated from the TG curves using Coats-Redfern method. The synthesized ligands, in comparison to their metal complexes also were screened for their antibacterial activity against bacterial species, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Fungi (Candida). The activity data show that the metal complexes to be more potent/antibacterial than the parent organic ligands against one or more bacterial species.     

Speciation study of trace elements by HPLC Part III. The effect of alcohols on the retention behaviour of Cr(III, VI)-APDC co-ordination complexes

Summary Reported here is the effect of alcohol modifiers on the retention behaviour of Cr(III, VI)-APDC complexes on both of Shimadzu CLC-C₈ and Shimadzu CLC-ODS columns. The results show that ln k' of the complexes depend mainly on the chromatographic column feature and the surface tension of the mobile phase, while the type of alcohols shows less contribution.Part I: Chem. Res. Chinese Univ. 7:37 (1991)Part II: Anal. Sci., in press.     

Magnetic coupling in end-to-end azido-bridged copper and nickel binuclear complexes: a theoretical study

The influence of structural parameters on the exchange coupling J between metal atoms in end-to-end azido-bridged binuclear complexes of Cu(II) and Ni(II) has been studied by means of density functional calculations. For the case of double-bridged Cu(II) compounds, four ideal pentacoordinate models have been employed in which the coordination spheres of the two metal atoms are either a trigonal bipyramid or a square pyramid, connected through equatorial or axial bridges. The distortion from those ideal geometries along a Berry pathway has also been analyzed. For the hexacoordinate Ni(II) compounds, models with two or one bridging ligands have been studied. The effect of the bridging M-N-N bond angles on the exchange coupling has been analyzed for both the Cu(II) and Ni(II) complexes.     

Cover Picture: Electrophoresis 12'2010

Issue no. 12 is a regular issue comprising 19 contributions distributed over five distinct parts. Part I has 7 articles describing novel methodologies pertaining to proteins and proteomics. Part II has 3 research papers on CEC stationary phases and CEC‐MS. Part III is on detection approaches including a review article on the advances and applications of chemiluminescence coupled to CE. Part IV has two papers on enantioseparations, and Part V has four contributions on aptamers, human genetic, preparative FFE and microchannels. Featured articles include: Simplified method for concentration of mitochondrial membrane protein complexes (( 10.1002/elps.201000019 )) Analysis of low‐molecular mass aldehydes in drinking waters through capillary electrophoresis with laser‐induced fluorescence detection (( 10.1002/elps.200900734 )) Selection of aptamers for signal transduction proteins by capillary electrophoresis (( 10.1002/elps.200900543 ))     

GC investigation of olefins with chemically bonded gamma-mercaptopropylsilane-copper(II) complexes

Summary A column packing containing thiol groups chemically bonded to the silica surface was synthesized. The thiol functional groups were used as ligands capable of forming stable complexes with Cu(II). The prepared material was characterized by gas chromatography using unsaturated linear and branched hydrocarbons as well as cyclic and aromatic hydrocarbons. The occurrence of specific metal—olefin interactions resulting from the formation of -complexes during the chromatographic process was observed.Part IV of a series on transition metal complexes in GC. Part III see ref. [1].     

Spectroscopic,magnetic and thermogravimetric studies of piperazine-bis-(dithiocarbamate) complexes

A new 1,4-piperazine-bis-dithiocarbamate sodium salt and its metal complexes have been prepared and characterized by elemental analyses, conductivity measurements, magnetic susceptibilities, thermal analyses (TG and DTG) and spectroscopic (i.r., electronic and EPR) techniques. The ligand is tetrasulphur coordinated to the metals in polymeric structures. The magnetic measurements are indicative of one unpaired electron in the copper(II) complex; a μ value typical of planar low-spin complexes has been obtained in the case of the cobalt(II) derivative, while a distortion from the planarity is suggested in the case of the nickel(II) complex. Tentative structures of the complexes are proposed on the basis of the obtained results.     

Synthesis,characterization, and catalytic activity of titanium iminophenoxide complexes in relation to the ring‐opening polymerization of L‐lactide and ε‐caprolactone

This study synthesized a series of titanium iminophenoxide complexes and investigated their suitability as catalysts for the ring‐opening polymerization of L ‐lactide (L ‐LA) and ε‐caprolactone (CL). Complexes with bidentate ligands demonstrate higher catalytic activity than their tridentate counterparts since the third coordination atom needs to contend with L ‐LA and CL. Differences in the geometric framework of bidentate ligands also influence the catalytic activity. Type II ligands (N, N‐trans form of Ti complex) prevent the coordination of monomers to Ti thereby decreasing the initiation rate. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Metal complexes of porphycene,corrphycene, and hemiporphycene: stability and coordination chemistry

Porphyrin (P), porphycene (Pc), corrphycene (Cn), and hemiporphycene (Hpc) represent a series of well defined "4-N in" constitutional porphyrin isomers. These isomers, in the form of their octaethyl derivatives, represent a congruent set of porphyrinoids whose properties can be compared. In this study we report how variations in electronic structure and nitrogen-core size in the free-base forms of these four systems are reflected in the properties of their corresponding metal complexes. Specifically, the effects that these differences have on the axial ligation properties of the Zn(II), Mg(II), Ni(II), and Co(II) complexes of P, Pc, Cn, and Hpc in toluene using pyridine as the axial ligand are detailed. Also reported are the relative stabilities of these complexes under acidic conditions. It is shown that for the zinc, magnesium, and cobalt complexes, there are distinct differences in the ability to maintain four-, five-, or six-coordinate geometries in the presence of similar concentrations of pyridine. By contrast, no apparent differences in axial ligand binding affinity are seen for the four nickel complexes. Little difference in stability was likewise seen when these same complexes were subject to acid-mediated demetallation, with all four falling into stability class II, according to the accepted porphyrin stability ranking system. High stabilities were also seen in the case of the cobalt complexes, with the Pc and Cn complexes being of stability class III and the P and Hpc derivatives falling into stability class II. The Zn(II) and Mg(II) complexes were all far less stable than the corresponding Ni(II) and Co(II) complexes. In this case, semiquantitative analyses of the rate of acid-induced decomposition revealed the following stability sequence P>Cn>Hpc>Pc for both the Zn(II) and Mg(II) complexes. Single-crystal X-ray diffraction structures were solved for the Zn(II), Mg(II), and Ni(II) complexes of the octaethyl derivatives of Hpc, Cn, and Pc as well as a Co(II) octamethylcorrphycene and are reported as part of this study. These solid-state structures confirm four-coordinate species for the Ni(II) complexes, four- and five-coordinate species for the Mg(II) and Zn(II) complexes, and a six-coordinate species for the lone Co(II) complex.     

Hetero atom derivatives of aziridine

Labile equimolecular coordination complexes of ethyleneimine with trimethyl and triphenyl borates (N-ethylene-B-trimethoxyborazane and N-ethylene-B-triphenoxyborazane) are prepared for the first time and their properties investigated.For Part II see [1].     

Retention characteristics of chlorinated polycyclic aromatic hydrocarbons in normal phase HPLC. II. Chloro-substituted PAHs

Summary The retention behaviour of chloro-substituted PAHs on several commercial normal bonded phase HPLC columns has been investigated. Chloro-substitution was shown to generally decrease the retention on stationary phases like amino-, diol- and nitrophenylpropyl-modified silica. Dimethylaminosilica exhibited more complex retention characteristics towards chloro-substituted PAHs. On this stationary phase, the position of the chlorine substituents on the aromatic solute seemed to be of greater importance for retention than on the amino-, nitro- and diolsilica. For some chloro-PAHs, the retention was shown to increase with the number of chloro-substitutions, probably due to the large affinity of the electron-rich nitrogen in the stationary phase for the electron deficient -system of the chloro-PAHs. Chloro-substituted PAHs were strongly retarded on the electron donating 2-(1-pyrenyl)-ethylsilica (PYE) stationary phase. However, the molecular shape of the chloro-derivatives had a large influence on retention, which was considerably decreased for some nonplanar chloro-derivatives of chrysene and benz(a)anthracene. A two-dimensional back-flush HPLC method, consisting of a combination of a nitrophenylsilica column and a PYE column of matched lengths, was shown to be useful for clean-up of chloro-substituted PAHs in environmental samples.     

Complex formation equilibria of some aromatic beta-amino-alcohols

Complex formation equilibria of some aromatic beta-amino-alcohols with zinc(II), cadmium(II) and silver(I) have been investigated. The structure of the considered ligands (2-amino-1-phenyl-1-propanol, 2-amino-3-phenyl-1-propanol and 2-amino-1,3-propanediol) are similar to some hormones and alcaloids, like adrenaline, noradrenaline and ephedrine, and differ each other for the number and the relative position of alcoholic and phenyl groups. Equilibria constants at 25 degrees C and micro = 0.5 M (KNO3) have been determined by potentiometric titrations. The comparison of the obtained values with those previously determined for some aliphatic beta-amino-alcohols with the same polar heads has allowed to evidence the influence of aromatic ring on the coordinating properties of ligands, which is different depending on the considered metal ion. In particular, two contrasting effects have been evidenced. The electron withdrawing effect of the aromatic ring causes a decrease of amine basicity, more relevant when phenyl and hydroxylic groups are in 1-3 position, which reflects in a reduction of metal-NH2 coordination bond. This effect is predominant in the case of zinc(II) complexes and causes a reduction of complex stability which results directly proportional to the amine group basicity. On the other hand, in the case of silver(I) and cadmium(II) complexes, phenyl group seems to contribute directly to the coordination of the metal ion causing a stabilization of complexes.     

Synthesis of highly reactive polyisobutylenes using solvent‐ligated manganese(II) complexes as catalysts

Manganese complexes with benzonitrile ligands were synthesized, characterized, and applied for the preparation of the isobutylene polymerization. Low and medium molecular weight polyisobutylenes containing high amount of exo‐type double bond end groups (70–80%) were successfully prepared using these manganese(II) complexes as catalysts at room temperature. The influence of monomer and catalyst concentration was intensively analyzed for achieving high monomer conversion and high exo double bond content of the products. Details on end group distribution in the products and development of the exo‐type end group content with reaction time were evaluated by ¹H NMR. The catalysts are also active for the homopolymerization of styrene and the copolymerization of isobutylene and styrene. The highly reactive polyisobutylene products obtained by these manganese complexes show features similar to products obtained by conventional cationic polymerization, but the polymerization characteristics clearly deviate. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5636–5648, 2007     

Synthesis, characterization, DNA binding and cytotoxic studies of platinum(II) and palladium(II) complexes of the 2,2'-bipyridine and an anion of 1,1-cyclobutanedicarboxylic acid.

Two neutral complexes of formula [M(bpy)(cbdca)] [where M is palladium(II) (Pd(II)) or platinum(II) (Pt(II)), bpy is 2,2'-bipyridine and cbdca is anion of 1,1-cyclobutanedicarboxylic acid] have been synthesized. These water soluble complexes have been characterized by chemical analysis and conductivity measurements as well as 1H-NMR, ultraviolet-visible and infrared spectroscopy. In these complexes the ligand cbdca coordinates to Pt(II) or Pd(II) as bidentate with two oxygen atoms. They are nonelectrolyte in conductivity water. These complexes inhibit the growth of P388 lymphocytic leukemia cells and their targets are DNA. They invariably show ID50 values less than cisplatin. [Pt(bpy)(cbdca)] and [Pd(bpy)(cbdca)] have been interacted with calf thymus DNA and bind to DNA through coordinate covalent bond. In addition, the influence of binding of these complexes on the intensity of EtBr-DNA have been studied. They bind to DNA via a nonintercalating mode.     

Reaction of beta-diketiminate copper(II) complexes and Na2S2

Reaction of beta-diketiminate copper(II) complexes and Na2S2 resulted in formation of (mu-eta2:eta2-disulfido)dicopper(II) complexes (adduct formation) or beta-diketiminate copper(I) complexes (reduction of copper(II)) depending on the substituents of the supporting ligands. In the case of sterically less demanding ligands, adduct formation occurred to provide the (mu-eta2:eta2-disulfido)dicopper(II) complexes, whereas reduction of copper(II) took place to give the corresponding copper(I) complexes with sterically more demanding beta-diketiminate ligands. Spectroscopic examinations of the reactions at low temperature using UV-vis and ESR as well as kinetic analysis have suggested that a 1 : 1 adduct LCuII-S-SNa with an end-on binding mode is initially formed as a common intermediate, from which different reaction pathways exist depending on the steric environment of the metal-coordination sphere provided by the ligands. Thus, with the sterically less demanding ligands, rearrangement of the disulfide adduct from end-on to side-on followed by self-dimerisation occurs to give the (mu-eta2:eta2-disulfido)dicopper(II) complexes, whereas such an intramolecular rearrangement of the disulfide co-ligand does not take place with the sterically more demanding ligands. In this case, homolytic cleavage of the CuII-S bond occurs to give the reduced copper(I) product. The steric effects of the supporting ligands have been discussed on the basis of detailed analysis of the crystal structures of the copper(II) starting materials.