Stereoisomeric Pd(II) complexes with serine,threonine, and allothreonine

The paper describes methods for the synthesis and isolation of solid phases of the individual stereoisomeric Pd(II) bis(amino acid) complexes with serine (SerH = NH₂C*H(CH₂OH)COOH, α-amino-β-hydroxypropionic acid), threonine (ThrH CH₃C*H(OH)C*H(NH₂)COOH, threo-α-amino-β-hydroxybutyric acid), and allothreonine (alloThrH is erythro-α-amino-β-hydroxybutyric acid): cis-[Pd(S-Ser)2], trans-[Pd(R-Ser)(S-Ser)], cis-[Pd(S-Thr)₂], trans-[Pd(S-Thr)₂], trans-[Pd(R-Thr)(S-Thr)], and cis-[Pd(R-alloThr)(S-alloThr)] (R, S are the absolute configurations of the asymmetric C* atom connected to the NH₂ group). The synthesized compounds were characterized by elemental analysis, IR and NMR (¹H and ¹³C) data, and X-ray diffraction analysis.     

Comparative EPR study of copper(II) complexes with threonine derivatives

Summary In order to get better insight into the structural reasons for different properties of copper(II) complexes withL-threonine,L-allo-threonine,L-N,N-dimethyl-threonine, andL-N,N-dimethyl-allo-threonine, their EPR spectra were studied as a function ofpH and temperature. AtpD9.4, in all complexes a change in the copper(II) coordination sphere from the glycine to the hydroxy type was observed. Inbis(L-threoninato)copper(II), the hydroxy type formed atpD9.4 was found to be stablized by increasing the temperature of the solution from 280 to 320 K. In all other copper(II) complexes, the conformational change is accompanied by the disruption of the Cu-N bond of one chelate ring.

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Vergleichende EPR-Untersuchungen von Kupfer(II)-Threonin-Komplexen

Zuzammenfassung Um einen besseren Einblick in die Beziehungen zwischen Struktur und Eigenschaften von Kupfer(II)-Komplexen mitL-Threonin,L-allo-Threonin,L-N,N-Dimethyl-Threonin undL-N,N-Dimethyl-allo-Threonin zu gewinnen, wurden ihre EPR-Spektren in Abhängigkeit vompH-Wert und von der Temperatur untersucht. Bei einempH-Wert von 9.4 (in deuterierter Lösung) wurde eine Veränderung in der Kupfer (II)-Koordinationssphäre festgestellt, die von einer Glycin-ähnlichen Konformation in eine vermutlich Hydroxy-ähnliche Konformation übergeht. Derbis(L-Threoninato)-Kupfer (II)-Hydroxy-Komplex wird durch eine Temperaturerhöhung von 280 auf 320K stabilisiert. Die Veränderung der Koordination vom Glycin-Typ wird von einem Bruch der Cu-N-Bindung eines Chelatrings begleitet.

     

Pt(II) stereoisomeric complexes with serine

There have been synthesized Pt(II) stereoisomeric complexes with hydroxy-α-amino acid serine (SerH = NH₂CH(CH₂OH)COOH is α-amino-β-hydroxypropionic acid): trans-[Pt(S-SerH)₂Cl₂], trans-[Pt(R-SerH)(S-SerH)Cl₂] with monodentately (through NH₂ group ) bound SerH and cis-, trans-[Pt(R-Ser)(S-Ser)], trans-[Pt(S-Ser)₂] with bidentately bound (through groups NH₂ and COO) ligands (R, S is the absolute configuration of asymmetric carbon atom). The successive phases in the synthesis of Pt(II) stereoisomeric complexes with serine were studied by ¹⁹⁵Pt NMR spectroscopy. To identificate the compounds synthesized the method of elemental analysis, IR and NMR (¹⁹⁵Pt, ¹³C, ¹H) spectroscopy were used. For trans-[Pt(R-Ser)(S-Ser)] the X-ray diffraction data were obtained.     

Thermal and photochemical reactions of copper(II) dithiocarbamate mixed-ligand complexes with chloroalkanes

Thermal and/or photochemical conversion of a series of copper(II) complexes containing mixed dithiocarbamato–alcohol ligands, Cu^II(Et₂dtc)⁺ . . . Y⁻ (Y=ClO₄⁻, NO₃⁻), into Cu^II(Et₂dtc)Cl in chloroalkane/alcohol solutions, where chloroalkane=CCl₄, CHCl₃ or CH₂Cl₂ and alcohol=MeOH, EtOH or i-BuOH, proceeds in chloroalkanes. Both reactions follow a similar pathway which is more effective the stronger the acceptor properties of chloroalkanes and the weaker the coordinating abilities of alcohols are. A detailed reaction mechanism is proposed which well fits the experimental results obtained by EPR and UV–VIS spectra and quantum yields.     

Stereoisomeric complexes of Pt(II) with threonine and allothreonine

The paper describes the synthesis of geometrical isomers and diastereomers of Pt(II) bischelates with diastereomeric hydroxy-amino acids threonine (threo-α-amino-β-hydroxybutyric acid CH₃C*H(OH)C*H(NH₂)COOH=ThrH) and allothreonine (erythro-α-amino-β-hydroxybutyric acid=alloThrH) containing two asymmetric carbon atoms C*: cis-,trans-[Pt(S-Thr)₂], cis-,trans-[Pt(RThr)(S-Thr)], cis-,trans-[Pt(R-alloThr)(S-alloThr)] (where R and S are the absolute configurations of the asymmetric carbon atom bonded to the carboxyl group). ¹⁹⁵Pt NMR spectroscopy is used to investigate the successive phases of the synthesis of the stereoisomeric Pt(II) complexes with threonine. The synthesized complexes are studied by ¹H, ¹³C, ¹⁹⁵Pt NMR spectroscopy, IR spectroscopy, and single crystal XRD.     

Template mechanism and kinetics for the complexation of ninhydrin with copper (II) complexes of asparagine and serine

Ninhydrin has been found to form a 1:1 complex with Cu(II) complexes of asparagine and serine. The kinetics of the complexation reaction has been studied spectrophotometrically in acetate buffer. The effect of the [ninhydrin], pH, and temperature on the reaction rate of the reaction was studied. The reaction follows fractional-order kinetics with respect to ninhydrin and first-order with respect to asparagine-Cu(II) and serine-Cu(II), respectively. The reaction proceeds through the coordination of ninhydrin with the same Cu(II) of asparagine and serine complexes. The results are best accounted by the “Template mechanism” for the inner sphere complexation. The values for the inner sphere complex formation constant were also calculated from the kinetic data. The role of Cu(II) in this reaction is to inhibit the breaking of C(SINGLEBOND)C (evolution of CO₂) as well as stabilize the C(DOUBLEBOND)N of Schiff base. On the basis of observed results, probable mechanism has been proposed. © 1996 John Wiley & Sons, Inc.     

Syntheses, crystal structures and properties of novel copper(II) complexes obtained by reactions of copper(II) sulfate pentahydrate with tripodal ligands

Three novel metal-organic frameworks (MOFs), [Cu(1)SO4].H2O (4), [Cu2(2)2(SO4)2].4H2O (5) and [Cu(3)(H2O)]SO4.5.5H2O (6), were obtained by hydrothermal reactions of CuSO4.5H2O with the corresponding ligands, which have different flexibility. The structures of the synthesized complexes were determined by single-crystal X-ray diffraction analyses. Complex 4 has a 2D network structure with two types of metallacycles. Complex 5 also has a 2D network structure in which each independent 2D sheet contains two sub-layers bridged by oxygen atoms of the sulfate anions. Complex 6 has a 2D puckered structure in which the sulfate anions serve as counter anions, which are different from those in complexes 4 (terminators) and 5 (bridges). The different structures of complexes 4, 5 and 6 indicate that the nature of organic ligands affected the structures of the assemblies greatly. The magnetic behavior of complex 5 and anion-exchange properties of complex 6 were investigated.     

Molecular complexes of hydrazides with copper(II)

Summary The reaction of substituted hydrazides with copper(II) chloride was investigated in the solid state or in solution in order to account for substituent effects. Spectroscopic results and values of the formation constants indicate the occurrence of strong complexes.

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Molekulare Komplexe von Hydraziden mit Kupfer(II)

Zusammenfassung Die Reaktionen von substituierten Hydraziden mit Kupfer(II)chlorid wurden im Festzustand und in Lösung untersucht. Die spektroskopischen Ergebnisse und die Werte der Bildungskonstanten zeigen die Koordinierung zu starken Komplexen an.

     

Electron transfer reactions of tris(1,10-phenanthroline)cobalt(II) with copper(III) imine-oxime complexes

Summary The kinetics of oxidation of [Co^II(phen)₃]²⁺ (phen = 1,10-phenanthroline) by copper(III) imine-oxime complexes are first-order in each reactant. All reactions proceed via two parallel pathways; one pH independent, the other pH dependent. The second-order rate constant varies with [H⁺] as k₂ = k _inf2 ^supo + k _inf2 ^supH [H⁺]. The rapidity of the electron transfer step, coupled with the relative inertness of [Co^II(phen)₃]²⁺ over the pH range studied and the absence of a bridging atom on the phen ligand, supports an outer-sphere mechanism for this process. Reasonably good agreement between the experimental rate constants and those calculated using the Marcus equation has been obtained.     

Nickel(II) complexes with cytosine and threonine: Synthesis and structure

Mono-and mixed-ligand complexes with the composition [Ni(Cyt)₂(H₂O)₂]Cl₂, [Ni(Thr^–)₂(H₂O)₂] and [Ni(Thr^–)(Cyt)(H₂O)₂]Cl are synthesized and studied. Using IR spectroscopy it is determined that in the complex compounds, cytosine is bidentate (C=O group oxygen and heterocycle N3), threonine interacts with the Ni(II) ion due to amino and carboxyl groups. The models of the atomic structure of the studied compounds are proposed based on the EXAFS and XANES spectroscopy results.     

Mannich aminomethylation reactions of a series of bis(α-amino acidato)metal(II) complexes with formaldehyde and diethylmalonate: Crystal structure of (5,5-dicarboxyethyl-3,7-diazanonanedioato)copper(II) monohydrate

Mannich aminomethylation reactions involving M(aa)₂, where M = Cu, Ni and aa = glycine(gly), dl-alanine(dl-ala), l-alanine(l-ala), with formaldehyde and diethylmalonate have been carried out, resulting in carboxylate appended systems in high yield. All the compounds have been characterized by UV-Vis spectroscopy, infrared spectroscopy and elemental analysis. One of the synthesized complexes, (5,5-dicarboxyethyl-3,7-diazanonanedioato)copper(II) monohydrate, has been characterized by single crystal XRD and has been used as catalyst in the hydrogen peroxide-induced degradation of pyrocatechol violet (PCV) dye. The variations in the rate of degradation of the dye with respect to change in concentration of hydrogen peroxide, dye, catalyst and pH have been studied. Effect of addition of NaCl has been studied and a suitable mechanism based on the formation of free radical species during the degradation process has been proposed.     

Polynuclear copper (II) complexes with aminoalcohol ligands

Copper complexes with aminoalcoholato ligands have attracted much attention recently because of their potential applications in ceramic materials. This review deals with polynuclear copper (II) complexes containing bidentate and triden-tate aminoalcoholato ligands. The focus of this article is on the synthesis, structure, and magnetic properties of polynuclear copper (II) complexes obtained recently by our group. Some relevant work reported previously by other researchers is also included.Dedicated to Professor Jiaxi Lu on the occasion of his 80th birthday.     

Solid state reactions of organopentafluorosilicates with copper(I) and copper(II) salts

Two types of solid state reaction of K₂[RSiF₅] have been developed: (1) CuCl promoted homo coupling of alkenyl- and phenyl-silicates, and (2) formation of RH fraom alkyl- and alkenyl-silicates by heating with CuF₂·2H₂O.     

Enantioselective and diastereoselective Mukaiyama-Michael reactions catalyzed by bis(oxazoline) copper(II) complexes.

The scope of highly enantioselective and diastereoselective Michael additions of enolsilanes to unsaturated imide derivatives has been developed with use of [Cu((S,S)-t-Bu-box)](SbF6)2 (1a) as a Lewis acid catalyst. The products of these additions are useful synthons that contain termini capable of differentiation under mild conditions. Michael acceptor pi-facial selectivity is consistent with two-point binding of the imide substrate and can be viewed as an extension of substrate enantioselection in the corresponding Diels-Alder reactions. A model analogous to the one employed to describe the hetero Diels-Alder reaction is proposed to account for the observed relation between enolsilane geometry and product absolute diastereocontrol. Insights into modes of catalyst inactivation are given, including spectroscopic evidence for inhibition of the catalyst by a dihydropyran intermediate that evolves during the course of the reaction. A procedure is disclosed in which an alcohol additive is used to hydrolyze the inhibiting dihydropyran and afford the desilylated Michael adduct in significantly shortened reaction time.     

Cyano-bridged homodinuclear copper(II) complexes

The synthesis and structural analysis (single crystal X-ray data) of two mononuclear ([Cu(L(1))(CN)]BF(4) and [Cu(L(3))(CN)](BF(4))) and three related, cyanide-bridged homodinuclear complexes ([{Cu(L(1))}(2)(CN)](BF(4))(3)·1.35 H(2)O, [{Cu(L(2))}(2)(CN)](BF(4))(3) and [{Ni(L(3))}(2)(CN)](BF(4))(3)) with a tetradentate (L(1)) and two isomeric pentadentate bispidine ligands (L(2), L(3); bispidines are 3,7-diazabicyclo[3.3.1]nonane derivatives) are reported, together with experimental magnetic, electron paramagnetic resonance (EPR), and electronic spectroscopic data and a ligand-field-theory-based analysis. The temperature dependence of the magnetic susceptibilities and EPR transitions of the dicopper(II) complexes, together with the simulation of the EPR spectra of the mono- and dinuclear complexes leads to an anisotropic set of g- and A-values, zero-field splitting (ZFS) and magnetic exchange parameters (Cu1: g(z) = 2.055, g(x) = 2.096, g(y) = 2.260, A(z) = 8, A(x) = 8, A(y) = 195 × 10(-4) cm(-1), Cu2: g and A as for Cu(1) but rotated by the Euler angles α = -6°, β = 100°, D(exc) = -0.07 cm(-1), E(exc)/D(exc) = 0.205 for [{Cu(L(1))}(2)(CN)](BF(4))(3)·1.35 H(2)O; Cu1,2: g(z) = 2.025, g(x) = 2.096, g(y) = 2.240, A(z) = 8, A(x) = 8, A(y) = 190 × 10(-4)cm(-1), D(exc) = -0.159 cm(-1), E(exc)/D(exc) = 0.080 for [{Cu(L(2))}(2)(CN)](BF(4))(3)). Thorough ligand-field-theory-based analyses, involving all micro states and all relevant interactions (Jahn-Teller and spin-orbit coupling) and DFT calculations of the magnetic exchange leads to good agreement between the experimental observations and theoretical predictions. The direction of the symmetric magnetic anisotropy tensor D(exc) in [{Cu(L(2))}(2)(CN)](BF(4))(3) is close to the Cu···Cu vector (22°), that is, nearly perpendicular to the Jahn-Teller axis of each of the two Cu(II) centers, and this reflects the crystallographically observed geometry. Antisymmetric exchange in [{Cu(L(1))}(2)(CN)](BF(4))(3)·1.35 H(2)O causes a mixing between the singlet ground state and the triplet excited state, and this also reflects the observed geometry with a rotation of the two Cu(II) sites around the Cu···Cu axis.     

Mechanistic insights from reactions between copper(II)-phenoxyl complexes and substrates with activated C-H bonds

The reactivities of two copper(II)-phenoxyl analogues of the oxidized, active form of the metalloenzyme galactose oxidase, [1tBu2]+ and [2tBu2]+, have been studied using the substrates benzyl alcohol and 9,10-dihydroanthracene, for a total of four reactions. The reaction stoichiometries in all cases show a 2:1 ratio of oxidant to benzaldehyde or anthracene product, indicating that [1tBu2]+ and [2tBu2]+ behave ultimately as only one-electron oxidants, but the reaction kinetics each indicate that only a single copper(II)-phenoxyl complex is involved in the rate-determining step. For each substrate, rate laws indicate that [1tBu2]+ and [2tBu2]+ react by different mechanisms: one proceeds by a simple bimolecular reaction, while the other first enters into a substrate-binding equilibrium before subsequently reacting by an intramolecular reaction. The reactions proceeding by the latter mechanism have faster overall rates, which correlates to a lower entropic barrier for the substrate-binding mechanism. Correlation of the reaction rates with the C-H bond dissociation energies of substrates as well as significant deuterium kinetic isotope effects indicates that the rate-determining steps involve hydrogen atom abstraction from the activated C-H bonds. A variable-temperature study (268-308 K) of the nonclassical KIE of the [1tBu2]+/benzyl alcohol reaction (kH/kD = 15 at 298 K) failed to show evidence for quantum tunneling. The rapid sequence by which a second 1 equiv of copper(II)-phenoxyl oxidant completes the reaction after the rate- and product-determining hydrogen atom abstraction step cannot be probed kinetically. Comparisons are made to the reactivities of other copper(II)-phenoxyl complexes reported in the literature and to galactose oxidase itself.     

Synthesis of copper(II) and nickel(II) triazacycloalkane complexes

Summary Copper(II) and nickel(II) complexes of triazacycloalkanes (pqr-cy), with p, q, r = 2–6, have been prepared and characterized by means of electronic and i.r. spectroscopy, and by magnetic measurements. With nickel(II) mononuclear octahedral complexes [Ni(pgr-cy)₂](CI0₄)₂ are formed, but for copper(II) mononuclear octahedral complexes were obtained only for 222-cy and 223-cy. The other ligands gave copper(II) complexes of the type [Cu(pgr-cy)CI]CIO₄, [Cu(pgr-cy)OH]ClO₄, Or [Cu(pgr-cy)CI_1/2OH_1/2]ClO₄. The hydroxy complexes have low magnetic moments and binuclear hydroxy bridged structures are proposed.Ligand names: e.g. p = q = r = 2 is 1,4,7-triazacvclononane     

Salen and tetrahydrosalen nickel(II) and copper(II) complexes

The synthesis and characterisation of novel bis salen complexes, M(salenH2), N,N-bis-[5(1,1,3,3-tetramethyl- butyl)salicylidene]-1,2-diaminoethane complexes, (M=Ni or Cu), and the corresponding less studied, bis-tetrahydrosalen complexes, M[H2(salenH2)], N,N-bis-[2-hydroxy-5(1,1,3,3-tetramethylbutyl)benzyl]-1,2-diaminoethane complexes, (M=Ni or Cu), with a highly branched substitution pattern at C-5 of the benzene ring is described. The Schiff bases behave as dibasic tetradentate ligands. The tetrahydrosalen complexes show structural properties, chemical and thermal behaviour which is different from those of the corresponding salen complexes. The melting points and decomposition temperatures of these complexes were determined by d.s.c. and t.g.a.     

QSAR of copper(II) complexes with cytotoxic properties

Summary A QSAR based on a multiple regression analysis for 15 copper(II) semi- and thiosemicarbazone complexes with cytotoxic properties is presented. In vitro cytotoxicity was selected as the dependent variable and Van der Waals volumes (Vm), octanol- water partition coefficients (logP), specific rate constants of the copper(II) complexes towards superoxide radicals (k _s ) and variation in C=N vibration bands (CN) in IR spectra of the complexes with respect to the free ligands were selected as the independent variables. The stepwise regression procedure and the all possible regressions were practiced in the analysis of the data. The orthogonality analysis proved noncollinearity among the variables. According to the obtained equation the two best copper(II) complexes were submitted to a broad in vivo screening study and resulted to be active against La, P-388 and L-1210 leukemias.

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QSAR von Kupfer(II)-Komplexen mit cytotoxischen Eigenschaften

Zusammenfassung Es wird eine quantitative Struktur-Aktivitäts-Beziehung basierend auf einer multiplen Regressionsanalyse für 18 Kupfer(II)-Semi- und Thiosemicarbazon-Komplexe präsentiert. Die in vitro-Cytotoxizität wurde als die abhängige Variable und Van-der-Waals-Volumina (Vm), Octanol-Wasser-Verteilungskoeffizienten (logP), spezifische Geschwindigkeitskonstanten der Kupfer(II)-Komplexe gegenüber Superoxid-Radikalen (k _s ) und die Variationen der C=N-Vibrationsbanden (CN) in den IR-Spektren der Komplexe gegenüber den freien Liganden als unabhängige Variablen eingeführt. Es wurde stufenweise Regression und die alle möglichen Regressionen-Prozedur in der Analyse der Daten verwendet. Die Orthogonalitätsanalyse zeigte Nichtkolinearität der Variablen an. Entsprechend den erhaltenen Gleichungen wurden die beiden besten Kupfer(II)-Komplexe einem breiten in vivo-Screening unterworfen. Sie waren gegenüber La, P-388 und L-1210 Leukemie aktiv.