ESR study on some copper(Ⅱ)complexes of bis(4''''-benzo-15-crown-5)

ESR measurements have been carried out for some copper(Ⅱ) complexes of bis(4'-ben-zo-15-crown-5) at 77 K.The results of ESR spectrometric titration indicated that the binuclear com-plexes were prepared in the present system.The binuclear complexes revealed characteristic ESRg-anisotropies (gZ相似文献   

Bis-η5-cyclopentadienyl and Bis-η5-methylcyclopentadienylN,N-dialkyldithiocarbamato(chloro)titanium(IV) compounds

Summary Titanium(IV)N,N-dialkyldithiocarbamates of the type ⁵-Cp₂Ti (S₂CNR₂)Cl and (⁵-MeCp)₂Ti(S₂CNR₂)Cl (R = Me, Et and i-Pr) have been prepared by the reaction of di--cyclopentadienyldichlorotitanium(IV) and bis-n-methylcyclopentadienyldichlorotitanium(IV) with sodium salts of dithiocarbamic acids in refluxing dichloromethane. Molecular weight, conductance and i.r. studies show these complexes to be monomeric nonelectrolytes in which the dithiocarbamate ligands are bidentate. Therefore, pentacoordination may be assigned to titanium(IV) atom in all six complexes. Electronic and proton n.m.r. studies spectra have also been recorded for the complexes.     

Selective synthesis and reactivity of eta5-arylcyclohexadienyliron complexes

A series of aryl-substituted cyclohexadienyliron complexes have been prepared by a general procedure that determines regioselectivity by correctly positioning leaving groups in the precursor complexes. The aryl groups at 1-C or 2-C have been shown to be omega directing by the study of reactions with a representative range of nucleophiles, and these regioselectivity properties have been related to the spectroscopic properties of the cationic cyclohexadienyliron complexes. A high level of electron-donating substituents on the arene, or switching between the [Fe(CO)3] and [Fe(CO)2PPh3] series, reduces the minor ipso pathway, improving regiocontrol. Placing opposed directing groups in the arylcyclohexadienyliron complexes reverts reactivity to the ipso pathway with stabilised enolate nucleophiles, and when the additional directing group reinforces the effect of the aryl group, the ipso pathway is stopped.     

Coordination compounds of hydrazine derivatives with transition metals. Part 27. Coordination chemistry of 4-amino-3-alkyl-5-thio-1,2,4-triazolines and 4-amino-5-oxo-3-thioxo-6-alkyl-2,3,4,5-tetrahydro-1,2,4-triazines

Summary Mono-, bis- and tris-ligand nickel(II) and cobalt(II) complexes with 4 amino-3-alkyl-5-thio-1,2,4-triazolines (HRL) (R=H, Me, or Et) and 4-amino-5-oxo-3-thioxo-6-methyl-2,3,4,5-tetrahydro-1,2,4-triazine (HL') have been prepared and characterized. In these complexes both HRL and HL' are in the neutral thione form. Nickel(II) and cobalt(II) complexes with mononegative thiolate ligands have been also isolated.The reaction of HL' with copper(II) salts in a molar ration of 11 results in the formation of [Cu(HL')X] (X=Cl or Br) and Cu(L')X (X=NO₃ or CH₃COO). However, in the presence of a large excess of HL' the reaction proceeds with partial reduction of Cu^II and both [Cu(HL')X₂] and [Cu(HL')₂]X have been isolated and characterized. The mechanism of copper(II) reduction by HL' is discussed.     

Spectrophotometric determination of uranium (VI) with 5-hydroxy-flavone and 5-hydroxy-7-methoxy-flavone

Summary 5-Hydroxy-flavone and 5-hydroxy-7-methoxy-flavone have been used for the spectrophotometric determination of uranium. With uranium(VI) both the reagents form yellowish-orange complexes soluble in 50% v/v ethanol. The characteristics of the complexes have been studied spectrophotometrically. The molar composition of uranyl-5-hydroxy-flavone complex shows that it contains uranium and the reagent in the ratio of 11, while in case of uranyl-5-hydroxy-7-methoxy-flavone complex, it contains uranium and the reagent in the molar ratio of 12. The logK values, as determined by method based on Beer's law have been found to be 9.22 and 9.70 respectively, at 30°C.

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Zusammenfassung 5-Hydroxy-flavon (I) und 5-Hydroxy-7-methoxy-flavon (II) wurden als Reagentien zur spektrophotometrischen Bestimmung von Uran benutzt. Beide Substanzen geben mit U^VI einen gelborange gefärbten Komplex, der in 50%igem Äthanol löslich ist. Die Eigenschaften der Komplexe wurden untersucht. Das Verhältnis U:Reagens im Komplex beträgt 11 (I) bzw. 12 (II). Die logK-Werte wurden zu 9,22 (I) bzw. 9,70 (II) gefunden (30° C).

     

Substituent effects on exchange coupling: 5-Aryl-substituted semiquinones and their complexes with MnII and CuII

A series of functionalized radical anion semiquinone (SQ-Ar) ligands and their MnII- and CuIIhydro-tris(3-cumenyl-5-methylpyrazolyl)borate (TpCum,MeMII) complexes were prepared and characterized. The semiquinone ligands have substituted phenyl rings (Ar = -C6H5NO2, -C6H5OMe, -C6H5-tert-Bu, etc.) attached to the SQ 5-position. Despite the "remoteness" of the phenyl ring substituents, the MII-SQ exchange parameters, J, were found to vary nearly 3-fold. Attempts to quantify the substituent effects on J are complicated by the fact that not all complexes could be structurally characterized. As such, substituent effects and phenyl-ring torsion angles could conspire to produce the observed variation in J values. Although there is no clear trend in the J values as a function of SQ substituent for the MnII complexes, for the CuII complexes, electron-withdrawing substituents on the phenyl ring have greater ferromagnetic J values than the CuII complexes of SQ ligands with electron-donating substituents. This trend suggests a FM contribution from MLCT excited states in the copper complexes.     

Synthesis, reactivity, spectroscopic characterization, X-ray structures, PGSE, and NOE NMR studies of (eta5-C5Me5)-rhodium and -iridium derivatives containing bis(pyrazolyl)alkane ligands

Rhodium(III) and iridium(III) complexes containing bis(pyrazolyl)methane ligands (pz = pyrazole, L' in general; specifically, L1 = H2C(pz)2, L2 = H2C(pzMe2)2, L3 = H2C(pz4Me)2, L4 = Me2C(pz)2), have been prepared in a study exploring the reactivity of these ligands toward [Cp*MCl(mu-Cl)]2 dimers (M = Rh, Ir; Cp* = pentamethylcyclopentadienyl). When the reaction was carried out in acetone solution, complexes of the type [Cp*M(L')Cl]Cl were obtained. However, when L1 and L2 ligands have been employed with excess [Cp*MCl(mu-Cl)]2, the formation of [Cp*M(L')Cl][Cp*MCl3] species has been observed. PGSE NMR measurements have been carried out for these complexes, in which the counterion is a cyclopentadienyl metal complex, in CD2Cl2 as a function of the concentration. The hydrodynamic radius (rH) and, consequently, the hydrodynamic volume (VH) of all the species have been determined from the measured translational self-diffusion coefficients (Dt), indicating the predominance of ion pairs in solution. NOE measurements and X-ray single-crystal studies suggest that the [Cp*MCl3]- approaches the cation, orienting the three Cl-legs of the "piano-stool" toward the CH2 moieties of the bis(pyrazolyl)methane ligands. The reaction of 1 equiv of [Cp*M(L')Cl]Cl or [Cp*M(L')Cl][Cp*MCl3] with 1 equiv of AgX (X = ClO4 or CF3SO3) in CH2Cl2 allows the generation of [Cp*M(L')Cl]X, whereas the reaction of 1 equiv of [Cp*M(L')Cl] with 2 equiv of AgX yields the dicationic complexes [Cp*M(L')(H2O)][X]2, where single water molecules are directly bonded to the metal atoms. The solid-state structures of a number of complexes were confirmed by X-ray crystallographic studies. The reaction of [Cp*Ir(L')(H2O)][X]2 with ammonium formate in water or acetone solution allows the generation of the hydride species [Cp*Ir(L')H][X].     

Synthesis,crystal structures,characterization and antimicrobial activities of 5-hydroxyisophthalate complexes

Two 5-hydroxyisophthalate complexes of nickel(II), formulated as [Ni(μ-Hhip)(2-hepy)₂] _n (1) and [Ni₂(μ-Hhip)₂(dap)₄] _n (2) (H₃hip = 5-hydroxyisophthalic acid, 2-hepy = 2-(2-hydroxyethyl)pyridine, dap = 1,3-diaminopropane), have been synthesized and characterized by chemical and spectroscopic methods. The molecular structures of the complexes have been determined by single-crystal X-ray diffraction analysis. The Ni(II) centres have distorted octahedral geometries in both crystals. Furthermore, both complexes have 1D chain structures in which the individual chains are linked together via hydrogen bonds to give 3D frameworks. Evaluation of the complexes by the agar diffusion method showed that they have weak antibiotic activities against the tested microorganisms.     

Copper(II), nickel(II), cobalt(II) and oxovanadium(IV) complexes of 1-(3-hydroxy-2-naphthyl)-5-(p-X-phenyl)pent-4-ene-1,3-diones

Complexes of 1-(3-hydroxy-2-naphthyl)-5-(p-X-phenyl)pent-4-ene-1, 3-diones (HXNP) (X = H, Cl, Me or OMe) with divalent metal ions, having the formula M(HXNP)2 (M = Cu, Ni or Co) and M(HXNP)2 · nB (n = 0,2: B = H2O or Py), have been prepared and characterized by elemental analyses, i.r., electronic, 1H-n.m.r. and e.s.r. spectroscopies and by magnetic susceptibility measurements. Spectral assignments show the metal ions to be coordinated through both carbonyl oxygen atoms and the effect of conjugation of the ligand structure (d–* interaction) is strong enough to stabilize the metal ligand bond. The observed hyperfine splitting constants and magnetic moments suggest that the copper complexes are monomers with a slightly distorted planar structure, having more covalent in plane -bonding. The magnetic and spectral properties of the dihydrates and dipyridinates of the cobalt and nickel complexes are commensurate with monomeric high-spin octahedral geometries; polymerization takes place on dehydration–depyridination of nickel(II) complexes. Oxovanadyl complexes of these -diketones have also been prepared; the ligand-to-metal ratio is 2:1 with square pyramidal geometry. The e.s.r. spectra of the complexes show the presence of one unpaired electron in the dxy orbital and the hyperfine splitting constants are sensitive to a change in solvent. The effect of bases on the redox behaviour of copper(II) complexes owing to geometry change is discussed.     

Versatile ligand behavior of hydrotris(4-ethyl-3-methyl-5-thioxo-1,2,4-triazolyl)borate. Syntheses and crystal structures of Cu(I) and Bi(III) complexes

Preparations of copper(I) and bismuth(III) complexes of hydrotris(4-ethyl-3-methyl-5-thioxo-1,2,4-triazolyl)borate (Tr(Et,Me)) are described. These complexes have been characterized by means of spectroscopy and microanalysis. Molecular structures of [Cu(Tr(Et,Me))](2) x 2.5CH(3)CN x 0.5H(2)O (3a) and [Bi(Tr(Et,Me))(2)]NO(3) x 2CHCl(3) (4a) have been determined by single-crystal X-ray diffraction. In the centrosymmetric dimeric copper(I) complex, Tr(Et,Me) acts in the k(3)S,S',H:kS' ' coordination mode. The metal is found in a distorted trigonal geometry as the ligand exhibits an "S(3)-inverted" conformation at the boron center so that a weak [B-H.Cu] agostic interaction renders the overall coordination of the (3 + 1) type. On the other hand, in the bismuth complex, Tr(Et,Me) presents the k(3)S,S',S' ' coordination mode and the "S(3)-normal" conformation. The metal is found in a regular octahedral geometry bound by six thioxo groups of two ligands. Species distributions in solution have been studied using electrospray ionization mass spectrometry upon dissolution of 3a and 4a crystals in acetonitrile. Monomeric and polynuclear copper(I) complexes with different M:L ratios are present in solution, while for 4a only the monomeric species is present.     

Transition metal derivatives of 3-4-diphenyl-5-mercapto-l,2,4-triazole

Neutral chelates of 3,4-diphenyl-5-mercapto-l,2,4-triazole (DPMTH) with Fe(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II) have been prepared and characterized by analytical and physicochemical techniques such as magnetic susceptibility measurements, TGA, electronic ESR and IR spectral studies. The IR data suggest that DPMTH behaves as a uninegative bidentate ligand in all the complexes except Fe(II) and Ni(II) where it is tridentate. The complexes have been found to display significant antifugal activity againstA. ahernata andA. flavus.     

Synthesis and crystal structure of nickel(II) complexes with bis(5-methyl-2-thiophenemethyl)(2-pyridylmethyl)amine

A series of nickel(II) complexes having the (Me-Tp)₂PMA ligand ((Me-Tp)₂PMA = bis(5-methyl-2-thiophenemethyl)(2-pyridylmethyl)amine) with nitrates (1), chlorides (2), and perchlorates (3) as anions were synthesized and isolated. All these complexes were successfully characterized by physicochemical methods including X-ray crystallographic analysis. In complex 1, the ligand binds in a bidentate N₂ fashion, whereas in the cases of 2 and 3 the ligand binds in the tridentate N₂S form. The coordination geometry around the nickel(II) atoms in these complexes is distorted octahedral.     

Macrocyclic [N<Subscript>5</Subscript>] transition metal complexes: synthesis,characterization and biological activities

Novel penta-azamacrocyclic 21-membered [N₅] ligand [L] and its transition metal complexes with Co(II), Ni(II), Cu(II), Ru(III) and Pd(II) have been isolated and characterized. The mode of bonding and overall geometry of the complexes have been inferred through IR, MS, UV–Vis, EPR, ¹H NMR spectral studies, molar conductivity, magnetic, thermal and microanalyses, On the basis of above studies, an octahedral geometry has been proposed for all complexes except Pd(II) chloride complex which adopt square planar geometry. The in vitro antitumor activity of the synthesized ligand and some selected complexes against human breast and human hepatocarcinoma cell lines (MCF-7) and (HePG2), respectively has been studied. The results show that the tested compounds are potent antitumor agents. Also the ligand and some selected complexes have been tested for their inhibitory effect on the growth of bacteria: Streptococcus pyogenes as Gram-positive bacteria and Escherichia coli as Gram-negative bacteria. The activity data show that most of the tested compounds exhibit remarkable antibacterial activity against these organisms.     

Electronic and vibrational studies of copper(II) complexes of 1-phenyl-3-methyl-4-acylpyrazolones-5

The interaction between Cu(II) and 1-pheny]-3-methyl-4-acylpyrazolones in aqueous medium has been investigated. The complexes were isolated and characterized using electronic and vibrational spectral measurments. Bathochromic shifts were observed for the complexes in the UV and infrared (IR) spectral regions. Analysis of the spectral properties of the complexes reveal that the stability of the

bond of the COCu bonding system decreases while that of the CuO bond in the same system increases as the carbon chain of the 4-acyl substituent increases. The complexes have μ_eff values within the range of 1.75–1.82 B.M.     

Models of the membrane-bound cytochromes: mössbauer spectra of crystalline low-spin ferriheme complexes having axial ligand plane dihedral angles ranging from 0 degree to 90 degrees

Crystalline samples of four low-spin Fe(III) octaalkyltetraphenylporphyrinate and two low-spin Fe(III) tetramesitylporphyrinate complexes, all of which are models of the bis-histidine-coordinated cytochromes of mitochondrial complexes II, III, and IV and chloroplast complex b(6)f, and whose molecular structures and EPR spectra have been reported previously, have been investigated in detail by M?ssbauer spectroscopy. The six complexes and the dihedral angles between axial ligand planes of each are [(TMP)Fe(1-MeIm)(2)]ClO(4) (0 degree), paral-[(OMTPP)Fe(1-MeIm)(2)]Cl (19.5 degrees), paral-[(TMP)Fe(5-MeHIm)(2)]ClO(4) (26 degrees, 30 degrees for two molecules in the unit cell whose EPR spectra overlap), [(OETPP)Fe(4-Me(2)NPy)(2)]Cl (70 degrees), perp-[(OETPP)Fe(1-MeIm)(2)]Cl (73 degrees), and perp-[(OMTPP)Fe(1-MeIm)(2)]Cl (90 degrees). Of these, the first three have been shown to exhibit normal rhombic EPR spectra, each with three clearly resolved g-values, while the last three have been shown to exhibit "large g(max)" EPR spectra at 4.2 K. It is found that the hyperfine coupling constants of the complexes are consistent with those reported previously for low-spin ferriheme systems, with the largest-magnitude hyperfine coupling constant, A(zz), being considerably smaller for the "parallel" complexes (400-540 kG) than for the strictly perpendicular complex (902 kG), A(xx) being negative for all six complexes, and A(zz) and A(xx) being of similar magnitude for the "parallel" complexes (for example, for [(TMP)Fe(1-MeIm)(2)]Cl, A(zz) = 400 kG, A(xx) = -400 kG). In all cases, A(yy) is small but difficult to estimate with accuracy. With results for six structurally characterized model systems, we find for the first time qualitative correlations of g(zz), A(zz), and DeltaE(Q) with axial ligand plane dihedral angle Deltavarphi.     

Synthesis and spectroscopic studies of metal(II) complexes prepared withN-2-(5-picolyl)-N′-phenylthiourea

Summary The chlorides and bromides of cobalt(II), nickel(II) and copper(II) along with the acetates of the latter two metal ions and copper(II) tetrafluoroborate were used to prepare complexes ofN-2-(5-picolyl)-N-phenylthiourea (5MTUH). 5MTUH coordinates as a bidentate ligand via the pyridyl nitrogen and the sulphur atoms in the cobalt(II) complexes and the compounds isolated with Cu(BF₄)₂ and CuCl₂. Complexes of stoichiometry [Cu(5MTU)X] (X=Br or C₂H₃O₂) appear to have the deprotonated ligand coordinated via the pyridyl andN thioamide nitrogens and the sulphur atom. The nickel(II) complexes involve monodentate 5MTUH with sulphur being the donor atom. A violet, octahedral [Co(5MTUH)₂Cl₂] complex and a blue, tetrahedral [Co(5MTUH)Cl₂] complex have been isolated, but with CoBr₂ only an octahedral complex could be prepared.     

Synthesis,physicochemical, antimicrobial,and 3D molecular modeling studies of oxomolybdenym(V) and dioxomolybdenum(VI) complexes with a Schiff base isonicotinoyl(5-bromo-2-hydroxybenzylidene)hydrazide

Synthesis of some new oxomolybdenum(V) and dioxomolybdenum(VI) complexes with a Schiff base isonicotinioyl(5-bromo-2-hydroxybenzylidene)hydrazide (L) derived from 5-bromosalicylaldehyde and isonicotinoylhydrazide are reported. The complexes have been characterized by elemental analyses, molar conductance, magnetic susceptibility data, IR, UV-Vis, EPR, ¹H NMR, and FAB mass spectral studies. The physicochemical studies and spectral data indicate that L acts as a monovalent tridentate chelating agent. The FAB mass and X-band EPR spectra indicate that the pentavalent Mo in the complex is monomeric in nature. The X-ray diffraction studies of the complex [MoO(L)Cl₂] (I) correspond to the orthorhombic crystal lattice with the unit cell dimensions a = 16.11, b = 12.20, and c = 7.5 Å. The electrochemical behavior of the complex was investigated by cyclic voltammetry. All the complexes are found to be neutral with the distorted octahedral geometry. The thermal properties of the complex I were investigated by thermogravimetric techniques. The ligand L and the complexes I and [MoO₂(L)Cl] (II) were screened for their in vitro antimicrobial activity. The complexes exhibited higher activity than L. The 3D molecular modeling and analysis for bond length and bond angles have also been carried out for complex I.     

Thermoanalytical study of selected transition bivalent metal complexes with 5-carbaldehyde-4-methylimidazole

To compare thermal stability of Co(II), Zn(II), and Cd(II) complexes with 4-CHO-5-MeIm, the two compounds of formula [MnL₂(NO₃)₂] and [NiL₃](NO₃)₂ have been prepared and structurally characterized. Elemental analysis and spectroscopic studies have confirmed a bidentate fashion of coordination of the ligand to Mn(II) and Ni(II) ions. IR and Raman spectra indicate that there are different coordination modes of the NO₃ ^? in compounds: non-coordinated and coordinated. The decomposition process of the studied complexes in nitrogen and argon (Ni(II) complex) atmosphere proceeds in three main stages, except Zn(II) complex, in temperature range 353?C1163?K. The final products of decomposition are CoO, MnO, Cd, ZnN₄, NiN₃. In addition, we have to admit that the different coordination mode of the NO₃ ^? ions in complexes: non-coordinated (in the (1), (4), and (5)) and coordinated (in the (2) and (3)) correlate with its thermal behavior. Thus, temperature ranges of its decompositions are observed: below 533?K and above 533?K, respectively. In Co(II), Mn(II), and Cd(II) complexes the fragments of N-donor atom-containing ligands decompose in the last stages, contrary to Zn(II) and Ni(II) compounds, in which metal ion surrounded by N atoms remains until the end. The course of pyrolysis and molecular structure of the complexes lead to the same conclusion about the strength of metal?Cligand bonds. On the basis of obtained results, it is concluded that the thermal stability of the studied compounds follows the order: (1)?<?(5)?<?(2)?<?(3)?<?(4).     

Photophysical properties and excitation polarization of fac/mer-ruthenium complexes with 5'-amino-2,2'-bipyridine-5-carboxylic acid derivatives

Novel ruthenium(II) complexes, fac/mer-[Ru(MeCO-5Bpy-R)3]2+ (H-5Bpy-OH = 5'-amino-2,2'-bipyridine-5-carboxylic acid; R = -NHtBu, -NH(cHex), -N(cHex)2), have been synthesized. The fac and mer isomers have been successfully separated using HPLC techniques, and their photophysical/electrochemical properties have been investigated. In the absorption and emission spectra of fac/mer-[Ru(MeCO-5Bpy-R)3]2+ with secondary amines (R = -N(cHex)2) in acetonitrile at room temperature, the maximum wavelengths based on the MLCT are longer than those for the amide derivatives with primary amines (R = -NHtBu, -NH(cHex)). A small solvent effect on the photophysical properties between fac- and mer-[Ru(MeCO-5Bpy-NHtBu)3]2+ has been observed. The excitation polarization spectra, giving P values reflecting the relation between the absorption and the emission oscillators, for the fac- and mer-ruthenium(II) complexes (C3 and C1 symmetry, respectively) have been measured for the first time. Almost no difference in the excitation polarization spectra between the fac and mer complexes is found, and these spectra are similar to that for [Ru(bpy)3]2+ with D3 symmetry. This finding suggests that the orientations of the absorption and emission oscillators, in the case of the ruthenium(II) tris(2,2'-bipyridine) derivatives, would not be affected by the symmetries of the complexes and that the P values for any derivatives would be similar to that for [Ru(bpy)3]2+.     

Novel 3d-metal complexes with 1,2-diamino-3-(2-benzothiazolyl)-4(5H)-ketopyrrole: Synthesis,spectroscopic and structural investigations

A series of new 3d-metal complexes have been prepared by the reaction of M(CH₃COO)₂ (M = Zn(II), Co(II), Ni(II)) and 1,2-diamino-3-(2-benzothiazolyl)-4(5H)-ketopyrrole (HL) in a methanol (3) or a methanol/dmf (1, 2) medium. All the complexes have been studied by elemental analyses, electronic and IR spectroscopies. The zinc(II) complex 1 and the ligand HL have been investigated using the method of ¹H NMR-spectroscopy at various temperatures. The disappearance of the signal from one proton of the amino group H(5) in the spectrum of complex 1 confirmed the existence of the ligand in the deprotonated form. According to the data of the ¹H NMR-spectroscopy, the ligand HL is coordinated to zinc(II) through the nitrogen atom of the deprotonated amino group and the nitrogen atom of the benzothiazole substituent. These data are in agreement with X-ray structural studies for the ligand HL and the zinc(II) complex 1.