Copper(I) and copper(II) complexes of biologically relevant tridentate ligands

The preparation of a series of tridentate ligands of formulae X(CH₂C₇H₅N₂)₂ (X = NH, S, O, S₂) is described. The ligands contain two benzimidazole moieties and one of NH, S, O, or S₂ as the donor groups. Cu(I) and Cu(II) complexes of these ligands are prepared and characterized. Spectroscopic and X-ray data imply that the geometric constraints of these ligands impose a distorted coordination geometry at copper. The implications and relevance of this chemistry to copper proteins is discussed.     

Platinum(II) complexes of pyrimidine-derived ligands

A series of new Pt(II) complexes of hydrazinouracils were synthesized and studied. The complexes have the general formula [Pt₂L2^?Cl₂]nH₂O, where L^? is a deprotonated molecule of a ligand, n = 1?3 and there are two bridging chloride ions. The ligands are bonded through the amino group of the hydrazine residue and the nitrogen atom of the pyrimidine cycle. From ¹H NMR data it is concluded that the preferred type of coordination is Pt- N(3), hydrazine chelation, which is characteristic for solid complexes. Although the participation of the N(1) atom in formation on the polynuclear complexes is possible, it may be that N(1) coordination occurs only in solutions.     

Monomeric molybdenum(V) complexes. 4. The structure of tetraphenylarsonium oxodichloro(N-2-oxophenylsalicylideniminato)molybdate(V), [Ph4As] [MoOCl2(SalphO)]

The structure of [Ph₄As] [MoOCl₂(SalphO)], where SalphO is N-2-oxophenylsalicylideniminate dianion, has been determined by X-ray crystallography. The complex crystallizes in the monoclinic space group P2₁/n with a = 11.829(2), b = 16.149(3), c = 17.410(3) Å, β = 97.485(15)° and Z = 4. The calculated and observed densities and 1.566 and 1.573(10) g cm^?3, respectively. Block-diagonal least-squares refinement of the structure using 4722 independent reflections with I ? 3σ(I) converged at R = 0.0345 and R_w = 0.0484. The crystal contains [Ph₄As]⁺ cations and [MoOCl₂(SalphO)]^? anions. The Mo atom in the anion is in a distorted octahedral coordination environment. A planar terdentate Schiff base ligand occupies meridional positions with the N atom trans to the terminal oxo group (O_t). Two Cl atoms are cis to the O_t atom. The Mo atom is displaced by 0.33 Å from the equatorial plane toward the O_t atom. The MoO_t distance is 1.673(3) Å. The MoN bond trans to the O_t atom is 2.298(4) Å. The two MoCl bond lengths are 2.371(1) and 2.408(1) Å. The difference of 0.037 Å is significant (30 σ). Preparations of the title complex and the related complexes are also described.     

Antitumor activity and metal complexes of the first transition series. Trans-bis(salicylaldoximato)copper(II) and related copper(II) complexes,a novel group of potential antitumor agents

The antitumor activity of forty nine different metal complexes of the first transition series against mouse leukemia L 1210 cells and of two of the complexes against Ehrlich ascites carcinoma have been tested in vitro by the method described in this paper. Eight complexes showed a 50% inhibition of tumor cell division at concentration level 5–6 μg/ml of the complex for the former and two most effective complexes also for the latter. The trans-bis-(salicylaldoximato)copper(II) and trans-bis(resorcylaldoximato)copper(II) complexes were found to possess the highest antitumor activity.     

Kinetics of electron transfer between Ce(IV) nitrate and iron(II) complexes

The rate constants for the oxidation of some 1,10- phenanthroline and 2,2’-bipyridine complexes of iron(II) by cerium(IV) in nitrate media are reported. In the acidity range investigated (0.05–2.0 M), the predominant reactive species is Ce⁴⁺, although CeOH³⁺ also contributes to the reaction progress.The results are shown to be consistent with the Marcus theory for outer-sphere electron transfer reactions, and the intrinsic parameter for Ce^4+/3+ couple was estimated.     

Mononuclear Ni(II) and Zn(II) complexes of some potentially binucleating Schiff base ligands

Mononuclear Zn(II) and Ni(II) complexes have been prepared from two new Schiff base ligands in which two alternative co-ordination sites (N₂O₂ or O₂O₂) occur. The first ligands is the Schiff base derived from 1,2-diaminobenzene and 2-hydroxy-3-carboxyl-1-napthaldehyde (bopaH₄). The complexes of this ligand contain the metal ions in the N₂O₂ coordination site as a result of the steric requirements of the co-ordinated ligand. The second ligand series are derivatives of X-substituted 1,2-diaminobenzenes, 2-hydroxy-3-carboxy-1-naphthaldehyde and 2-hydroxy-5-methyl isophthaldehyde (X-bolaH₃). In this case Ni(II) occupies the N₂O₂ site in its complexes with the X-bolaH₃ ligands, whereas the Zn(II) complexes are co-ordinate through the O₂O₂ site since the steric restrictions are less severe.     

The direct electrochemical synthesis of neutral and anionic halogen complexes of uranium(IV) and uranium(VI)

The electrochemical oxidation of anodic uranium into acetonitrile solutions of X₂ (X = Cl, Br) under nitrogen gives rise to UCl₄·4CH₃CN or UBr₄·2CH₃CN in good yield. These compounds are easily converted to other UX₄ adducts. In the presence of oxygen, solutions of UO₂X₂ are produced by the electrolysis, and the parent halide, or neutral addition compounds, are readily obtained from these. Addition of R₄NX to the cell results in the direct synthesis of (R₄N)₂UX₆ under nitrogen, or (R₄N)₂UO₂X₄ under oxygen. The only iodo compound which could be formed by electrolysis into N,N- dimethylformamide (=dmf) was UI₄·4dmf.     

Copper(II) halide complexes of 2-aminobenzophenone. Crystal and molecular structure of bis(2-aminobenzophenone)dichlorocopper(II)

The complexes CuX₂L₂ (X = Cl, Br; L = 2-aminobenzophenone) were prepared and characterized by means of magnetic and spectroscopic measurements. For the Cl compound the crystal structure was also determined. Crystals are triclinic, space group P$\text{1}$, with a = 13.397(3), b = 10.752(2), c = 9.205(2) Å, α = 72.26(1)°, β = 91.58(1)°, γ = 106.86(1)°, and Z = 2. The structure was solved by the heavy-atom method and refined by least-squares calculations to R = 0.034 for 2581 counter data. It consists of discrete CuX₂L₂ monomers showing distorted trigonal bipyramidal coordination geometry about the copper ion. The amino nitrogens are axial ligands, with the equatorial positions occupied by two chlorine atoms and a carbonyl oxygen from one L molecule acting as a bidentate ligand. Infrared and ligand field spectroscopies and magnetic measurements, interpreted on the basis of the known crystal structure, also suggest a similar structure for the related Br compound.     

Preparation of heterocyclic thialato ligands and their Copper(II) complexes

A number of different heterocyclic aldehydes substituted in the β-position with the t-butylthio moiety were converted into new S₂N₂ ligands containing protected thiol groups. Reaction of the protected ligands 2 with copper(II) salts resulted in elimination of isobutene and formation of copper(II) complexes of mercaptoimines 3.     

Metal complexes of the schiff bases 2-pyridinylhydrazine and 2-quinolinyl-hydrazine with 2-pyridinecarboxaldehyde N-oxide,including some N-oxide-bridged antiferromagnetic complexes of cobalt(II) and nickel(II)

Metal complexes of 2-pyridine carboxaldehyde 2′-pyridinylhydrazone 1-oxide (poph) and 2-pyridinecarboxaldehyde 2′-quinolinylhydrazone 1-oxide (poqh) are reported with copper(II), nickel(II), cobalt(II), iron(II) and manganese(II). Each ligand appears to function as an ONN donor, via the pyridine N-oxide oxygen, the imine nitrogen, and a pyridine or quinoline nitrogen. The complexes have been characterised by magnetic susceptibility measurements to liquid nitrogen temperature, and also by electronic, infrared, X-ray powder diffraction, and Mössbauer spectra. No magnetic interaction was detected with the copper(II) complexes. All the complexes of metal nitrates appear to be monomers.The complexes of poph with the halides and thiocyanates of nickel(II) and cobalt(II) appear to be six-coordinate and N-oxide-bridged; they exhibit varying degress of antiferromagnetic interaction and the magnetic data for the nickel(II) complexes have been fitted to various models. In contrast, the bulky ligand poqh produces halide-bridged six-coordinate nickel(II) complexes and monomeric five-coordinate cobalt(II) complexes.This behaviour by poqh resembles that of the related NNN ligands paphy and paqhy, which are the Schiff bases of 2-pyridinecarboxaldehyde with 2-pyridinylhydrazine and 2-quinolinylhydrazine, respectively.     

Circularly polarized luminescence studies of the adducts formed with Eu(III) β-diketone complexes and (—)-sparteine

The optical activity resulting from the complexation of (—)-sparteine by a series of Eu(III) β-diketone compounds has been studied by means of circularly polarized luminescence spectroscopy. It was found that the presence of at least one perfluoro group was necessary for the formation of an adduct complex. With Eu(III) complexes containing achiral β-diketone ligands, it was found that the observed chirality could be considered to result from a combination of vicinal and conformational effects. With Eu(III) complexes containing chiral β-diketone ligands, the optical activity was found to be dominated by confïgurational effects.