Mohamed A. Khalifa

Metal chelates of some transition and non-transition metal ions with Schiff base derived from isatin witho-phenylenediamine

SummaryNew Cr(III), Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and Pb(II) chelates of the Schiff base derived from isatin witho-phenylenediamine have been synthesized and characterized on the basis of elemental analyses, electronic, IR and1H NMR spectra, and also by aid of molar conductivity and magnetic moment measurements. It has been found that the Schiff base behaves as ONNO tetradentate dibasic ligand forming chelates with 1:1 (metal:ligand) stoichiometry. Square planar environment is suggested for nickel(II) chelate. All the metal chelates show non-electrolytic behaviour.ZusammenfassungEs wurden neue Chelate von Cr(III), Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) und Pb(II) mit Schiff-Basen aus Isatin undo-Phenylendiamin hergestellt und mittels Elementaranalysen, Elektronen-, IR- und1H-NMR-Spektroskopie, sowie durch Messung der molaren Leitfähigkeit und der magnetischen Momente charakterisiert. Es wurde festgestellt, daß sich die Schiff-Base als vierzähniger zweibasischer ONNO-Ligand verhält, wobei 1:1-stöchiometrische Metall:Ligand-Komplexe gebildet werden. Für das Nickel(II)-Chelat wird eine quadratisch-planare Geometrie vorgeschlagen. Alle untersuchten Metallchelate zeigen ein nicht-elektrolytisches Verhalten.

Inhibition of succinate-cytochrome C reductase by a ferromacrocyclic complex

Succinate-cytochrome c reductase (SCR) from mouse liver was inhibited strongly and reversibly by an iron (II) macrocyclic complex 3. The inhibition was observed for the enzyme toward the reduction of both 2,6-dichlorophenol indophenol (DCIP) and cytochrome c (cyt c). The inhibition was a mixed type and noncompetitive with respect to the reduction of DCIP and cyt c, respectively. Values of the inhibition constant ranged from 6.6 to 8.3 μM. The IC50 for the complex 3 was found to be 16.6 × 0.8 and 12.1 × 0.5 μM for the enzyme toward DCIP and cyt c, respectively. The reduced form of complex 3 also exhibited enzyme inhibition but to a less extent. Complex 3, at a lower level, equal to 25% of its LD50 showed about 50% inhibition of the enzyme through in vivo dose-dependent effect. These findings suggested that the structure of the equatorial benzoquinoid macrocyclic ligand of the Fe(II) complex is involved in the enzyme inhibition.

Axial ligand substitution reactions of phosphine derivatives of ruthenium(II) and ruthenium(III) benzoquinone dioxime complexes

Abstract The synthetic, spectral and kinetic studies of ruthenium(II) macrocyclic complexes, Ru(BQDH) 2 L 2 (where BQDH = benzoquinone dioximate), are reported. Axial ligands include nitrogen, phosphorus and sulphur donors. An oxidized species, Ru(BQDH)(BQD)(PPh 3 ) 2 , formed via one-electron oxidation followed by loss of a bridging hydrogen, was characterized as a ruthenium(III) complex. Kinetic and thermodynamic data of axial ligand substitution showed that the reaction mechanism is dissociative (D) and that the five-coordinate intermediate possesses little or no ability to discriminate between nucleophiles. The ruthenium(II) complexes were found to be more labile than the corresponding ruthenium(III) complexes. Trans -group and leaving-group effects are discussed. The BQDH ruthenium complexes differ from the DMGH analogues in that the former are much more labile, owing to the high delocalization of the conjugated π system of the BQDH. The ruthenium BQDH complexes were also found to be much more inert than the analogous iron complexes implying that the M → L π-back bonding is more important for ruthenium.

Axial ligand substitution reactions of phosphite derivatives of Fe(II) macrocyclic complexes

Abstract Kinetic studies of ligand substitution reactions of six-coordinated Fe(II) macrocyclic complexes were investigated (T)Fe(N 4 )(L) + X→(T)Fe(N 4 )(X) + L where N 4 =DMGH, BQDH and Tim. The T, L and X ligands include nitrogen and phosphorous donors. The reaction mechanism is strictly dissociative (D), and the five-coordinate intermediate (T)Fe(N 4 ) possesses little or no ability to discriminate between nucleophiles, cis effect was well as trans group and leaving group effects are reported.

The influence of solvent structure on the solvolysis of a ruthenium(II) complex in water–acetonitrile mixtures

The solvent effect on the rate of aquation of trans-[Ru(py)4Cl2] has been investigated by u.v. spectroscopy in the 40–55 °C range in MeCN–H2O media. The thermodynamic activation parameters are calculated and discussed in terms of solvation effects. Log k was correlated with the reciprocal of the dielectric constant. A non-linear correlation was obtained and is discussed on the basis of specific solvation.

Bis-adducts formed by nickel(II) and zinc(II) chelates of pyridine-2-(1H)thiones with nitrogen donors

SummaryThe bis-adducts formed by nickel(II) and zinc(II) chelates of 3-cyano-4-aryl-6-phenyl pyridine-2-(1H)thiones with pyridine and N-methylimidazole have been prepared and characterized by microelemental analyses, i.r., u.v., vis., and 1Hn.m.r. spectra and magnetic measurements. Owing to Lewis acid-base interactions, the diamagnetic square planar nickel(II) or zinc(II) chelates interact with two molecules of pyridine or N-methylimidazole in the two axial positions forming the corresponding octahedral bis-adducts.

SYNTHESIS AND CHARACTERIZATION OF COMPLEXES OF CO(II), NI(II), CU(II) AND ZN(II) WITH 6-SUBSTITUTED-4-ARYL-3-CYANO-PYRIDINE-2(1H)-THIONES

Abstract Complexes of Co(II), Ni(II), Cu(II) and Zn(II) with 6-substituted 4-aryl-3-cyano-pyridine-2-(1H)-thiones have been prepared and characterized by elemental analysis, IR, UV-Visible and 1H-NMR spectroscopy, molar conductivity, magnetic moment measurements and x-ray diffraction analysis. According to magnetic measurements and UV-Visible spectra, nickel(II) and copper(II) complexes are suggested to have square-planar structure whereas cobalt(II) complexes has either tetrehedral or square planar geometries. X-ray diffraction analyses suggested the orthorhombic powder structure unit for Ni(II) and Cu(II) complexes and triclinic for Co(II) ones.

Ewing’s Sarcoma Presenting as Hip Monoarthritis in a Spondyloarthritis Patient

Seronegative spondyloarthritis (SpA) and Ewing’s sarcoma (ES) are common disorders affecting young males. A great challenge is to diagnose both diseases in the same patient. Here we describe a case of a young male patient having SpA, who developed ES that presented as monoarthritis of left hip which was misdiagnosed twice; first as peripheral manifestation of SpA and second as septic arthritis; before the correct diagnosis was reached. A 17 year-old boy presented with inflammatory low back pain of gradual onset lasting for 4 months and knee arthralgias. Examination revealed the presence of localized tenderness over both SIJs and limited lumbar flexion. Plain x-ray showed bilateral grade 2 sacroiliitis and he was Rheumatoid factor negative. The diagnosis of seronegative SpA was made based on fulfillment of the Association of Spondyloarthritis International Society classification criteria for axial SpA. Nonsteroidal anti-inflammatory drugs (NSAIDs) and sulphasalazine were prescribed resulting in rapid improvement of back pain and knee arthralgia. Four months later, the patient had increased severity of his back pain with pain at the left hip region associated with painful limited internal hip rotation. The diagnosis of left hip arthritis associated with SpA was made without requesting imaging study at that time. The dose of NSAIDs was increased and a low dose steroid was added. Few days later, the general condition of the patient deteriorated with the development of night fever, poor night sleep and poor appetite. On presentation, the patient looked very ill with fever. Hip examination revealed marked painful limited hip movement with flexion deformity. New investigations revealed an ESR of 110 mm/hr, and a CRP of 88 mg/L. There was normochromic normocytic anemia (HB: 9g/dl) and leucocytosis (WBC: 13.300/µL). The diagnosis initially considered was acute septic arthritis. Left hip arthrocentesis failed to aspirate any fluid and ultrasound revealed the absence of joint effusion. A multislice computerized tomography (CT) revealed the presence of a destructive osseous lesion targeting the left pubic bone and the left acetabulum with intra-articular extension into the left hip joint causing bony erosion of the medial aspect of the left femoral head. An MRI showed intra-pelvic extension with enlarged iliac lymph nodes. A biopsy was obtained from the mass. Histopathology revealed a malignant round-cell tumor consistent with ES. The patient was referred for chemotherapy and we knew that he was started on a combination of drugs for a short time before he died. To the best of our knowledge this is the first report in literature of ES in SpA patient and the second report of ES presenting as hip monoarthritis.

Kinetic studies on the solvolysis and axial ligand substitutions of bis-triphenylphosphine(cyclohexane-1,2-dione-dioximato)ruthenium(II) in non-aqueous solvents

AbstractKinetic studies of ligand substitutions of the six-coordinated RuII pseudo-macrocyclic complex [Ru(CHDH)2- (PPh3)2] (CHDH = cyclohexanedione-dioximato) have been spectrophotometrically investigated in a variety of solvents and at 70, 80, 85 and 90°C. The reactions studied are of the form:[(PPh3)Ru(CHDH)2(PPh3)] + L  = [(PPh3)Ru(CHDH)2L] + PPH3 where L is imidazole, pyridine, piperidine or thiophene or a solvent molecule (PhCl, PhMe, MeCN, DMSO or DMF). The solvolysis reactions with chlorobenzene and toluene proceed to an equilibrium position favoring the bis-triphenylphosphine complex. All other reactions proceed to completion. From a mechanistic point of view the reactions were found to proceed through the formation of a five coordinate intermediate that possesses little or no discriminating ability towards the incoming nucleophiles. The rate data were thus interpreted in terms of a dissociative (D) or dissociative interchange (Id) mechanism. Activation parameters ΔH‡ and ΔS‡ are reported. Preliminary studies on the solvatochromic behavior of [Ru(CHDH)2(PPh3)2] and the corresponding mixed complexes are discussed.