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Synthesis, Characterization and Modeling of Active Sites in Dinuclear Metalloenzymes

Khadir, Narjes | 2015

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 47683 (03)
  4. University: Sharif University of Technology
  5. Department: Chemistry
  6. Advisor(s): Mohammadi Boghaei, Davar
  7. Abstract:
  8. In order to have more understanding of the cooperative effect between the metal centers in the multimetallic complexes, on their physicochemical properties and chemical reactivity, some new bi- and tetra-nuclear Cu(II), Ni(II) and Pd(II) complexes of compartmental binucleating ligands were synthesized and characterized. In this study, a series of new compartmental binucleating thiophenol-based proligands PL1-PL4 from the Schiff base condensation of 2 equiv. of o-aminophenol or 2-amino-4-methylphenol with 1 equiv. of 2,6-diformyl-4-alkyl- thiocarbamoyl were synthesized and characterized. New Bi- and tetra-nuclear copper (II) complexes derived from these binucleating compartmental proligands,with general formula of [Cu2L(pz)] (pz= the exogenous bridging pyrazolyl ligand), were synthesized and characterized by elemental analysis, IR and UV–Vis spectroscopies. All of these complexes have also been characterized by single crystal X-ray diffraction analysis.The EPR study of the binuclear µ-thiophenolato-µ-pyrazolato copper (II) complex, [Cu2L1(pz)(DMSO)](1), performed in the temperature range between 4 and 293 K, showed an antiferromagnetic interaction between CuII ions, and allowed evaluating anisotropic g factors gx = 2.068(1), gy = 2.091(1) and gz = 2.165(1), an exchange coupling parameter J0 = -26(1) cm-1 and a zero field splitting of the ground triplet state described by D = 86(2)x10-4 cm-1 and E = -48(3)x10-4 cm-1. Magnetic susceptibility of the tetranuclear copper(II) complex, [Cu2L2(pz)]2(2), were measured as a function of T, between 2 and 300 K, with several values of constantapplied B0, 1, 5 and 9 T, and as a function of B0 for several fixed values of T (23, 40 and 100 K) and allowed evaluating antiferromagnetic coupling parameters J1 = (-27.2±1.0) cm-1 and J2 = (-31±2) cm-1. In order to the investigation of the cooperative effects between the two metal centers on their catalytic properties, four new binuclear palladium(II) complexes derived from the compartmental binucleating proligands, PL1-PL4, and two new binuclear nickel(II) complexes derived from the compartmental binucleating proligands, PL1 and PL2, with general formula of[M2L(pz)] (M= Ni(II) and Pd(II))were synthesized and characterized by elemental analysis, IR and UV–Vis spectroscopies and also by single crystal X-ray diffraction analysis. The binuclear Pd(II) complexes have also been characterized by1H NMR spectroscopy. The catalytic activity of these four new binuclear palladium complexes was studied in Mizoroki-Heck C-C coupling reaction between methyl- and n-butyl acrylate with various types of aryl iodides and bromides. These complexes were active and efficient catalyst for these reactions and all reactions were completed for very short times with very excellent yield. To the best of our knowledge, this study presents the first catalytic employment of bridged binuclear palladium(II) complexes with relatively short metal-metal distances (3.57Å) in Mizoroki-Heck C-C coupling reaction. The catalytic activity of two binuclear µ-thiophenolato-µ-pyrazolato nickel (II) complexes was evaluated for the selective oxidation of the aromatic and aliphatic sulfides to the corresponding sulfoxides in the presence of urea hydrogen peroxide (UHP) as oxidant. The resulting products were obtained in good to excellent yields within a reasonable time. With the aim to study on the model compound of catechol oxidase, binuclear µ-phenolato-µ-hydroxo copper(II) complex ,[Cu2L(OH)(NO3)2] (9),from the condensation of 2 equiv. of N-(2-aminoethyl)piperazine with 1 equiv. of 2,6-diformyl-4-tert-butyl-phenol by applying template synthesis technique was prepared and characterized by elemental analysis, IR and UV–Vis spectroscopies and also by single crystal X-ray diffraction analysis. The catecholase activity of the complex was investigated following the oxidation of 3,5-di-tert-butylcatechol (3,5-DTBC) to 3,5-di-tert-butylbenzoquinone (3,5-DTBQ) in methanol medium. Kinetic experiments were performed to determine initial rate of this reaction and a treatment on the basis of Michaelis-Menten model was applied for this kinetic study. The present complex exhibit extraordinarily high catecholase activity in methanol medium (kcat = 8.2×104(h-1)) reducing the gap between the native enzyme activity and its synthetic analogues
  9. Keywords:
  10. Binucleating Complex ; Heck Reaction ; Sulfide Oxidation ; Binucleating Compartmental Proligands ; Catecholase Activity

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