Synthesis and Coordination Chemistry of a New (mercaptoimidazolyl)pyridine Ligand

Synthesis and Coordination Chemistry of a New (mercaptoimidazolyl)pyridine Ligand
Author: Jessica Lauren Bongiovanni
Publisher:
Total Pages: 248
Release: 2011
Genre:
ISBN:

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A new mixed-donor ligand containing both pyridine and thione donor groups, o-(3-methyl-2-mercaptoimidazolyl)pyridine (o-mpyMe), has been synthesized. The ligand has good solubility and stability in organic solvents, as well as partial solubility in water. The coordination chemistry of this new ligand with metals such as manganese(I), rhenium(I), cobalt(II), nickel(II), copper(I), silver(I), zinc(II), cadmium(II), mercury(II), indium(III), antimony(III) and bismuth(III), leading to an assortment of coordination modes and reactivity. Most significantly, copper(I) complexes of o-mpyMe were prepared with the aim of generating potential synthetic analogues of the metal center in methanobactin, a copper-binding compound. Methanobactin (mb) is responsible for the uptake and transport of copper to the enzyme methane monooxygenase (MMO), which oxidizes methane gas to methanol in the global carbon cycle. The active site of mb consists of a tetrahedral Cu(I) center with N2S2 coordination. Characterization, reactivity and biological activity of [Cu(o-mpyMe)2]X (X = BF4, PF6) to determine if these complexes are viable analogues of methanobactin has been carried out.

Synthesis and Reactivity of BIS(PYRIDYL) and BIS(PICOLYL) Mercaptoimidazoles

Synthesis and Reactivity of BIS(PYRIDYL) and BIS(PICOLYL) Mercaptoimidazoles
Author: Jessica Marie Hanley
Publisher:
Total Pages: 194
Release: 2012
Genre:
ISBN:

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Mixed-donor ligands are particularly attractive in inorganic chemistry due to their steric and electronic versatility and the multiple coordination modes they may exercise when bound to metal centers. Although pyridines are arguably the most common nitrogen-donor ligands and the coordination chemistry of heterocyclic thiones is well-established, the reactivity of simple tridentate ligands containing a combination of such functionalities is virtually unknown. The synthesis and reactivity of two new mixed-donor ligands, the bis(pyridyl)mercaptoimidazole (2-py)2m, and the bis(picolyl)mercaptoimidazole (2-pic)2m, have been developed. Several coordination complexes of (2-py)2m and (2-pic)2m have been prepared and fully characterized, including the complete series of group 12 metal compounds {(2-py)2m}MX2 and {(2-pic)2m}MX2 (M = Zn, Cd, Hg; X = CI, Br, I). In addition, an investigation of the coordination of these two N2S donor ligands with copper(I) was pursued because one of the key goals of this project is the preparation of synthetic analogues of methanobactin (mb), a small protein responsible for the uptake and delivery of copper(I) ions to various copper-dependent enzymes such as the particulate form of methane monooxygenase (pMMO). The copper(I) derivatives {(2-py)2m}CuX (X = Br, I) and {(2-pic)2m}CuX (X.

Rational Design, Synthesis and Characterization of Amide Functionalized Pyridine and Benzimidazole Transition Metal Complexes

Rational Design, Synthesis and Characterization of Amide Functionalized Pyridine and Benzimidazole Transition Metal Complexes
Author: Samuel S. K. Asem
Publisher:
Total Pages: 576
Release: 2011
Genre: Benzimidazoles
ISBN:

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This study expands our efforts to make a new class of Pt (II) compounds analogous to cisplatin and its derivatives using sterically hindered ligands. Pt compounds in this series have been synthesized using specially designed pyridine and benzimidazole ligands. These heterocycles, amide functionalized at position 2 with aryl and alkyl pendants, rapidly change their mode of coordination depending on the pH of the medium. These ligands, synthesized using condensation chemistry, also coordinate to Co(II), Ni(H), Cu(lI), and Zn(1I) generally as anionic bis-chelates through the benzimidazole nitrogen and the carbonyl oxygen, creating a four-coordinate complex with the exception of an unusual trigonal bipyramidal Zn(H) complex. I H NMR temperature studies reveal that these ligands interconvert between imide and amide isomers and that electron withdrawing pendants favor amide isomers. Crystal structures of Co(II) and Ni(1I) complexes of N-( I-methylbenzimidazol-2-yl)cyclohexanecarboxamide, for example, show two ligands bind per metal ion when reacted with acetate and nitrate salts. The bischelates of these Ni(1I) complexes also show expansions of their coordination spheres from four to five-coordinate. Furthermore, these Ni(II) bis-chelated complexes possess square planar or distorted 4-coordinate geometries. The synthesis and properties of several new Pt (II) complexes containing these ligands will be presented. A second generation and novel complex class containing metal-binding, linker and recognition domains is reported. Both classes of Pt complexes were obtained using a synthetic methodology which favors the cis isomers. The second generation complex crystallizes in the monoclinic space group P2dn with lattice dimensions a = 17.7393(5) A, b = 11.4632(3) A, c = 19.3959(5) A and ~ = 99.794(3)°. These complexes have been characterized using physical methods that include X-ray crystallography, IH &13C NMR, Mass spectrometry, UV and IR spectroscopies. Complexes similar in structure to cisplatin and carboplatin show varying cytotoxic properties toward different cancer cell lines. Additionally, some of these new Pt complexes show comparable and promising cytotoxicity against prostate cancer cell lines.

Coordination Chemistry of Functionalized Mercaptoimidazoles

Coordination Chemistry of Functionalized Mercaptoimidazoles
Author: Jonathon Andrew Maner
Publisher:
Total Pages: 168
Release: 2011
Genre:
ISBN:

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The coordination chemistry of three mixed-donor ligands mebMe, mmteMe, and mteSimMe has been developed. Each ligand contains a mercaptoimidazole group and a pendant group containing a different potential donor. Thus methyl-mercaptoimidazolyl ethyl benzene (mebMe) is a mixed-donor containing mercaptoimidazole and an arene donor group separated by two carbons. Similarly, methyl-mercaptoimidazolyl (methylthio)ethane (mmteMe) is a mixed-donor containing mercaptoimidazole and thioether donor groups, and (methylthio)ethyl methyl-mercaptoimidazolyl sulfide (mteSimMe) contains imine and thioether donor groups. Previously, the Rabinovich group has investigated the chemistry of toxic metals such as Cd(II), Hg(II), and Pb(II) using the 6w(mercaptoimidazolyl)xylene (BmxR) and Z>/.s(mercaptoirnidazolyl)methane (BmmR) ligands. Both of these systems are bidentate 6/s(thione) ligands that bind metals to form tetrahedral and octahedral structures. As an extension of this work, the coordination chemistry of mebMe, mmteMe, and mteSimMe has been explored using the same heavy metals. A study of the reactivity of mebMe towards Pb(II) ions, the reactivity of mmteMe towards Hg(II) ions, and the reactivity of mteSimMe towards Hg(II) and Cd(II) ions has been performed.