Use of sterically hindered carboxylate ligands to model structural and functional features of dioxygen-activating centers in non-heme diiron enzymes

Chapter I. Modeling Dioxygen-Activating Centers in Non-Heme Diiron Enzymes: Carboxylate Shifts in Diiron(II) Complexes Supported by Sterically Hindered Carboxylate Ligands General synthetic routes are described for a series of diiron(II) complexes supported by sterically demanding carboxylate ligands 2,6-di(p-tolyl)benzoate (ArTolCO2-) and 2,6-di(4-fluorophenyl)benzoate (Ar4-FPhCO2-). The interlocking nature of the m-terphenyl units in self-assembled [Fe2(p-O2CArTol)2(O2CArTol)2L2] (L = C5H5N (4); 1-MeIm (5)) promotes the formation of coordination geometries analogous to those of the non-heme diiron cores in the enzymes RNR-R2 and A9D. Magnetic susceptibility and MOssbauer studies of 4 and 5 revealed properties consistent with weak antiferromagnetic coupling between the high-spin iron(II) centers. Structural studies of several derivatives obtained by ligand substitution reactions demonstrated that the [Fe2([mu]O2CAr')2L2] (Ar'=ArTol; Ar 4-FPh) module is geometrically quite flexible. Details of the core rearrangement within the tetracarboxylate diiron framework, facilitated by carboxylate shifts, were probed by solution VT 19F-NMR spectroscopic studies of [Fe2(ap-O2CAr4-FPh)2(O2CAr4-FPh)2(THF)2] (8) and [Fe2(p-O2CAr4-FPh)4(4-tBuC5H4N)2] (12). The dynamic motion in the primary coordination sphere controls the positioning of open sites and regulates the access of exogenous ligands, processes that also occur at the catalytic sites of non-heme diiron enzymes. Chapter II. Structural Flexibility within a Sterically Hindered Ligand Platform: Mononuclear Iron(II) Carboxylate Complexes as Subsite Models for Diiron(II) Centers The synthesis and characterization of a series of mononuclear iron(II) carboxylate complexes are described.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Chemistry.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2002

Author dc:creator

• Lee, Dongwhan, 1970-

Advisor dc:contributor.advisor

• Stephen J. Lippard.

• Chemistry.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/8367

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/8367