Copper-dioxygen complex mediated aliphatic carbon-hydrogen bond and DNA nucleobase oxidation

Copper-dioxygen species are utilized by copper enzymes to effect aliphatic C-H bond oxidations. The investigation of biomimetic substrate oxidations with copper-O2 species employing polydentate ligands may be helpful in the elucidation of enzymatic reaction mechanisms, or even application to practical systems. On the other hand, highly reactive copper-O 2 intermediates could mediate DNA or protein oxidation reactions in vivo; thus, copper-O2 reactivity studies may shed light on their biological reactivity and/or control.; In Chapters 1 and 2, a dinuclear phenolate-containing copper(II) complex [CuII2(PD'O)(H2O)]3+ is discussed and its specific guanine (G) nucleobase oxidation reaction in the presence of 3-mercaptopropionic acid and molecular O2 is described. Required reaction conditions have been thoroughly studied in terms of a serious of freyed duplex DNA sequences, nature of copper complex and reductants, as well as the necessity of O2 involvement. The guanine oxidation products have been determined by electronspray ionization spectrometry (ESI-MS). Structural analysis of a copper guanosine complex [CuII 2(PD'O)(guanosine)]3+ suggests that copper-G coordination likely plays a role in reaction target recognition. A mu-hydroperoxide dicopper(II) species is suggested to be responsible for the G oxidation reaction.; In Chapters 3 and 4, the synthesis and spectroscopic characterization of the mu-hydroperoxide dicopper(II) species [CII2(PD'O -)(-O2H)]2+ are discussed. The most striking feature of this species is its aliphatic C-H bond oxidation reactivity. Upon thermal decay, it not only hydroxylates the nitrile solvent, releasing aldehyde and cyanide, but also oxidatively N-dealkylates and further dehydrogenates the ligand itself to give a Schiff base product. With added excess PPh3, decomposition of [CuII2(PD'O -)(-O2H)]2+ leads to the formation of a crosslinked ligand with a new C-O bond formed between the phenolate oxygen and a ligand methylene arm. A tetranuclear copper cluster {lcub}[Cu II2(PD'O-)(-OH)]2{rcub} 4+ with two OH- ligands bridging the dicopper(II) moieties is also obtained from the [CuII2(PD'O-)( -O2H)]2+ decay reaction.; In Chapter 5, the formation of an end-on peroxide species [{lcub}Cu II(L){rcub}2(O22-)]2+ (2) with an anisole containing polypyridylamine ligand L is described. Though 2 is a close analogue of the well characterized while oxidative "inert" end-on peroxide [{lcub}CuII(TMPA){rcub}2(O 22-)]2+ (3), as revealed by UV and rR spectroscopy, it exhibits a very interesting alkylbenzene C-H bond oxidation reactivity. Toluene is converted to benzaldehyde and ethylbenzene to acetophenone and 1-phenylethanol. The nature of this active Cu2O 2 species is discussed and the possible electrophilic character of the end-on peroxo species 2 is suggested.