The last step in the denitrification process is the reduction of N2O to N2, catalyzed by nitrous oxide reductase (N 2OR). The novel mu4-sufide bridged tetranuclear copper cluster, CuZ, is the catalytic center of N2OR, but questions still remain regarding the properties and catalytic mechanism of CuZ . In our efforts to pursue the goal of modeling CuZ of N 2OR, we have investigated the copper coordination chemistry of pyridylmethylamide ligands with different substituent groups on the amide side arm (HL R, R = H, Me3, Ph and Ph3). Generally, pyridylamide ligands HLR exhibit two principal coordination modes that depend on the state of the amide group: the neutral amide form generally coordinates via the pyridyl N atom and the amide carbonyl O atom, or only via the pyridyl N atom; under basic conditions the anionic amidate form additionally coordinates via the amidate N atom, allowing a chelating/bridging coordination mode. New copper(I) complexes with neutral ligands were obtained and X-ray crystallography analysis showed monomeric, dimeric and one-dimensional structural features of these complexes (Chapter 2). Copper (II) complexes with ligand HL, HL Me3 and LPy(OH)2 were synthesized and exhibited monomeric, dimeric and trimeric structures (Chapter 3). In addition, we synthesized and characterized a family of dinuclear or trinuclear mixed-valence copper clusters with pyridylamide ligands HLR (R = none, Ph or Ph3) and H2LPy(ac)2. X-ray crystallography, UV-Vis, EPR and electrochemical studies indicated the type III mixed-valence Cu 1.5Cu1.5 moiety in these complexes (Chapter 4). Finally, novel [CunSm]4- (n = 12, m = 8; n = 16, m = 10) clusters with mu4-sufide tetranuclear copper centers or mu3-sufide trinuclear copper centers were synthesized and displayed rare triangular gyrobicupola and square gyrobicupola polyhedral structures. Spectroscopic and electrochemical studies indicate the electron rich properties of both clusters, and the ESI-MS data show the clusters are stable in organic solution. The preliminary UV-Vis and solution IR studies imply the possible reactivity of the two clusters towards N2O (Chapter 5).X-ray crystal structure and packing structure diagram for [Cu(HL)(CH3CN)(PPh3)] (PF6)2 (4) ..................................................... 70 Figure 2a10. ... 84 Figure 2a13. X-ray crystal structure (top) and hydrogen bonding (bottom) for [Cu2(HL)4Cl2] (6) .
|Title||:||Synthesis and Characterization of Model Complexes of the Copper(Z) Center from Nitrous Oxide Reductase|
|Publisher||:||ProQuest - 2008|