Models for The Trinuclear Copper(II) Clusters of the Particulate Methane Monooxygenase from Methanotrophic Bacteria: Synthesis, Spectroscopic and Theoretical Characterization of Trinuclear Cu(II) complexes

• Main Authors: Po-Chun Liu, 劉柏君
• Other Authors: Sunney I. Chan
• Format: Others
• Language: en_US
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/86601938514574352900

碩士 === 國立清華大學 === 化學系 === 91 === The catalytic sites in the particulate methane monooxygenase from Methylococcus capsulatus (Bath) involve two sets of trinuclear Cu(II) clusters. It has been proposed that when the trinuclear copper clusters of pMMO are fully oxidized, each of the oxidased clusters consists of three type 2 copper centers that are mutually weakly ferromagnetically coupled (J ~ 20cm-1) and D ≦ 0.05 cm-1. Toward elucidating these results, several trinuclear Cu(II) model complexes are synthesized and characterized. The complexes, [Cu3C18H42N6O3(μ3-Br)2](Br)4 and [Cu3C18H42N6O3(μ3-Cl)2](Cl)4, are ferromagnetically coupled with J = 430 cm-1 and 470 cm-1, respectively. Both cases show the isotropic EPR signal at g = 2.092 and g = 2.104 with D ≦ 0.009 cm-1. Density functional calculations reproduce well these geometric, electronic and magnetic properties of these tricopper complexes, and provide insights into the spin coupling interactions mediated by the bridging ligands. Furthermore, they reasonably explain that the anisotropic EPR signal abserved of [Cu3C18H42N6O3(μ3-OH)2](Cl)4 might arise from the antiferromagnetic interactions among the three copper(II) ions.