| Abstract
| - We report the synthesis and characterization of a hydroxo-bridged dinuclear phenanthroline cupric complex,[(phen)2Cu−OH−Cu(phen)2](ClO4)3 (HPC, phen = phenanthroline), dispersed in molecular sieves: MCM-41's and sodium zeolite Y. We employed spectroscopic techniques (FT-IR, UV−visible, EPR, and EXAFS)to characterize and study the catalytic activities of immobilized HPC in the oxidation of 3,5-di-tert-butylcatechol(DTBC) to the corresponding quinone (3,5-di-tert-butylquinone, DTBQ) to mimic the functionality of catecholoxidases. HPC complexes can adsorb only on the outside surface of the Y zeolite due to its smaller pore size.The EXAFS spectrum gives 3.51 Å for the Cu···Cu distance in HPC encapsulated in the nanochannels ofAl−MCM-41 mesoporous solids, which is comparable to the O···O distance of the two hydroxyl groups ofDTBC, and this made a simultaneous coordination of the diol group to the dicupric center possible. Theresultant complex then allows the transfer of two electrons from DTBC to the dicupric center leading to theproduction of DTBQ. The nanochannels of calcined Al−MCM-41 mesoporous solids provide stability, dueto confined space and surface charge, which could prevent excessive separation of the dinuclear cupric centersafter removal of the hydroxo bridge in the catalytic process. A catalytic reaction scheme is proposed basedon the spectroscopic data obtained in the characterization. The study demonstrates that HPC encapsulated inthe nanochannels of Al−MCM-41 mesoporous materials could be a viable system for a broad range of catalyticoxidation to mimic natural occurring enzymes.
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