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Mononuclear–Dinuclear Equilibrium of Grafted Copper Complexes Confined in the Nanochannels of MCM‐41 Silica
Author(s) -
Zhang Kun,
Lam KoonFung,
Albela Belén,
Xue Teng,
Khrouz Lhoussain,
Hou QiongWei,
Yuan EnHui,
He MingYuan,
Bonneviot Laurent
Publication year - 2011
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201102026
Subject(s) - copper , chemistry , electron paramagnetic resonance , perchlorate , counterion , magic angle spinning , x ray photoelectron spectroscopy , hydroxide , dimer , inorganic chemistry , crystallography , denticity , nuclear magnetic resonance spectroscopy , hydrogen bond , ion , stereochemistry , crystal structure , molecule , organic chemistry , chemical engineering , physics , nuclear magnetic resonance , engineering
Following the structural concept of copper‐containing proteins in which dinuclear copper centers are connected by hydroxide bridging ligands, a bidentate copper(II) complex has been incorporated into nano‐confined MCM‐41 silica by a multistep sequential grafting technique. Characterization by a combination of EPR spectroscopy, X‐ray photoelectron spectroscopy (XPS), UV/Vis spectroscopy, IR spectroscopy , and solid‐state 13 C and 29 Si cross‐polarization magic‐angle spinning (CP‐MAS) NMR suggests that dinuclear Cu complexes are bridged by hydroxide and other counterions (chloride or perchlorate ions), similar to the situation for EPR‐undetectable [Cu II ⋅⋅⋅Cu II ] dimer analogues in biological systems. More importantly, a dynamic mononuclear–dinuclear equilibrium between different coordination modes of copper is observed, which strongly depends on the nature of the counterions (Cl − or ClO 4 − ) in the copper precursor and the pore size of the silica matrix (the so‐called confinement effect). A proton‐transfer mechanism within the hydrogen‐bonding network is suggested to explain the dynamic nature of the dinuclear copper complex supported on the MCM‐41 silica.