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Combined Electrochemical and EPR Studies of Manganese Schiff Base Complexes Encapsulated within the Cavities of Zeolite Y
Author(s) -
Doménech Antonio,
Formentin Pilar,
García Hermenegildo,
Sabater María J.
Publication year - 2000
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/(sici)1099-0682(200006)2000:6<1339::aid-ejic1339>3.0.co;2-h
Subject(s) - chemistry , electron paramagnetic resonance , manganese , zeolite , schiff base , electrochemistry , inorganic chemistry , polymer chemistry , organic chemistry , catalysis , nuclear magnetic resonance , electrode , physics
Encapsulation of manganese(III) and manganese(V) Schiff base complexes within the cavities of zeolite Y has been accomplished by means of established synthetic procedures. The samples have been characterized by a combination of various analytical and spectroscopic techniques that probe either the bulk encapsulated complexes or the species present in the outermost layers of the zeolite grains. Importantly, whereas EPR measurements indicated that aerial oxidation had transformed only about 15−20% of the initially present Mn II cations to Mn III , electrochemical techniques revealed a predominance of Mn III at the external surface. This striking result is due to the fact that electrochemical techniques specifically probe the fraction of electroactive species present in the outermost layers of the zeolite particles. In view of the fact that these complexes are the most accessible and active in heterogeneous catalytic reactions in the liquid phase, the voltammetric measurements provide important information concerning the specific evolution of the reversible Mn III /Mn II redox couple near the surface of the zeolite particles. Furthermore, the unequivocal electrochemical detection of intra‐zeolite Mn V species (not observable by EPR spectroscopy) highlights the importance of combining surface characterization tools (electrochemistry) with conventional spectroscopic techniques (IR, UV/Vis, and EPR) of the bulk particle in order to assess the differing nature and distribution of the entrapped transition metal complexes.