A STUDY OF THE COORDINATION GEOMETRY OF THE TETRAPYRIDINE COPPER(II) COMPLEX IN NAY AND MCM-41 BY 2-DIMENSIONAL ELECTRON-SPIN-RESONANCE HYSCORE SPECTROSCOPY

The coordination geometry of the tetrapyridine copper(II) complex in z eolite Cu-NaY and mesoporous siliceous MCM-41 material is investigated by two-dimensional proton and deuterium hyperfine sublevel correlatio n (HYSCORE) spectroscopy. Different orientations of the pyridine ligan ds with respect to the complex plane of the tetrapyridine copper(II) c omplex were found in the two materials. The ligands are predominately arranged with their molecular plane perpendicular to the complex plane in zeolite Cu-NaY. Otherwise, in Cu-MCM-41 materials the ligands have a mean orientation of their molecular plane parallel to the complex p lane. However, the two-dimensional hyperfine sublevel correlation spec tra reveal severe distortions of the overall complex. The different co ordination geometries of the tetrapyridine copper(II) complex in both materials result from the interaction of the complex with the inner su rface of each molecular sieve. Consequently, much severe distortion of the complex geometry was found in the mesoporous Cu-MCM-41 material w ith its amorphous wall structure in comparison to crystalline Y zeolit e. The-incorporation of the tetrapyridine Cu(II) complex into Y zeolit e also alters the electron spin density distribution within the comple x. The results indicate a substantial influence of the framework of th e Y zeolite on the unpaired electron of the encapsulated complex.