Electron paramagnetic resonance study of partially oriented clay platelets intercalated with copper(II) 1,4,8,11-tetraazacyclotetradecane

Abstract

Electron paramagnetic resonance (EPR) spectra of powder and oriented films of montmorillonite, hectorite, and saponite intercalated with [Cu(cyclam)] 2+ (cyclam = 1,4,8,11-tetraazacyclotetradecane) exhibit three components: an orientation-dependent component without hyperfine features, an orientation-dependent component with hyperfine features, and an orientation-independent component without hyperfine feature. EPR spectra of [Cu(cyclam)] 2+-saponite, which exhibit only two components and the best resolved hyperfine features, were simulated. The spectra indicate that a large portion of the saponite platelets are inclined to the glass surface, although they tend to align with their basal planes parallel to the glass surface. The orientation-dependent spectra could be simulated by introducing a Gaussian distribution with a standard deviation of 20° for the inclination angle. The standard deviation may be used as a disorder parameter for the microcrystals assembled on glass plates. Spectral simulation also shows that the CuN 4 plane of [Cu(cyclam)] 2+ is parallel to the clay layers. EPR spectra of some other partially oriented systems are also discussed. © 2005 American Chemical Society.