ELECTRON-SPIN-RESONANCE STUDIES OF FEO6 TRIS CHELATE COMPLEXES - MODELS FOR THE EFFECTS OF ZERO-FIELD SPLITTING IN DISTORTED S=5/2 SPIN SYSTEMS

The electron spin resonance (ESR) spectra of a series of substituted malonato and oxalato, high-spin, tris chelate complexes of iron(III) have been determined at both X- and Q-band frequencies for powdered polycrystalline samples in the temperature range 300-77 K. A diverse range of frequency-dependent spectra are reported, and these spectra are interpreted by using a spectrum simulation program based on matrix diagonalization methods for a general spin Hamiltonian incorporating electronic Zeeman and zero-field splitting terms. Data are presented that serve to form a library of spectra for octahedrally distorted S = 5/2 spin systems. The observed spectra of these tris-chelate complexes vary with counterion, substituent on the ligand, and degree of hydration in an unpredictable manner. © 1990, American Chemical Society. All rights reserved.