An EPR Study of Some Highly Distorted Tetrahedral Manganese(II) Complexes at High Magnetic Fields

Abstract

EPR spectra at 94.5 GHz (3 mm) and 249.9 GHz (1 mm) have been measured for the dichloro-, dibromo-, and diiodobis(triphenylphosphine oxide)manganese(II) complexes. These compounds have a distorted tetrahedral geometry, and the highest possible symmetry obtainable is C2v. Because the spectra are taken in the high-field limit, they are simple and much easier to interpret than at lower magnetic fields. Accurate values of the zero-field splitting parameters, D and η (E/D), are determined by least-squares fitting and homotopy using matrix diagonalization. The compounds have g-values near 2 and large values of D and η. Across the series, D increases from 0.165 to 0.906 cm-1, while η decreases slightly from 0.273 to 0.246.