ESR Studies of an Oxo-Bridged Manganese(III. IV) Complex of 2,2′-Bipyridine

Abstract

Abstract ESR spectra were recorded on the single crystal of di-μ-oxo-tetrakis(2,2′-bipyridine)dimanganese(III,IV) perchlorate trihydrate. ESR signals attributable to the excited quartet state were observed in addition to an ESR signal due to the ground doublet state. From the temperature dependence of the signal intensities, the exchange integral was determined as J⁄k=−207 K. The spectrum of the quartet state exhibits a fine structure: |D| and |E| were estimated to be equal to 0.39 and 0.12 cm−1, respectively. The constants are interpreted in terms of the dipole-dipole interaction and the crystal-field effect; the anisotropic part of the exchange interaction is negligibly small. The hyperfine structure in the spectrum of the doublet state indicates that odd electrons are distributed unequally on two manganese atoms in the dimer. This is due to an odd e electron (in the t23-t23e1system) localized mostly on one of the paired manganese atoms.