Single crystals of [Fe(mesitylene)22+] [C 3(C(CN)2)3-]2 exhibit an intense EPR spectrum with anisotropy and fine structure typical of an electronic triplet species (S=1). From measurements of the fine-structure splitting as a function of angle in three orthogonal crystal planes, it has been established that the spin-spin interaction tensor is nearly axial, D = (-218, 116, 105 MHz), and that the g tensor is almost isotropic with giso = 2.0027. The zero-field splitting parameters were determined as |D| = 327.8 MHz (117 G) and |E| = 5.7 MHz (2 G). Comparison of the principal directions of D with vectors within the known crystal structure shows that the triplet comprises a radical pair formed between nearest neighboring anions. The principal values and directions of D for the biradical compare well with those calculated for the unpaired spin density distribution deduced for the monoradical from its isotropic spectrum and from INDO calculations.
ASJC Scopus subject areas
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry