On the electronic structure ofN,N′-ethylenebis(acetylacetonatiminato)Co(II), Co(II)acacen

Abstract

A single crystal ligand ENDOR study on N,N′-ethylenebis(acetylacetonatiminato)Co(II), Co(acacen), is reported. The hyperfine tensors of the two nitrogens, of four carbon-13 and of five protons as well as the nitrogen quadrupole tensors have been evaluated. A DOUBLE ENDOR experiment was carried out in order to determine the signs of the carbon-13 hyperfine couplings. The problems of asymmetric contributions to the hyperfine tensors, which are especially important for low symmetry systems with low-lying excited states, are discussed. The ligand hyperfine tensors can be understood assuming π-spin density on the ligand system and hence support the |2 A, yz⟩ groundstate for Co(acacen). They furthermore provide detailed knowledge on the electronic structure of the complex via the spin density distribution. The structural information derived from the proton ENDOR results is in good agreement with the X-ray data.