Theoretical modeling of the L2,3-edge X-ray absorption spectra of Mn(acac)2 and Co(acac)2 complexes

Mn(acac)(2) (I) and Co(acac)(2) (II) L-2,L-3-edge absorption spectra have been modeled using the DFT/ROCIS method. In addition to the agreement between experiment and theory, the combined use of the B3LYP exchange-correlation functional and the def2-TZVP(-f) basis set provided useful information about the coordinative geometry around the M(II) ions as well as about the nature and the strength of the Mn-O and Co-O interaction. The lower excitation energy (EE) side of both L-I/II(3) and L-I/II(2) intensity distributions mainly includes states having ground state spin multiplicity (S = 5/2 in I and S = 3/2 in II), whereas states with lower spin multiplicity (S = 3/2 in I and S = 1/2 in II) significantly contribute to the higher EE side of both L-I/II(3) and L-I/II(2). Hence, the occurrence of states involving metal to ligand charge transfer transitions in the presence of ligands with low lying empty pi* orbitals on the L-3 and L-2 higher EE sides is herein confirmed.