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) L2,3-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 I/IIL3 and I/IIL2 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 I/IIL3 and I/IIL2. Hence, the occurrence of states involving metal to ligand charge transfer transitions in the presence of ligands with low lying empty p* orbitals on the L3 and L2 higher EE sides is herein confirmed.