XANES spectroscopy for electronic characterization of manganese (II) coordination complexes

EUGENIA A. OROSCO CONDORÍ; LUCIANA C. JUNCAL; CARLOS O. DELLA VÉDOVA; ROSANA M. ROMANO

Campinas

Otro; 26th RAU Annual Users Meeting LNLS; 2016

Laboratório Nacional de Luz Síncrotron

Manganese (II) with five unpaired d electrons has been considered in the last years a good candidate for the design of contrast agents for medical Magnetic Resonance Imaging [1,2]. In this way we have prepared and characterized Mn (II) complexes containing xanthates (ROC(S)S−) and N-donor molecules (pyridine, 2,2?-bipyridine, 1,10-phenantroline) as ligands. Their characterization included vibrational (IR and Raman) and UV-visible spectroscopies, together with single-crystal X-ray diffraction analysis and TD-DFT calculations. In order to determine the electronic structure of the complexes the sulfur and manganese K-edge X-ray absorption spectra were measured. Measurements were carried out at the SXS beamline for S K-edge and at the XAFS-1 beamline for Mn K-edge. The XANES spectra in the S K-edge region show two main resonances between 2468 and 2471 eV corresponding to S1s → π*C-S and S1s → σ*C-S transitions. In the Mn K-edge region spectra there are pre-edge structures in the region of 6535 to 6540 eV, that arise from Mn1s → Mn3d transitions while the main edge was observed at 6550 eV. These results are of special interest to obtain information about occupied and unoccupied orbitals, and furthermore, to find a relationship with the stability of these compounds.