XANES studies of nickel(II) coordination complexes: comparison of the electronic structure for different geometries and of the ligand alkylic chain length

LUCIANA C. JUNCAL; ROSANA M. ROMANO

Campinas

Otro; 26th RAU Annual Users Meeting LNLS; 2016

Laboratório Nacional de Luz Síncrotron

The aim of this work is the electronic structure determination of nickel(II) coordination complexes with ligands of the general formula ROC(S)S−, motivated in their wide variety of applications, ranging from their use in the preparation of NiS nanoparticles and thin films, the applications in semiconductor materials, heterogeneous catalysis, their ability as activators in froth flotation processes, to their potential pharmacological uses. In a recent investigation, we report an experimental quantitative molecular orbital diagram of Ni(CH3(CH2)2OC(S)S)2 constructed using the information extracted from the different techniques (PES, XANES, UV-visible and resonance Raman spectroscopy combined with theoretical methods).[1] In this work we present a comparative study of the electronic properties of a series of Ni (II) complexes with different coordination numbers and geometries, and with ligands of different sizes, synthesized in our Laboratory in La Plata. The XANES spectra in the S K-edge region were measured at the DO4A-SXS beamline at room temperature and a pressure below 5x10-8 mbar, in the 2430-2530 eV energy range. Solid samples were ground to a fine powder and placed on a double-sided sulfur free carbon tape. Energy was calibrated with the 2520 eV value of the excitation energy of the Mo 1s electrons. The DO4B-XAFS1 beamline was used to measure the Ni K-edge spectra. Uniform shaped tablets of 1 mm thickness, obtained from solid samples diluted in boron nitride, were placed in a sample holder, together with a nickel foil used for the energy calibration. Figure 1 resumes some of the obtained results, revealing clear differences between the different complexes, that were discussed in terms of their electronic structure.