X-ray absorption spectroscopic and multiple scattering formalism investigation of a possible S-Cu interaction in the Cu- sulfenilcarbonilic ligands

L. ANDRINI; LJ. GIOVANETTI; M.F. ERBEN; C.O. DELLA VEDOVA; F.G. REQUEJO

Campinas

Workshop; Reunião Anual de Usuários (23º RAU); 2013

Brazilian Center for Research in Energy and Materials (CNPEM) - LNLS

Chemical, biochemical, biogeochemical, and environmental studies of sulfur have proliferated because of the recognition of its role in many important processes on the earths various ecosystems. For example, the sulfur has an important role in electron transfer systems (ETs), being the ETs an integral component in a diverse range of important biological functions including photosynthesis, respiration, and nitrogen fixation. Sulfur is also present in urea, which is the main end product of protein metabolism in humans and other mammalian animals.In this work, we published a series of results obtained to investigate the sulfur and copper environments in new synthetic covalent sulfenilcarbonilic compounds which can be used as ligands in the coordination chemistry. Previous studies have illustrated the utility of Cu and S K-edge XAS for establishing the electronic structure of copper-sulfur complexes. The K XANES involving 1s-np transitions, more specifically, the XANES pre-edge region has been identi¯ed as providing information on the amount of covalent mixing of sulfur and ligand atomic orbitals in various S-compounds. The shape of XANES spectra will reflect the density of empty states, because in X-ray absorption the excited electron is not free and the dipole transition poses strong selection rules to the ¯nal state (i.e., we will sense site and symmetry for S-atom). The Cu K XANES involving 1s-np and 1s-3d transitions, which enables sensing states of hybridization, unoccupied states like symmetries and charge transfers.Show the differences between S-ligands and Cu-S-ligands in the S K XANES spectra. Using de FDMNES program in multiple scattering formalism, we could attribute these differences to the conformations of sulfur environment and correlated with those obtained by other techniques (XRD and NMR).The Cu K EXAFS/XANES study allowed us to obtain the coordination numbers and average distances of ¯rst neighbors sulfur (Feffit pack), and hybridizations responsible in the complex formation, respectively. Also, using de FDMNES program, we could investigate the electronic state responsible in the charge transfer in the system.