Solvation Structure of Zn2+ and Cu2+ Ions in Acetonitrile: A Combined EXAFS and XANES Study

The solvation- structure of Zn2+ and Cu2+ in acetonitrile has been determined by a combined.approaclitising both X-ray absorption near ecrge, structure (XANES) and the exteridectX7ray absorption fine struCtiire (EXAFS) spectrbscopy. For the fbriner cation an octahedral geometry of the acetonitrile solvate complex has been found with a Zn N distance of 2.12(1) angstrom. For the Cu2+ solvates the EXAFS techniquebas been found to be not able to provide a conclusive determination of the coordination numbers and polyhedral environment, While the analysis Of the XANES spe ctra. unambiguously shows the existence of an axially elongated square pyramidal coordination, ruling out the previously proposed octahedral Jahn Teller (JT) distorted geometry. The Cu N distances obtained are 2.00(1) and 2.28(2) angstrom for the equatorial and axial ligands, respectively, and the EXAFS and XANES techniques find values of thebond distances in good agreement. The XANES technique has proven to be extremely powerful in providing a reliable resolution of solution structure for dynamic ion complexes.