Local structure of concentrated NaFSA solutions in propylene carbonate studied by X-ray and neutron diffraction methods

Abstract

Abstract The microscopic structure of 10 mol% NaFSA [FSA: bis(fluorosulfonyl)amide]-propylene carbonate (PC) solution has been investigated by means of X-ray and neutron diffraction techniques. The solvation structure of Na+ has been determined from least-squares fitting analysis of X-ray intermolecular difference interference terms observed for 10 mol% NaFSA-PC solution and pure liquid PC. In the present solution, onaverage, 6(1) PC molecules are involved in the first solvation shell of Na+ with intermolecular distance rNaO = 2.26(7) Å, and bond angle ∠Na+…O = C = 169(9)°. Intermolecular correlation between neighboring PC molecules in the solution has been derived from simultaneous least-squares fitting analysis of observed H–H, H–X, and X–X (X: atoms except for H) intermolecular partial structure factors determined from neutron diffraction data for H/D isotopically-substituted sample solutions. An indication of anti-parallel configuration of the nearest neighbor PC molecules has been suggested.