Comparison of electron magnetic resonance and x-ray studies of the structure of solvated vanadyl (VO(H2O)52+)

Abstract

Some structural parameters of VO(H/sub 2/O)/sub 5//sup 2 +/ determined by electron spin echo modulation (ESEM) in frozen solutions and by electron nuclear double resonance (ENDOR) in single crystals of the Mg(NH/sub 4/)/sub 2/(SO/sub 4/)/sub 2/-6H/sub 2/O Tutton salt are different. It was determined that the single-crystal ENDOR results are consistent with powder INDOR results. X-ray results did not strictly correspond to the structure of VO(H/sub 2/O)/sub 5//sup 2 +/ but was a close approximation. The structure of VO(H/sub 2/O)/sub 5//sup 2 +/ was interpreted by all techiques as four equatorial waters in a plane perpendicular to the V=O bond and one axial water in the plane of the V=O bond with the axial water being more distant than the equatorial waters from V. V-O distances were determined directly in the x-ray studies. Comparison of the isotropic hyperfine coupling determined by single-crystal ENDOR with that determined by powder ESEM was included. Also the typical approach used in powder ESEM and ENDOR analyses were compared. 1 table.