Electronic structure of the aqueous vanadyl ion probed by 9 and 94 GHz EPRand pulsed ENDOR spectroscopies and density functional theory calculations

The aqueous vanadyl ion ([VO(H2O)(5)](2+)) has been investigated by X-band EPR, 94 GHz W-band EPR, and ESE-ENDOR. These-experiments reveal information about the hyperfine (\A(xx)\ = 208.5 MHz, \A(yy)\ = 208.5 MHz, \A(zz)\ = 5 47.0 MHz), and nuclear quadrupole coupling (\e(2)qQ\ = 5.6 MHz) of the V-51 nucleus. The measured nuclear quadrupole coupling parameters are compared to values determined by density functional theory calculations (\e(2)qQ\ = 5.2 MHz). These theoretical calculations illustrate that axial ligands and molecular distortions can alter the magnitude of the nuclear quadrupole int eraction.