Several Fenske-Hall type molecular orbital calculations have been carried out in order to elucidate electronic and structural changes that occur upon methyl substitution of the DL isomer of binuclear vanadyl(IV) tartrate(4−). In addition, in order to confirm those structural changes that accompany methyl substitution, as observed in a recent crystal structure determination on tetrasodium [μ-(+)-dimethyltartrato(4−)]·[μ(−)dimethyltartrato(4−)]-bis(oxovanadate(IV)] dodecahydrate, an X-ray structure determination on a second crystal form, a hexahydrate, has been completed. The salt Na 4[VO) 2-((+)-dmt((−)-dmt]·6H 2O, ‘dmt’ = dimethyltartrate-(4−), OOCC(CH 3)(O)C(CH 3)(O)COO 4−, crystallizes in the monoclinic space group P2 1/ c with a = 10.624(2), b = 11.621(2), c = 11.719(3) », β = 124.07(2)°, Z = 2. The structure was refined to R = 0.041, R w = 0.041 for 2248 independent, observed reflections. Like the blue dodecahydrate studied earlier, the pink hexahydrate exhibits a decreased VV distance, a dropping of the vanadium atom toward the plane of the four equatorial oxygen ligators, an increased vanadium to tartrate hydroxyl oxygen atom distance (all relative to the nonmethyl-substituted complex), and sixth-site coordination by an ionized tartrate hydroxyl oxygen atom in the other half of the binuclear complex. The complex present in the hexahydrate salt is even more severely distorted from the idealized D 2h geometry than is the dodecahydrate structure (though a crystallographic center of symmetry is maintained in both). The molecular orbital calculation confirm an energy level ordering for the HOMO and the lowest four LUMOs of a′(d x 2-y2 ), a′(d xz), a′′(d yz), a′′(d xy), and a′′(d z 2 ) in C 2 localized symmetry with the A′(d xz), a′′(d yz) pair having nearly the same energy.