We experimentally determined the spin density distribution to investigate the electronic states of the ͑DMe-DCNQI͒ 2 M systems, where M is Li, Ag, and Cu. The Knight shift is measured with solid-state highresolution NMR of 1 H and 13 C and is analyzed together with the reported 15 N data. The Knight shift data at each atom of the DMe-DCNQI molecule give the -electron spin distribution of the Li salt, which might correspond to the charge distribution in the insulating and localized spin system

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... the Li salt. The average fraction of the spin susceptibility DCNQI / 0 in the DMe-DCNQI molecule of the Ag and Cu salts relative to that of the Li salt is obtained to be 0.82 and 0.71, respectively. Thus, if the valence of the Ag ion is unity, the DMe-DCNQI molecule of the Ag salt has the missing spin fraction by 0.18. One possible origin of this missing spin is a modification of the lowest unoccupied molecular orbital of the DMe-DCNQI molecule due to the -d hybridization with the Ag d xy orbitals, which could be one of the origins for the difference of the physical properties from the Li salt, as in the enhancement of the charge hopping rate between the neighboring DMe-DCNQI columns in the Ag salt. In the Cu salt case, the missing spin fraction of 0.29 would correspond to the d-spin hole number of 0.28 of the Cu d xy orbital. Finally, it is stressed that all the present results are consistent with both the first-principles calculation and the X-ray photoelectron spectroscopy study.