Studies of mixed-valence states in one dimentional halogen-bridged gold compounds [(AuX)-X-I(DBS)][(AuX3)-X-III(DBS)](X=Cl, Br, I: dbs=dibenzylsulfide)

We have investigated the crystal structure and the Au valence states in [Au -I X(DBS)][(AuX3)-X-III(DBS)] (X=Cl, Br, I). From the analysis of Au-197 Mo ssbauer spectra in AuClx(DBS) (X = 1, 2, 3), it is proved that AuCl2(DBS) h as a mixed-valence state of Au-I and Au-III. Comparing with the isomer shif ts of Au-I and Au-III in Cs-2[(AuCl2)-Cl-I][(AuCl4)-Cl-III], it is consider ed that the charge transfer interaction between Au-I and Au-III in AuCl2(DB S) is smaller than that in Cs-2[(AuCl2)-Cl-I][(AuCl4)-Cl-III]. The isomer s hifts of Au-I and Au-III in AuCl2 (DBS) are much larger than those in Cs-2[ (AuCl2)-Cl-I][(AuCl4)-Cl-III], which should be attributed to the highly cov alent bond between Au and S. From the ESR spectra, it is shown that the Au- II states exist as the mismatch of the valence alternation in AuCl2(DBS). T he half-field ESR signal for Delta M=+/-2 at low temperature indicates the dimerization of the Au-II state with ferromagnetic exchange interaction. Al so, the X-ray powder patterns of AuX2(DBS) (X=Cl, Br) shows these two compl exes to be isomorphous.