Cs2[AuIX2][AuIIIX4](X= Cl, Br, and I) is well known for the perovskite-type gold mixed-valencesystem. This system undergoes pressure-induced and photo-induced Au valencetransition from the mixed valence state of AuI,III to the singlevalence state of AuII. Recently, we have succeeded in synthesizingnew gold mixed-valence complexes having perovskite-type structure, Cs2[AuIX2][AuIIIY4](X,Y = halogen, X a Y), in organic solvent by using anew method. This hetero-halogen bridged gold mixed-valence system was confirmedby means of Raman spectroscopy. From the analysis of 197Au Mossbauer spectra,it was elucidated that the charge transfer interaction between AuI(5dx2-y2)and AuIII(5dx2-y2)in the a-b plane becomesdominant for the AuI-AuIII interaction in Cs2[AuIX2][AuIIIY4](X, Y = Cl, Br, and I) in the order of X = Cl < Br < I, where Y is fixed.In order to elucidate the Au valence transition for Cs2[AuIX2][AuIIIY4],we have investigated the X-ray diffraction and Raman spectra under highpressure. Moreover, we have synthesized TlAuX3(X = Cl and Br) havingcubic perovskite structure and highly conducting behavior. The Au valence statein TlAuX3 is considered to be AuII at ambient pressure.
