P-T phase diagram and gold valence state of new gold mixed-valence complexes, Cs2[Au1X2][AuIIIY4](X, Y=Cl, Br, I;: X≠Y)

Cs-2[Au-1,X-2][(AuX4)-X-111](X= Cl, Br, and I) is well known for the perovskite-type gold mixed-valence system. This system undergoes pressure-induced and photo-induced Au valence transition from the mixed valence state of Au-1.111 to the single valence state of Au-11. Recently, we have succeeded in synthesizing new gold mixed-valence complexes having perovskile-type structure, Cs-2[(AuX2)-X-1][(AuY4)-Y-111](X, Y = halogen, X = Y), in organic solvent by using a new method. This hetero-halogen bridged gold mixed-valence system was confirmed by means of Raman spectroscopy. From the analysis of Au-197 Mossbauer spectra, it was elucidated that the charge transfer interaction between Au-1(5d(x2-y2)) and Au-111(5d(x2-y2))in the a-b plane becomes dominant for the Au-1-Au-111 interaction in Cs-2[(AuX2)-X-1][(AuY4)-Y-111] (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 Cs-2[(AuX2)-X-1][(AuY4)-Y-111], we have investigated the X-ray diffraction and Raman spectra under high pressure. Moreover, we have synthesized TlAuX3(X= Cl and Br) having cubic perovskite structure and highly conducting behavior The Au valence state in TlAuX3, is considered to be Au-11 at ambient pressure.