EXTREME PRESSURE-INDUCED SHIFTS OF EMISSION ENERGIES IN M[AU(CN)(2)] AND M(2)[PT(CN)(4)]CENTER-DOT-NH(2)O - COMPOUNDS WITH LOW-DIMENSIONAL METAL-METAL INTERACTIONS

Emission properties of dicyanoaurates(I) and tetracyanoplatinates(II) are investigated under high hydrostatic pressure up to approximate to 20 kbar and approximate to 40 kbar, respectively, at T = 295 K. One ob serves pressure-induced red shifts of the emission energies, which are the largest values known for solid state compounds: Delta<(nu)over ba r>/Delta p (cm(-1)/kbar) = -120 (Cs2Na[Au(CN)(2)](3)); -150 (Cs[Au(CN) (2)]); -300 ((E) over right arrow\\(c) over right arrow) and -250 ((E) over right arrow perpendicular to (c) over right arrow) (Li-2[Pt-(CN) (4)]. 4H(2)O). In the investigated pressure range the energy shifts ar e linear and no phase transition is observed. Interestingly, Li-2[Pt(C N)4]. 4H(2)O is a very particular compound of the series of tetracyano platinates(II). Using this material it is possible to tune the emissio n in the visible energy range continuously over more than 6000 cm(-1) by high pressure application up to 20 kbar. For both types of compound s, the reported large values of pressure induced shifts are related to low-dimensional metal-metal interactions. These interactions lead to the formation of electronic energy bands, delocalized free exciton sta tes, and self-trapped states. The importance of such states for the em ission properties of these compounds is also discussed.