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Extreme pressure-induced shifts of emission energies in M[Au(CN)₂] and M₂[Pt(CN)₄] and M₂[Pt(CN)₄•nH₂O - Compounds with low-dimensional metal-metal interactions

By Hartmut Yersin and U. Riedl


Emission properties of dicyanoaurates(I) and tetracyanoplatinates(II) are investigated under high hydrostatic pressure up to ca. 20 kbar and ca. 40 kbar, respectively, at T = 295 K. One observes pressure-induced red shifts of the emission energies, which are the largest values known for solid state compounds: Δν/Δp (cm⁻¹/kbar) = -120 (Cs₂Na[Au(CN)₂]₃); -150 (Cs[Au(CN)₂]); -200 (K[Au(CN)₂]); -300 (E parallel c and -250 (E perpendicular c (Li₂[Pt-(CN)₄]•4H₂0). In the investigated pressure range the energy shifts are linear and no phase transition is observed. Interestingly, Li₂[Pt-(CN)₄]•4H₂0 is a very particular compound of the series of tetracyanoplatinates(II). Using this material it is possible to tune the emission in the visible energy range continuously over more than 6000 cm⁻¹ by high pressure application up to 20 kbar. For both types of compounds, 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 states, and self-trapped states. The importance of such states for the emission properties of these compounds is also discussed

Topics: 540 Chemie, ddc:540
Publisher: 'American Chemical Society (ACS)'
Year: 1995
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