Pressure-sensitive Optical Properties of Bis(1,2-dionedioximato)-Palladium (II) Complexes.

Abstract

The absorption spectra of Pd(niox)2, Pd(dmg)2 and Pd(dpg)2 have been studied at high pressures. The absorption bands based on the 4dz2-5pz transition shifted rapidly to longer wavelengths with increasing pressure. The mean rates of the red shift with pressure were ca. -1170cm-1/GPa for Pd(niox)2, ca. -1300cm-1/GPa for Pd(dmg)2 and ca. -1990cm-1/GPa for Pd(dpg)2. A new pressure-induced absorption band at around 410nm was observed for Pd(niox)2 above 10GPa. The electronic states of the palladium complexes are discussed. The colors of the complexes in the diamond-anvil pressure cell were observed visually at various pressures. The colors of the complexes turn from yellow to orange and then to successive colors in the visible spectrum with increasing pressure. These materials can be utilized as a pressure indicator over the wide pressure range.