Spectroscopic studies of 9,10-phenanthrenequinones in solution and on a silica surface

Spectroscopic properties and oxygen quenching of substituted symmetric 9,10-phenanthrenequinones (with methoxy, chloro and methyl at 3 and 6 positions) are reported. The triplet states were studied in benzene and acetonitrile solutions as well as on a silica surface using nanosecond laser Rash photolysis in transmitance and diffuse reflectance modes. The time resolved spectra (TRS) are identical in solution and on a silica porous surface showing absorption band maxima in the range of 460-480 and 640-660 nm. By contrast, triplet lifetimes vary with the environment and temperature from few microseconds in solution to hundred microseconds on silica. (C) 2001 Elsevier Science B,V. All rights reserved.