Photophysical properties of dibenzotropylium cation incorporated within acidic ZSM-5 zeolite

Dibenzotropylium ion (DT+) has been generated as an indefinitely persistent species within the channels of ZSM-5 in its H+-form. Diffuse reflectance l aser flash photolysis has allowed detection of a transient (two bands: 300 run, sharp and similar to 440 nm broad) decaying in the mus time-scale that has been assigned to the corresponding triplet excited state. The tight fi t of DT+ within the straight channels (5.2x5.7 Angstrom (2)) of ZSM-5 and t he presence of coadsorbed water explain why the DT+ triplet excited state i s not quenched by oxygen but interacts with triethylamine, which is highly water-soluble. In the latter case, formation of a new transient compatible with DT. (lambda (max) = 270 and 350 nm) through electron transfer from the amine to DT+ triplet is observed. (C) 2001 Published by Elsevier Science B .V.