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 laser flash photolysis has allowed detection of a transient (two bands: 300 nm, sharp and ∼440 nm broad) decaying in the μs time-scale that has been assigned to the corresponding triplet excited state. The tight fit of DT+ within the straight channels (5.2×5.7 Å2) of ZSM-5 and the presence of coadsorbed water explain why the DT+ triplet excited state is 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 (λmax=270 and 350 nm) through electron transfer from the amine to DT+ triplet is observed.