Resorufin in the Channels of Zeolite L

Abstract

Zeolite L containing the resorufin anion (Res-) in its anionic framework can be prepared by incorporating the neutral resorufin molecule (ResH) from the gas phase and then exchanging the protons with potassium ions which leads to dark violet colored microcrystals. The reversibility of the deprotonation/protonation reaction of resorufin can be monitored by measuring the UV/vis absorption spectrum of the samples. The absorption spectra of Res- and ResH and their solvent dependence was interpreted using the EHMO-EDiT theory. While Res- is strongly fluorescent in solution, the fluorescence is completely quenched when Res- is located inside the channels of potassium zeolite L. This allows the investigation of the exit kinetics of the resorufin molecules as a function of the size of the solvent molecules which enter the zeolite channels and displace the incorporated resorufin molecules irreversibly. The following series was found for the displacement rate: water ≫ methanol > ethanol > 1-propanol ≳ 1-butanol. T...