Intrazeolite Photochemistry. 13. Photophysical Properties of Bulky 2,4,6-Triphenylpyrylium and Tritylium Cations within Large- and Extra-Large-Pore Zeolites

Abstract

The photophysical properties of 2,4,6-triphenylpyrylium (TPP + ) and three para-substituted tritylium ions encapsulated within Y, β, and MCM-41 have been studied. It was found that TPP + adsorbed within MCM-41 or silica only emits fluorescence (λ max 470 nm), whereas when this cation is incorporated within HY and LaY, simultaneous emission of fluorescence and room-temperature phosphorescence (λ max 560 nm) was observed. The fluorescence decay consists of two consecutive first-order processes and is dominated by the fast (0.2-0.7 ns) component. In addition to the prompt fluorescence, delayed emission observable 40 µs after excitation was also detected for the three TPP + samples. Weak fluorescence was observed for the series of tritylium ions embedded within zeolites. The characteristic T-T absorption spectrum of the TPP + triplet excited state has been detected using time-resolved diffuse reflectance. Depending on the zeolite, shifts in the reflectance maximum and changes in the extinction coefficient of the long-wavelength band have been noted. Similar transient spectra have also been obtained for the tritylium samples, which also show long-wavelength bands that are attributed to the corresponding triplet excited state.

Specific Binding Effects for Cucurbit[8]uril in 2,4,6‐Triphenylpyrylium–Cucurbit[8]uril Host–Guest Complexes: Observation of Room‐Temperature Phosphorescence and their Application in Electroluminescence

“…[19,23,31,32,37,40,41] Figure 3 shows the emission spectrum of an aqueous solution of TP + . This emission matches the expected band for TP + fluorescence very well.…”

“…This emission matches the expected band for TP + fluorescence very well. [19,23,31,32,34,37,40,41] Upon addition of CB [5] and CB [6], very minor changes in fluorescence are recorded. In contrast, the presence of CB [7] causes a significant blueshift of l fl (10 nm).…”

Supramolecular photochemistry in zeolites: From catalysts to sunscreens

“…Once formed, the synthesized molecules are permanently entrapped within the zeolite supercage and can neither escape nor diffuse between cavities. This strategy was initially applied to the preparation of metallic complexes [47,48] but has been expanded in recent years to the synthesis of encapsulated metallophthalocyanines [49] and organic ions and molecules [50][51][52][53]. This topic has also been recently reviewed [12,34].…”

“…It has also been demonstrated that a number of organic cations, having a submillisecond lifetime in solution, become indefinitely persistent when incorporated inside the rigid framework of a zeolite [50][51][52]140]. In one example, the encapsulated dibenzotropylium cation was observed to persist within the zeolite nanochannel for longer than 10 years.…”

Ship‐in‐a‐Bottle Synthesis of a Large Guest Occupying Two Y Zeolite Neighbour Supercages: Characterisation and Photocatalytic Activity of the Encapsulated Bipyrylium Ion

“…[1,2] The identity of encapsulated TP was then confirmed spectroscopically, particularly by the match of the IR spectra of the encapsulated organic material and that of the tetrafluoroborate solid of TP (TPBF 4 ). In addition, the electrochemical response of zeolite Y encapsulated TP (TP@Y) consisted of a reversible single reduction process taking place at the same redox potential as that measured for TPBF 4 solutions. [3] Encapsulation of TP has a dramatic influence on its photophysical and photochemical properties.…”