Cucurbit[7]uril‐Encapsulation‐Controlled Supramolecular Photoproduct and Radical Fluorescence Emission

Abstract

Herein, a host-guest interaction-controlled photoproduct created by using cucurbit[7]uril (Q[7])-based pseudorotaxane structures is reported. The assembly exhibited controlled behavior towards the reduction of the ethylene (C=C) bond in the tetrakis(pyridin-4-yl)ethylene (TPyE) guest molecule under UV light irradiation. This can be attributed to the Q[7] encapsulation masking the four pyridinium arms of the guest, which inhibits planarization of the TPyE core to form the cyclization product. In particular, the strong affinity of Q[7] for the butyl-substituted guest (TPyE-4C) led to an unusual radical fluorescence emission of the photoirradiationtriggered intermediate of the guest molecule being observed in aqueous solution. This work provides a valuable paradigm and new insight for macrocycle-based host À guest interactions in supramolecular catalysis and luminescent radical materials.

Emissive‐Dye/Cucurbit[n]uril‐Based Fluorescence Probes for Sensing Applications

“…Further increase of Hg 2 + ions (beyond 100 μM) led to the fluorescence turn off mechanism with blue shifts from 570 nm to 563 nm (Figure 4C). The calculated detection limit of t-CB [14] ⋅ TO towards Hg 2 + was 7.8 × 10 À 8 mol/L.…”

“…[41] At pH 2, 1 : 2 binding ratio observed in the t-CB [14] ⋅ TO complex with significant changes of fluorescence. Upon incremental addition of acidic TO solution in to t-CB [14], resulted in a dramatic heightening in TO's emission intensity at around 575 nm. Fluorescence quenching and blue shift were observed in case of Ba 2 + and Pb 2 + , whereas, upon addition of Hg 2 + in acidic aqueous solution of the t-CB [14] ⋅ TO complex, the fluorescence turn on mechanism was observed (Figure 4B).…”

“…In this review, we will mainly focus on fluorescent "CB-[n]s ⋅ Dye" inclusion complex based on CB[n]s as host such as CB [6], CB[7], CB [8], twisted CB [14] (t-CB [14]) (Figure 1B Tetramethylbenzobis(imidazolium) drivatives (MBBI), 1-naphtylamine-5sulfonic acid (NSA), 3-amino-9-ethylcarbazole derivative (AEC), Epigallocatechin gallate (EGCG), Hoechst-33258 (H33258), Pyronine (PyY), and some structure-directing agent including 5,5'dithiobis-(2-nitrobenzoic acid) (H 2 DTNB), Naphthalene disulfonic acids (H 2 NDA), Anthracene-9-carboxylic acid (HACA), 1,3,5-Benzenetricarboxylicacid (H 3 BTC), Isonicotinic acid (HINA) (Some specific guest molecules shown in Figure 2) for certain metal ions, biomolecules and toxic chemicals sensing application. Specifically, it is our goal to define in detail the recent progresses of CB[n]s-containing HÀ G complexes and some CB[n]s-based coordination compounds and their sensing properties toward various essential and non-essential metal ions ChemistrySelect such as Na + , Ca 2 + , Ba 2 + , Cs + , Ag + , Fe 3 + , Cu 2 + , Zn 2 + , Cd 2 + , Hg 2 + , Pb 2 + (listed in Table 1), biomolecules such as amino acids, peptides, proteins, drugs, ATP, DNA, alkaloids deoxyadenosine, biogenic polyamines, enzymatic activity, azoreductase activity, cytosolic enzyme indoleamine 2,3-dioxygenase 1 (IDO1) activity, (listed in Table 2), and some toxic chemicals such as toxic gas, solvents, pesticides, amines, dye, anion, perfluorinated, fungicides, and aromatic compounds (listed in Table 3).…”

“…The CB [8] ⋅ 2PyY fluorescent probe can be used to detect FBZ, TBZ and CBZ with high sensitivity and selectivity with a detection limit of ∼ 10 À 8 mol/L. ThT is a strong staining agent and fluorescent dye and its dimethylamino phenyl moiety are responsible for the increasing fluorescent intensity of t-CB [14] ⋅ ThT complex (Figure 21D). [106] This HÀ G complex shows a "turn-off" fluorescence response toward flusilazole fungicides because the interaction of the azole group of flusilazole interacts with the quaternary ammonium group of ThT reduced the electron-withdrawing ability of the quaternary ammonium group (Figure 21D).…”

“…(A) Synthesis of CB[n]s homologues by condensation of formaldehyde and glycoluril under acidic conditions. (B) Model representations of CB[6], CB[7], CB[8], and t-CB[14].…”