ORALS

SESSION: SolutionChemistryWedPM2-R11	Marcus International Symposium (Intl. symp. on Solution Chemistry Sustainable Development)
Wed. 30 Nov. 2022 / Room: Game
Session Chairs: Na'il Saleh; Rukayat Shola Bojesomo; Session Monitor: TBA

15:55: [SolutionChemistryWedPM209] OS
Benzimidazole-Piperazine-Coumarin/CB7 Supramolecular PET Fluorochrome for Detection of Carnosol by Stimuli-Responsive Dye Displacement and pKa Tuning
Rukayat Shola Bojesomo¹ ; Na'il Saleh² ; ¹United Arab Emirate University, Abu Dhabi, United Arab Emirates; ²United Arab Emirates University, Al-Ain, United Arab Emirates;
Paper Id: 162 [Abstract]

In recent years, the number of indicator displacement assays (IDAs) [1] has increased as an eminent strategy for changing a synthetic receptor (host) into an optical sensor. In a conventional IDA, an indicator (dye) is first permitted to reversibly bind a host, before being dislodged from the host by a competitive analyte (drug) and thus the strategy regulates an optical signal despite the analyte and the host are both spectroscopically inactive. It is quite crucial that the indicator and analyte have similar affinity for the receptor.[2–6] A new fluorescent dye (4PBZC) comprises of coumarin, piperazine and benzimidazole (BZ) was designed, prepared and complexed to cucurbit[7]uril (CB7) to detect carnosol (CAR) anticancer drug in sub-nanomolar concentrations utilizing the supramolecular indicator displacement assay (IDA) strategy, the CB7-assisted pKa shift and the CB7-retarded photoinduced electron transfer (PET) process. The 2:1 host−guest complexation was confirmed by UV−visible absorption, fluorescence and proton NMR spectroscopy, which confirm binding to 4PBZC via the BZ and coumarin moieties. Also, CB7 preferentially binds the indicator dye via the protonated BZ group compared to the neutral BZ group, demonstrated by a high 2:1 binding constant (e.g., K = 5.5 × 106 M−1) of the complex in its protonated form, which led to an increase in the pKa of the BZ moiety by ca. 3.0 units after the addition of CB7. In the aqueous solution under pH of 6, switching the emission signals between 4PBZH+C/CB7 (ON state) and CAR/CB7NPs (OFF state) was achieved by displacement of the protonated dye from the cavity of CB7 by the CAR analyte. An efficient sensor was fabricated for the highly sensitive detection of CAR in aqueous solution at pH 6 with a low-detection limit (LOD) of 0.06 ng/mL (0.2 nM).

References:
(1) Nguyen, B. T.; Anslyn, E. V. Indicator–Displacement Assays. Coordination Chemistry Reviews 2006, 250 (23), 3118–3127. https://doi.org/10.1016/j.ccr.2006.04.009.
(2) Sinn, S.; Biedermann, F. Chemical Sensors Based on Cucurbit[n]Uril Macrocycles. Israel Journal of Chemistry 2018, 58 (3–4), 357–412. https://doi.org/10.1002/ijch.201700118.
(3) Ghale, G.; Nau, W. M. Dynamically Analyte-Responsive Macrocyclic Host–Fluorophore Systems. Acc. Chem. Res. 2014, 47 (7), 2150–2159. https://doi.org/10.1021/ar500116d.
(4) Mako, T. L.; Racicot, J. M.; Levine, M. Supramolecular Luminescent Sensors. Chem. Rev. 2019, 119 (1), 322–477. https://doi.org/10.1021/acs.chemrev.8b00260.
(5) Sinn, S.; Krämer, J.; Biedermann, F. Teaching Old Indicators Even More Tricks: Binding Affinity Measurements with the Guest-Displacement Assay (GDA). Chem. Commun. 2020, 56 (49), 6620–6623. https://doi.org/10.1039/D0CC01841D.
(6) Sinn, S.; Spuling, E.; Bräse, S.; Biedermann, F. Rational Design and Implementation of a Cucurbit[8]Uril-Based Indicator-Displacement Assay for Application in Blood Serum. Chemical Science 2019, 10 (27), 6584–6593. https://doi.org/10.1039/C9SC00705A.

SESSION: SolutionChemistryWedPM2-R11	Marcus International Symposium (Intl. symp. on Solution Chemistry Sustainable Development)
Wed. 30 Nov. 2022 / Room: Game
Session Chairs: Na'il Saleh; Rukayat Shola Bojesomo; Session Monitor: TBA

16:45: [SolutionChemistryWedPM211] OS
COMPLEXATION of CINNAMIC ACID by CUCURBIT[7]URIL for ENHANCING PHOTOISOMERISATION CONVERSION
Na'il Saleh¹ ; ¹United Arab Emirates University, Al-Ain, United Arab Emirates;
Paper Id: 23 [Abstract]

The paper presents the supramolecular control of photoisomerization reactions of cinnamic acid (CA), belonging to the class of α,β-unsaturated carbonyl compounds, utilizing the rigid cavity of cucurbit[7]uril (CB7). Irradiation by UV light (300 and 254 nm) of an aqueous solution of the complex induces the E-to-Z-conformational change, as evidenced by UV-visible absorption spectroscopic and 1H-NMR techniques. CA and CB7 form a stable 1:1 host–guest complex with moderate binding constant (K = 3.3 x 103 M-1). The photo-switchable “on-off” host–guest system shows a higher reversibility and switching efficiency, when compared to the unbound molecules, which makes it potentially useful in designing photoresponsive gating systems. The results presented herein highlight the value of a supramolecular approach in achieving selectivity in photoreactions and opening reaction pathways that are latent in solution chemistry.

References:
REFERENCES:
[1] A. G. Mejuto, J. Morales, J. Rial-Otero, R., S. J. Gándara (2010). Factors controlling flavors binding constants to cyclodextrins and their applications in foods. Food Res. Int., 43 ( 2010) 1212-1218.