TY - JOUR
T1 - Solubilization of Pyridone-Based Fluorescent Tag by Complexation in Cucurbit[7]uril
AU - Alzard, Reem H.
AU - Bufaroosha, Muna S.
AU - Al-Shamsi, Noura
AU - Sohail, Amir
AU - Al-Dubaili, Naji
AU - Salem, Alaa A.
AU - Abdou, Ibrahim M.
AU - Saleh, Na'Il
N1 - Funding Information:
All authors thank the research program in United Arab Emirates University for financial grant numbers ECEER-1-2017 and 09_2_SURE +2017. The authors thank the undergraduate students Khadeejha Weiss, Ahmed Elsir, Mohammed Kamal, and Elmutasim Ahmed for collecting preliminary measurements during their undergraduate research courses.
Publisher Copyright:
© 2019 American Chemical Society.
PY - 2019/1/10
Y1 - 2019/1/10
N2 - Aimed at further exploring the hosting properties of cucurbit[7]uril (CB7), we have exploited the spectroscopic and photophysical properties of a known fluorescent label as the guest molecule, namely, 3-cyano-6-(2-thienyl)-4-trifluoromethyl pyridine (TFP), in neat solvents. The formation of an inclusion host-guest complex with CB7 was checked by UV-vis absorption spectroscopy, and the value of binding constant (9.7 × 105 M-1) was extracted from the spectrophotometric data. The modulation of keto-enol equilibrium in TFP by the local environment is governed by the interplay between dimerization through intermolecular hydrogen bonding between individual solute molecules, favoring the enol form, and intermolecular hydrogen bonding between TFP and the surrounding solvents, favoring the keto form. Time-resolved fluorescence results established that the macromolecular CB7 host stabilizes preferentially the neutral enol form over the keto form of TFP. Unprecedentedly, our results reveal a linear dependence of the amplitudes of the extracted decay-associated spectra from the time-resolved fluorescence spectra of TFP on the sum of polarity/polarizability and hydrogen bonding parameters of the local environment, confirming that TFP at micromolar concentration in the CB7 complexes is experiencing a methanol-like environment. The results rationalized the 42-fold enhancement in the solubility of TFP in water media by complexation in CB7.
AB - Aimed at further exploring the hosting properties of cucurbit[7]uril (CB7), we have exploited the spectroscopic and photophysical properties of a known fluorescent label as the guest molecule, namely, 3-cyano-6-(2-thienyl)-4-trifluoromethyl pyridine (TFP), in neat solvents. The formation of an inclusion host-guest complex with CB7 was checked by UV-vis absorption spectroscopy, and the value of binding constant (9.7 × 105 M-1) was extracted from the spectrophotometric data. The modulation of keto-enol equilibrium in TFP by the local environment is governed by the interplay between dimerization through intermolecular hydrogen bonding between individual solute molecules, favoring the enol form, and intermolecular hydrogen bonding between TFP and the surrounding solvents, favoring the keto form. Time-resolved fluorescence results established that the macromolecular CB7 host stabilizes preferentially the neutral enol form over the keto form of TFP. Unprecedentedly, our results reveal a linear dependence of the amplitudes of the extracted decay-associated spectra from the time-resolved fluorescence spectra of TFP on the sum of polarity/polarizability and hydrogen bonding parameters of the local environment, confirming that TFP at micromolar concentration in the CB7 complexes is experiencing a methanol-like environment. The results rationalized the 42-fold enhancement in the solubility of TFP in water media by complexation in CB7.
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U2 - 10.1021/acsomega.8b02761
DO - 10.1021/acsomega.8b02761
M3 - Article
AN - SCOPUS:85059898600
SN - 2470-1343
VL - 4
SP - 953
EP - 960
JO - ACS Omega
JF - ACS Omega
IS - 1
ER -