Solubilization of Pyridone-Based Fluorescent Tag by Complexation in Cucurbit[7]uril (original) (raw)
Related papers
The journal of physical chemistry. B, 2014
Supramolecular interaction between an intramolecular charge transfer (ICT) probe, N,N-dimethylaminonaphthyl-(acrylo)-nitrile (DMANAN), and two well-recognized macrocyclic hosts, cucurbit[7]uril (CB7) and β-cyclodextrin (β-CD), has been studied in aqueous medium by absorption, emission, time-resolved measurements, and (1)H NMR spectroscopic methods. The changes in the profiles of the fluorescence spectra illustrate significant modifications in fluorescence intensity, decay time, and quantum yield upon confinement of probe within the hydrophobic cavity of the hosts. Using the Benesi-Hildebrand relationship, the stoichiometric ratio as well as the binding constant of the host-guest complexation has been estimated. The stable inclusion complexes of the probe with different hosts have been supported by DFT and ONIOM based quantum chemical calculations. These methods of measurement establish that the acceptor group of the probe resides inside the hydrophobic cavity of the macrocycle. The ...
Journal of Polymer Science Part …, 2010
The effects of cucurbit[n]uril on the dissolution and the photophysical properties of nonionic conjugated polymers in water are described. For this purpose, a fluorine-based polymer, namely, poly [9,9-bis{6(N,N-dimethylamino)hexyl}fluoreneco-2,5-thienylene (PFT) was synthesized and characterized by spectroscopic techniques including 1D and 2D NMR, UV-vis, fluorescent spectroscopy, and matrix-assisted laser desorption mass spectrometry (MALDI-MS). For the first time, it was demonstrated that a nonionic conjugated polymer can be made soluble in water through an inclusion complex formation with CB8. The structure of the complex was elucidated by NMR experiments including 1 H and selective 1D-NOESY. This complex emits green and is highly fluorescent with fluorescent quantum yield of 35%. In contrast, CB6 or water-soluble CB7 although they are chemically identical to CB8 do not have any effect on the dissolution and photophysical properties of PFT. By preparing a protonated version of PFT, the optical properties of PFT in methanol, protonated PFT and PFT@CB8 in water have been studied and compared. It was also observed that the morphology of the polymer PFT was affected by the presence of CB8. Thus CB8-assisted self-assembly of polymer chains leads to vesicles formation; these structures were characterized by DLS, AFM, SEM, and TEM fluorescent optical microscopy. V C 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: [4894][4895][4896][4897][4898][4899] 2010
Journal of Photochemistry and Photobiology A-chemistry, 2018
The complex formation of thiamonomethine cyanine dyes bearing two N-ammoniohexyl or two N-ethyl substituents with cucurbit[5,7]urils (CB[5,7]) in aqueous solutions was studied by electronic and 1 H NMR spectroscopy, including spectrophotometric, fluorescence, and 1 H NMR titration methods. It was found that CB[5] forms external complexes with the dyes, while CB[7] forms internal (inclusion) complexes of 1:1 and 1(dye):2(CB[5,7]) composition. The complexation with CB[5,7] changes the absorption spectra of cyanine dyes and induces a considerable fluorescence enhancement. The stability constants of the complexes were determined (logK 1:1 varies in the range from 3.53 to more than 6, and logK 1:2 varies in the range from 3.5 to 4.32). The dye with ammoniohexyl substituents forms more stable complexes owing to hydrogen bond formation between the NH 3 + groups and the carbonyl groups of the CB[5,7] portals. The structure of supramolecular complexes was confirmed by quantum chemical calculations.
Photochemical & Photobiological Sciences, 2014
Inclusion of 6-methoxy-1-methylquinolinium (C 1 MQ) in the cavity of cucurbit[7]uril (CB7) was studied by absorption, fluorescence, NMR and isothermal calorimetric methods in aqueous solution at 298 K. The free C 1 MQ exhibited dual-exponential fluorescence decay kinetics due to the two torsional isomers differing in the orientation of the methoxy moiety relative to the heterocyclic ring. The enthalpy-driven encapsulation of the heterocycle in CB7 led to a very stable 1 : 1 complex with a binding constant of (2.0 ± 0.4) × 10 6 M −1. The rate of C 1 MQ-CB7 complex dissociation was found to be comparable to the NMR timescale. Because the methoxy moiety is oriented outward from the host, its s-cis-s-trans isomerization is slightly affected by the confinement. Inclusion complex formation significantly slowed down the photoinduced electron transfer from I − and N 3 − to the singlet-excited C 1 MQ, but did not preclude the reaction because long distance electron transfer occurred through the wall of the CB7 macrocycle. Due to the large difference in the quenching rate constant for free and encapsulated forms, C 1 MQ is an excellent probe for the study of the inclusion of nonfluorescent compounds in CB7 in the presence of Cl − or Br −. † Electronic supplementary information (ESI) available. See
Molecules
With the emergence of host-guest systems, a novel branch of complexation chemistry has found wide application in industries such as food, pharmacy, medicine, environmental protection and cosmetics. Along with the extensively studied cyclodextrins and calixarenes, the innovative cucurbiturils (CB) have enjoyed increased popularity among the scientific community as they possess even better qualities as cavitands as compared to the former molecules. Moreover, their complexation abilities could further be enhanced with the assistance of metal cations, which can interestingly exert a dual effect on the complexation process: either by competitively binding to the host entity or cooperatively associating with the CB@guest structures. In our previous work, two metal species (Mg2+ and Ga3+) have been found to bind to CB molecules in the strongest fashion upon the formation of host–guest complexes. The current study focuses on their role in the complex formation with three dye molecules: thia...
Journal of Photochemistry and Photobiology A: Chemistry, 2018
Supramolecularly assisted modulations in the photophysical properties of the well known and practised antibiotic drug ciprofloxacin (Cpf) with versatile macrocyclic cavitand molecule cucurbit[7]uril (CB7) has been explored under different pH conditions. Both the cationic (Cpf-H +) and neutral (Cpf) forms of the drug exhibits strong binding interaction with CB7. Ground state absorption, steady-state fluorescence, time-resolved emission and fluorescence anisotropy decay measurements documented the host assisted intriguing changes in the photophysical properties of the drug, occurred through the successive formations of the 1:1 and 1:2 (drug to host) inclusion complexes, and thereby causing the intriguing small initial enhancement in fluorescence intensity at lower host concentrations and subsequently leading to a strong fluorescence quenching at higher CB7 concentration. Inferences drawn from the photophysical studies are nicely supported by the results obtained from the 1 H NMR measurements. Investigations on the photodegradation studies involving the Cpf-H + and Cpf forms of the drug, both in the absence and in the presence of CB7 host, revealed that there is a large enhancement in the photostability for both the prototropic forms of the drug, by about 3 times, on their inclusion complex formation with the CB7 host. Observed results from the supramolecular interactions of the ciprofloxacin drug with CB7 macrocycle are suggested to have implications in improving drug stability and in the possible deployments in drug formulations and drug delivery systems.
Physical Chemistry Chemical Physics, 2017
Biosupramolecular assemblies combining cucurbit[n]urils (CB[n]s) and proteins for the targeted delivery of drugs has the potential to improve the photoactivity of photosensitizers used in the photodynamic therapy of cancer. Understanding the complexity of these systems and how it affects the properties of photosensitizers is the focus of this work. We used acridine orange (AO +) as a model photosensitizer and compared it with methylene blue (MB +) and a cationic porphyrin (TMPyP 4+). Encapsulation of the photosensitizer into CB[n]s (n = 7,8) modified their photoactivity. In particular for AO + the photo-oxidation of HSA was enhanced in the presence of CB[7], meanwhile it was decreased when included into CB[8]. Accordingly, peroxide generation and protein fragmentation were also increased when AO + was encapsulated into CB[7]. The triplet excited state lifetimes of all the photosensitizers were lengthened by their encapsulation into CB[n]s, while the singlet oxygen quantum yield was enhanced only for AO + and TMPyP 4+ , being decreased for MB +. The results obtained in this work promt the necessity of further investigating this kind of hybrid assemblies as drug delivery systems because of their possible applications in biomedicine.