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Wintgens V.,Systemes Polymeres Complexes | Biczok L.,Hungarian Academy of Sciences | Miskolczy Z.,Hungarian Academy of Sciences
Supramolecular Chemistry | Year: 2010

The thermodynamics of 1:1 inclusion complex formation between 1-alkyl-3-methylimidazolium type ionic liquids and cucurbit[7]uril was studied by isothermal titration calorimetry in aqueous solution at 298K. The encapsulation proved to be enthalpy driven for all cations used. The enthalpy change upon binding (H) became more negative when the 1-alkyl moiety of the imidazolium ring was gradually lengthened reaching the most exothermic association with the hexyl derivative. Further increase of the number of carbon atoms in the aliphatic chain led to less negative H values. The much smaller entropy change followed the trend of H. The slope of the linear enthalpy-entropy correlation found in the present work is significantly smaller than that reported previously for cyclodextrin complexes, because the more rigid CB7 macrocycle cannot undergo significant conformational change upon complexation. © 2010 Taylor & Francis. Source


Biczok L.,Hungarian Academy of Sciences | Wintgens V.,Systemes Polymeres Complexes | Miskolczy Z.,Hungarian Academy of Sciences | Megyesi M.,Hungarian Academy of Sciences
Israel Journal of Chemistry | Year: 2011

The encapsulation of biologically important compounds in the cavity of cucurbit[7]urils (CB7) brings about a variety of effects. The binding of lumichrome to CB7 promotes the tautomerization from alloxazine- to isoalloxazinetype structure in the ground-state, leading to substantial changes in the absorption and fluorescence properties. Even partial embedding in CB7 macrocycle is able to protect sanguinarine, a natural alkaloid, against nucleophilic addition and photooxidation. The inclusion of berberine in CB7 results in about 500-fold enhancement of its fluorescence intensity, and the change in its fluorescence decay characteristics indicates ternary complex formation with cations. DAPI (4',6-diamidino-2-phenylindole dication) is an excellent fluorescent probe for the study of the CB7 complex formation with ionic liquids, surfactants, and biologically important compounds. The binding of 1-alkyl-3-methylimidazolium ions to CB7 is strongly exothermic; both the enthalpy and the entropy change in the reaction go through a minimum when the 1-alkyl group is lengthened, reaching the smallest values for the hexyl derivative. © 2011 Wiley-VCH Verlag GmbH &Co. KGaA. Source


Wintgens V.,Systemes Polymeres Complexes | Amiel C.,Systemes Polymeres Complexes | Biczok L.,Hungarian Academy of Sciences | Miskolczy Z.,Hungarian Academy of Sciences | Megyesi M.,Hungarian Academy of Sciences
Thermochimica Acta | Year: 2012

The inclusion of 1-alkyl-3-methylimidazolium ions (C nmim +) in 4-sulfonatocalix[8]arene was studied by isothermal titration calorimetry in aqueous solution at 298 K. Sequential formation of 1:1 and 2:1 complexes occurred in enthalpy driven reactions. The alteration of the molecular structure of the guest barely affected the driving force of the confinement of the first C nmim +. However, the binding affinity of the second C nmim + went through a maximum when the number of carbon atoms in the side chain was increased. The enthalpy and entropy change diminished linearly with the length of the aliphatic substituent of C nmim + for 1:1 complexation, but reached a minimum for the hexyl homologue in the case of 2:1 inclusion. Linear entropy-enthalpy correlations were found with smaller slope and intercept for the second binding step. © 2012 Elsevier B.V. All rights reserved. Source


Harangozo J.G.,Hungarian Academy of Sciences | Miskolczy Z.,Hungarian Academy of Sciences | Biczok L.,Hungarian Academy of Sciences | Wintgens V.,Systemes Polymeres Complexes | Lorthioir C.,Systemes Polymeres Complexes
Journal of Inclusion Phenomena and Macrocyclic Chemistry | Year: 2015

The complexation of the highly fluorescent 6-methoxy-1-methyl-quinolinium (C1MQ) and the widely used herbicide, difenzoquat (DFQ), with 4-sulfonatocalix[4]arene (SCX4) macrocycle was studied by isothermal titration calorimetry, fluorescence and NMR spectroscopy in aqueous solutions at 298 K. Both guests produced 1:1 complexes with SCX4, but the binding affinity of C1MQ was more than one order of magnitude larger than that of DFQ in neutral medium. The higher stability of C1MQ-SCX4 complex originated from the significant enthalpy gain upon its formation. The encapsulation of C1MQ in SCX4 in the ground state resulted in an efficient fluorescence quenching due to electron transfer from the host to the excited guest. The marked difference in the fluorescence quantum yields for free and bound C1MQ was used to detect the competitive complexation of DFQ in SCX4. © Springer Science+Business Media Dordrecht 2014. Source


Wintgens V.,Systemes Polymeres Complexes | Le Coeur C.,Systemes Polymeres Complexes | Amiel C.,Systemes Polymeres Complexes | Guigner J.-M.,University Pierre and Marie Curie | And 3 more authors.
Langmuir | Year: 2013

The interaction of 4-sulfonatocalix[6]arene (SCX6) macrocycle with 1-alkyl-3-methylimidazolium type of ionic liquids possessing dodecyl, tetradecyl, or hexadecyl substituent was studied in aqueous solution at 298 K. Host-guest complexation promoted the spontaneous self-assembly into nanoparticles of 7:1 ionic liquid:SCX6 stoichiometry. Positively charged and stable nanoparticles were produced in solutions of 7-200-fold excess of ionic liquid as compared to the amount of SCX6. The negatively charged nanoparticles formed in solutions having 2-7 ionic liquid:SCX6 molar ratios evolved into larger species. The stability of the nanoparticles increased with the lengthening of aliphatic chain of the ionic liquid. Cryo-TEM experiments showed dense particles generally with spherical shape and multilayered structure, which has been confirmed by small-angle neutron scattering. © 2013 American Chemical Society. Source

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