Supramolecular Interaction Between Cucurbit[8]uril and the Quinolone Antibiotic Ofloxacin

2019 ◽  
Vol 72 (12) ◽  
pp. 983
Author(s):  
Chun-Rong Li ◽  
Hua-Ming Feng ◽  
Jin-Yi Zhao ◽  
Zhu Li ◽  
Bing Bian ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Nmr Spectroscopy ◽  
Inclusion Complex ◽  
1H Nmr Spectroscopy ◽  
Molar Ratio ◽  
Titration Calorimetry ◽  
Supramolecular Interaction ◽  
Enthalpy And Entropy Changes ◽  
Acidic Conditions ◽  
Enthalpy And Entropy

The host–guest inclusion complex of cucurbit[8]uril (Q[8]) and ofloxacin (OFLX) has been prepared and characterised by means of 1H NMR spectroscopy, MALDI-TOF mass spectrometry, isothermal titration calorimetry (ITC), fluorescence spectroscopy, and UV-vis absorption spectroscopy. The findings demonstrated that a host–guest inclusion complex could be formed through an encapsulation of the methylmorpholine and piperazine rings in OFLX. ITC results indicated that the formation of this inclusion complex (1:1 molar ratio) was primarily dependent on enthalpy and entropy changes. In addition, the release of OFLX from the inclusion complex was increased under acidic conditions.

scholarly journals CRYSTAL STRUCTURE AND TAUTOMERISM OF ALKYLAMINO-β-KETOENOLS IN SOLUTIONS

2019 ◽  
Vol 85 (8) ◽  
pp. 73-82
Author(s):  
VIKTOR CHERNII
Keyword(s):  
Mass Spectrometry ◽  
Nmr Spectroscopy ◽  
1H Nmr ◽  
Trifluoroacetic Acid ◽  
1H Nmr Spectroscopy ◽  
Keto Group ◽  
Polymethine Chain ◽  
X Ray Diffraction ◽  
The Stability ◽  
Crystalline System

The structure of alkylamino-β-ketoenols obtained by opening of the pyran cycle of chalcones based on dehydracetic acid was studied by X-ray diffraction, IR, 1H NMR spectroscopy and chromatography-mass spectrometry. The infrared spectra of the compounds appear to be typical of β-ketoenols. The crystalline structure (2Z,5Z,7E,9E)-6-hydroxy-2-(methylami-no)-10-phenylethoxy-2,5,7,9-tetraene-4-one was first determined. A comparative analysis of it with 2 pre-viously published structures has been carried out. All of these compounds are crystallized in the form of yellow plates in the monoclinic crystalline system (spatial group P21/n), they have a planar arrangement of the polyene chain and β-ketoenol fragment con-jugated to the aromatic ring. It has been established that the planar configuration of the β-ketoenol fragment is stabilized by hydrogen bonds between the hydroxy and keto group and the amino and keto group in the crystalline state. The length of the polymethine chain, the nature of the substituents in the aromatic and aliphatic part of the molecule do not significantly affect the size and geometry of the alkylamino-β-ketoenolate fragment. Approximately the same lengths of bonds, the distance between atoms and the corners indicate that all these com-pounds may have similar chelating properties. Ac-cording to 1H NMR spectroscopy in various deu-terated solvents (benzene, DMSO, chloroform, ace-tone, methanol and trifluoroacetic acid), most of the main signals of the obtained compounds have sa-tellites, which indicates the existence of several isomeric forms in solutions. The analysis of integral intensities of labile protons in 1H NMR spectra does not allow to obtain accurate results regarding the ratio of tautomers in a solution, but for a series of compounds their approximate ratio in chloroform, DMSO and trifluoroacetic acid have been established (from 70:30 in CDCl3 to 90:10 in DMSO and CF3CO2D). The stability of the tautomers in the solutions is confirmed by the data of chromatogra-phy-mass spectrometry.

On the Interaction of Ionic Liquid 1-Butyl-3-Methylimidazolium Hexafluorophosphate with β-Cyclodextrin in Aqueous Solutions

2010 ◽  
Vol 224 (06) ◽  
pp. 893-906 ◽  
Author(s):  
Jakub Rak ◽  
Daniel Ondo ◽  
Marcela Tkadlecova ◽  
Vladimir Dohnal
Keyword(s):  
Ionic Liquid ◽  
Inclusion Complex ◽  
Aqueous Solutions ◽  
Room Temperature ◽  
Inorganic Salt ◽  
Formation Enthalpy ◽  
Titration Calorimetry ◽  
Imidazolium Cation ◽  
Phosphorus Nmr ◽  
Enthalpy And Entropy

AbstractThe formation of inclusion complex of β-cyclodextrin (β-CD) with the hydrophobic room temperature ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF6) in aqueous solutions was studied at 298.15 K using 1H, 13C, 19F and 31P NMR spectroscopy and isothermal titration calorimetry (ITC). Currently, there is a disagreement in the literature concerning the structure of the complex formed. In contrast to some results published recently in the literature, we found no reasonable support for β-CD to form an inclusion complex with 1-butyl-3-methyl-imidazolium cation of bmimPF6 in water. Our measurements on bmimPF6, the ionic liquid 1-butyl-3-methylimidazolium chloride (bmimCl), and the inorganic salt potassium hexafluorophosphate (KPF6) consistently support the formation of a weak 1:1 inclusion complex of β-CD with hexafluorophosphate anion instead of the bmim+ cation. The thermodynamic parameters of the respective complexation were calculated. The binding constant was evaluated from ITC and proton, fluorine and phosphorus NMR measurements, and the complex formation enthalpy and entropy were obtained from ITC.

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