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The absorption spectra for 4.0×10 −4 mol L -1 MMF at various pH values. The pH values are (a) 5.0, (b) 6.5, (c) 7.0, (d) 7.5, (e) 8.0, (f) 8.5, (g) 9.0 and (h) 9.5. [Reprinted from Khalafi L, Rafiee M, Mahdiun F, Sedaghat S. / Spectro‐
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![Figure 2. NMR spectra of the trans-1,4-bis[(4-pyridyl)ethenyl]benzene (...](profile/Lida-Khalafi/publication/243464702/figure/fig2/AS:298492099612675@1448177470455/NMR-spectra-of-the-trans-1-4-bis4-pyridylethenylbenzene-BPEB-bridged-ligand-as_Q320.jpg)
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... absorption spectrum of mycophenolate mofetil (MMF) at mild acidic solutions shows an absorption band which has an absorption maximum at 302 nm for its acidic form (HMF). With the increasing of pH, the absorption at 302 nm gradually decreased whereas the absorption with the 340 nm maximum, for the basic (MF − ) form, increased, Fig.4. These spectral changes and presence of an isobestic point indicate the presence of acid base equilibrium for this immunosuppressant drug. ...
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... 8,9 Displacement of indicators in β-CD cavity by any other molecule results in significant color changes (spectral changes) that provide a basis for detection of many colorless molecules. 10 Although this phenomenon occurs in a much smaller world than the one we are habituated to, information about it can be conveniently transmitted to us via simple color change. Detection of colorless molecules based on such a reversible and fast color changes is an example of "molecular recognition" because it strongly depends on molecular shapes and structure. ...
A laboratory experiment is described in which students measure the amount of cetirizine in allergy-treatment tablets based on molecular recognition. The basis of recognition is competition of cetirizine with phenolphthalein to form an inclusion complex with β-cyclodextrin. Phenolphthalein is pinkish under basic condition, whereas it's complex form with β-cyclodextrin is colorless. Addition of the cetirizine leads to release of phenolphthalein from the phenolphthalein-β-cyclodextrin inclusion complex that alters the solution color under basic conditions. The intensity of the color change is proportional to the cetirizine concentration. This simple experiment provides an opportunity for students to become familiar with the concepts of inclusion complexes and molecular recognition. Students also gain hands-on experience with a spectrophotometer and engage in plotting a calibration curve based on absorbance or color changes and determination of cetirizine. © 2015 The American Chemical Society and Division of Chemical Education, Inc.
... Nevertheless, the ionization of C7-OH on the A ring and the presence of neutral and mono-anionic species at pH 6.8 could affect the UV-vis absorbance spectra [37,39]. As a result of inclusion complex formation, physical properties of the guest molecule such as solubility, absorbance and fluorescence spectra can be considerably changed [47] For example, complex formation with -CyD results in a bathochromic shift and decreased absorption intensity in the absorbance spectrum of rutin [48]. Complex formation with ␥-CyD resulted in a bathochromic shift (5 nm) in band I while there was no shift in band II. ...
The binding abilities of α- and β-cyclodextrins (α-CD and β-CD) with some heterocyclic azo compounds (1,1'-(azodicarbonyl)dipiperidine (ADP) and azodicarboxylic dimorpholide (ADM)) were studied at different pHs (4, 7.4 and 10) by UV-Vis spectroscopy and square-wave voltammetry techniques. The association constants (Ki) and stoichiometries of the binding of these azo compounds with α-CD and β-CD were determined by using square-wave voltammetry technique. These bindings were formed with a stoichiometry of 1: 1 in solution. The solid samples, obtained from the mixtures (molar ratio of 1: 1) of these azo dyes and CDs in aqueous phase were analyzed by FT-IR spectroscopy and thermal analysis methods. Thermal analysis results showed that ADP and ADM formed the inclusion complexes with α-CD; however, the binding of the azo dyes with β-CD gave non-inclusion complexes.
