P-CD protons

In this procedure, the plot of chemical shift changes (A6) for the P-CD protons against [FLZ] in the form of [FLZ]/A6obs versus [FLZ] (referred to as y-recip-rocal plot) should be linear for 1 1 inclusion complex. The slope of the plot thus equals to 1/A5max and the intercept with the vertical axis to A5max/Ka, allowing the estimation of association constant (Ka). A typical Scott s plot for FLZ P-CD inclusion complex is shown in figure 3 and the association constant (Ka) was calculated to be 68.7 M-1. 

The assignment of the P-CD protons was made on the basis of their splitting pattern, H NMR and 2D H- H COSY and H- H ROESY spectral data. Comparison the IH NMR spectra of pure P-CD and FLZ P-CD mixture, suggests that the chemical shift of P-CD proton is changes upon bonding to FLZ. P-CD cavity protons H-3 and H-5 show maximum shielding compared to H-1 , H-2 ... 

Figure 4. Expansion of a part of IH NMR data (500 MHz), showing p-CD protons in the presence as well as in the absence of FLZ.

F ure 7. Expanded region of 2D ROESY (500 MHz) spectra of FLZ p-CD mixture (1 1) showing the intermolecular NOE s between p-CD protons and aromatic protons of FEZ. 

A complete NMR approach has been employed to evaluate the complexation process of catechin A with p-CD and synthetic analogues.125 The analysis of the variation of the proton chemical shifts indicated the formation of a 1 1 stoichiometric complex. 2D-ROESY provided detailed spatial information of the complex while the binding constants were obtained by using diffusion-order spectroscopy (DOSY) techniques. 

The structures of P-CD-modified ligands were routinely elucidated by H-NMR and ESI mass spectroscopy. Formation of Ru chloro complex 97 from 49 and 47 was demonstrated to be quantitative by H-NMR (Fig. 28). Si ificant downfield shifts (0.36-0.56 ppm) in 97 of several protons relative to free ligand 49 were observed. 

ROESY spectra of ligand 49 and p-tert-butylacetophenone 100 provided evidence for the binding of the aromatic ring within the cavity of P-CD because strong cross peaks of H at C3 and H at C5 of P-CD with the fer -butyl group of the ketone could be observed. Further, moderate cross peaks were observed for meta- and ort/io-protons of the aromatic ring, indicating that the carbonyl compound enters the cavity with the hydrophobic fer -butyl rest ahead (Fig. 29). 

Hybrid silica materials were prepared via a sol-gel pathway at pH 9. The influence of anionic surfactant (SDS) was studied by comparing templated materials (TbSn series) with hybrid materials obtained without surfactant (Tbn series). Two mechanisms of mesostructure formation can be considered as represented on Fig. 2. The pka of aminopropyl chain is about 10.6 in the reaction mixture propyl-amines are partially protonated. Electrostatic interactions between dodecylsulfate anion and NH and sodium cation neutralization may then occur, resulting in the condensation of the silica structure around surfactant micelles and aminopropyl groups at the surface of the pores. The other mechanism is SDS chains complex-ation by P-CD cavity, which wonld result in P-CD gronps located at the surface of the pores and aminopropyl less accessible, due to steric hindrance caused by P-CD bulky groups. A complete characterization of the prodncts and adsorption capacities will help nnderstanding the formation mechanism of mesoporons hybrid silica. 

Fig. 2 Schematic representation of the two mechanisms of mesostructure formation expected electrostatic interaction between SDS dodecylsulfate anion and protonated propylamine and SDS chain complexation by P-CD cavity...

This may be explained as follows the SDS interacts with the maximum of partially protonated aminopropyl groups, by electrostatic interactions between dodecylsulfate anion and and sodium cation neutralization. The remaining amino groups are entrapped into the silica network. The amount of P-CD moieties incorporated depend on the initial molar ratio of P-CD APS, and not of the presence or not of SDS. P-CD groups may not interact with SDS. We can say, that for these hybrid materials, the templated mechanism is a S P one (S for anionic surfactant, P for cationic aminosilica species). 

We successfully formed an inclusion compound (IC) between a commercial flame retardant (FR = Antblaze RD-1) [13], which is shown below in its protonated form, and P-cyclodextrin (CD). The FR-P-CD-IC was melt-processed into PET films which were tested for flammability. The flammabilities of pure PET films, PET... 

D-ROESY measurements can be evaluated along with the constitution of the complexes (Fig. 2) [23], Cross peaks can be detected between the protons of the guest molecule and the inner protons of the Me-p-CD torus. 

In aqueous neutral solutions, 47 has two emission bands corresponding to the fluorescence of the neutral = 353 nm) and anionic = 420nm) forms [168]. Fluorescence was quenched by I in water and in the presence of y-CD, the quenching was the same in the presence of a-and P-CD, the quenching was depressed [167]. Addition of a- and p-CD increased the fluorescence yield and lifetime of the neutral form of 47 and depressed the yield of the anionic form [142, 166, 167]. No variation was induced by y-CD. A depression of the proton dissociation of the included molecule explains these results. In fact, the fcj and fc, rate constants found for the protolytic equilibrium... 

Depression of proton dissociation for a- and -naphthol and 1,6-naph-thalenediol was confirmed [169]. The effect of p-CD on the fluorescence emission of 1,6-naphthalenediol at different pH values was interpreted by hypothesi2dng four emitting species one molecular, two monoanionic, and one dianionic forms (the last not previously identified). 

In neutral solutions, pH = 7, the fluorescence of both the neutral and the dissociated forms of a-naphthol was observed in the presence of / -CD and lV(lV -formyl-L-phenylalanyl)- -CD, while only the fluorescence of the ionic form could be observed in water [170]. The emission of the dissociated form was enhanced by P-CD and depressed by the functionalized CD. Be-nesi-Hildebrand treatment of the fluorescence variations gave evidence of the formation of a 2 1 complex for the functionalized CD, but not for -CD. The inhibition of the proton dissociation by functionalized CD was hence attributed to the strongly hydrophobic environment in which a-naphthol is embedded in the 2 1 complex shown in Figure 13. 

The bromonaphthalenes, 56, have a pH-controlled phosphorescence. At pH lower than ground-state pA , the protonation of the amino group hampers the quenching of the bromonaphthyl moiety emission by the electron-transfer process. The addition of 5 x 10" P-CD caused a... 

The photoisomerization of retinal has been studied using super-short light pulses, and the neutral and protonated forms of the retinal analogue (47) have been examined by time-resolved methods.The irradiation of 3-ionone as a complex with P-CD in water leads only to the formation of retro-y-ionone." ... 

The usefulness of pH-dependent NMR measurements for the determination of pA a values, the order and locus of protonation, and information about structural changes upon protonation has often been shown. Instead of the time-consuming pA"a and NMR measurements in a series of samples of varying pH, the automated NMR-controlled titration method using P, Cd, C, H and F atoms can be employed. 

In contrast to this, ID-ROESY cross-peaks were observed between phenyl protons of (+)-BPh, not only with the internal H-3 and H-5 protons of P-CD but also with external protons (Figure 10-7). Further studies are required in order to examine a possible external complexation together with an inclusion of BPh in the case of p-CD. 

Another interesting point is the positive NOE-effect on the maleate protons observed by-irradiation of internal protons in the P-CD. Although a simultaneous inclusion of both p-bromphenyl and maleate residues is impossible in the cavity of the same CD the formation of sandwich-like complexes with the 2 1 stoichiometry of P-CD to brompheniramine is possible. This hipotetic structure is somewhat supported also with x-ray experiments performed on the single monociystals obtained from the solution of P-CD and brompheniramine. 

The NMR spectra of 6-hydrocinnamoyl P-cyclodextrin (6-HyCiO-p-CD) in D2O showed that the phenyl protons shifted in the same direction as those of ethylhydrocinnamate (a model compound) upon addition of p-cyclodextrin, indicating that phenyl ring is included in the cyclodextrin cavity. The shifts are independent of concentration, indicating that 6-HyCiO-P-CD forms intramolecular... 

---