4- Nitrophenol, cyclodextrin inclusion complexes with

GEOMETRY OF a-CYCLODEXTRIN INCLUSION COMPLEX WITH m-NITROPHENOL DEDUCED FROM QUMTUM CHEMICAL ANALYSIS OF CARBON-13 CHEMICAL SHIFTS... 

Chujo - The geometry of the alpha cyclodextrin inclusion complex with m-nitrophenol deduced from quantum chemical analysis and i C chemical shifts Ishlzakl, H. - See Sakuraba, H. et al. 

High resolution carbon-13 NMR spectroscopy is one of the most useful methods in the analysis of the structure and molecular dynamics of cyclodextrin inelusion-complexes both in aqueous solution[1,2] and in the solid state[3]. Earlier cariDon-13 NMR studies of a-CD inclusion complexes with benzoic acid, p-nitrophenol, and p-nitrophenolate in aqueous solution have shown that the included lead(head see Fig.lA) carbons show high-field shifts compared to low-field shifts of corresponding para(tail Fig.lA) carbons[4,5]. Similar distinctive patterns of carbon-13 displacement s have been also observed for p-hydroxybenzoic acid and it has been concluded that the carboxyl group of p-hydroxybenzoic acid is directed into the a-CD cavity [4]. A variety of substituted benzenes are known to show quite similar carbon-13 high (head) and low (tail) field shifts, irrespective of the kinds of substituents if their size are matched to the a-CD cavity [4,5]. These characteristic carbon-13 displacements induced by complexation with a-CD... 

The importance of the proximity effect in cyclodextrin catalysis has been discussed on the basis of the structural data. Harata et al. 31,35> have determined the crystal structures of a-cyclodextrin complexes with m- and p-nitrophenols by the X-ray method. Upon the assumption that m- and p-nitrophenyl acetates form inclusion complexes in the same manner as the corresponding nitrophenols, they estimated the distances between the carbonyl carbon atoms of the acetates and the adjacent second-... 

Figure 2. Computer imaging of crystal structures of the inclusion complexes of para (A), meta (B) and ortho (C) nitrophenol with a-cyclodextrin. The complex is shown with van der Waal s radii, and the front section of the complex cut away in order to expose the nitrophenol molecule.

ABSTRACT. The geometries of inclusion complexes of a-cyclodextrin(a-CD) with guests, benzoic acid, p-hydroxy benzoic acid, and p-nitrophenol in aqueous solution have been determined by comparing the complexation induced C-13 shifts of guest molecules with quantum chemical predictions. In the calculations, the non-polar environmental effect produced by the a-CD cavity on the C-13 shifts of included guest molecule has been formulated by the so-called solvent effect theory. The geometries of the complexes predicted theoretically were consistent with those... 

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