Supramolecular Recognition and Structural Elucidation of Inclusion Complexes of an Achiral Carbene Precursor in β- and Permethylated β-Cyclodextrin

Abstract

[structure: see text] Inclusion of achiral carbene precursor endo-8-azibicyclo[3.2.1]octan-3-ol (1) in chiral beta-cyclodextrin (7-Cy) and tri-O-methyl-beta-cyclodextrin (TRIMEB) leads to 1:1 complexes 1@7-Cy and 1@TRIMEB, respectively. The combined methods of induced circular dichroism, NMR spectroscopy, and X-ray structure determination were employed for the first time for structural elucidation of the complexes in solution and the solid state. Significantly different orientations of 1 were observed. Compared with 1@7-Cy, 1@TRIMEB exhibits a different guest orientation and an association constant one-twentieth lower.

Encapsulation of Reactive Intermediates

“…63 For 90b @TRIMEB, a single crystal suitable for X -ray analysis could be grown ( Figure 10.6 ). 61 The structure obtained ascertains the complete separation of one guest molecule from another and explains why azine 94 is lacking in the product mixture resulting from the photolysis of 90b @TRIMEB. 90b @TRIMEB is a good example for a complex for which the orientation of the guest depends on its environment.…”

“…Therefore, after a few experiments with hydrophilic cyclodextrins derivatives, i.e., permethylated cyclodextrins (TRIMEB in the case of β -CD, TRIMEA for α -CD) were performed successfully as molecular reactors for supramolecular carbene chemistry. 61 This is due to their ready availability, 62 their high solubility in water and in organic solvents and their good crystallization properties. The absence of OH groups at the rims of TRIMEB makes this host inert toward reactions of carbenes.…”

“…However, owing to the lack of intramolecular hydrogen bridges, TRIMEB is more fl exible and forms less stable complexes with lower association constants in comparison to native β -cyclodextrin. 61 …”

A fluorescent chemosensor based on optically active 2,2′‐binaphtho‐20‐crown‐6 for metal ions

“…Supramolecular host–guest interactions and molecular recognition have attracted much attention in recent decades, and cation sensing has risen to a dominant position in research devoted to the detection of designated species. One of the keys in designing a useful chemosensor is to effectively convert molecular recognition into optical signals 1–5. Fluorescent chemosensors are dye molecules whose fluorescence excitation/emission changes in response to the surrounding medium or through specific molecular recognition events.…”

Different self-assembly behaviors of mono-modified β-cyclodextrin substituted by benzoic acid derivatives

“…Currently, most investigations of the self-assembly behavior are to establish control over the preparation of self-assemblies so that their architectures and properties are, at least to some extent, predictable. Thus researchers aim to produce controllable self-assembly by using the wide range of possible intermolecular interactions [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]. Some of these approaches are producing more predictable results.…”