Cyclodextrins receptors, structures

A further contribution from this group, in collaboration with Pikramenou, deals with energy transfer processes in self-assembled structures of multin-uclear complexes. Each ligand of a Ru(bpy)32+ unit is connected to the rim of a /1-cyclodextrin receptor to form Ru(/J-CD-mbpy), which can complex in a polar medium the biphenyl (or adamathyl) tail of an Ir(III)-terpyridine complex, Fig. 24c [131]. In order to provide complexation of the Ir guest and because of the low association constant, a consistent excess of the Ru(/J-CD-mbpy) host is required, (80-90% of host relative to guest). Under these... 

Potentiometric sensing based on type 3 derivatives of a-, P-, and y-cyclodextrins has been reported.We have been interested in the type 1 cyclodextrin derivatives developed by Tagaki, e.g., host 41. This type of cyclodextrin derivative is characteristic in that the primary hydroxyl groups at the C-6 positions are exhaustively substituted with long alkyl chains. At the surface of an oiganic membrane, this structural feature allows the secondary hydroxyl side (wider open end of the cavity) to face the aqueous solution to accommodate a guest molecule. The interfacial receptor functions of these cyclodextrin hosts have been confirmed mainly by rt-A isotherm studies. 

TABLE 3.1 Structures of Unmodified Cucurbit[/ Juril (Left) and Cyclodextrin (Right) Receptors and Relevant Parameters for the Most Representative Members of These Host Families... 

Table 1 General structures of cyclodextrin (left) and cucurbit[n]uril (right) receptors and relevant parameters for the most representative members of both host families...

Interest in phosphorus-containing calixarenes continues. Structures reported include hexa(diethoxyphosphoryloxy)calix[6]arene (8), inherently chiral 1,2-bridged calix[4]arene diphosphates, and a calixarene like C3 symmetric receptor with a phosphate function at the cavity bottom. " The purification of phosphate substituted calixarenes has been studied by chiral HPLC and by normal reverse phase HPLC. Mono(6-0-diphenoxyphosphoryl)-P-cyclodextrin (9) and mono(6-0-ethoxyhydroxyphosphoryl)-p-cyclodextrin (10) have been synthesised and show enantioselective inclusion of D and L amino acids e.g. 3.6 for D/L serine in the case of 9). ... 

Figure 20. Structures of dimeric P-cyclodextrin-based receptors and peptide se-...

Several studies of the interactions of hydrochlorothiazide (20 R = H) and its nitrosation product 41 (Section 9.05.3.1.5) with macrocyclic receptors have been carried out. The former produces a 1 1 inclusion complex with /3-cyclodextrin <1996SPJ23>, while the latter gives different crystalline complexes with 18-crown-6 and cis-anti-cis-dicyclohexyl-18-crown-6, the structures of which have been analyzed in detail by X-ray diffraction <2005T6596> (see Section 9.05.3.1.5). 

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