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Primary Face (primary + face)

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Chemistry100%

Selected Abstracts

Synthesis and Electrochemical Study of an Original Copper(II)-Capped Salen,Cyclodextrin Complex

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 29 2010
Elise Deunf
Abstract A new metallocapped cyclodextrin (CD) was synthesized by the regioselective debenzylation, induced by diisobutylaluminium hydride (DIBAL-H), of perbenzylated cyclodextrins. This reaction allowed for the efficient preparation of an unprecedented CD,salen type copper(II) complex. The electrochemical behavior of both the bound and unbound CD,salen compounds was investigated by cyclic voltammetry. Notably, it was shown that the presence of tert -butyl groups at the ortho - and para -positions of the salen aromatic rings stabilized the copper(II) phenoxyl radical species that was generated upon the one-electron oxidation of the starting compound. Importantly, this stabilization remained effective when the salen-type ligand was covalently attached to the CD. This allowed for investigations of the reactivity of the copper(II) phenoxyl radical complex towards a primary alcohol to be performed by cyclic voltammetry. This reaction can be considered as mimicking the behavior of galactose oxidase. However, under these conditions, no reactivity was observed in the presence of benzyl alcohol. This may be due to distortion, either of the initially square planar salen ligand after its grafting to the CD primary face, and/or of the CD itself. On the other hand, the electrochemical reduction of the un-grafted copper(II) salen-type ligand led to a transient anionic species that exhibited significant stability on the time-scale of the slow cyclic voltammetry measurement in the absence of the CD, but was unstable in the presence of the CD. In the latter case, it was demonstrated that the anionic species was protonated by the CD. Importantly, this protonation was not fast enough to prevent catalytic activation of iodomethane by the electro-generated copper(I)-capped salen CD complex. [source]

Amphiphilic ,-cyclodextrins modified on the primary face: Synthesis, characterization, and evaluation of their potential as novel excipients in the preparation of nanocapsules

JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 5 2002
Erem Memi
Abstract The purpose of this study was to synthesize and characterize amphiphilic ,-cyclodextrins modified on the primary face with substituents of varying chain lengths (C6 and C14) and bond types (ester or amide). We also aimed to evaluate the potentiality of the new amphiphilic ,-cyclodextrins as excipients for the preparation and optimization of nanocapsules without using surface-active agents. Amphiphilic ,-cyclodextrin derivatives were characterized by 1H-nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, mass spectroscopy, differential scanning calorimetry, and elemental analysis. Nanocapsules prepared by nanoprecipitation were characterized by particle size and zeta potential determination and freeze fracture followed by transmission electron microscopy. The appropriate amphiphilic ,-cyclodextrin and its optimum concentration to be used were determined. Formation and characteristics of the nanocapsules were highly dependent on the structural properties of the modified cyclodextrin, its behavior in the oil,water interface and the viscosity and miscibility of the organic solvent with water. Physical stability after 5-month storage was also evaluated. The results indicated that derivatives with 6C aliphatic chains on the primary face proved to be the most efficient among the amphiphilic ,-CDs in this study. They avoid the use of surfactants in parenteral formulations of nanocapsules. © 2002 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 91: 1214,1224, 2002 [source]

Site-Selective Formation of Optically Active Inclusion Complexes of Alkoxo-Subphthalocyanines with ,-Cyclodextrin at the Toluene/Water Interface

CHEMISTRY - A EUROPEAN JOURNAL, Issue 16 2006
Kenta Adachi
Abstract Several subphthalocyanine derivatives that contain an alkoxo substituent as an axial ligand (RO-Subpc, R = 9-anthracenemethyl, benzyl, phenyl, 3,5-dimethylbenzyl, 3,5-dimethylphenyl, 4-methylbenzyl, and 4-methylphenyl) were synthesized. The formation of inclusion complexes of RO-Subpc with ,-CD in DMSO and at the toluene/water interface was investigated by UV/Vis absorption spectroscopy, induced circular dichroism (ICD), and nuclear magnetic resonance (NMR) measurements. Interfacial tension measurements suggested that ,-CD adsorbed as a monolayer at the toluene/water interface and probably orientated towards the toluene phase with its primary face. The 1:1 composition of ,-CD,RO-Subpc inclusion complexes was confirmed in DMSO and at the toluene/water interface for BzO-Subpc, PhO-Subpc, MeBzO-Subpc, and MePhO-Subpc. A 2:1 inclusion complex of AnO-Subpc formed in DMSO. The observed ICD spectra of ,-CD,RO-Subpc inclusion complexes are discussed with respect to molecular modeling and the simulation based on Tinoco,Kirkwood theory. Interestingly, the ICD spectra of ,-CD,BzO-Subpc and ,-CD,MeBzO-Subpc inclusion complexes exhibited a negative sign in DMSO and a positive sign at the toluene/water interface. This reversal of the ICD sign strongly suggests a difference in the structure of the inclusion complexes: ,-CD at the interface formed the inclusion complex with its primary face, whereas the secondary face of ,-CD bound favorably to RO-Subpc in DMSO. [source]