2H NMR study of the self-assembly of an azo dye-cyclomaltooctaose (γ-cyclodextrin) complex

✍ Scribed by Miyoko Suzuki; Michiko Tsutsui; Hidenobu Ohmori

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 563 KB
• Volume: 261
• Category: Article
• ISSN: 0008-6215
• DOI: 10.1016/0008-6215(94)84019-9

✦ Synopsis

Orange II and y-cyclodextrin form 2 : 1 and 2 : 2 complexes. These complexes self-associate, and microscopic viewing indicates the formation of a fibroid aggregate. The deuteron resonance (in 2H NMR spectroscopy) from deuteron exchange and solvation between the aggregate and deuterium oxide exhibits quadrupole splitting (Au) in the region of O-l.2 KHz. The orientation behavior obtained from this splitting suggests the formation of a liquid-cxystaloid substance. (1) The aggregate aligned by means of the super conductive and permanent magnetic fields shows a different NMR pattern and turbidity. (2) Dilution of the 0.12 M aggregate with deuterium oxide proceeds discontinuously via the nonoriented pattern to the oriented-pattern.

(3) With an increase in temperature, the 2H NMR spin-spin splitting values decrease continuously. A phase diagram that plots melting points in variable concentrations reveals separate solution and aggregate layers. (4) When the 0.06 M aggregate is diluted by deuterated solvents (water, methanol, ethanol, propanol, dimethyl sulfoxide, and acetone), increases in the amount added and the length of solvent molecules cause a regular reduction of Av. The deuterium signal of the methyl group in dimethyl sulfoxide-d, exhibits a small Av, suggesting that this solvent is included in the orientation system.