Salicylic acid/gamma-cyclodextrin 2:1 and 4:1 complex formation by sealed-heating method.
A novel complex of salicylic acid (SA) and gamma-cyclodextrin (gamma-CD) was obtained via the sealed-heating method. The influence of the water content of gamma-CD on the complex formation with SA by sealed-heating process was investigated. Quantitative determination of SA revealed that sealed-heated samples of SA and gamma-CD with low water content (0.8-5.4%) formed the SA/gamma-CD = 2:1 complex, while the samples with high water content (8.5-11.5%) formed the SA/gamma-CD = 4:1 complex. The molecular arrangements of gamma-CD in 2:1 and 4:1 complexes were determined by powder X-ray diffraction measurements to be in monoclinic-columnar and tetragonal-columnar forms, respectively. The results of infrared spectroscopy and (13)C solid-state NMR measurements showed that two types of SA molecules resided in the 4:1 complex, whereas only one type of SA molecules existed in the 2:1 complex. The obtained 2:1 complex was assumed to contain two SA molecules per one gamma-CD, with the SA molecules existing in the intermolecular spaces formed by the gamma-CD columns. In the case of the 4:1 complex, two SA molecules were incorporated into the intermolecular spaces while the other two SA molecules were included within the gamma-CD cavity.
Higashi
Kenjirou
K
Graduate School of Pharmaceutical Sciences, Chiba University, 1-33, Yayoi-cho, Inage-ku, Chiba 263-8522, Japan. ken-h@p.chiba-u.ac.jp
Tozuka
Yuichi
Y
Moribe
Kunikazu
K
Yamamoto
Keiji
K
D002152:Calorimetry, Differential Scanning; D018360:Crystallography, X-Ray; D009682:Magnetic Resonance Spectroscopy; D020156:Salicylic Acid / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D047408:gamma-Cyclodextrins / Q000737:chemistry*
D047408:gamma-Cyclodextrins; C023792:gamma-cyclodextrin; D020156:Salicylic Acid