Molecular Recognition in Ternary Complexes of γ-Cyclodextrin with Naphthalenedicarboxylate Ions and a Space-Regulator Ion

• Published in: Bulletin of the Chemical Society of Japan 1998-10, Vol.71 (10), p.2323-2329
• Main Authors: Tan, Wei Hua, Ishikura, Takahiro, Maruta, Aya, Yamamoto, Tatsuyuki, Matsui, Yoshihisa
• Format: Article
• Language: English
• ISSN: 0009-2673; 1348-0634
• DOI: 10.1246/bcsj.71.2323

Complexation of γ-cyclodextrin (γ-CD) with the 2,6-naphthalenedicarboxylate ion (2,6-NDC) in alkaline D2O was greatly enhanced by the addition of 2,6-bis(1-pyridiniomethyl)naphthalene dibromide (2,6-PMN) as a space-regulator. Formation of a ternary 1 : 1 : 1 complex between γ-CD, 2,6-NDC, and 2,6-PMN was confirmed by means of 1H NMR spectroscopy, together with the measurements of induced circular dichroism spectra and UV absorption spectra. Changes in chemical shifts (δ) of the γ-CD protons in the presence of an excess amount of 2,6-PMN with the addition of NDC regioisomers were analyzed by a curve-fitting procedure to give binding constants (K6) for complexation of NDC’s with a γ-CD–2,6-PMN binary complex. The K6 values increased in the order of 1,5-NDC < 1,4-NDC < 1,8-NDC < 1,3-NDC < 1,6-NDC < 2,3-NDC < 2,7-NDC < 2,6-NDC, indicating that a binary complex of γ-CD with 2,6-PMN is able to recognize the molecular structures of NDC’s. The open space between the γ-CD cavity and 2,6-PMN will be favorable for the accommodation of a slender molecule such as 2,6-NDC, but unfavorable for the accommodation of a bulky molecule such as 1,5-NDC.