Carbohy drate Research, 192 (1989) 147-157 Elsevier Science Publishers B.V., Amsterdam - Printed in The Netherlands zyxwvutsrqponmlkjihgfedcbaZY 147 COMPLEXATION OF AROMATIC CARBOXYLIC ACIDS WITH HEPTA- KIS(2,6-DI-0-METHYL)CYCLOMALTOHEPTAOSE IN CHLOROFORM AND WATER zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA NAGAO KOBAYASHI* AND TETSUO OSA Pharmaceutical Institute, Tohoku University, Aobayama, Sendai 980 (Japan) (Received December 22nd, 1988; accepted for publication, March 14th, 1989) ABSTRACT Complexation of various aromatic carboxylic acids with heptakis(2,6-di-O- methyl)cyclomaltoheptaose (DM-PCD) in chloroform and water has been studied by U.V. absorption, induced c.d., and n.m.r. spectroscopy. The inclusion complex of dimethylaminobenzoic acid is axial in water but equatorial or lid-type in chloro- form, that of anthracene-9-carboxylic acid is axial in water and equatorial in chloro- form, that of pyrene-1-carboxlic acid is lid-type in water at pH 9.0, and that of ferrocenecarboxylic acid depends on the dissociation of the carboxyl group. INTRODUCTION The inclusion complexes of cyclomalto-oligosaccharides (cyclodextrins, CDs) with aromatic molecules have been studied by U.V. absorption, induced c.d.‘, fluorescence2, and n.m.r. spectroscopy3. The accuracy of induced c.d. for determin- ing the orientation of aromatic guest molecules in 1: 1 complexes has been con- firmed severally’, and so-called axial’, equatoriaFb, and lid-type4 inclusion com- plexes are known. The type and stoichiometry of inclusion depend on the type of aromatic molecules and the CD. For example, cyclomaltoheptaose (@CD) forms only 1: 1 axial inclusion complexes with p-disubstituted benzene+, most naphthaleneslbsd+, anthracenesld~f~a, or pyrene1dT2c in water. Although N, N-di- methylformamideld, methyl sulfoxide5, ethylene glycolid, etc. have been employed as solvents in addition to water, this behaviour has been thought to hold for many solvents. On the other hand, mainly non-modified CDs have been used especially in studies of induced cd. The availability6 of di- and tri-O-methyl derivatives of CDs has enabled such hydrophobic solvents as benzene and chloroform7 to be used. However, to our knowledge, no studies of induced c.d. have been reported hitherto on host-guest complexes using di- or tri-O-methyl CDs. 2,6-Di-O-methyl CDs are not only soluble in many common organic solvents, but are also more soluble than non-modified CDs in waters. *Author for correspondence. OOOS-6215/89/$03.50 @ 1989 Elsevier Science Publishers B.V.