Noncovalently-Bound Cyclodextrin Dimers and Related Compounds. (Review)

Abstract

In the review noncovalently-bound cyclodextrin (CD) dimers, i. e., CD host-guest 2:1 complexes as well as CD self-assembled inclusion oligomers, are briefly characterized, showing methods of their investigations; the properties and possible applications of these species are also described.Cyclodextrins (CD) are a topic of intense research due to their ability to form inclusion complexes which find application in a number of industrial fields [1]. In a continuation of our works [2-8] we present here selected examples of CD host-guest 2:1 complexes, i.e., noncovalently-bound CD dimers formed by the templating effect of guest molecules as well as self-assembled inclusion oligomers. CD dimers coordinated by transition metal ions are not included here [9, 10].The amount of 1:1 host-guest complexes of CDs is enormous [11-13], while 2:1 host-guest complexes are not so common [14, 15]. Besides 2:1 host-guest CD complexes, i.e., noncovalently-bound CD dimers, a great number of covalently linked CD dimers have been synthesized [2]. The first part of the review shows CD hostguest 2:1 complexes containing small and large guest molecules; then covalently-linked CD dimers, including guest molecules, are briefly described. The next part of the review deals with CD self-assembled inclusion oligomers. CD HOST-GUEST 2:1 COMPLEXES WITH SMALL GUEST MOLECULESThe crystal structure of the 2:1 host-guest complex of β-CD with 1,12-dodecanediol has been determined [16]. The host-guest complex forms a [3] pseudorotaxane. Both hydroxy groups of 1,12-dodecanediol protrude from β-CD primary faces and form hydrogen bonds with water molecules. In the study of diphenyl ether derivatives it was found that β-CD gives with 1a and 1b crystalline 2:1 host-guest complexes [17].

Supramolecular Species Bearing Quaternary Azaaromatic Moieties

“…The association constant values are higher for pseudorotaxanes containing threads (17) than for those containing threads (18) due to the stronger stability of the former, resulting from the hydrogen bonds of N + CH 3 group with polyether.…”

“…In a continuation of our work concerning quaternary azaaromatics, 14,15 rotaxanes 16 and catenanes 17 of quaternary azaaromatic character, as well as cyclodextrins [18][19][20] and calixarenes, 21 we describe here selected examples of supramolecular species bearing quaternary azaaromatic moieties.…”