Excimer Formation and Induced-Fit Type of Complexation of β-Cyclodextrin Capped by Two Naphthyl Moieties

Abstract

Host–guest complexation of β-Cyclodextrin bearing two naphthyl moieties (1) has been studied by circular dichroism and fluorescence spectroscopic methods. The circular dichroism spectrum exhibits a positive band around 225 nm while the fluorescence spectrum exhibits a predominant monomer peak with a shoulder of excimer emission. These data suggest that 1 can take two forms, one of two naphthyl moieties being included in the cavity of the predominant form (A) while both naphthyl moieties being located outside of the cavity in another form (B). With increasing concentration of guests, the dichroism intensity diminishes but the excimer intensity increases. This result indicates that 1 moves the included naphthyl moiety outward from the interior of the cavity during guest binding and then the two naphthyl moieties act as hydrophobic caps. The binding of 1 was stronger for cyclohexanol and 1-adamantanecarboxylic acid but weaker for cyclododecanol than that of the corresponding γ-cyclodextrin derivative in correspondence with size-fitting between the guests and hosts.

Chemical Sensors Based on Cyclodextrin Derivatives

“…The fluorescent CD exhibited strong emission in the self-inclusion state due to the hydrophobic environment of the CD cavity and exclusion of the fluorophore from the cavity to bulk aqueous media weakened its fluorescence intensity. They synthesized “turn-off” fluorescent chemical sensors of CD derivatives carrying fluorophore compounds such as dansyl [30-35], dimethylaminobenzoyl [36-38], naphthyl [39-41], pyrene [42] and anthracene [43,44] moieties. Moreover, a new type of “turn-on” fluorescent chemical sensors, in which fluorescence intensity was increased by formation of host-guest complexes, was also reported (Figure 2b).…”

INTRAMOLECULAR EXCIMER FORMATION and MOLECULAR RECOGNITION OF MODIFIED CYCLODEXTRINS APPENDED BY TWO NAPHTHALENE RINGS*

“…2). Moriwaki et al (1987) reported that 6A,6D-bis(2-naphthylacetyl)-P-CD exhibits similar induced-fit type of complexation. A smaller extent of enhancement in the excimer emission was observed for 5, so there exists some difficulty for the two naphthyl rings of 5 to form the excimer both in and outside the cavity.…”

Cyclodextrin Combinations with Azocompounds

“…Camphor, fenchone, menthol, geraniol, nerol, cyclohexanol, and cyclooctanol compete with azobenzene residue to a lesser extent than l-borneol, 1adamantanol, or 1-adamantanecarboxylic acid [53,54]. Ueno et al [55,56] showed that β-cyclodextrin arched with azobenzene-4,4'dicarbonyl-and azobenzene-4,4'-disulfonyl-residues ( Figure 19) have enlarged hydrophobic cavity, particularly in the case of the cis isomers. The respective AD and AE regioisomers of azobenzene-4,4'-disulfonyl derivative of γ-cyclodextrin were obtained by Hamada et al [57] (Figure 19).…”