Synthesis of Novel Bis(β‐cyclodextrin)s Linked with Glycol and Their Inclusion Complexation with Organic Dyes

Abstract

Three novel bis(b-cyclodextrin (CD))s with flexible glycol linkers, i.e., ethylene glycol-bridged bis(6-hydroxy-6-deoxy-b-CD) (2), diethylene glycol-bridged bis(6-hydroxy-6-deoxy-b-CD) (3), and triethylene glycol-bridged bis(6-hydroxy-6-deoxy-b-CD) (4) have been synthesized by the reaction of mono[6-O-(p-toluenesulfonyl)]-b-CD with corresponding materials. The inclusion complexation behaviors of these compounds 2 -4 with organic dyes; that is, acridine red (,3-trimethylphenazine-2,8-diamine hydrochloride; NR), ammonium 8-anilinonaphthalene-1-sulfonate (ANS), sodium 6-(p-toluidinyl)-naphthalene-2-sulfonate (TNS), rhodamine B (RhB) and brilliant green (¼ N-(4-{[4-(diethylamino)cyclohexa-2,5-dien-1-yl](phenyl)methyl}cyclohex-2-en-1-ylidene)-N-ethyl-ethanaminium hydrogen sulfate; BG), have been investigated at 258 in phosphate buffer (pH 7.20) by ultraviolet, fluorescence, and 2D-NMR spectroscopy. The results indicate that the two linked CD units may cooperatively bind a guest, and the molecular binding ability toward dye guests, especially bent ANS, T-shaped RhB, and triangular BG, can be extended. This cooperative binding mode is confirmed by Jobs experiments and 2D-NMR investigations. Furthermore, the complex stability depends greatly on the linker length of these glycol-bridged bis(b-CD)s and the size and shape of guest. The higher binding ability and selectivity of dye molecules by bis(b-CD)s 2 -4 are discussed from the viewpoint of size/shape-fit concept and multiple recognition mechanism.

β-Cyclodextrin as a Photosensitizer Carrier: Effect on Photophysical Properties and Chemical Reactivity of Squaraine Dyes

“…From the observed fluorescence quantum yield (Φ f ) and fluorescence lifetime (τ f ) of dye 2a , the rate constants for radiative decay ( k r ), nonradiative internal conversion ( k nr ), and intersystem crossing ( k isc ) can be calculated using the equations normalΦ normalf = k normalf k normalr + k isc + k nr normalτ normalf = 1 k normalr + k isc + k nr Because the triplet quantum yield (Φ T ) of the dye is negligible, k isc ≪ k r + k nr , so eqs and can be simplified to give k normalr = normalΦ normalf normalτ normalf k nr = k normalr ( 1 normalΦ normalf − 1 ) Substituting the values for the quantum yield (0.018) and lifetime (160 ps) of 2a in a 10% (v/v) ethanol/water mixture, we obtained the estimates k r = 1.1 × 10 8 s –1 and k nr = 6.0 × 10 9 s –1 . However, in the presence of β-CD, the fluorescence quantum yield and lifetime increased to 0.1 and 1.6 ns (average lifetime), respectively. Analysis of these data using eqs and gives radiative and nonradiative decay rate constants of k r = 6.3 × 10 7 s –1 and k nr = 5.7 × 10 8 s –1 respectively.…”

Cyclodextrin-Promoted Fluorescence Detection of Aromatic Toxicants and Toxicant Metabolites in Commercial Milk Products

“…These results show that the energy transfer efficiencies were highest in the presence of fluorophore acceptor 11 , which is a consequence of the high quantum yield of that fluorophore (0.96 in tetrahydrofuran) (Zhang et al 2016; Zhao et al 2017), its electrostatic potential surface which is strongly complementary to that of the aromatic analytes (see ESI for more details), and its demonstrated ability to bind in or near the γ-cyclodextrin cavity and facilitate proximity-induced energy transfer (Milles et al 2013). In contrast, the structure of fluorophore 12 makes it less able to penetrate the cyclodextrin cavity (both because of the large steric size as well as its central twisted biphenyl axis) (Zhao et al 2010), and the quantum yield of fluorophore 13 is lower than that of fluorophore 11 (Rodionova et al 2008). The energy transfer efficiencies observed in the soy milk samples were markedly lower than those observed in the other milk samples, likely as a result of soy protein aggregation ( vide infra ).…”

Mono-6-Substituted Cyclodextrins—Synthesis and Applications

“…Zhao et al [ 82 ], on the other hand, worked with aliphatic alcohols, specifically ethylene, diethylene, and triethylene glycol, purified the products by column chromatography, and obtained them only in 10, 12, and 14% yield, respectively. The authors tested inclusion complexation abilities of these dimers with various organic dyes.…”