Sanyo Hamai

Inclusion complexes of Fe(III) tetrakis(4-sulfonatophenyl)porphyrin with cyclodextrins in aqueous solutions

In aqueous solutions, inclusion complexation of Fe(III) tetrakis(4-sulfonatophenyl)porphyrin (FeTSPP) with alpha-cyclodextrin (alpha-CD), beta-CD, gamma-CD, and heptakis(2,3,6-tri-O-methyl)-beta-CD (TM-beta-CD) has been examined by means of absorption and induced circular dichroism spectroscopy. FeTSPP has been found to form inclusion complexes with beta-CD, gamma-CD, and TM-beta-CD in pH 3.2 buffers. At pH 10.1, where FeTSPP self-associates to form an oxo-bridged dimer, FeTSPP also forms inclusion complexes with alpha-CD, beta-CD, gamma-CD, and TM-beta-CD. The stoichiometries of the CD-FeTSPP inclusion complexes are 1:1, except for TM-beta-CD in pH 10.1 buffers where its 1:1 inclusion complex associates with TM-beta-CD to form a 2:1 inclusion complex at high TM-beta-CD concentrations. Equilibrium constants of FeTSPP for the formation of the 1:1 inclusion complexes have been evaluated for beta-CD, gamma-CD, and TM-beta-CD. Induced circular dichroism spectra of FeTSPP in alpha-CD and beta-CD solutions exhibit a signal pattern (a negative sign) that is different from those in acidic and basic solutions containing gamma-CD and that in basic solution containing TM-beta-CD, suggesting different inclusion modes towards FeTSPP.

The room-temperature phosphorescence of 2-chloronaphthalene induced by inclusion complexation with 6-iodo-6-deoxy-β-cyclodextrin and the excimer fluorescence of a β-cyclodextrin-2-chloronaphthalene inclusion complex in aqueous solution

Abstract In aqueous solution, 6-iodo-6-deoxy-β-cyclodextrin (β-CDI) forms a 1:1 inclusion complex with 2-chloronaphthalene (2CN), with a formation constant of 1400 ± 300 mol −1 dm 3 . The fluorescence of 2CN is quenched by the formation of the inclusion complex with β-CDI. In addition, in deaerated aqueous solution, the room-temperature phosphorescence of 2CN is observed from the inclusion complex. Although parent β-cyclodextrin (β-CD) also induces the room-temperature phosphorescence of 2CN on formation of an inclusion complex with this compound, β-CDI as a heavy atom perturber is more than 1.2 times as effective in enhancing the room-temperature phosphorescence than β-CD. β-CD forms an inclusion complex with 2CN, from which the excimer fluorescence of 2CN is observed. It is probable that the excimer fluorescence is due to a 2:2 β-CD-2CN inclusion complex.

Effects of cyclodextrins on the complexation between Methylene Blue and tetrakis(4-sulfonatophenyl)porphyrin in aqueous solutions

In aqueous solutions buffered at pH 10.1, Methylene Blue (MB) forms a complex with tetrakis(4-sulfonatophenyl)porphyrin (TSPP). The equilibrium constant for the formation of the MB-TSPP complex has been evaluated to be 2.35 x 10(5) mol(-1) dm3 from the fluorescence quenching of MB by TSPP. Effects of alpha-, beta-, and gamma-cyclodextrin (CD), and heptakis(2,3,6-tri-O-methyl)-beta-cyclodextrin on the complexation between MB and TSPP have been examined by means of absorption and fluorescence spectroscopy. The binding of CDs to TSPP and/or MB in the MB-TSPP complex causes the dissociation of the MB-TSPP complex.

2H2O effects on the inclusional complexation of β-cyclodextrin with sodium 2-naphthalenesulfonate in capillary electrophoresis and UV spectrophotometry

Abstract In capillary electrophoresis, deuterium isotope effects of 2H2O in the running buffer on the equilibrium constant (K) for the formation of an inclusion complex between β-cyclodextrin and sodium 2-naphthalenesulfonate (2NS) have been investigated. The K value for 2H2O is 27% greater than that for H2O. A similar trend in the K value of 2NS has been obtained from the results employing a UV spectrophotometric method.

External heavy atom effects of 6-deoxy-6-iodo-α-cyclodextrin on the room-temperature phosphorescence of 6-bromo-2-naphthol and 3-bromoquinoline in aqueous solutions

Abstract 6-Deoxy-6-iodo-α-cyclodextrin (α-CDI) has been found to form a 1:1 inclusion complex with 6-bromo-2-naphtho). A further association occurs between the 1:1 inclusion complex and an additional α-CDI molecule, leading to the formation of a 2:1 α-CDI-6-bromo-2-naphthol inclusion complex. The room-temperature phosphorescence of 6-bromo-2-naphthol is observed from the 2:1 α-CDI-6-bromo-2-naphthol inclusion complex, whereas the 1:1 inclusion complex does not emit it. The room-temperature phosphorescence intensity for the 2:1 α-CDI-6-bromo-2-naphthol inclusion complex is reduced by about 18% relative to that for the 2:1 inclusion complex composed of the parent α-CD, indicating the external heavy atom effects of α-CDI on the bound guest. The external heavy atom effects of α-CDI have also been examined on the room-temperature phosphorescence intensity of 3-bromoquinoline buried within the α-CDI cavity. At the same CD concentrations (2.O × 10−3 mol dm−3), the room-temperature phosphorescence for α-CDI has been decreased by about 10% relative to that for α-CD.

Inclusion effects of cyclomaltohexa- and heptaose (α- and β-cyclodextrins) on the acidities of several phenol derivatives

Abstract By means of spectrophotometry, equilibrium constants for the formation of 1:1 inclusion complexes of cyclomaltohexaose (α-cyclodextrin, α-CD) or cyclomaltoheptaose (β-CD) in aqueous solutions have been evaluated for neutral and anionic species of 3-cyanophenol, 4-cyanophenol, 3-nitrophenol, 4-nitrophenol, 4-bromophenol, and 4-methoxyphenol. Using the equilibrium constants of the neutral and anionic species, p K a values have been determined for the phenols bound to the α- and β-CD cavities. These phenols, which are accommodated in the α-CD cavity, have been found to be stronger acids than the free, uncomplexed ones, except for 4-methoxyphenol. On the other hand, 4-cyanophenol, 3-nitrophenol, and 4-methoxyphenol bound to the β-CD cavity are weaker acids than the uncomplexed ones, although 3-cyanophenol, 4-nitrophenol, and 4-bromophenol bound to β-CD show the same trend as those bound to α-CD. The different influences of α- and β-CDs on the p K a values are likely due to the difference in the magnitudes of the induced dipole moments of the guest caused by α- and β-CDs; depending on the magnitude of the induced dipole moment, the inclusion complexes are stabilized through the dipole-dipole interaction between the host and guest.

Capillary electrophoretic and spectrophotometric investigations of the complexation of Methylene Blue with 2-naphthol-6-sulfonate and 1,2-naphthoquinone-4-sulfonate in solution

Abstract In capillary electrophoresis of Methylene Blue (MB), a signal was observed below about pH 5.4. Upon the addition of 2-naphthol-6-sulfonate (NS) or 1,2-naphthoquinone-4-sulfonate (NQS) to MB solution buffered at pH 2.7, the migration time of MB was prolonged. The delay of the migration time has been attributed to the formation of an organic cation–organic anion complex between MB and NS (or NQS). From variations of the migration time, the equilibrium constants ( K ) for the formation of 1:1 complexes with NS and NQS have been found to be 430±10 and 480±70 mol −1 dm 3 , respectively. In the presence of NS or NQS, the absorption spectrum of MB was shifted to longer wavelengths, supporting the suggestion of formation of a complex between MB with NS or NQS. From absorbance changes, the K values for NS and NQS were found to be 350±20 and 730±260 mol −1 dm 3 , respectively.

1H-NMR Study on Inclusion Modes of 2-Chloronaphthalene and α-Cyclodextrin in D2

Abstract With a 1:1 and a 2:1 host-guest stoichiometry, α-cyclodextrin (α-CD) forms inclusion complexes with 2-chloronaphthalene. From simulations concerning observed chemical-shift differences (Δδobs) of proton signals of 2-chloronaphthalene, intrinsic Δδ values are estimated for all the guest protons in the 1:1 and 2:1 inclusion complexes. The intrinsic Δδ values indicate that α-CD first binds to a part of a naphthalene ring bearing a C1 atom to form the 1:1 inclusion complex. In the 1:1 and 2:1 inclusion complexes, the symmetry axes of α-CD are tilted approximately 30° relative to a naphthalene longitudinal axis. In the 2:1 inclusion complex, the association through hydrogen bonding most likely occurs between two α-CD molecules whose symmetry axes are laterally shifted.

Inclusion Behavior of α-Cyclodextrin with 2-Methylnaphthalene in Aqueous Solutions

By means of absorption and fluorescence spectroscopy, 2-methylnaphthalene (2MN) was found to be incorporated into the cavity of α-cyclodextrin (α-CD) to form a 1 : 1 inclusion complex. The 1 : 1 inclusion complex further associated with another α-CD molecule, resulting in the formation of a 2 : 1 α-CD-2MN inclusion complex. The equilibrium constants for the formation of the 1 : 1 and 2 : 1 inclusion complexes were estimated to be 44.6 and 376 mol-1 dm3, respectively, on the basis of a simulation of the observed 2MN fluorescence intensities. The induced circular dichroism spectra suggested that 2MN, buried within the α-CD inclusion complexes, resided in a different orientation relative to the CD symmetry axis, as compared to 2MN within a β-CD inclusion complex.

Spacer effect of appended moieties for molecular recognition in doubly-sodium anthranilate modified γ-cyclodextrin

Abstractγ-Cyclodextrin with two sodium anthranilate moieties (1) has been prepared as a sensor for detecting organic compounds including terpenoids and steroids. Compound1 shows a pure monomer fluorescence whose intensity is increased or decreased upon addition of the guest species examined. In this system, the sodium anthranilate moieties act either as a spacer, which enables the cyclodextrin to form a 1:1 host-guest complex by narrowing the γ-cyclodextrin cavity, or as a hydrophobic cap.1 recognizes steroids with much higher sensitivity than terpenoids, in which the appended moieties act as a hydrophobic cap for terpenoids and a spacer for steroids, respectively.