Huapeng Yu

A Preliminary Investigation of the Complexation of Dopamine by p‐Sulfonated Calix[4, 6] Arene and β‐Cyclodextrin Using Fluorescence Spectrometry

Abstract The inclusion complexes of p‐sulfonated calix[4, 6] arene and β‐cyclodextrin with dopamine were studied by fluorescence spectrometry in aqueous media. It was found that the fluorescence intensity of dopamine regularly decreased upon the addition of p‐sulfonated calix[4, 6] arene, on the contrary, it increased upon the addition of β‐cyclodextrin. 1H NMR spectra were applied to verify the formation of the complexes. According to the experimental results, 1:1 stoichiometry for the complexes was established and their association constants at 25°C were calculated by applying a deduced equation. Judging from the magnitude of their inclusion constants, the p‐sulfonated calix[4, 6] arene showed better inclusion capability than β‐cyclodextrin. The probable interaction mechanisms are proposed.

Spectrofluorometric study on the inclusion behavior of p-(p-carboxyl benzeneazo) calix[4]arene with norfloxacin.

Spectrofluorometric titrations have been performed to investigate the inclusion behavior of p-(p-carboxyl benzeneazo) calix[4]arene (CBC4A) with norfloxacin (NFLX) in NaAc-HAc buffer solution (pH=5.0). It was found that the fluorescence intensity of NFLX quenched regularly upon the addition of CBC4A. The results indicated 1:1 complex stoichiometry and an association constant of 8.21 x 10(5) L mol(-1) at 20.0 degrees C were calculated by applying a deduced equation. Jobs plot also verified the existence of 1:1 inclusion complex. The proposed interaction mechanism indicates that NFLX goes into (or partially goes into) the cavity of CBC4A with the help of hydrogen bonding and other forces. The various factors (pH value, ionic strength, and surfactants) affecting the inclusion process were examined in details.

Preparation and Property Screening of the Solid Inclusion Complex of Norfloxacin with p-Sulfonated Calix[4]arene

The complexation of norfloxacin (NFLX) by p-sulfonated calix[4]arene (SC4A) in aqueous solution has been studied by fluorescence spectroscopy and 1H NMR spectroscopy. A 1:1 stoichiometry and a 8086 L mol(-1) stability constant of the NFLX-SC4A complex was obtained by spectrofluorometric titrations. The equimolar solid state inclusion complex of NFLX-SC4A was prepared by the co-precipitation method and then characterized by various techniques, including differential scanning calorimetry (DSC), X-ray powder diffractometry (XRD), Fourier-transform infrared analysis (FT-IR) and scanning electron microscopy (SEM). The experimental results of these chemical property screenings confirmed that NFLX and SC4A can form a stable host-guest complex in the solid state, and SC4A appears to function as a complexing and solubilizing agent for NFLX.

Inclusion complex of riboflavin with cucurbit[7]uril: study in solution and solid state

The aqueous solution of riboflavin and cucurbit[7]uril complex has been studied based on fluorescence and 1H NMR spectroscopic results. Upon addition of cucurbit[7]uril, the fluorescence intensity of riboflavin was quenched and a slight red shift was observed for the maximum emission peak. These results indicated that the cucurbit[7]uril–riboflavin complex was formed at a 1:1 mole ratio. The temperature-dependent inclusion constants were calculated, from which ΔH and ΔS values were calculated. Meanwhile, rationale of the interaction mechanism was also discussed based on 1H NMR results. The solid inclusion complex was prepared from co-evaporation method and characterised by differential thermal analysis and fluorescence lifetime analysis methods. The experimental results indicated that riboflavin and cucurbit[7]uril formed stable host–guest inclusion complex in both solution and solid states.