Spectral properties and supramolecular inclusion complexes of β-cyclodextrin with flexible amphiphilic and rigid compounds

Stability improvement of UV-filter between methoxy cinnamic acid derivatives and cyclodextrins inclusion complexes based on DFT and TD-DFT investigations

Structures and UV-vis absorption spectra of the host-guest interaction of the methoxy cinnamic acid (MCA) derivatives and cyclodextrins (CDs) were performed by using the density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations. All geometries of MCA derivatives (4-MCA, 245-MCA, 246-MCA), three types of CD (αCD, βCD, γCD), and five host-guest inclusion complexes between MCA and CD consisting of 4-MCA/αCD (1), 4-MCA/βCD (2), 245-MCA/βCD (3), 246-MCA/βCD (4), and 246-MCA/γCD (5) were fully optimized by using the M06-2X/6-31G (d,p) levels of theory. Two orientations (A and B) of the MCA guest molecule were considered. Upon examining the optimized geometry, five complexes of the methoxy cinnamic acid molecules are located inside the cavity of CD. Orientation B was more stable than orientation A because of the stronger intermolecular hydrogen bonds between the hydroxyl group of CD and the carboxylic group of MCA. The results indicated that the intermolecular hydrogen bond is mainly the driving force of formation between methoxy cinnamic acid and cyclodextrins. To reveal the host-guest interaction that is relevant to UV-filter compounds, the UV-vis absorption spectra were performed using TD-DFT calculations. The obtained results confirmed that orientation B is the most stable orientation and can absorb in both UVB and UVA regions which is similar to the parent MCA. Therefore, this knowledge will bring to understand the host-guest interaction between methoxy cinnamic acid and cyclodextrin complexes. The theoretical results are expected to provide valuable information for improving the stability of further UV-filter compounds.

Influence of cyclodextrin on the solubility and the polymerization of (meth)acrylated Triton(®) X-100

Triton(®) X-100 (poly(ethylene glycol) tert-octylphenyl ether) was (meth)acrylated and polymerized in the absence and presence of randomly methylated β-cyclodextrin (RAMEB-CD). Triton(®)-polymers that were polymerized with RAMEB-CD in water were compared with polymers that were synthesized in organic solvents after the addition of RAMEB-CD. The polymers were characterized by (1)H NMR and FTIR spectroscopy, matrix-assisted laser desorption ionization mass spectrometry (MALDI-TOF MS), dynamic light scattering (DLS), gel-permeation chromatography (GPC) and turbidity measurements. Additionally, the viscosity change of the methacrylic homopolymer with RAMEB-CD was evaluated.

Spectral properties and inclusion of a hetero-chalcone analogue in organized media of micellar solutions and beta-cyclodextrin

The absorption and fluorescence emission spectral properties of 3-(4'-dimethylaminophenyl)-1-(2-thienyl)prop-2-en-1-one, abbreviated as DMATP, have been investigated in organized media of aqueous micellar and beta-cyclodextrin (CD) solutions. While the absorption spectra are less sensitive to the nature of the added surfactant or CD, the characteristics of the intramolecular charge transfer (ICT) fluorescence are highly sensitive to the properties of the medium. The ICT maximum is strongly blue-shifted with a great enhancement in the fluorescence quantum yield on adding micellar or CD solutions. This indicates the solubilization of DMATP in the micellar core and formation of an inclusion complex with beta-CD. The critical micelle concentration (CMC) as well as the polarity of the micellar core of SDS, CTAB and TX-100 have been determined. The CMC values are in good agreement with the reported values while the polarity is lower indicating that DMATP molecules are incorporated in the micellar core not at the micellar interface. The inclusion constants of binding of DMATP in micellar or CD have been also determined. The thermodynamic parameters of formation of DMATP:CD inclusion complex have been calculated from the temperature dependence of the fluorescence spectra of the formed complex. The negative enthalpy and free energy of formation indicate that the inclusion process is energetically favorable. The highly negative value of formation entropy (DeltaS = -162.3 J mol(-1) K(-1)) reflects the high restrictions imposed on the movement of both the host and included guest molecules which is consistent with the increase of the fluorescence yield and blue shift of the fluorescence maximum.