Effect of cyclodextrins inclusion complexes into absorption and emission spectra of P-methylaminobenzoate derivatives: A DFT and TD-DFT investigation.

In this study, density functional theory (DFT) and time-dependent DFT (TD-DFT) studies of methyl 4-aminobenzoate and methyl 4- amino-2-hydroxybenzoate and their inclusions complexes with α and γ-cyclodextrins were applied to control the effect of cyclodextrins on the absorption and emission properties of P-methylaminobenzoate derivatives. Absorption and emission spectra of free and encapsulated P-methylaminobenzoate derivatives were successfully analysed and compared with experimental results. Interestingly, conformational changes between ground and excited states of both fluorophores were also studied.

Structural and energetic investigation on the host/guest inclusion process of benzyl isothiocyanate into ß-cyclodextrin using dispersion-corrected DFT calculations.

The formation of host-guest complex between benzyl isothiocyanate (BITC) and ß-cyclodextrin (ß-CD) was studied using dispersion-corrected density functional theory calculations. The complexation process was monitored using molecular docking simulations, natural bond orbital (NBO) technique, nuclear magnetic resonance (1H NMR) chemical shift calculations and non-covalent interactions (NCI) analysis. All these approaches are consistent with experimental findings. The calculated complexation energy was negative indicating the formation of inclusion complex. The most stable complexation of BITC involves the inclusion of its aromatic moiety in ß-CD cavity (model A) in accord with experimental NMR chemical shift data. The non-covalent interactions (NCI) based on the reduced density gradient (RDG) analysis reveal that mainly weak Van der Waals intermolecular interactions between BITC and ß-CD provide and ensure stability for the complexation process.