DFT-D4 Insight into the Inclusion of Amphetamine and Methamphetamine in Cucurbit[7]uril: Energetic, Structural and Biosensing Properties

The host-guest interactions of cucurbit[7]uril (CB[7]) as host and amphetamine (AMP), methamphetamine (MET) and their enantiomeric forms (S-form and R-form) as guests were computationally investigated using density functional theory calculations with the recent D4 atomic-charge dependent dispersion corrections. The analysis of energetic, structural and electronic properties with the aid of frontier molecular orbital analysis, charge decomposition analysis (CDA), extended charge decomposition analysis (ECDA) and independent gradient model (IGM) approach allowed to characterize the host-guest interactions in the studied systems. Energetic results indicate the formation of stable non-covalent complexes where R-AMP@CB[7] and S-AMP@CB[7] are more stable thermodynamically than R-MET@CB[7] and S-MET@CB[7] in gas phase while the reverse is true in water solvent. Based on structural analysis, a recognition mechanism is proposed, which suggests that the synergistic effect of van der Waals forces, ion-dipole interactions, intermolecular charge transfer interactions and intermolecular hydrogen bonding is responsible for the stabilization of the complexes. The geometries of the complexes obtained theoretically are in good agreement with the X-ray experimental structures and indicate that the phenyl ring of amphetamine and methamphetamine is deeply buried into the cavity of CB[7] through hydrophobic interactions while the ammonium group remains outside the cavity to establish hydrogen bonds with the portal oxygen atoms of CB[7].

Effectively enhancing the enantioseparation ability of β-cyclodextrin derivatives by de novo design and molecular modeling

Rational engineering of native β-CD as an ideal chiral selector for a definite analyte in capillary electrophoresis represents a challenge in separation science. Herein, a rational and systematic strategy that combines the de novo design and molecular modeling is firstly described to expedite the manipulation and selection of effective selector for enantioseparation in capillary electrophoresis. Using β-adrenoreceptor agonists as model analytes, we demonstrate how this strategy efficiently improves the enantiorecognition in chiral discrimination sites of inclusion complexes. The evolved β-CD derivative could be utilized as a chiral receptor to achieve the effective enantioseparation (R_s > 1.5) of racemic β-adrenoreceptor agonists. We highlight a novel strategy for efficiently and rapidly manipulating native CD based on the characteristics of analyte so as to gain an excellent chiral selector.

Qualitative analysis of chiral alanine by UV-visible-shortwave near infrared diffuse reflectance spectroscopy combined with chemometrics

UV-vis-SWNIR DRS is firstly and successfully used to discriminate the chirality of compounds in powder with a good accuracy.