Hydrogen-bonding Interactions between Apigenin and Ethanol/Water: A Theoretical Study

Abstract

In this work, hydrogen-bonding interactions between apigenin and water/ethanol were investigated from a theoretical perspective using quantum chemical calculations. Two conformations of apigenin molecule were considered in this work. The following results were found. (1) For apigenin monomer, the molecular structure is non-planar, and all of the hydrogen and oxygen atoms can be hydrogen-bonding sites. (2) Eight and seven optimized geometries are obtained for apigenin (I)–H2O/CH3CH2OH and apigenin (II)–H2O/CH3CH2OH complexes, respectively. In apigenin, excluding the aromatic hydrogen atoms in the phenyl substituent, all other hydrogen atoms and the oxygen atoms form hydrogen-bonds with H2O and CH3CH2OH. (3) In apigenin–H2O/CH3CH2OH complexes, the electron density and the E(2) in the related localized anti-bonding orbital are increased upon hydrogen-bond formation. These are the cause of the elongation and red-shift of the X−H bond. The sum of the charge change transfers from the hydrogen-bond acceptor to donor. The stronger interaction makes the charge change more intense than in the less stable structures. (4) Most of the hydrogen-bonds in the complexes are electrostatic in nature. However, the C4−O5···H, C9−O4···H and C13−O2···H hydrogen-bonds have some degree of covalent character. Furthermore, the hydroxyl groups of the apigenin molecule are the preferred hydrogen-bonding sites.

Tetrafluoroborate and Hexafluorophosphate Ions are not Interchangeable: A Density Functional Theory Comparison of Hydrogen Bonding

“…Positive values for the ∇ 2 ρ BCP therefore suggest that the charge is depleted at the BCP and the electronic charge is not shared, indicating the presence of closed‐shell interactions, such as ionic and hydrogen bonding . The typical value of the Laplacian for a hydrogen bond ranges from 0.023–0.139 a.u., however, the value can be more positive when an O−H bond donor is involved ,. The values for the water and methanol complexes are within that range, but those of phenol are larger than the upper limit, which may be attributed to resonance‐assisted hydrogen bonding …”

“…The results of AIM analysis in Table are also consistent with the calculated energies listed in Table , suggesting that the hydrogen bonds within the H 3 O + complexes are the strongest, as indicated by the high ρ BCP . In fact, the calculated ρ BCP for the dimers are greater than the upper limit, which suggests that the H‐bonds formed are partially covalent in nature ,. The ∇ 2 ρ BCP for the H 3 O + complexes are greater than the upper limit, however, presumably due to charge‐assisted (cation‐anion) hydrogen bonding, consistent with a mixture of covalency and electrostatic stabilization in the hydrogen bonding.…”

Synthesis and crystallographic, spectroscopic and computational characterization of 3,3′,4,4′-substituted biphenyls: effects of ORsubstituents on the intra-ring torsion angle

“…When H BCP > 0, the hydrogen bond is electrostatically dominant. Some critical viewpoints concerning the application of this method when absolute AIM values are analyzed have recently been raised (Spackman, 2015); nevertheless, its use for relative comparisons is still growing (Wang et al, 2016;Zheng et al, 2016).…”

Theoretical Study of the Adsorption Process of Antimalarial Drugs into Acrylamide-Base Hydrogel Model Using DFT Methods: The First Approach to the Rational Design of a Controlled Drug Delivery System

“…In this way, second-order perturbation theory was used in order to gain insights about the donor (i) acceptor (j) orbital binding. Associated stabilization energy was calculated using Equation (3), from Fock matrix analysis on NBO calculation [29,[52][53][54].…”