Experimental and theoretical study on the molecular structure, covalent and non-covalent interactions of 2,4-dinitrodiphenylamine: X-ray diffraction and QTAIM approach

Theoretical study of the interaction of fullerenes with the emerging contaminant carbamazepine for detection in aqueous environments

The global increase in drug consumption exposes the growing need to develop new systems for the detection, capture, and treatment of bioactive molecules. Carbamazepine is one instance of such contaminants at the top of the ranking commonly found in sewage treatment systems. This work, therefore, presents a theoretical study of fullerene C₆₀ and its derivatives with substitutional doping with B, Al, Ga, Si, Ge, N and P, for the detection and capture of carbamazepine is aqueous medium. Solvation effects were included by means of the Polarizable Continuum Solvent method. The results indicate that doped fullerenes are sensitive for the detection of carbamazepine both in gaseous and aquatic environments. Investigation on the intermolecular interactions between the drug and the fullerene molecule were carried out, allowing the characterization of the interactions responsible for stabilizing the adsorption of carbamazepine to the fullerenes. The theoretical survey revealed that fullerenes doped with Al, Ga, Si and Ge chemically adsorb carbamazepine whereas for the case of fullerenes doped with other heteroatoms physisorption is responsible for the molecular recognition. Relying on DFT calculations, the fullerene derivatives C₅₉Al, C₅₉Si and C₅₉Ga are the most suitable to act both as a sensor and to uptake carbamazepine in aquatic environments.

Conceptual DFT, QTAIM, and Molecular Docking Approaches to Characterize the T-Type Calcium Channel Blocker Anandamide

The anandamide is a relevant ligand due to its capacity of interacting with several proteins, including the T-type calcium channels, which play an important role in neuropathic pain and depression disorders. Hence, a detailed characterization of the chemical properties and conformational stability of anandamide may provide valuable information to understand its behavior in a biological context. Herein, conceptual DFT and QTAIM analyses were performed to theoretically characterize the chemical reactivity properties and the structural stability of conformations of anandamide, using the BP86/cc-pVTZ level of theory. Global reactivity description, based on conceptual DFT, indicates that the hardness increases and the electrophilicity index decreases for both, the hairpin and U-shape conformers relative to the extended conformers. Also, an increase in the chemical potential value and a decrease in the electronegativity and the electrophilicity index is observed in the ethanolamide open ring conformers in comparison with the corresponding closed ring structures. In addition, regarding the characterization of local reactivity descriptors, the maximum values of the Fukui and Parr functions indicate that the most probable location for a nucleophilic attack is either the hydroxyl oxygen located in the ethanolamide closed ring conformers or the carbonyl oxygen present in the open ring conformers. The most probable location for an electrophilic attack is in the alkyl double bond region in all anandamide conformers. According to the QTAIM results, the intramolecular hydrogen bond formation stabilizing the structure of anandamide has interaction energy values for the closed ring conformations of 12.33–12.46 kcal mol⁻¹, indicating a strong interaction. Lastly, molecular docking calculations determined that a region in the pore, denominate as pore-blocking, is a probable site for the interaction of anandamide with the human Ca_v3.2 isoform of the T-type calcium channel family. The pore-blocking site contains hydrophobic residues where the non-polar part in the final alkyl region of anandamide established mainly alkyl-alkyl interactions, while the polar part (the ethanolamide group) interacts with the polar residue S900. The information based on conceptual DFT presented may aid in the design of drugs with similar chemical characteristics as those identified in anandamide so as to bind anandamide-interacting proteins, including the T-type calcium channels.

Halogen Interactions in Halogenated Oxindoles: Crystallographic and Computational Investigations of Intermolecular Interactions

X-ray structural determinations and computational studies were used to investigate halogen interactions in two halogenated oxindoles. Comparative analyses of the interaction energy and the interaction properties were carried out for Br···Br, C-H···Br, C-H···O and N-H···O interactions. Employing Møller-Plesset second-order perturbation theory (MP2) and density functional theory (DFT), the basis set superposition error (BSSE) corrected interaction energy (E_int(BSSE)) was determined using a supramolecular approach. The E_int(BSSE) results were compared with interaction energies obtained by Quantum Theory of Atoms in Molecules (QTAIM)-based methods. Reduced Density Gradient (RDG), QTAIM and Natural bond orbital (NBO) calculations provided insight into possible pathways for the intermolecular interactions examined. Comparative analysis employing the electron density at the bond critical points (BCP) and molecular electrostatic potential (MEP) showed that the interaction energies and the relative orientations of the monomers in the dimers may in part be understood in light of charge redistribution in these two compounds.