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Essential oils are volatile oil-like liquids with a characteristic strong smell and taste. They are formed in plants and are then extracted. Essential oils have extremely strong physiological and pharmacological properties, which are used in the medicine, cosmetics, and food industries. In this study, the molecules caryophyllene oxide, β-pinene, 1,8-cineol, α-cubebene, and β-caryophyllene, which are the molecules with the highest contents in the essential oil of the plant mentioned in the title, were selected and theoretical calculations describing their interactions with water were performed. Because oil–water mixtures are very important in biology and industry and are ubiquitous in nature, quantum chemical calculations for binary mixtures of water with caryophyllene oxide, β-pinene, 1,8-cineol, α-cubebene, and β-caryophyllene were performed using the density functional theory (DFT)/B3LYP method with a basis of 6–31 G (d, p). Molecular structures, HOMO–LUMO energies, electronic properties, reactivity (ELF, LOL, and Fukui), and NCI-RDG and molecular electrostatic potential (MEP) on surfaces of the main components of Phlomis bruguieri Desf. essential oil were calculated and described.

Layered two-dimensional transition metal dichalcogenides and their heterostructures are of current interest, owing to the diversity of their applications in many areas of materials nanoscience and technologies. With this in mind, we have examined the three molecular dimers of the tungsten dichalcogenide series, (WCh2)2 (Ch = S, Se, Te), using density functional theory to provide insight into which interactions, and their specific characteristics, are responsible for the interfacial/interlayer region in the room temperature 2H phase of WCh2 crystals. Our calculations at various levels of theory suggested that the Te···Te chalcogen bonding in (WTe2)2 is weak, whereas the Se···Se and S···S bonding interactions in (WSe2)2 and (WS2)2, respectively, are of the van der Waals type. The presence and character of Ch···Ch chalcogen bonding interactions in the dimers of (WCh2)2 are examined with a number of theoretical approaches and discussed, including charge-density-based approaches, such as the quantum theory of atoms in molecules, interaction region indicator, independent gradient model, and reduced density gradient non-covalent index approaches. The charge-density-based topological features are shown to be concordant with the results that originate from the extrema of potential on the electrostatic surfaces of WCh2 monomers. A natural bond orbital analysis has enabled us to suggest a number of weak hyperconjugative charge transfer interactions between the interacting monomers that are responsible for the geometry of the (WCh2)2 dimers at equilibrium. In addition to other features, we demonstrate that there is no so-called van der Waals gap between the monolayers in two-dimensional layered transition metal tungsten dichalcogenides, which are gapless, and that the (WCh2)2 dimers may be prototypes for a basic understanding of the physical chemistry of the chemical bonding environments associated with the local interfacial/interlayer regions in layered 2H-WCh2 nanoscale systems.

This work used the 6-311++G(d, p) basis set in the DFT/B3LYP and DFT/CAM-B3LYP technique to build the molecular structures of the nicotine and caffeine molecules. The minimum energy gives stability to these molecules with their corresponding dipole moment. The optimized structure to compute Raman spectroscopy and UV-Vis in CCl4 and DMSO solvent, employing the basis set 6-311++G(d, p), the DFT/B3LYP and CAM-B3LYP hybrid function, with the C-PCM model. The re-optimized molecule is used to study NLOs property which also give the dipole moment, polarizability and hyperpolarizability of titled molecules. We used AIM to investigate these molecules’ intramolecular interactions, bond critical points, and interbasin paths. Multiwfn software 3.8 produces the NCI-RGD diagram, which we use to determine weak interaction, electron density, Van der Waals interaction, steric effect, and hydrogen bond. Similarly, we analyze the covalent bond with the molecular surface using ELF and LOL techniques.

This study aims to experimentally and theoretically examine the nature and energy of intermolecular bond interactions between thiourea and water molecules using natural bond orbital (NBO), non-linear optical (NLO), atoms in molecules (AIM), and reduced density gradient (RDG) analyses based on the quantum chemical approach and spectroscopic analysis on X-ray and FTIR. Geometry optimizations of Thio-(H 2 O) 1–5 complexes were carried out in the gas phase by B3LYP/6-311++G(d,p) level of density functional theory. The nature of the molecular interactions between the water and thiourea through hydrogen bonding has been investigated using RDG and AIM methods. NBO analysis shows that the Thio-(H 2 O) 5 complex has higher stabilization energy values than the other complexes. The non-linear optical properties, such as dipole moment ( μ ), the polarizability ( α 0 ), and the first hyperpolarizability ( β tot ), and thermodynamic functions, such as entropy ( S ), specific heat capacity ( C v ), and thermal energy ( E ), were calculated using the same method. It was observed that thermodynamic parameters, polarizability, and the first hyperpolarizability increased with the number of water molecules. X-ray diffraction analysis confirmed that thiourea is single crystal, and the thiourea/water complexes are crystalline in nature. Besides, the infrared spectrum shows the existence of water molecules and it is used to get details of the structure of the complex.

This study describes the non-covalent interactions of the charge transfer complex (CT), which was responsible for the synthesis of Linagliptin (LNG) with 2,3-Dichloro-5,6-Dicyano-1,4-benzoquinone (DDQ), or with Chloranilic acid (CHA) complexes in acetonitrile (MeCN) at temperatures of (25 ± 2 °C). Then, a UV–Vis spectrophotometer was utilized to identify Linagliptin (LNG) from these complexes. For the quantitative measurement of Linagliptin in bulk form, UV–Vis techniques have been developed and validated in accordance with ICH criteria for several aspects, including selectivity, linearity, accuracy, precision, LOD, LOQ, and robustness. The optimization of the complex synthesis was based on solvent polarization; the ratio of molecules in complexes; the association constant; and Gibbs energy (ΔG°). The experimental work is supported by the computational investigation of the complexes utilizing density functional theory as well as (QTAIM); (NCI) index; and (RDG). According to the optimized conditions, Beer’s law was observed between 2.5–100 and 5–100 µM with correlation coefficients of 1.9997 and 1.9998 for LGN-DDQ and LGN-CHA complexes, respectively. For LGN-DDQ and LGN-CHA complexes, the LOD and LOQ were (1.0844 and 1.4406 μM) and (3.2861 and 4.3655 μM), respectively. The approach was successfully used to measure LGN in its bulk form with high precision and accuracy.

In this paper, both methods (DFT and HF) were used in a theoretical investigation of 3-bromo-2-Hydroxypyridine (3-Br-2HyP) molecules where the molecular structures of the title compound have been optimized. Molecular electrostatic potential (MEP) was computed using the B3LYP/6-311++G(d,p) level of theory. The time-dependent density functional theory (TD-DFT) approach was used to simulate the HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) on the one hand to achieve the frontier orbital gap and on the other hand to calculate the UV–visible spectrum of the compound in gas phase and for different solvents. In addition, electronic localization function and Fukui functions were carried out. Intermolecular interactions were discussed by the topological AIM (atoms in molecules) approach. The thermodynamic functions have been reported with the help of spectroscopic data using statistical methods revealing the correlations between these functions and temperature. To describe the non-covalent interactions, the reduced density gradient (RDG) analysis is performed. To study the biological activity of the compound of the molecule, molecular docking studies were executed on the active sites of BRD2 inhibitors and to explore the hydrogen bond interaction, minimum binding energies with targeted receptors such as PDB ID: 5IBN, 3U5K, 6CD5 were calculated.

The hydrogen-bond charge transfer complex (HB-CTC) formed between the donor, 1,10-phenanthroline ( Phen ), and the π-acceptor, p -nitrophenol ( PNP ), has been thoroughly investigated through theoretical studies. The molecular structure and the HOMO–LUMO energy gap (ΔE H–L ) of this complex have been investigated by the density functional theory. This work has studied the HB-CTC complex through FTIR, 1 HNMR, 13 CNMR, and electronic absorption spectra. A molecular electrostatic potential surface (MESP) study allowed us to explore key aspects of intermolecular interaction. Moreover, reduced density gradient analysis was conducted to visualize valuable insights into non-covalent interactions within the complex components. Quantum Theory of Atoms in Molecules was used to analyze the interaction between the 1,10-phenanthroline and p -nitrophenol. The findings from this research not only enhance our understanding of HB-CT complexes but also highlight their exciting potential for innovative applications in various fields.

Imidazole derivatives have found wide application in organic and medicinal chemistry. In particular, benzimidazoles have proven biological activity as antiviral, antimicrobial, and antitumor agents. In this work, we experimentally and theoretically investigated N-Butyl-1H-benzimidazole. It has been shown that the presence of a butyl substituent in the N position does not significantly affect the conjugation and structural organization of benzimidazole. The optimized molecular parameters were performed by the DFT/B3LYP method with 6-311++G(d,p) basis set. This level of theory shows excellent concurrence with the experimental data. The non-covalent interactions that existed within our compound N-Butyl-1H-benzimidazole were also analyzed by the AIM, RDG, ELF, and LOL topological methods. The color shades of the ELF and LOL maps confirm the presence of bonding and non-bonding electrons in N-Butyl-1H-benzimidazole. From DFT calculations, various methods such as molecular electrostatic potential (MEP), Fukui functions, Mulliken atomic charges, and frontier molecular orbital (HOMO-LUMO) were characterized. Furthermore, UV-Vis absorption and natural bond orbital (NBO) analysis were calculated. It is shown that the experimental and theoretical spectra of N-Butyl-1H-benzimidazole have a peak at 248 nm; in addition, the experimental spectrum has a peak near 295 nm. The NBO method shows that the delocalization of the aσ-electron from σ (C1–C2) is distributed into antibonding σ* (C1–C6), σ* (C1–N26), and σ* (C6–H11), which leads to stabilization energies of 4.63, 0.86, and 2.42 KJ/mol, respectively. Spectroscopic investigations of N-Butyl-1H-benzimidazole were carried out experimentally and theoretically to find FTIR vibrational spectra.

Artificial neural networks in drug discovery have shown remarkable potential in various areas, including molecular similarity assessment and virtual screening. This study presents a novel multimodal Siamese neural network architecture. The aim was to join molecular electrostatic potential (MEP) images with the texture features derived from reduced density gradient (RDG) diagrams for enhanced molecular similarity prediction. On one side, the proposed model is combined with a convolutional neural network (CNN) for processing MEP visual information. This data is added to the multilayer perceptron (MLP) that extracts texture features from gray-level co-occurrence matrices (GLCM) computed from RDG diagrams. Both representations converge through a multimodal projector into a shared embedding space, which was trained using triplet loss to learn similarity and dissimilarity patterns. Limitations associated with the use of purely structural descriptors were overcome by incorporating non-covalent interaction information through RDG profiles, which enables the identification of bioisosteric relationships needed for rational drug design. Three datasets were used to evaluate the performance of the developed model: tyrosine kinase inhibitors (TKIs) targeting the mutant T315I BCR-ABL receptor for the treatment of chronic myeloid leukemia, acetylcholinesterase inhibitors (AChEIs) for Alzheimer's disease therapy, and heterodimeric AChEI candidates for cross-validation. The visual and texture features of the Siamese architecture help in the capture of molecular similarities based on electrostatic and non-covalent interaction profiles. Therefore, the developed protocol offers a suitable approach in computational drug discovery, being a promising framework for virtual screening, drug repositioning, and the identification of novel therapeutic candidates.