Atomic Theory Research Articles

Cooperativity between Intermolecular Hydrogen and Carbon Bonds in ZY···CH3CN/CH3NC···HX Trimers (ZY = H2O, H2S, HF, HCl, HBr, NH3, and H2CO; HX = HF, HCl, and HBr).

Hydrogen-bonding and carbon-bonding interactions are widespread in nature. We studied the cooperativity between these interactions in 42 trimeric complexes ZY···CH3CN/CH3NC···HX, where ZY molecules are H2O, H2S, HF, HCl, HBr, NH3, and H2CO, and HX molecules are HF, HCl, and HBr. Acetonitrile (CH3CN) and isoacetonitrile (CH3NC) act as hydrogen bond acceptors as well as carbon bond donors in these trimers. Various theoretical methods, such as electronic structure calculations, quantum theory of atoms in molecule (QTAIM), natural bond orbital (NBO), and reduced density gradient analysis, are employed to study these trimers, and the results are compared with the corresponding ZY···CH3CN/CH3NC and CH3CN/CH3NC···HX dimers. Electronic structure calculations are performed at the second-order Mo̷ller-Plesset perturbation theory using the 6-311++G(2d,2p) basis set. We show that both the interactions act synergistically in these trimers leading to an increase in their bond strength as compared to the strength in the individual dimers. The cooperative energies for these trimers are in the range of 0.69 to 3.22 kJ/mol. It is seen that the carbon bonds benefit more from the cooperativity than the hydrogen bonds. The trends of cooperativity and correlations of interaction energies and cooperative energies with relevant QTAIM and NBO parameters are reported.

How electrons still guard the space: Electron number distribution functions based on QTAIM∩ELF intersections.

Despite the importance of the one-particle picture provided by the orbital paradigm, a rigorous understanding of the spatial distribution of electrons in molecules is still of paramount importance to chemistry. Considerable progress has been made following the introduction of topological approaches, capable of partitioning space into chemically meaningful regions. They usually provide atomic partitions, for example, through the attraction basins of the electron density in the quantum theory of atoms in molecules (QTAIM) or electron-pair decompositions, as in the case of the electron localization function (ELF). In both cases, the so-called electron distribution functions (EDFs) provide a rich statistical description of the electron distribution in these spatial domains. Here, we take the EDF concept to a new fine-grained limit by calculating EDFs in the QTAIM ∩ ELF intersection domains. As shown in AHn systems based on main group elements, as well as in the CO, NO, and BeO molecules, this approach provides an exquisitely detailed picture of the electron distribution in molecules, allowing for an insightful combination of the distribution of electrons between Lewis entities (such as bonds and lone pairs) and atoms at the same time. Besides mean-field calculations, we also explore the impact of electron correlation through Hartree-Fock (HF), density functional theory (DFT) (B3LYP), and CASSCF calculations.

Theoretical study on the capture of toxic gases by ionic liquids encapsulated in assembled belt[14[pyridine

In the current study, self-assembled belt[14]pyridine (BP) encapsulated IL (tetramethylammonium chloride (TMACl)) is theoretically explored to capture greenhouse gases (GHGs) at B3LYP-D3/6-311G(d,p) level of theory. The encapsulation of TMACl in assembled belt[14]pyridine is thermodynamically feasible as revealed through high interaction energy value of −50.7 kcal/mol. Moreover, the results of capturing of gas molecules (SO2, CO2, CO and CH4) show that attractive forces involved in capturing of gases are strong van der Waals forces i.e., London dispersion forces and electrostatic interactions. The synergic effect of self-assembled belts and ionic liquid results in significantly high interaction energy values ranging from −7.88 to −25.92 kcal/mol for capturing of gas molecules. Furthermore, the interaction between BP-TMACl and gas molecules is studied in detail through natural bond orbital (NBO) analysis. NBO results show the charge transfer between the fragments (BP-TMACl and gases) which is further validated through EDD analysis. The charge shifts towards all of the captured gas molecules but the most prominent change in NBO charges is shown by captured SO2. The successful charge transfer indicates better interaction in the designed systems. Additionally, the type and strength of interactions involved in the process of encapsulation is studied through quantum theory of atoms in molecules (QTAIM) and noncovalent interactions (NCI) analysis. NCI analysis clearly shows that gases are captured by BP-TMACl complex through strong van der Waals forces. However, in capturing of SO2, strong electrostatic attractive forces are also involved. The nature of attractive forces is confirmed through QTAIM analysis. Furthermore, the relation between recovery time and desorption energy of captured gas molecules has been studied. The strongest absorption for SO2 results in prolonged recovery time for it (as compared to the other gas molecules). AIMD analysis is performed to find the dynamical stability of assembled-belts before and after loading ionic liquids along with gases to be captured. These results reveal that assembled-belts are suitable for encapsulation of ionic liquids along with capturing of gases. Overall, the best results are shown for SO2 capture. The study intends to deliver valuable information on the important progress in the environmental-remediation field and we hope our work is going to inspire more investigators to provide novel research on such challenging tasks.

Experimental and theoretical investigation of 1,3-bis(3-hydroxypyridinium)propane dibromide dihydrate, tetrabromozincate hydrate, and tetrabromocuprate

Three gemini hydroxypyridine salts: 1,3-bis(3-hydroxypyridinium)propane dibromide dihydrate (1), 1,3-bis(3-hydroxypyridinium)propane tetrabromozincate hydrate (2), and 1,3-bis(3-hydroxypyridinium)propane tetrabromocuprate (3) were synthesized and characterized by X-ray diffraction, FTIR, Raman, NMR, and DFT methods. The dibromide salt (1) crystallizes with two water molecules. One of the two bromide anions is connected to the hydroxyl group of one pyridinium cation moiety through the O(10)-H(10)···Br(2)− hydrogen bond of 3.146(2) Å, while the other bromide anion, Br(1)− is surrounded by three water molecules. In 1,3-bis(3-hydroxypyridinium)propane tetrabromozincate (2) the water molecule acts as a bridge between the hydroxypyridinium cation and the tetrabromozincate anion, while the tetrabromocuprate anion interacts directly with the hydroxypyridinium cation. The molecular structures of the studied 1,3-bis(3-hydroxypyridinium)propane derivatives 1a, 2a, and 3a were optimized using the APF-D/6–311++G(d,p) method. The optimized structure of salt 1a resembles the crystal structure, while in salts 2a and 3a the structure of 1,3-bis(3-hydroxypyridinium)propane dication is bent to the U-form and the tetrabromomethallate anion is located in a niche. The significant role of the intermolecular interactions and hydrogen bonds was revealed based on IR spectra. The interpretation of 1H and 13C NMR spectra in DMSO-d6 was based on 2D experiments. The quantum theory of atoms in molecules (QTAIM) was employed to classify the strength of hydrogen bonds in salts 1, 2, and 3. Based on the σ-hole concept, intermolecular interactions in 2 and 3 were described.

Ordering self-assembly structures via N[sbnd]H⋯S and Br⋯S interactions in (E)-2-(4-bromobenzylidene)hydrazinecarbothioamide : Insights from crystallographic and computational study

In this research paper, the compound (E)-2-(4-bromobenzylidene)hydrazinecarbothioamide (NC2) was synthesized and characterized by spectroscopic techniques and crystal structure was elucidated using single crystal X-ray diffraction method. The Hirshfeld surface analysis revealed the relative contributions of different intermolecular interactions to crystal packing, while the 2D fingerprint plots provided a visual representation of the intermolecular interactions via the surface area corresponding to each type of interaction. The findings revealed that the crystal packing of the molecule is mostly determined by H…H, C-Br…S and NH…S interactions. We investigated the structural and electronic properties of the compound NC2 using density functional theory (DFT). The optimized geometry, total energy, HOMO-LUMO gap, and vibrational spectra were calculated at the ωB97X/6–311+G(d,p) level of theory. The calculated results showed that the molecule has a stable geometry with a trans-conformation. The HOMO-LUMO gap of 3.813 eV indicates that the molecule has moderate stability. The nature of noncovalent interactions are investigated using the methods reduced density gradient (RDG) and topology analysis like quantum theory of atoms in molecules (QTAIM) proposed by Bader et al. The compound NC2 is found to adhere to the Lipinski's rule of five and exhibit good pharmacokinetic properties.

Design, Synthesis, and Antimicrobial Evaluation of Novel Sulfonamide Modified with Azoles

Abstract: Sulfonamide, imidazole, and triazole chemical nuclei possess good antimicrobial potential. This study aimed to amalgamate sulfonamide, imidazole, and triazole moieties in a single molecular framework with the intent of improving their antimicrobial activities. The objective of this study was the synthesis of conjugates containing sulfonamide and azole moieties along with in vitro and in silico evaluation as antimicrobial candidates. A series of sulfonamide-modified azoles (7a-r) was synthesized by multicomponent condensation of 1,2-dicarbonyl compounds, ammonium acetate and aryl-substituted aldehydes in glacial acetic acid. The structure of synthesized molecules was elucidated with the help of various spectroscopic techniques, such as FTIR, NMR, and HRMS. The target molecules were tested for in vitro antimicrobial potency against four bacterial strains and two fungal strains. Molecules 7c (MIC 0.0188 μmol/mL), 7f (MIC 0.0170 μmol/mL) and 7i (MIC 0.0181 μmol/mL) were most active against S. aureus and C. albicans. Against E. coli, molecules 7d (MIC 0.0179 μmol/mL), 7f (MIC 0.0170 μmol/mL) and 7i (MIC 0.0181 μmol/mL) were found to be highly active. Moreover, the binding conformations were investigated by insilico molecular docking, and QTAIM (Quantitative theory of atoms in the molecule) analysis was also performed. Molecular properties, such as the heat of formation, HOMO energy, LUMO energy and COSMO volume, were found to be in direct correlation with the antimicrobial potency of molecules 7c, 7f and 7i against S. aureus and C. albicans. All the synthesized molecules were more potent than clinically approved sulfonamides, namely sulfadiazine and sulfabenzamide.

Supramolecular assembly in Cu(II) and Zn(II) compounds with pyridine and anthraquinone-1,5-disulfonate: Experimental and theoretical analysis

Two new multi-component coordination compounds of Cu(II) and Zn(II) viz. [Cu(py)2(H2O)4]ADS·2H2O (1) and [Zn(4-CNpy)2(H2O)4]ADS·2H2O (2) (py = pyridine, 4-CNpy = 4-cyanopyridine, ADS = anthraquinone-1,5-disulfonate) have been synthesized in aqueous media at room temperature and characterized using elemental and spectroscopic analyses (FT-IR, electronic), TGA and single crystal X-ray diffraction techniques. Both the compounds crystallize as metal–organic multi-component compounds containing complex cationic moieties along with uncoordinated anionic ADS moieties in the crystal structures. Crystal structure analysis of 1 reveals the stabilisation of the layered assembly of the compound assisted by CH⋯O, OH⋯O hydrogen bonding and π-stacking interactions. Antiparallel CN⋯CN and aromatic π-stacking interactions provide rigidity to the crystal structure of compound 2. In addition, enclathration of lattice water molecules within the supramolecular cavity of 2 provides additional reinforcement to the crystal structure. We have carried out theoretical investigations to analyze π-stacking, H-bonding and antiparallel CN···CN non-covalent interactions observed in the compounds using DFT calculations, quantum theory of atoms in molecules (QTAIM) and non-covalent interaction (NCI) plot index computational tools. The binding energies of the supramolecular assemblies are quite significant due to the ion-pair nature of the interactions which lack directionality; however, the aforementioned weaker non-covalent interactions play crucial roles in the final arrangement of molecules in the solid state due to their directional nature.

A combined experimental and theoretical approach for doxycycline sensing using simple fluorescent probe with distinct fluorescence change in wide range of interferences

Overuse of doxycycline (DOXY) can cause serious problems to human health, environment and food quality. So, it is essential to develop a new sensing methodology that is both sensitive and selective for the quantitative detection of DOXY. In our current research, we synthesized a simple fluorescent probe 4,4′-bis(benzyloxy)-1,1′-biphenyl (BBP) for the highly selective detection of doxycycline by through fluorescence spectroscopy. The probe BBP displayed ultra-sensitivity towards doxycycline due to Forster resonance energy transfer (FRET). Fluorescence spectroscopy, density functional theory (DFT), 1H NMR titration, UV–Vis, and Job's plot were used to confirm the sensing mechanism. The charge transfer between the probe and analyte was further examined qualitatively by electron density differences (EDD) and quantitively by natural bond orbital (NBO) analyses. Whereas the non-covalent nature of probe BBP towards DOXY was verified by theoretical non-covalent interaction (NCI) analysis as along with Bader's quantum theory of atoms in molecules (QTAIM) analysis. Furthermore, probe BBP was also practically employed for the detection of doxycycline in fish samples, pharmaceutical wastewater and blood samples.

Colorimetric detection of clotrimazole environmental pollutant using a newly developed chemosensor; an experimental and theoretical study

ABSTRACT Clotrimazole (CTZ), as an antifungal medication, is used to treat dermatological infections in humans, and to remove fungal infections from plants in agriculture, but its widespread usage has led to pharmaceutical pollution and environmental concerns. In this study, a new bromopyrogallol red (BPR) and N i 2 + based colorimetric sensor was developed for the selective and sensitive detection of CTZ. The BPR-Ni complex showed a clear colour change from purple to violet in the presence of CTZ, and a significant change was observed in the UV-Vis spectrum. The stoichiometric ratio of 1:1 between BPR and N i 2 + was determined using the Benesi-Hildebrand method. DFT and time-dependent DFT (TD-DFT) were applied to identify the molecular and electronic structures of the BPR, BPR-Ni, and BPR-Ni-CTZ in ground and excited states. The nature of electronic excitations and charge transfers was evaluated using the natural transition orbitals (NTO). The NTO analysis reveals that the Ni atom facilitates the charge transfer process between BPR and CTZ and improves the sensitivity of the chemosensor. The quantum theory of atoms in molecules (QTAIM) was employed to determine the nature of interactions between BPR, N i 2 + , and CTZ. This study paves the way for the detection of environmentally harmful pharmaceutical pollution using simple but effective colorimetric sensors.

Butterfly Effect in Cytarabine: Combined NMR-NQR Experiment, Solid-State Computational Modeling, Quantitative Structure-Property Relationships and Molecular Docking Study.

Cytarabine (Ara-C) is a synthetic isomer of cytidine that differs from cytidine and deoxycytidine only in the sugar. The use of arabinose instead of deoxyribose hinders the formation of phosphodiester linkages between pentoses, preventing the DNA chain from elongation and interrupting the DNA synthesis. The minor structural alteration (the inversion of hydroxyl at the 2' positions of the sugar) leads to change of the biological activity from anti-depressant and DNA/RNA block builder to powerful anti-cancer. Our study aimed to determine the molecular nature of this phenomenon. Three 1H-14N NMR-NQR experimental techniques, followed by solid-state computational modelling (Quantum Theory of Atoms in Molecules, Reduced Density Gradient and 3D Hirshfeld surfaces), Quantitative Structure-Property Relationships, Spackman's Hirshfeld surfaces and Molecular Docking were used. Multifaceted analysis-combining experiments, computational modeling and molecular docking-provides deep insight into three-dimensional packing at the atomic and molecular levels, but is challenging. A spectrum with nine lines indicating the existence of three chemically inequivalent nitrogen sites in the Ara-C molecule was recorded, and the lines were assigned to them. The influence of the structural alteration on the NQR parameters was modeled in the solid (GGA/RPBE). For the comprehensive description of the nature of these interactions several factors were considered, including relative reactivity and the involvement of heavy atoms in various non-covalent interactions. The binding modes in the solid state and complex with dCK were investigated using the novel approaches: radial plots, heatmaps and root-mean-square deviation of the binding mode. We identified the intramolecular OH···O hydrogen bond as the key factor responsible for forcing the glycone conformation and strengthening NH···O bonds with Gln97, Asp133 and Ara128, and stacking with Phe137. The titular butterfly effect is associated with both the inversion and the presence of this intramolecular hydrogen bond. Our study elucidates the differences in the binding modes of Ara-C and cytidine, which should guide the design of more potent anti-cancer and anti-viral analogues.

Theoretical Investigation of the Green-Synthesized Carbon-Based Nanomaterial Potential as Inhibitors of ACE2 for Blocking SARS-CoV-2 Binding.

Since the emergence of SARS-CoV-2 in 2020, the world has faced a global pandemic, emphasizing the urgent need for effective treatments to combat COVID-19. This study explores the use of green-synthesized carbon-based nanomaterials as potential inhibitors of ACE2, a critical receptor for SARS-CoV-2 entry into host cells. Specifically, the study examines four carbon-based nanomaterials, namely, CD1, CD2, CD3, and CD4 in amino, graphitic, pyridinic, and pyrrolic forms, respectively, synthesized from curcumin, to investigate their binding affinity with ACE2. Molecular docking studies revealed that CD3 (pyridinic form) exhibited the highest binding affinity with ACE2, surpassing that of the control compound, curcumin. Notably, CD3 formed hydrophobic interactions and hydrogen bonds with key ACE2 residues, suggesting its potential to block the binding of SARS-CoV-2 to human cells. Moreover, molecular dynamics simulations demonstrated the stability of these ligand-ACE2 complexes, further supporting the promise of CD3 as an inhibitor. Quantum chemical analyses, including frontier molecular orbitals, natural bond orbital analysis, and the quantum theory of atoms in molecules, unveiled valuable insights into the reactivity and interaction strengths of these ligands. CD3 exhibited desirable chemical properties, signifying its suitability for therapeutic development. The study's findings suggest that green-synthesized carbon-based nanomaterials, particularly CD3, have the potential to serve as effective inhibitors of ACE2, offering a promising avenue for the development of treatments against COVID-19. Further experimental validation is warranted to advance these findings and establish new therapies for the ongoing global pandemic.

An experimental and theoretical study on the molecular interactions of N-aromatic L-proline in the condensed phase

Intermolecular interactions, such as halogen bonding, π-π stacking, F…π interactions, and anion-π interactions, play pivotal roles in the fields of chemistry, materials science, and biological technology. In this study, N-aromatic L-proline and its fluorinated derivatives were chosen as exemplars. X-ray diffraction and NMR techniques were employed to investigate these interactions in both solid-state and solution phases respectively. Theoretical investigations encompassing geometry optimization along with QTAIM (Quantum Theory of Atoms in Molecule) and IGMH (Independent Gradient Model based on the Hirshfeld partition) analyses provided profound insights into the intermolecular interactions. Parameters obtained from X-ray diffraction analysis of single crystals provide compelling evidence for F…F interaction with intermolecular F…F distances measuring 2.879 Å and 3.125 Å in compounds 2 and 3 crystal structures respectively. QTAIM and IGMH analyses indicate that F…π contacts significantly contribute to the formation of these two fluorinated crystals while H-bonding and CH…π contacts predominantly shape the crystal structure of the non-fluorinated L-proline derivative.

Towards universal substituent constants: Parameterizing bond critical point properties with electronegativity descriptors

AbstractThe properties of substituents have long been quantified by their effect elsewhere in a molecule. Ideally, intrinsic properties detailing the true properties of a substituent would be used. These properties are ideally transferable between molecules, to be robust and applied in different situations. Through a study on the bond critical point (BCP) properties of 117 substituents and 17 substrates we find that BCP properties from the quantum theory of atoms in molecules are not transferable between different bonded atoms. However, a substituent's changing electronegativity between substrates help quantify the observed variation. The relationship between changing electronegativities and critical point properties enables development of a relationship to predict critical point properties between a substituent and a new substrate, using only the electronegativity of a substituent attached to hydrogen, and the critical point property between the substituent and H.

Dancing with Falsification: The Dynamic of Chemistry Atomistic Theories Across Centuries

This research aimed to explore the contribution of the falsification process to the progress of science in the field of atomic theory. The analysis focused on the history of atomic development and how this theory underwent a process of falsification. This research was qualitative research using a literature study with a narrative review method. The results showed that the development of a theory, including the theory of atoms, has undergone many improvements. Falsification is an essential aspect of scientific progress, especially in atomic theory, involving testing the theory through experimentation and observation to determine accuracy. In the development of atomic theory, falsification played a key role, as in Dalton's atomic theory. Although revolutionary, subsequent experiments revealed subatomic particles, resulting in the falsification of Dalton's ideas and the emergence of a more complex understanding of atomic structure. The evolution of atomic theory shows that scientific knowledge is dynamic, continuing to develop through falsification. New evidence continues to refine ideas, ensuring scientific knowledge accurately reflects the natural world. The scientific method emphasizes openness to falsification, stating that theories must be testable and can be replaced when significant evidence refutes the theory. This openness is the basis for scientific progress and a deeper understanding of the universe.

Study on separation of acetonitrile and methanol azeotropic system using tetraethylammonium chloride-based deep eutectic solvents

Large quantities of waste streams containing mixed acetonitrile (ACN) and methanol (MeOH) are generated during pharmaceutical and chemical production. The polarity of these two substances is extremely similar, resulting in the formation of an azeotrope at room temperature and atmospheric pressure. In this study, deep eutectic solvents (DESs) were selected as extractants for the separation of ACN-MeOH binary azeotrope. To obtain suitable DESs, the σ-profiles of ACN, MeOH, DESs were calculated using the COSMO-SAC model, and the results demonstrated that the DESs synthesized when tetraethylammonium chloride (TEAC) was chosen as the hydrogen bond acceptor (HBA) and acetamide as the hydrogen bond donor (HBD) could effectively break the azeotropy of ACN and MeOH. Therefore, four DESs were synthesized with molar ratios of TEAC: acetamide = 1: n (n = 1, 2, 3, 4) for subsequent ACN-MeOH-DESs ternary vapor–liquid phase equilibrium (VLE) experiments at 101.3 kPa to determine the optimal extractant. The measured VLE data revealed the higher separation of DES TEAC-2acetamide on the ACN-MeOH binary azeotrope compared with other DESs. Afterward, the NRTL model was adopted to calculate the binary interaction parameters between ACN/MeOH and DESs. The results of the fitting indicated agreement with the experimental data. Finally, the separation mechanism was further analyzed using the interaction energy analysis, improved independent gradient model (IGMH), and the theory of atoms in molecules (AIM). The results indicated that the strong interaction between DESs and MeOH is the primary factor in the ability of DESs to break the azeotrope of the system.

Theoretical investigation of formaldehyde recognition by aluminum nitride nanoclusters(Al12N12): a DFT approach

This study analyses how formaldehyde molecules (H2CO and (H2CO)2) interact with a Al12N12 nanocluster with a specific theoretical approach (B3LYP/6-311++G(d,p)). We use the GAMESS software package for all calculations. Scientists have used the Atoms in Molecules (AIM) theory to better grasp how gases stick to and interact with Al12N12 nanoclusters The Al12N12 nanocluster electronic properties change significantly when exposed to formaldehyde adsorption. Furthermore, the pure Al12N12 cluster can capture up to four single molecules and three pairs of formaldehyde, leading to a decrease in the HOMO–LUMO gap by around 37–54%. The Al12N12 nanocluster can detect formaldehyde because its conductivity changes when formaldehyde molecules are present. The Bader theory of atoms in molecules (AIM) is used to study how formaldehyde interacts with a nanocluster. The pure Al12N12 nanocluster may be a good choice for finding formaldehyde molecules. The results show that Al12N12 could be a good chemical sensor for detecting formaldehyde.

Unraveling the crystal structure, stability and drug likeness of 1,3,4-oxadiazole derivatives against Myelofibrosis: a combined experimental and computational investigation

Herein, we report the synthesis and characterization of novel 1,3,4-oxadiazole derivatives, 2-methoxybenzyl 5-(4-chlorophenyl)-1,3,4-oxadiazole-2-carboxylate (C1) 2-methoxybenzyl 5-(2-chlorophenyl)-1,3,4-oxadiazole-2-carboxylate (C2), and methoxybenzyl 5-(3-chlorophenyl)-1,3,4-oxadiazole-2-carboxylate (C3) obtained through desulfurative cyclization reaction. The compound C2 was crystallized, and its crystal structure was elucidated using single-crystal X-ray diffraction technique. The Hirshfeld surface analysis was carried out to analyze, visualize and globally appreciate the weak interactions involved in crystal packing. These analyses were complemented by Quantum Theory of Atoms In Molecules (QTAIM) and Reduced Density Gradient (RDG), which allowed us to decipher the nature and types of attractive forces that contribute to maintain the crystal structure of the titled compound. Moreover, the ADME profile of the compound was predicted to assess its drug likeness. Finally, in silico studies were performed to explore the binding affinity of the compounds (C1–3) against Myelofibrosis through molecular docking and molecular dynamic simulations. Communicated by Ramaswamy H. Sarma

Spectroscopic and computational studies of the biomolecular complex of chemotherapy drug, lomustine and a nucleotide base adenine

Cancer is still the leading cause of death in both developing and economically developed countries. There is still a need to create new drugs with higher efficacy despite substantial research on the biological pathways of cancer, target identification, and development of therapeutic interventions. Lomustine is an anticancer medication, while Adenine is a purine derivative with great potential for use as a cancer therapy. The present study is carried out to understand the geometrical and quantum chemical parameters of the Adenine + Lomustine as a potential anti-cancer agent by means of the density functional theory method and vibrational spectroscopic techniques. Natural bond orbital analysis, powder X-ray diffraction and quantum theory of atom in molecule analysis are used for investigating the intermolecular hydrogen bond formed in the biomolecular complex. The oral bioavailability and pharmacological activity of the Adenine + Lomustine complex is estimated by drug likeness and bioactivity score prediction. Docking of the biomolecular complex is also carried out against the chosen receptors.

Three-Center Tight-Binding Together with Multipolar Auxiliary Functions.

We present an ab initio tight-binding method that allows to improve on the effective potential and minimal basis approximations employed in semiempirical calculations. Three-center expansions are used to evaluate the zeroth-order Hamiltonian matrix elements and repulsive energy terms in the spirit of the Horsfield method. Self-consistency is handled by expanding atomic orbital products in an auxiliary basis following the work of Giese and York, combined with a two-center expansion of the exchange-correlation kernels. Together with nonminimal main basis sets (double-ζ plus polarization), we show that the resulting method trades a modest amount of accuracy for a significant gain in speed, compared to that of numerical atomic orbital density functional theory, in calculations on small molecules, bulk compounds, and metal nanoclusters.

A theoretical study on 1H-indole-2,3-dione complexes with lithium, sodium, and potassium cations.

A comparative study of the change in different properties of electronic and structural of the free 1H-indole-2,3-dione molecule and its complexes has been obtained. HOMA analysis was performed to investigate the effects of lithium sodium and potassium cations on the aromaticity of lithium sodium and potassium complexes of 1H-indole-2,3-dione. Several 1H-indole-2,3-dione complexes with lithium, sodium, and potassium cations were optimized at the B3LYP/6-311G(d,p) level. The cation and π interaction has been investigated from different aspects, including interaction energy calculations, charge transfer values, and changes in the aromaticity of the ring upon complexation. The charge transfer and natural population analysis for the complexes were performed with the natural bond orbital (NBO) analysis. The properties of bond critical points in complexes were studied by applying the quantum theory of atoms in molecules (QTAIM). Finally, the aromaticity change of phenyl induced upon complex formation was evaluated by applying the harmonic oscillator model of aromaticity (HOMA). [Li-INa]+ and [[Li-INb]+ were optimized with the wB97XD function using a version of Grimme's D2 dispersion model, and the absorption energy was compared with the calculation made with the B3LYP functional.