Quantum Theory Of Atoms In Molecules Research Articles

Effect of Terminal Hydroxy Groups on the Structural Properties of Acyl Thioureas.

The 1-acyl thiourea family [R1C(O)NHC(S)NR2R3] exhibits the flexibility to incorporate a wide variety of substituents into their structure. The structural attributes of these compounds are intricately tied to the type and extent of substitution. In the case of 3-mono-substituted thioureas (R2 = H), the conformational behavior is predominantly shaped by the presence of an intramolecular N-H···O=C hydrogen bond. This study delves into the structural consequences stemming from the inclusion of substituents possessing hydrogen-donor capabilities within four novel 1-acyl-3-mono-substituted thiourea derivatives. A comprehensive suite of analytical techniques, encompassing FTIR, Raman spectroscopy, multinuclear (1H and 13C) NMR spectroscopy, single-crystal X-ray diffraction, and supported by computational methods, notably NBO (Natural Bond Orbital) population analysis, Hirshfeld analysis, and QTAIM (Quantum Theory of Atoms in Molecules), was harnessed to scrutinize and characterize these compounds. In the crystalline state, these compounds exhibit an intricate interplay of intermolecular interactions, prominently featuring an expansive network of hydrogen bonds between the hydroxy (-OH) groups and the carbonyl and thiocarbonyl bonds within the 1-acyl thiourea fragment. Notably, the topological analysis underscores significant distinctions in the properties of the acyl thiourea fragment and the intramolecular >C=O···H-N bond when transitioning from the isolated molecule to the crystalline environment.

Thionation‐Induced Enhancement of Optical and Electronic Properties in NDI Molecule for Molecular Electronic Applications: A Computational Study Using DFT/TD‐DFT and QTAIM Theory

AbstractThe study investigates the impact of thionation on N,N'‐di(dodecyl)‐4,5,8,9‐naphthalene diimide (NDI) through computational methods such as density functional theory (DFT/TD‐DFT), quantum theory of atoms in molecules (QTAIM), and Landauer theory (LT). Thionation, involving the replacement of diamide oxygens with sulfurs in NDI, significantly enhances quantum‐electronic/thermoelectric properties. Computational analyzes of energy of frontier orbitals HOMO/LUMO, dipole moment, polarizability, first superpolarizability, UV spectrum, and cohesive energy show the superior performance of the thione structure (M2) compared to the pristine structure (M1). Thionation decreased the energy gap from 01.3 eV (in M1 structure) to 1.87 eV (in M2 structure). The absorption wavelength in the pristine structure (M1) is calculated to be 507 nm, which increased to 1067 nm after thionation (M2). Cohesive energy values for each of M1 and M2 structures are calculated as 12.76 and 12.89 Kcal mol−1, respectively, which indicates the improvement of stability after thionation. After connecting M1 and M2 to gold electrodes (Au‐M1‐Au and Au‐M2‐Au) and applying electric fields, the Au‐M2‐Au structure shows a lower energy gap, lower thermoelectric activity and higher conductivity at field intensities with higher than 140 × 10−4 (a.u.), indicating its use as a field‐effect molecular device (such as molecular wire or molecular switch).

6-(6-Methyl-1,2,4,5-Tetrazine-3-yl)-2,2'-Bipyridine: A N-Donor Ligand for the Separation of Lanthanides(III) and Actinides(III).

Here, we report the synthesis of the 6-(6-methyl-1,2,4,5-tetrazine-3-yl)-2,2'-bipyridine (MTB) ligand that has been developed for lanthanide/actinide separation. A multimethod study of the complexation of MTB with trivalent actinide and lanthanide ions is presented. Single-crystal X-ray diffraction measurements reveal the formation of [Ce(MTB)2(NO3)3], [Pr(MTB)(NO3)3H2O], and [Ln(MTB)(NO3)3MeCN] (Ln = Nd, Sm, Eu, Gd). In addition, the complexation of Cm(III) with MTB in solution was studied by time-resolved laser fluorescence spectroscopy. The results show the formation of [Cm(MTB)1-3]3+ complexes, which occur in two different isomers. Quantum chemical calculations reveal an energy difference between these isomers of 12 kJ mol-1, clarifying the initial observations made by time-resolved laser fluorescence spectroscopy (TRLFS). Furthermore, quantum theory of atoms in molecules (QTAIM) analysis of the Cm(III) and Ln(III) complexes was performed, indicating a stronger covalent contribution in the Cm-N interaction compared to the respective Ln-N interaction. These findings align well with extraction data showing a preferred extraction of Am and Cm over lanthanides (e.g., max. SFAm/Eu = 8.3) at nitric acid concentrations <0.1 mol L-1 HNO3.

Insights into 5-fluorouracil anti–cancer drug encapsulation within the pristine and palladium-doped carbon, silicon-carbide, and germanium-carbide nanotubes: A DFT investigation for advanced nanomedicine applications

In this study, we investigated the interaction and binding properties of 5-Fluorouracil (5-FU), an anti-cancer drug, encapsulated within pristine and palladium-doped carbon, silicon-carbide, and germanium-carbide nanotubes (CNT, SiCNT, GeCNT). Using density functional theory (DFT), we conducted a comprehensive analysis at both aqueous and gas phases. This included geometrical, structural, electrical, bonding, and thermodynamic properties, optimized geometries, adsorption energies, quantum molecular descriptors, frontier molecular orbitals, and topological parameters at the M06-2X level of theory. Our findings indicate that Pd-doping enhances the encapsulation capabilities of nanotubes, strengthening interactions with 5-FU and improving water solubility. Calculations of recovery time required for drug release suggest that Pd-doped nanotubes effectively control the release of 5-FU. Notably, the decapsulation time of 5-FU from of Pd-doped nanotubes was longer in the gas phase than in aqueous conditions. Using the quantum theory of atoms in molecules (QTAIM) method, we investigated intermolecular interactions and critical bonding points. Natural bond orbital (NBO) analysis revealed enhanced stabilization of the 5-FU molecule post-encapsulation, with charge transfer primarily directed from nanotubes to the 5-FU. Hirshfeld surface analysis highlighted that hydrogen bonds between 5-FU active sites and nanotubes are crucial in encapsulation and fixation. Reduced Density Gradient (RDG) analysis confirmed Pd-doping as a primary source of strong attractive interactions in 5-FU/Pd-doped nanotube complexes compared to pristine nanotubes.

Sunlight-activated dye degradation of ZnO/CdO-decorated graphene oxide and its antibacterial activity

The pollution of water sources by hazardous substances such as sulfates, cyanides, and heavy metals represents a major environmental challenge. Addressing these issues requires the degradation of pollutants in wastewater to mitigate our environmental crises. Graphene oxide (GO) significantly enhances the mechanical and functional properties of GO-ZnO and GO-CdO nanocomposites, making them promising materials for applications in both sensors and catalysts. In this context, two optically active metal oxide-decorated graphene oxides (GO-ZnO and GO-CdO) were synthesized, and their photocatalytic efficacy against methylene blue (MB) was evaluated. Using an FT-IR spectrophotometer, the vibrational modes of hydroxyl (OH), carbonyl (C=O), and carboxylic (COOH) groups were identified. Raman spectroscopy analysis provided additional insights, confirming these vibrational properties. These materials exhibited peak photon absorption (λmax) at 242 nm and an optical band gap of 3.7 eV. Frontier molecular orbital (FMO) analyses indicated significant electronic charge transfer on the materials' surfaces, demonstrating their excellent capacity for adsorbing MB. An optimal catalyst dosage of 50 mg was found to be most effective in accelerating the degradation of MB. Additionally, variations in the initial pH of the solution showed a direct correlation, with higher pH levels leading to enhanced degradation efficiency, reaching up to 97% after 120 minutes. Quantum Theory of Atoms in Molecules (QTAIM) analyses revealed that MB is extensively adsorbed and degraded through a series of hydrogen bonding interactions. Moreover, experimental results indicate that both materials have a significant impact on bacterial destruction, suggesting their potential as novel antibacterial agents.

The Perfluoro‐o‐phenylene‐mercury Trimer [Hg(o‐C6F4)]3 – a Textbook Example of Phase‐Dependent Structural Differences

AbstractThe geometric and electronic structure of [Hg(o‐C6F4)]3 (1) in the gas phase, i. e. free of intermolecular interactions, was determined by a synchronous gas‐phase electron diffraction/mass spectrometry experiment (GED/MS), complemented by quantum chemical calculations. 1 is stable up to 498 K and the gas phase contains a single molecular form: the trimer [Hg(o‐C6F4)]3. It has a planar structure of D3h symmetry with a Hg–C distance of 2.075(5) Å and a Hg–Hg distance of 3.614(7) Å (both rh1). Structural differences between the crystalline and gaseous state have been analyzed. Different DFT functional‐basis combinations were tested, demonstrating the importance to consider the relativistic effects of the mercury atoms. The combination PBE0/MWB(Hg),cc‐pVTZ(C,F) turned out to be the most appropriate for the geometry optimization of such organomercurials. The electronic structure of 1, the nature of the chemical bonding in C−Hg−C fragments and the nature of the Hg⋅⋅⋅Hg interactions have been analyzed in terms of the Natural Bond Orbital (NBO) and Quantum Theory of Atoms in Molecules (QTAIM) approaches. The influence of the nature of halogen substitution on the structure of the molecules in the series [Hg(o‐C6H4)]3, [Hg(o‐C6F4)]3, [Hg(o‐C6Cl4)]3, [Hg(o‐C6Br4)]3 was also analyzed.

Unveiling spectroscopic behaviour and molecular features (DFT studies) of Exemestane-maleic acid cocrystal as model multicomponent system

The present study aimed to investigate the Exemestane - maleic acid (Ex-Mal) cocrystal using Fourier-transform Raman (FT-Raman), Fourier-transform Infrared (FT-IR), Powder X-ray Diffraction (PXRD) and Differential Scanning Calorimeter (DSC) experimental techniques and quantum chemical calculations. Exemestane (Ex) is an irreversible aromatase inhibitor, clinically used for the treatment of postmenopausal women having primary or advanced breast cancer. Maleic acid (Mal), a dicarboxylic acid is found in many vegetables and fruits and is used as a food additive and sweetener. Solution crystallization of Ex and Mal was done in the generation of Ex-Mal cocrystal (1:1). PXRD and DSC analysis confirmed the successful generation of Ex-Mal Cocrystal. Intermolecular hydrogen bonding (O4-H12···O13 & C8-O3···H36) also suggested the formation of a multi-component system, Ex-Mal cocrystal (1:1), as the respective modes shifted in the vibrational (Raman & IR) spectra of cocrystal than the Ex. Further, the quantum theory of atoms in molecules (QTAIM) has been done to analyze the strength and nature of inter-/intra molecular hydrogen bonding. Natural bond orbital (NBO) analysis was performed to check the stabilization energy of the system. The frontier molecular orbital (FMO) analysis predicted that Ex-Mal cocrystal is more reactive and less stable than Ex. Molecular electrostatic potential (MEP) surface showed that electrophilic (C16-H36)/(O4-H12), and nucleophilic (C8=O3)/(C17=O13) reactive groups in Ex/Mal and Mal/Ex, respectively, neutralized after the formation of Ex-Mal cocrystal, confirming the presence of hydrogen bonding interactions (C16-H36∙∙∙O3=C8) and (C17=O13∙∙∙H12-O4). Molar Refractivity (MR) was calculated to check the drug-likeness behaviours of Ex-mal cocrystal. This study provided a comparison of experimental and theoretical results to understand the hydrogen bonding interactions and structural activity of the system.

Rationalizing the stability and noncovalent interactions of N-(benzo[d][1,3]dioxol-5-ylmethyl)-2-(methylthio)thiazole-4-carboxamide: Insights from X‐ray structure and QTAIM analysis

A novel thiazole derivative, N-(benzo[d][1,3]dioxol-5-ylmethyl)-2-(methylthio)thiazole-4-carboxamide was synthesized and the structural interpretations were accomplished unambiguously by single crystal X-ray diffraction study. Structure investigation revealed that the crystal packing is stabilized by CH…N, and NH…O intermolecular interactions. Hirshfeld surface analysis used to explore the quantitative details of noncovalent interactions which are responsible for the crystal packing. The 3D energy framework, interaction energies and lattice energy of the compound were computed. Density functional theory (DFT) calculation was also employed to study various physicochemical properties of the compound. Quantum theory of atoms in molecules (QTAIM) analysis have been performed to study the intra and intermolecular interactions present in the thiazole derivative and also validate with the experimental results.

Deciphering the adsorption and sensing performance of Al24N24 and B24N24 nanoclusters as a drug delivery system for nitrosourea anticancer drug: A DFT insight

Nanomaterials for drug detection are crucial in pharmaceutical research, especially in cancer therapy applications like nitrosourea. The purpose of this work was to examine the sensitivity of Al24N24 and B24N24 nanocages for the detection of nitrosourea by using density functional theory (DFT). Different analyses were performed such as adsorption energy (Eads) studies, frontier molecular orbitals (FMOs), natural bond orbitals (NBO), global indices of reactivity, UV-Vis studies, molecular electrostatic potential (MEP), non-covalent interaction (NCI), quantum theory of atoms in molecules (QTAIM) and sensor mechanism. The adsorption of nitrosourea on Al24N24 shows the highest values of adsorption energies with the value of −59.239, −55.986, and −51.019 kcal/mol for O/6m-AN, plan/6m-AN, and plan/8m-AN respectively. On the other hand, B24N24 complexes show fewer adsorption energies with the notable presence in plan/6m-BN, O/4m-BN, and plan/8m-BN that have the values of −11.064, −10.983, and −10.064 kcal/mol respectively. The energy gap of Al24N24 and B24N24 complexes decrease from 4.120 eV and 6.493 eV respectively for bare nanocage showing the potential of using these cages for nitrosourea (NUr) detection. FMOs studies reveal that among all designed complexes the lowest energy gap is present in O/4m-AN having a value of 2.913 eV. Moreover, global indices of reactivity suggest the increase in softness for Al24N24 complexes from 0.2427 eV for bare nanocage to 0.3433 eV for O/4m-AN. Similarly, the softness for B24N24 complexes also increases from 0.1540 eV for bare cage to 0.3012 eV for O/B-BN. Sensitivities for NUr in O/B-BN, O/4m-BN, plan/6m-BN and plan/8m-BN are 0.896, 0.870, 0.834 and 0.815 respectively. Moreover, the recovery time of NUr drug from BN nanocage is also very short as 7.53 × 10-12 s for O/N-BN. Topological analysis predict the non-covalent nature of interaction present between AN and BN nanocages. The electrical conductivity values are increased after the adsorption process. The highest electrical conductivity is present in AN complexes such as 4.41 × 1012 S/m for O/4m-AN due to low energy gap of 2.91 eV. The sensor mechanism reflects the high values of sensitivity for B24N24 complexes due to narrow energy gaps. Thus, B24N24 could be a fine candidate for the detection of nitrosourea and as a drug delivery vehicle for nitrosourea to treat cancer.

Exploration of Free Energy Surface of the Au10 Nanocluster at Finite Temperature.

The first step in comprehending the properties of Au10 clusters is understanding the lowest energy structure at low and high temperatures. Functional materials operate at finite temperatures; however, energy computations employing density functional theory (DFT) methodology are typically carried out at zero temperature, leaving many properties unexplored. This study explored the potential and free energy surface of the neutral Au10 nanocluster at a finite temperature, employing a genetic algorithm coupled with DFT and nanothermodynamics. Furthermore, we computed the thermal population and infrared Boltzmann spectrum at a finite temperature and compared it with the validated experimental data. Moreover, we performed the chemical bonding analysis using the quantum theory of atoms in molecules (QTAIM) approach and the adaptive natural density partitioning method (AdNDP) to shed light on the bonding of Au atoms in the low-energy structures. In the calculations, we take into consideration the relativistic effects through the zero-order regular approximation (ZORA), the dispersion through Grimme's dispersion with Becke-Johnson damping (D3BJ), and we employed nanothermodynamics to consider temperature contributions. Small Au clusters prefer the planar shape, and the transition from 2D to 3D could take place at atomic clusters consisting of ten atoms, which could be affected by temperature, relativistic effects, and dispersion. We analyzed the energetic ordering of structures calculated using DFT with ZORA and single-point energy calculation employing the DLPNO-CCSD(T) methodology. Our findings indicate that the planar lowest energy structure computed with DFT is not the lowest energy structure computed at the DLPN0-CCSD(T) level of theory. The computed thermal population indicates that the 2D elongated hexagon configuration strongly dominates at a temperature range of 50-800 K. Based on the thermal population, at a temperature of 100 K, the computed IR Boltzmann spectrum agrees with the experimental IR spectrum. The chemical bonding analysis on the lowest energy structure indicates that the cluster bond is due only to the electrons of the 6 s orbital, and the Au d orbitals do not participate in the bonding of this system.

Energetic features of H-bonded and antiparallel π-stacked supramolecular assemblies in pyrazolones: Experimental, computational and biological analyses

The work presented herein outlines a straightforward synthetic route to produce a series of pyrazolone compounds, which are significant in both coordination chemistry and pharmaceutical research. These heterocyclic compounds were thoroughly characterized using FTIR, 1H and 13C NMR spectroscopy, and their molecular structures were conclusively determined through X-ray crystallography. The resulting supramolecular architectures feature a variety of noncovalent interactions, including conventional NH…O and CH…O hydrogen bonds, CH…halogen contacts, CH…N interactions, and offset π-π stacking. Density Functional Theory (DFT) calculations, alongside Molecular Electrostatic Potential (MEP) surface analysis and Quantum Theory of Atoms in Molecules (QTAIM)/Non-Covalent Interaction (NCI) plot methodologies, were employed to probe these interactions further. This analysis highlighted the significance of both CH…O and NH…O hydrogen bonds and revealed the critical role of antiparallel π-stacking interactions, particularly within chlorophenyl and benzonitrile substituted pyrazolones, underscoring their stabilizing effects on the molecular structure. Biological assessment against urease enzyme unveiled compound 3a as the lead inhibitor with an IC50 value of 0.71 ± 0.09 μM and 31-folds strong inhibition than thiourea, thus making pyrazolone heterocycles as potential drug candidates.

Nature of the bond in intermetallic compounds

By studying 398 binary compounds crystallizing in five different crystal structures, it is shown that atomic radii of the elements RA and RB change to reach a constant radius ratio rA/rB(≡ϒ) in a cubic system. In systems of lower symmetry, a range of ϒ values, each corresponding to a certain axial ratio, is possible. Accurate charge values on atoms in solids are derived from the experimental internal radii rA and rB, using Shannon’s compilation of radii versus charge states for elements. It is found, for the first time, that charge transfer and radii change reverse their direction at the ϒ point. Electronegativity difference relative to its value at the ϒ point is recognized to correctly predict the charge transfer and radii changes with RA/RB. The deduced electronic structure of solids, based on spherical ions carrying partial charges, confirms that the metallic atom-pair bond is a resonating polar covalent bond. Identification of the number of electrons that contribute to cohesion and electrical conduction individually, allows successful prediction of electrical conductivity variation for transition metals and p-elements in the periodic table. From a knowledge of accurate valence of elements and of charge on the atoms, variation in the 197Au isomer shift of the gold compounds of CsCl type structure is predicted. The charges on atoms computed using the Quantum Theory of Atoms in Molecules (QTAIM) technique agree with those obtained in our work for compounds belonging to two of the structure types. For compounds belonging to the other three, the charge values obtained by the two methods do not agree. The disagreement correlates to not reckoning the role of the ϒ point. The effect of ϒ point is so fundamental and universal that most physical properties obtained by the secondary processing of primary DFT data, can be influenced by it.

Sensitive determination of Gabapentin in plasma sample using dispersive liquid-liquid microextraction coupled with ion mobility spectrometry

Gabapentin (GBP) is an anticonvulsant agent and its determination using a fast and simple method is challenging. In this research, a novel sensitive, and economical method for the fast determination of GBP in biological samples was developed. This method benefits from the advantages of ion mobility spectrometry (IMS) as a fast detection and separation system and dispersive liquid-liquid microextraction (DLLME) for the preconcentration/extraction of GBP. In the developed method (DLLME-IMS), Ag nanoparticles serve as modifiers. Moreover, the quantum theory of atoms in molecules (QTAIM) analysis was employed to investigate the interaction mechanism between GBP and Ag nanoparticles. Also, a delay time after the injection of the sample was applied to improve the method sensitivity. Under the optimum condition, the developed method showed a linear response over the concentration range of 0.3–12 μg mL−1 and a detection limit of 0.12 μg mL−1. Eventually, DLLME-IMS was successfully employed in plasma sample, and was validated against the HPLC method with UV detection as a reference method. The developed method will open up a new avenue for the development of effective, rapid, and simple analytical methods.

Investigating the potential of monocyclic B9N9 and C18 rings for the electrochemical sensing, and adsorption of carbazole-based anti-cancer drug derivatives: DFT-based first-principle study.

For the first time, the use of monocyclic rings C18 and B9N9 as sensors for the sensing of carbazole-based anti-cancer drugs, such as tetrahydrocarbazole (THC), mukonal (MKN), murrayanine (MRY), and ellipticine (EPT), is described using DFT simulations and computational characterization. The geometries, electronic properties, stability studies, sensitivity, and adsorption capabilities of C18 and B9N9 counterparts towards the selected compounds confirm that the analytes interact through active cavities of the C18 and B9N9 rings of the complexes. Based on the interaction energies, the sensitivity of surfaces towards EPT, MKN, MRY, and THC analytes is observed. The interaction energy of EPT@B9N9, MKN@B9N9, MRY@B9N9, and THC@B9N9 complexes are observed - 20.40, - 19.49, - 20.07, and - 18.27kcal/mol respectively which is more exothermic than EPT@C18, MKN@C18, MRY@C18, and THC@C18 complexes are - 16.37, - 13.97, - 13.96, and - 11.39kcal/mol respectively. According to findings from the quantum theory of atoms in molecules (QTAIM) and the reduced density gradient (RDG), dispersion forces play a significant role in maintaining the stability of these complexes. The electronic properties including FMOs, density of states (DOS), natural bond orbitals (NBO), charge transfer, and absorption studies are carried out. In comparison of B9N9 and C18, the analyte recovery time for C18 is much shorter (9.91 × 10-11 for THC@C18) than that for B9N9 shorter recovery time value of 3.75 × 10-9 for EPT@B9N9. These results suggest that our reported sensors B9N9 and C18 make it faster to detect adsorbed molecules at room temperature. The sensor response is more prominent in B9N9 due to its fine energy gap and high adsorption energy. Consequently, it is possible to think of these monocyclic systems as a potential material for sensor applications.

A General Photoactive H-Bonding EDA Complex Model Drives the Selective Hydrothiolation and Hydroxysulfenylation of Carbonyl Activated Alkenes.

Excitation of photoactive electron donor-acceptor (EDA) complexes to generate radical is a promising approach in radical chemistry. In this study, we introduce a new model of H-bonding EDA complexes for the selective hydrothiolation and hydroxysulfenylation of carbonyl-activated alkenes with diverse thiols under visible light conditions. The reliability of this H-bonding EDA complex model has been confirmed by meticulous experimental and theoretical calculations. Mechanistic investigations have revealed the significant influence of the solvent in determining whether the excitation of photoactive H-bonding EDA complex leads to charge transfer (CT) or energy-charge transfer (En-CT), thereby controlling Markovnikov and anti-Markovnikov selectivity. Notably, the Quantum Theory of Atoms in Molecules (QTAIM) analysis clearly shows that the excited state of the C＝O---H-S EDA complex involves closed-shell partially covalent interactions.

A General Photoactive H‐Bonding EDA Complex Model Drives the Selective Hydrothiolation and Hydroxysulfenylation of Carbonyl Activated Alkenes

Excitation of photoactive electron donor−acceptor (EDA) complexes to generate radical is a promising approach in radical chemistry. In this study, we introduce a new model of H‐bonding EDA complexes for the selective hydrothiolation and hydroxysulfenylation of carbonyl‐activated alkenes with diverse thiols under visible light conditions. The reliability of this H‐bonding EDA complex model has been confirmed by meticulous experimental and theoretical calculations. Mechanistic investigations have revealed the significant influence of the solvent in determining whether the excitation of photoactive H‐bonding EDA complex leads to charge transfer (CT) or energy‐charge transfer (En‐CT), thereby controlling Markovnikov and anti‐Markovnikov selectivity. Notably, the Quantum Theory of Atoms in Molecules (QTAIM) analysis clearly shows that the excited state of the C＝O‐‐‐H‐S EDA complex involves closed‐shell partially covalent interactions.

Prediction of Covalent Metal-Metal Bonding in Cp-M-M'-Nacnac Complexes of Group 2 and 12 Metals (Be, Mg, Ca, Zn, Cd, Hg).

Bimetallic CpMM'Nacnac molecules with group 2 and 12 metals (M = Be, Mg, Ca, Zn, Cd, Hg) that contain novel metal-metal bonding have been investigated in a theoretical study of their molecular and electronic structure, thermodynamic stability, and metal-metal bonding. In all cases the metal-metal bonds are characterized as electron-sharing covalent single bonds from natural bond orbital (NBO) and energy-decomposition analysis with natural orbitals of chemical valence (EDA-NOCV) analysis. The sum of [MM'] charges is relatively constant, with all complexes exhibiting a [MM']2+core. Quantum theory of atoms in molecules (QTAIM) analysis indicates the presence of non-nuclear attractors (NNA) in the metal-metal bonds of the BeBe, MgMg, and CaCa complexes. There is substantial electron density (0.75-1.33 e) associated with the NNAs, which indicates that these metal-metal bonds, while classified as covalent electron-sharing bonds, retain significant metallic character that can be associated with reducing reactivity of the complex. The predicted stability of these complexes, combined with their novel covalent metal-metal bonding and potential as reducing agents, make them appealing targets for the synthesis of new metal-metal bonds.

DFT insights into the electronic properties and gas sensing performance of C19X (X = C, N, and Si) nanocages for the detection of CO2, CO, N2, and H2 gases

The development of carbon nanocage-based sensors for the detection of toxic and pollutant gases has attracted significant attention from researchers. In this computational study, the interactions of CO2, CO, N2, and H2 gases with the C19X nanocages (X = C, N, and Si) were evaluated using the M062X/6-31G(d) level of density functional theory (DFT) calculations. The results demonstrated a reduction in the energy gap (Egap) across all studied systems, especially pronounced in the C19N and C19Si nanocages, compared to the complexes with a higher priority of the C19Si nanocages. The gas molecules were found to have weak adsorption in all the C20 nanocage complexes, while the adsorption of CO gas was more pronounced in the C19N and C19Si nanocages compared to the other gases studied. A quantum theory of atoms in molecule (QTAIM) analysis was conducted to examine the interactions and their features, through which the physical interactions that contribute to the formation of the complexes were identified. Further electrical characterizations revealed that the C19Si nanocage has a high sensitivity for the detection of CO gas, making it a promising sensor material. In conclusion, the engineered C19N and C19Si nanocages demonstrated significant improvements over the original C20 nanocage in terms of adsorption capabilities for CO2, CO, N2, and H2 gases, making them promising candidates for sensor applications.

Toxic gas removal using transition metal-decorated Cyclo[18]carbon: A first principles prevision

Carbon monoxide (CO), nitric oxide (NO), and ammonia (NH3) are highly toxic gases that are hazardous to human health and the environment. This study dives into the examination of interaction mechanism between transition metal-decorated Cyclo[18]carbon or C18TM (TM = Ni, Pd, Pt) nanoclusters and aforementioned gas molecules. The analysis of structural, electronic, topological, spectroscopic, and sensing properties, uncovers significant findings. The computed adsorption energies exhibit highly negative values. Notably, a substantial sensing response is observed, particularly in the context of NO adsorption over C18Ni and CO adsorption over C18Pd nanoclusters. Employing the Quantum Theory of Atoms in Molecules (QTAIM), we discern the strength of each interaction. Raman spectra analyses provide additional details regarding the vibrational aspects of these interactions. Our Non-Covalent Interaction (NCI) study effectively elucidates the mechanisms underlying van der Waals interactions. Evidently, the longer recovery times observed in our calculations, owing to the highly negative adsorption energies with −2.31 eV being the most negative value for CO molecule over C18Pt nanocluster and −1.09 eV value for NO over C18Pd being the least, suggest that C18TM nanoclusters are better suited for gas removal applications rather than rapid-response sensors.

Synthesis and structural investigation of salts of 2-amino-3-methylpyridine with carboxylic acid derivatives: an experimental and theoretical study.

The salts bis(2-amino-3-methylpyridinium) fumarate dihydrate, 2C6H9N2+·C4H2O22-·2H2O (I), and 2-amino-3-methylpyridinium 5-chlorosalicylate, C6H9N2+·C7H4ClO3- (II), were synthesized from 2-amino-3-methylpyridine with fumaric acid and 5-chlorosalicylic acid, respectively. The crystal structures of these salts were characterized by single-crystal X-ray diffraction, revealing protonation in I and II by the transfer of a H atom from the acid to the pyridine base. In the crystals of both I and II, N-H...O interactions form an R22(8) ring motif. Hirshfeld surface analysis distinguishes the interactions present in the crystal structures of I and II, and the two-dimensional (2D) fingerprint plot analysis shows the percentage contribution of each type of interaction in the crystal packing. The volumes of the crystal voids of I (39.65 Å3) and II (118.10 Å3) have been calculated and reveal that the crystal of I is more mechanically stable than II. Frontier molecular orbital (FMO) analysis predicts that the band gap energy of II (2.6577 eV) is lower compared to I (4.0035 eV). The Quantum Theory of Atoms In Molecules (QTAIM) analysis shows that the pyridinium-carboxylate N-H...O interaction present in I is stronger than the other interactions, whereas in II, the hydroxy-carboxylate O-H...O interaction is stronger than the pyridinium-carboxylate N-H...O interaction; the bond dissociation energies also confirm these results. The positive Laplacian [∇2ρ(r) > 0] of these interactions shows that the interactions are of the closed shell type. An in-silico ADME (Absorption, Distribution, Metabolism and Excretion) study predicts that both salts will exhibit good pharmacokinetic properties and druglikeness.