Atomic Theory Research Articles

Computational insight into the formation of cation-π/cation-lone pair complexes between 3d-metal (II) ions and furan.

Cation-π and cation-lone pair interactions between 3d-metal (II) ions [Fe(II), Co(II), Ni(II) and Cu(II)] and furan are explored in the formation of 1:1 and 1:2 type complexes. Both cation-π (IEgas = -192.27 to -312.65 kcal mol-1) and cation-lone pair (IEgas = -163.13 to -271.76 kcal mol-1) interactions are reasonably strong and lead to the formation of stable 1:1 and 1:2 type complexes in gas phase. The complexes are also stable in solvent phase, but their stability is reduced significantly in presence of solvent dielectrics, especially in ethanol, DMSO and water. Formation of the complexes is thermodynamically favourable (exothermic and spontaneous). Charge transfer (Δq = 0.62 to 1.92 e-), Laplacian of electron density (∇2ρ = 0.1435 to 0.6628 au) and total electron energy density (H(r) = -0.0019 to -0.0436 au) analysis have argued in favour of partial ionic and partial covalent character of the interactions. Density functional theory (DFT) is exclusively used for the study. Polarizable continuum model (PCM) is used to perform solvent phase study. Natural bond orbital (NBO), quantum theory of atoms in molecules (QTAIM) and non-covalent interaction (NCI) analyses are performed for understanding other aspects of complex formation.

Capturing the Effect of Anion Type on the Intermolecular Interactions between Water and Imidazolium-Based Ionic Liquids: A Comparative DFT Study.

The studies on ionic liquids (ILs) and their interaction with different solvents have always been an interesting topic for experimental and computational chemists. Recently, however, deep insights on the molecular structures of the IL-water binary mixtures have been mainly performed through classical simulations. Here, a comprehensive quantum mechanical study is presented on seven 1-butyl-3-methylimidazolium-based ILs in the absence and presence of water. As the most important intermolecular interaction between ionic moieties of ILs and water molecules, hydrogen bonding is studied through different bonding analyses. The effect of different anions, [NO3]-, [HSO4]-, [SCN]-, [DCA]-, [BF4]-, [PF6]-, and [NTf2]-, on the behavior of ILs interacting with a sample of water molecules is investigated. Comparing the implicit and explicit approaches to consider water solvent indicated that the structure of ILs in the solvent depends on the selected solvent model. By considering explicit water molecules, we analyzed the intermolecular interactions between ILs and the water sample. The energy decomposition analysis indicated that the stability of the IL···water systems is mainly due to the electrostatic component of the total interaction energy. The interaction region indicator (IRI) analysis discovered that chemical bond and van der Waals (vdW) interactions are important in the IL···water systems. Indeed, investigation of each ion/ion pair surrounded by ten nearest neighbor water molecules discovered that the vdW interactions are responsible for the cation···anion and the cation···water interactions, while chemical bonding is important in the anion···water and the water···water interactions. Therefore, the anion···water interaction requires further analysis. The quantum theory of atoms in molecules verified the ionic nature of the H-bond in the anion···water interaction. The IRI analysis showed that the interaction between water molecules and cyano-based anions, [SCN]- and [DCA]-, is only due to chemical bonding, while in the oxygenated anions, [NO3]- and [HSO4]-, the vdW forces are also important. For the other anions, [BF4]-, [PF6]-, and [NTf2]-, the vdW forces have the main contribution in the anion···water interaction. Natural bond orbital analysis indicated that these intermolecular interactions originate from nanion → σO-H* electron transfer. Finally, the law of matching water affinity (LMWA) using energy-based parameters was used to predict the hydrophilicity of ILs as follows: [BMIM][NO3] > [BMIM][SCN] > [BMIM][DCA] > [BMIM][HSO4] > [BMIM][BF4] > [BMIM][NTf2] > [BMIM][PF6]. Results obtained in the current work give insights into the electronic nature of intermolecular interactions between ILs and water molecules, which is necessary due to importance of water in modifying properties of ILs in various applications.

Electrostatic and Electronic Effects on Doped Nickel Oxide Nanofilms for Water Oxidation.

An ideal water-splitting electrocatalyst is inexpensive, abundant, highly active, stable, selective, and durable. The anodic oxygen evolution reaction (OER) is the main bottleneck for H2 production with a complex and not fully resolved mechanism, slow kinetics, and high overpotential. Nickel oxide-based catalysts (NiOx) are highly active and cheaper than precious metal catalysts. However, rigorous catalyst tests and DFT calculations are still needed to rationally optimize NiOx catalysts. In this work, we combine plasma-enhanced atomic layer deposition (PE-ALD) and density functional theory (DFT) to address the role of dopants in promoting NiOx OER activity. Ultrathin films of NiOx doped with Zn2+, Al3+, and Sn4+ presented improved intrinsic activity, stability, and durability for the OER. The results show a low to high catalytic performance of ZnNiOx < NiOx < AlNiOx < SnNiOx, which we attribute to an increase in the concentration of valence band (VB) holes combined with conduction band (CB) electron conductivity, characterized by electrochemical impedance spectroscopy (EIS). The influence of doping on the electronic structure and catalytic activity was investigated using advanced characterization techniques and density functional theory (DFT) calculations (PEB0/pob-TZVP). DFT complements the experimental results, showing that the dopant charge states and orbital hybridization enhance the OER by improving the charge carrier concentration and mobility, thus allowing optimal binding energies and charge dynamics and delocalization. Our findings demonstrate the potential of PE-ALD-doped nanofilms NiOx and DFT to rationally design and develop catalysts for sustainable energy applications.

Synthesis, Antibacterial, and Antibiofilm Activities of Imidazo[2,1-b]Thiazole Chalcone Derivatives: In Vitro and In Silico Studies.

In recent years, imidazothiazole-chalcone conjugates have emerged as notable pharmacophores with potential applications in discovering biologically active compounds. This study focuses on synthesizing novel imidazo[2,1-b]thiazole chalcone derivatives through a facile and conventional process adhering to several principles of green chemistry, facilitating scalable production. The synthesized compounds underwent comprehensive spectroscopic analysis, including 1H NMR, 13C NMR, LC-MS, and FT-infrared (IR) techniques. Theoretical FT-IR and NMR analysis, frontier molecular orbitals (FMOs), and global reactivity descriptors were calculated and interpreted. Furthermore, molecular electrostatic potential (MEP) surface, Mulliken atomic charge, electron localization function (ELF), localized orbital locator (LOL), and quantum theory of atoms in molecules (QTAIM) were analyzed. The newly synthesized compounds were screened in vitro for their antibacterial and antibiofilm activities. In addition, computational docking studies were performed to gain further insights into molecular interactions and found to support the results.

Chemical Bond Overlap Descriptors From Multiconfiguration Wavefunctions.

The chemical bond is a fundamental concept in chemistry, and various models and descriptors have evolved since the advent of quantum mechanics. This study extends the overlap density and its topological descriptors (OP/TOP) to multiconfigurational wavefunctions. We discuss a comparative analysis of OP/TOP descriptors using CASSCF and DCD-CAS(2) wavefunctions for a diverse range of molecular systems, including X-O bonds in X-OH (XH, Li, Na, H2B, H3C, H2N, HO, F) and Li-X' (XF, Cl, and Br). Results show that OP/TOP aligns with bonding models like the quantum theory of atoms in molecules (QTAIM) and local vibrational modes theory, revealing insights such as overlap densities shifting towards the more electronegative atom in polar bonds. The Li-F dissociation profile using OP/TOP descriptors demonstrated sensitivity to ionic/neutral inversion during Li-F dissociation, highlighting their potential for elucidating complex bond phenomena and offering new avenues for understanding multiconfigurational chemical bond dynamics.

Stacking interactions in stabilizing supramolecular assembly of M[9C]2M complexes: dynamic stability with remarkable nonlinear optical features.

Continual attempts have been made to discover excellent nonlinear optical (NLO) materials. Here, we investigate the role of stacking interactions and van der Waals forces in the designed parallel stacked complexes M[9C]2M (where M = Li, Na, K, Be, Mg, and Ca) using various quantum chemical and molecular dynamics methods. The thermodynamic stability of the present complexes is also revealed by the computed interaction energy, enthalpy of formation, and Gibbs free energy of formation (ΔGf). Molecular dynamics simulations were performed at room temperature to determine the stability of the dimer formation and their complexes. Alkali metals act as a more prominent source of excess electrons at long-range interaction distances. Charge decomposition analysis (CDA) and natural bonding orbital (NBO) analyses suggest excellent charge transfer in the alkalide complexes. In this series, Li[9C]2Li exhibits an excellent hyperpolarizability response up to 2.3 × 106 a.u., while Ca[9C]2Ca performs well in alkaline-earth metal complexes. The NLO response is mostly influenced by the alkalide and earthide characteristics. Dynamic NLO features were computed at externally applied frequencies. Scattering first hyperpolarizability (βHRS) and its associated components were also measured. The effect of solvents on hyperpolarizability is also considered. The quantum theory of atoms in molecules (QTAIM) and NCI are employed to investigate the bonding nature and vdW forces in addition to stacking interactions. TD-DFT and vibrational studies are also performed. We aim for this research to pave the way for the innovative strategies in designing supramolecular assemblies tailored for NLO applications.

Nanoring interactions with bio-relevant molecule: A quantum chemical approach to C18 and B9N9 systems.

This study investigates the interaction of a synthetic bio-relevant molecule with C18 and B9N9 nanorings, exploring their potential applications in sensing and drug delivery. Employing Density Functional Theory (DFT) at the ωB97XD level with the 6-31G(d,p) basis set, we computed the adsorption and electronic properties of the resulting nanocomplexes. A total of ten distinct configurations were identified for the interactions, with adsorption energies ranging from -6.75 to -12.62kcal/mol for the C18@target molecule and -9.01 to -18.46kcal/mol for the B9N9@target molecule. Notably, alterations in the energy gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) upon interaction suggest an enhancement in electrical conductivity. The effect of aqueous media was also examined, revealing an increase of approximately 2.0 Debye in the dipole moments of the most stable nanocomplexes. Additional analyses, including reduced density gradient (RDG), UV-Vis spectroscopy, and Quantum Theory of Atoms in Molecules (QTAIM), were conducted in both gas and aqueous phases. Our findings indicate that C18 and B9N9 nanorings exhibit significant promise as candidates for drug delivery and sensing applications, particularly due to their enhanced electronic properties upon interaction with the bio-relevant molecule.

ESTUDO COMPUTACIONAL DA INFLUÊNCIA DE CO2 NO EMPILHAMENTO-π DE MONÔMEROS DE CORONENO SUBSTITUÍDOS COM ENXOFRE

COMPUTATIONAL STUDY OF THE INFLUENCE OF CO2 ON THE π-STACKING OF SULFUR-SUBSTITUTED CORONENE MONOMERS. Asphaltenes are complex molecules with a tendency to aggregate. This property can be an issue for the oil industry due to CO2 reinjection into reservoirs to mitigate these gas emissions. The present theoretical study aimed to study the CO2 interaction with no-substitute and substituted coronene as an asphaltene model compound at CAM-B3LYP-D3/6-311G(d,p) level. The electronic properties were evaluated using harmonic oscillator model of aromaticity (HOMA), quantum theory of atoms in molecules (QTAIM), and reduced density gradient (RDG) methods. The results showed that the coronene’s functionalization by a sulfur atom changes the coronene’s electronic structure. However, functionalization does not change the type of interactions between the monomers, as they remain predominantly van der Waals interactions. CO2 interaction with substituted coronene barely changed due to the presence of sulfur atoms. However, in dimers, the position of the heteroatom directly influences the interaction with CO2, although it is insufficient to change the interaction’s magnitude. For this reason, our results indicate that the sulfur heteroatom in asphaltenes should be addressed. However, new studies must be conducted by increasing the number of substituents, CO2 numbers, and the model size.

Smart drug delivery: a DFT study of C24 fullerene and doped analogs for pyrazinamide.

The potential applicability of the C24 nanocage and its boron nitride-doped analogs (C18B3N3 and C12B6N6) as pyrazinamide (PA) carriers was investigated using density functional theory. Geometry optimization and energy calculations were performed using the B3LYP functional and 6-31G(d) basis set. Besides, dispersion-corrected interaction energies were calculated at CAM (Coulomb attenuated method)-B3LYP/6-31G(d,p) and M06-2X/6-31G(d,p) levels of theory. The adsorption energy (E ads), enthalpy (ΔH), and Gibbs free energy (ΔG) values for C24-PA, C18B3N3-PA, and C12B6N6-PA structures were calculated. The molecular descriptors such as electrophilicity (ω), chemical potential (μ), chemical hardness (η) and chemical softness (S) of compounds were investigated. Natural bond orbital (NBO) analysis confirms the charge transfer from the drug molecule to nanocarriers upon adsorption. Based on the quantum theory of atoms in molecules (QTAIM), the nature of interactions in the complexes was determined. These findings suggest that C24 and its doped analogs are promising candidates for smart drug delivery systems and PA sensing applications, offering significant potential for advancements in targeted tuberculosis treatment.

Chiral recognition of amino acids through homochiral metallacycle [ZnCl2L]2.

Chiral recognition holds tremendous significance in both life science and chemistry. The ability to differentiate between enantiomers is crucial because one enantiomer typically holds greater biological relevance while its counterpart is often not only unnecessary but also potentially harmful. In this regard, homochiral metallacycle [ZnCl2L]2 is used in this study to understand and differentiate between the R and S enantiomers of amino acids (alanine, proline, serine, and valine). The electronic, geometric, and thermodynamic stabilities of the amino acid enantiomers inside the metallacycle are determined through various analyses. The greater interaction energy (Eint) is obtained for the ser@metallacycle complexes i.e., -33.03 and -30.75 kcal mol-1, respectively for the S and R enantiomers. The highest chiral discrimination energy of 3.11 kcal mol-1 is achieved for ala@metallacycle complexes. Regarding the electronic properties, the frontier molecular orbital (FMO) analysis indicates that the energy gap decreases after complexation, which is confirmed through density of states (DOS) analysis. Moreover, natural bond orbital (NBO) analysis determines the amount and direction of charge transfer i.e., from metallacycle towards amino acids. The maximum NBO charge transfer is observed for S-pro@metallacycle complex i.e., -0.291 |e|. Electron density difference (EDD) analysis further proves the direction of charge transfer. Noncovalent interaction index (NCI) and quantum theory of atoms in molecules (QTAIM) analyses demonstrate that the noncovalent interactions present between the host and guest are the weak van der Waals forces and hydrogen bonding. The results of NCI and QTAIM analyses for all the complexes are in alignment with those of the interaction energy (Eint) and chiral discrimination energy (Echir) analyses, i.e., significantly greater non-bonding interactions are observed for the complexes with greater Echir, i.e., for ala@metallacycle. Overall, our analyses demonstrate the excellent chiral discrimination ability of metallacycle towards chiral molecules, i.e., for enantiomers of amino acids through host-guest supramolecular chemistry.

CONCEITOS EM CRISTALOGRAFIA ESTRUTUAL: UMA ABORDAGEM COMPREENSIVA DA LEI DE BRAGG E DO FATOR DE ESTRUTURA

CONCEPTS IN STRUCTURAL CRYSTALLOGRAPHY: A COMPREHENSIVE APPROACH TO BRAGG’S LAW AND THE STRUCTURE FACTOR. It is not uncommon that as a chemistry course progresses, along with the deepening of the content studied, the tendency of not carefully revisiting the foundations of the concepts covered and deepened also increases. The understanding of the structure of matter that develops throughout the course, starting from the first concepts of atomic theory, going through chemical bonds, molecules, intermolecular interactions to the study of how matter is aggregated in the solid state, is an example of knowledge that grows in depth and complexity. In this context, crystallography presents itself as a vast interdisciplinary area that contributes to understanding the matter. This article explores fundamental mathematical, historical, chemical, and physical concepts, connecting them to offer a more comprehensive and logically coherent understanding of key crystallography principles.

Experimental, Theoretical, and In Silico Studies of Potential CDC7 Kinase Inhibitors.

In this work, we present the synthesis, solid-state characterization, and in silico studies of two pyrazole derivatives: 5-(2-methylphenoxy)-3-methyl-1-phenyl-1H-pyrazole-4-carbaldehyde (I) and 5-(4-methylphenoxy)-3-methyl-1-phenyl-1H-pyrazole-4-carbaldehyde (II). The molecular crystal properties, in terms of intermolecular hydrogen bonds and other weak interactions, are analyzed using single crystal X-ray diffraction. The Hirshfeld surfaces computational method is used to quantify the intermolecular interactions, density functional theory for theoretical structural optimization, and its comparison with the experimental structure and in-silico studies using docking and molecular dynamics studies of I and II with CDC7-kinase. In addition, the quantum theory of atoms in molecules (QTAIM) approach is applied to calculate the topological properties of electron density and the Laplacian of electron density of the chemical bonds of both molecules. Compounds I and II crystallize in a monoclinic crystal system, and molecules are connected via C-H···O intermolecular hydrogen bonds. Hirshfeld surfaces analysis revealed that the H···H type intercontact contributes more toward the crystal packing. DFT-optimized structures show a perfect overlay with the experimental structures. The in silico results show that both I (-41.50 kcal/mol) and II (-44.53 kcal/mol) exhibit strong binding free energies as ligands binding to the active sites of the CDC7-kinase. The most significant contributions for ligand and protein binding in both compounds are dominated by van der Waals interactions.

Adsorption and Sensing Performance of Transition Metal Decorated Graphene Quantum Dots for AsH3, NH3, PH3, and H2S.

We have conducted a systematic study employing density functional theory (DFT) and quantum theory of atoms in molecules (QTAIM) to explore the gas sensing capabilities of nitrogen-doped single vacancy graphene quantum dots (SV/3N) decorated with transition metals (TM = Mn, Co, Cu). We have studied the interactions between TM@SV/3N and four different target gases (AsH3, NH3, PH3, and H2S) through the computation of adsorption energies, charge transfer, noncovalent interaction, density of states, band gap, and work function for 12 distinct adsorption systems. Our comprehensive analysis included an in-depth assessment of sensors' stability, sensitivity, selectivity, and reusability for practical applications. Our findings indicate that the Co@SV/3N surface strongly interacts with PH3, with the highest adsorption energy (-1.15 eV). It shows remarkable sensitivity and selectivity toward PH3, making it a promising candidate for PH3 gas sensing applications. Similarly, Mn@SV/3N exhibits high sensitivity and selectivity toward NH3, positioning it as a suitable candidate for NH3 gas sensing applications. We believe this study will provide valuable theoretical guidance for developing TM@SV/3N-based gas sensors.

When Escitalopram is Surrounded by Ethanol: A DFT and QTAIM Approach to Analyze The Drug and The Alcohol Interactions and It’s Possible Outcomes

In the scope of this work the antidepressant escitalopram was surrounded by ethanol commonly referred as alcohol step by step and the possible results of this invasion on escitalopram drug molecule were examined principally by density functional theory methods. Also for analyzing hydrogen bonding interactons, quantum theory of atoms in molecules was used. In this method, the nature of interaction is classified whether it is covalent, partially covalent or noncovalent. According to the results it was observed that the escitalopram under attack by ethanol shows quite different chemical properties which must be taken into account when used together with alcohol.

Synthesis, Crystallographic Structure, Stability, and HSA-Binding Affinity of a Novel Copper(II) Complex with Pyridoxal-Semicarbazone Ligand

Copper–semicarbazone ligands have been extensively investigated for several medicinal applications. In this contribution, a novel copper(II) complex with a pyridoxal–semicarbazone ligand, [Cu(PLSC)Cl(H2O)](NO3)(H2O), was synthesized and characterized by X-ray crystallography, elemental analysis, UV-VIS, and FTIR spectroscopies. The stabilization interactions within the structure were assessed using the Hirshfeld surface analysis. The crystallographic structure was optimized at the B3LYP/6-311++G(d,p)(H,C,N,O)/LanL2DZ(Cu) level of theory. A comparison between the experimental and theoretical bond lengths and angles was undertaken to verify the applicability of the selected level of theory. The obtained high correlation coefficients and low mean absolute errors confirmed that the optimized structure is suitable for further investigating the interactions between donor atoms and copper, along with the interactions between species in a neutral complex, using the Quantum Theory of Atoms in Molecules approach. The electrostatic potential surface map was used to reveal distinct charge distributions. The experimental and calculated FTIR spectra were compared, and the most prominent bands were assigned. The interactions with human serum albumin (HSA) were assessed by spectrofluorometric titration. The spontaneity of the process was proven, and the thermodynamic parameters of binding were calculated. Molecular docking analysis identified the most probable binding site, providing additional insight into the nature of the interactions.

Physical and Surface Chemical Analysis of High-Quality Antimicrobial Cotton Fabrics Functionalized with CuOx Grown In Situ from Different Copper Salts: Experimental and Theoretical Approach.

The emergence of harmful microorganisms poses a public health challenge. Antimicrobial cotton textiles with semiconductor oxides offer a promising solution to mitigate pathogen spread. Here, we study the physicochemical interactions between copper oxides (CuOx) and cellulose in cotton fiber functionalized with these same oxides for antimicrobial properties. Fabrics were treated by an exhaust dyeing method using a 2% on-weight-of-fiber (owf) copper precursor with acetate, nitrate, and sulfate anions. Nonfunctionalized (NF) fabrics with a yellow hue turned reddish brown after the functionalization with CuOx. Copper (Cu) content in the functionalized fabrics increased by 27-40% compared to 0.009% in the NF fabric. The percentage of Cu exhaustion was higher with the acetate salt than nitrate and sulfate, resulting in darker fabrics according to colorimetry. XPS analysis of cotton suggests a chemical interaction between the hydroxyl groups of cellulose and CuOx. The nature and strength of potential interactions between Cu cations and the cellulose surface were investigated using the quantum theory of atoms in molecules and crystals. Based on topological parameters, the interaction between Cu and the hydroxyl groups of cellulose exhibits a covalent character. Furthermore, the XPS spectrum of functionalized fabrics exhibited peaks corresponding to Cu1+ and Cu2+ ions, assigned to the Cu2O and CuO phases, respectively. Electron diffraction patterns confirmed copper oxide crystalline phases, where Cu2O was indexed in the cuprite system and CuO in the tenorite system. Regarding morphology, no defined forms of CuOx were observed on the cotton surface, regardless of the salt used for treatment. Likewise, all fabrics functionalized with CuOx inhibited the growth of Escherichia coli and Pseudomonas aeruginosa strains by more than 99%. Therefore, cotton fabrics functionalized with a mixture of Cu2O and CuO have excellent antimicrobial properties that can be used in environments with a high bacterial load.

Interaction of CO, CO2, CSO, H2O, N2O, NO, NO2, O2, ONH, and SO2 gases onto BNNT(m,n)_x, (m = 3, 5, 7; n = 0, 3, 5, 7; x = 3-9).

This research investigates two critical areas, providing valuable insights into the properties and interactions of boron nitride nanotubes (BNNTs). Initially, a variety of BNNT structures (BNNT(m,n)_x, where m = 3, 5, 7; n = 0, 3, 5, 7; x = 3-9) with different lengths and diameters are explored to understand their electronic properties. The study then examines the interactions between these nanotubes and several gases (CO, CO2, CSO, H2O, N2O, NO, NO2, O2, ONH, and SO2) to identify the most stable molecular configurations using the bee colony algorithm for global optimization. The primary findings highlight the impact of nanotube diameter on these properties. It was observed that smaller diameters result in a larger energy gap due to increased quantum confinement. Significant charge transfer, especially with CO, was detected, affecting the electronic structure of the nanotubes. The study highlighted that BNNTs exhibit the strongest adsorption tendencies for NO₂, O₂, and SO₂. These findings underscore the critical roles of nanotube diameter and charge transfer in sensor applications and demonstrate the comprehensive utility of various analytical methods in understanding BNNT-gas interaction mechanisms. The research employs a comprehensive computational framework based on density functional theory (DFT). Various DFT methods, such as PBE0, B3LYP(GD3BJ), CAM-B3LYP, HSE06i, M06-2X, and ωB97XD functionals, are utilized along with the Def2tzvp basis set for the calculations. Structural optimizations are performed to ensure accuracy, and modifications to the energy gaps are analyzed using conceptual DFT. Additionally, Total Density of States (TDOS) analyses are conducted. Charge transfer mechanisms are investigated through Natural Bond Orbital (NBO) analysis. The interactions between gases and nanotubes are characterized at critical points using the Quantum Theory of Atoms in Molecules (QTAIM) framework.

A real-time deep learning model to narrow the gap between atomic scanning transmission electron microscopy and theory calculations: Recognition, reconstruction, and simulation

A real-time deep learning model to narrow the gap between atomic scanning transmission electron microscopy and theory calculations: Recognition, reconstruction, and simulation

Insights Into the Uranium Phosphine Bonds in [UCp3(PR3)]: A Combined Molecular Orbital, QTAIM and EDA‐NOCV Study

AbstractA series of ten uranium(III) complexes with cyclopentadienyl and monodentate phosphine ligands [UCp3(PR3)] with R=Me, Et, nPr, iPr, tBu, Ph, Cy, F and CF3 was investigated using density functional theory calculations. The ligand dissociation energies were calculated, as well as bonding analysis of the uranium‐phosphorus bond performed, using molecular orbitals, bond orders, quantum theory of atom in molecules (QTAIM) analysis and energy decomposition analysis with natural orbitals for chemical valence (EDA‐NOCV). It was found that the bond orders correlate well with the U−P bond lengths and phosphine cone angles, indicating a large influence of phosphine sterics on the bond properties. All bonding analyses show partial covalent character of the U−P bond, which is most pronounced for PF3 and least for PtBu3. π‐Backbonding was found for the most π‐acidic phosphine ligands. No good correlation was found between the ligand dissociation energies and bond metrics.

Controlled tuning of HOMO and LUMO levels in supramolecular nano-Saturn complexes.

Optoelectronics usually deals with the fabrication of devices that can interconvert light and electrical energy using semiconductors. The modification of electronic properties is crucial in the field of optoelectronics. The tuning of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) and their energy gaps is of paramount interest in this domain. Herein, three nano-Saturn supramolecular complex systems are designed, i.e., Al12N12@S-belt, Mg12O12@S-belt, and B12P12@S-belt, using S-belt as the host and Al12N12, Mg12O12, and B12P12 nanocages as guests. The high interaction energies ranging from -22.03 to -63.64 kcal mol-1 for the complexes demonstrate the stability of these host-guest complexes. Frontier molecular orbital (FMO) analysis shows that the HOMO of the complexes originates from the HOMO of the host, and the LUMO of the complexes originate entirely from the LUMO of the guests. The partial density of states (PDOS) analysis is in corroboration with FMO, which provides graphical illustration of the origin of HOMO and LUMO levels and the energy gaps. The shift in the electron density upon complexation is demonstrated by the natural bond orbital (NBO) charge analysis. For the Al12N12@S-belt and B12P12@S-belt complexes, the direction of electron density shift is towards the guest species, as indicated by the overall negative charge on encapsulated Al12N12 and B12P12. For the Mg12O12@S-belt complex, the overall NBO charge is positive, elaborating the direction of overall shift of electronic density towards the S-belt. Electron density difference (EDD) analysis verifies and corroborates with these findings. Noncovalent interaction index (NCI) and quantum theory of atoms in molecules (QTAIM) analyses signify that the complexes are stabilized via van der Waals interactions. Absorption analysis explains that all the complexes absorb in the ultraviolet (UV) region. Overall, this study explains the formation of stable host-guest supramolecular nano-Saturn complexes along with the controlled tuning of HOMO and LUMO levels over the host and guests, respectively.