Quantum Theory Of Atoms In Molecules Research Articles

Theoretically designed M@diaza[2.2.2]cryptand complexes: the role of non-covalent interactions in promoting NLO properties of organic electrides

ABSTRACT Organic excess electron compounds with significant nonlinear optical (NLO) properties are widely employed in optoelectronic applications. Herein, single-alkali metals with diaza[2.2.2] cryptand (M@crypt,M=Li, Na, and K) are investigated for optoelectronic and NLO properties by using the density functional theory. Thermodynamic and kinetic stabilities of present complexes are computed through interaction energy (Eint) and ab-initio molecular dynamic (AIMD) simulations. M@crypt complexes carry excess electrons and mimic molecular electrides. Quantum theory of atoms in molecules (QTAIM) analysis and reduced density gradient (RDG) spectra demonstrate the roles of the weak van der Waals (vdW) interactions between metal and complexant. The remarkable hyperpolarizability (βo) value up to 1.41 × 106 au may be credited to the presence of loosely bound excess electrons. The hyper Rayleigh scattering hyperpolarizability (βHRS) is recorded up to 1.31 × 106 au for the K@crypt. Furthermore, frequency-dependent first-order and second-order hyperpolarizability is more prominent at the applied frequency of ω = 0.042823 au. The electron localizing function (ELF) and localized orbital locator (LOL) analysis further disclose the nature of interaction between alkali metal and complexant. The TD-DFT method is adopted to get excited state parameters and absorbance properties. An electron density difference map (EDDM) is exploited to evaluate the orbital contributions in excited states. Hence, the studied electride may become a promising candidate for NLO materials. We anticipate that the present work will provide insight into further development of molecular electride for optoelectronic applications.

Supramolecular Assemblies in Mn(II) and Zn(II) Metal–Organic Compounds Involving Phenanthroline and Benzoate: Experimental and Theoretical Studies

Two new Mn(II) and Zn(II) metal–organic compounds of 1,10-phenanthroline and methyl benzoates viz. [Mn(phen)2Cl2]2-ClBzH (1) and [Zn(4-MeBz)2(2-AmPy)2] (2) (where 4-MeBz = 4-methylbenzoate, 2-AmPy = 2-aminopyridine, phen = 1,10-phenanthroline, 2-ClBzH = 2-chlorobenzoic acid) were synthesized and characterized using elemental analysis, TGA, spectroscopic (FTIR, electronic) and single crystal X-ray diffraction techniques. The crystal structure analysis of the compounds revealed the presence of various non-covalent interactions, which provides stability to the crystal structures. The crystal structure analysis of compound 1 revealed the formation of a supramolecular dimer of 2-ClBzH enclathrate within the hexameric host cavity formed by the neighboring monomeric units. Compound 2 is a mononuclear compound of Zn(II) where flexible binding topologies of 4-CH3Bz are observed with the metal center. Moreover, various non-covalent interactions, such as lp(O)-π, lp(Cl)-π, C–H∙∙∙Cl, π-stacking interactions as well as N–H∙∙∙O, C–H∙∙∙O and C–H∙∙∙π hydrogen bonding interactions, are found to be involved in plateauing the molecular self-association of the compounds. The remarkable enclathration of the H-bonded 2-ClBzH dimer into a supramolecular cavity formed by two [Mn(phen)2Cl2] complexes were further studied theoretically using density functional theory (DFT) calculations, the non-covalent interaction (NCI) plot index and quantum theory of atoms in molecules (QTAIM) computational tools. Synergistic effects were also analyzed using molecular electrostatic potential (MEP) surface analysis.

Investigation of drug delivery capability of single-walled carbon and boron-nitride nanotubes, boron-nitride (B16N16), and C32 fullerenes as nanocarriers of captopril drug; DFT study

Density functional theory (DFT) calculations were performed on M062X/6-31G (d) and M062X/6-311G (d, p) surfaces to investigate the interaction of captopril molecules with single-walled carbon nanotubes (SWCNT) and C32 nanoclusters. In order to enhance adsorption, a doping method was employed, and structures of single-walled boron nitride nanotubes (SWBNNT) and boron nitride nanoclusters (B16N16) were selected for improved drug delivery purposes in this study. The adsorption energy of captopril on the nanostructures was calculated in both phases. In both phases, captopril adsorption energy on nanostructures was calculated. The negative values of adsorption energy showed that the interaction between captopril and nanostructures is exothermic. The adsorption energy values were higher in the gas phase compared to the aqueous phase, indicating a stronger interaction in the gas phase. The density of states (DOS) study was employed to evaluate the effect of molecular adsorption on the electronic properties of nanostructures. The results revealed that the B16N16 nanocluster approached the Fermi level more closely after drug adsorption compared to other nanostructures. Quantum Theory of Atoms in Molecules (QTAIM) calculations showed that there is a weak interaction between captopril and both nanostructures. Based on the adsorption energy values obtained from both methods, the interaction between captopril and SWCNT was found to be stronger than that between captopril and SWBNNT, whereas the interaction in the B16N16 nanocluster was found to be equal to that in C32-fullerene. Significant changes in ΔEg values were observed for Captopril@SWCNT and Captopril@B16N16-fullerene in each method, indicating the conductivity of these two structures increased more after captopril adsorption compared to other nanostructures. Therefore, SWBNNT and B16N16-fullerene can serve as captopril nanosensors.

Determination of GaN nanosensor for scavenging of toxic heavy metal ions (Mn2+, Zn2+, Ag+, Au3+, Al3+, Sn2+) from water: Application of green sustainable materials by molecular modeling approach

Gallium nitride nanocage (GaN_NC) can select toxic heavy metals from water. Therefore, it has been found a selective competition for metal cations in the GaN_NC. The electromagnetic and thermodynamic attributes of heavy metals cations-trapped gallium nitride nanocage (GaN_NC) was depicted by material modeling. The data display that heavy metals cations-trapped in the GaN_NC system are resistant materials, with the firm adsorption zone in the center of the cage. Furthermore, charge transfer from GaN_NC to the heavy metals cations demonstrates clear n-type adsorbing manner. The encapsulation of heavy metals cations occurs via chemisorption. In this article, the behavior of trapping of heavy metal ions of Mn2+, Zn2+, Ag+, Au3+, Al3+ and Sn2+ by gallium nitride nanocone for sensing the water metal cations was observed. The nature of covalent features for these complexes has represented the analogous energy amount and vision of the PDOS for the p states of N and d states of heavy metal cations of Mn2+, Zn2+, Ag+, Au3+, Al3+ and Sn2+ through water treatment. The partial density of states (PDOS) can also evaluate an appointed charge group between Mn2+, Zn2+, Ag+, Au3+, Al3+, Sn2+ and GaN_NC which indicate the most stable complex of metallic visage and a certain degree of covalent specifications between heavy metals cations and gallium nitride nanocage. Furthermore, the NMR analysis indicated the notable peaks surrounding metal elements of Mn2+, Zn2+, Ag+, Au3+, Al3+ and Sn2+ through the trapping in the GaN_NC during ion detection and removal from water; however, it can be seen some fluctuations in the chemical shielding treatment of isotropic and anisotropy tensors. Based on the results in this research, the selectivity of metal ion adsorption by gallium nitride nanocage (ion sensor) has been approved as: Ag+ ˃ Au3+ ˃ Mn2+ ≫ Zn2+ ˃ Sn2+ ˃ Al3+. Using quantum theory of atoms in molecules (QTAIMs) method, intermolecular interactions and corresponding parameters at critical bonding points were also investigated.

Efficient wastewater decontamination using magnetic bentonite-alginate beads: A comprehensive study of adsorption dynamics, regeneration, and molecular interactions

This study enhances wastewater treatment methodologies by developing magnetic bentonite-alginate beads (MBent-A beads) for adsorbing methylene blue (MB) from aqueous solutions. Experimental and computational analyses were employed to evaluate the beads' adsorption efficiency, utilizing characterization techniques including Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), point of zero charge (pHpzc), Brunauer-Emmett-Teller method (BET), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) to examine the composite’s morphology and chemistry. Findings reveal a significant adsorption capacity with the beads' specific surface area at 3.94 m2/g and a maximum adsorption capacity of 774.32 mg/g. Adsorption kinetics adhered closely to the pseudo-second-order model, indicating a rapid adsorption process, while Langmuir isotherm analysis confirmed a uniform monolayer adsorption and temperature-dependent capacities. Thermodynamic analysis showed the adsorption process to be spontaneous and exothermic, reflecting a strong affinity between MB molecules and the bead surface. The beads demonstrated durability with more than 90% removal efficiency after five regeneration cycles, highlighting a minimal decrease from 98.54% to 90.60%. In-depth theoretical investigations using density functional theory (DFT), frontier molecular orbital (FMO), reduced density gradient (RDG), and quantum theory of atoms in molecules (QTAIM) analyses identified van der Waals forces and hydrogen bonding as primary interactions driving the adsorption. The synthesis of MBent-A beads and their confirmed efficacy in dye adsorption integrates experimental research with theoretical modeling, offering a robust solution for treating dye-contaminated wastewater and underlining the potential of MBent-A beads in environmental remediation.

Selective Gold Precipitation by a Tertiary Diamide Driven by Thermodynamic Control.

The simple diamide ligand L was previously shown to selectively precipitate gold from acidic solutions typical of e-waste leach streams, with precipitation of gallium, iron, tin, and platinum possible under more forcing conditions. Herein, we report direct competition experiments to afford the order of selectivity. Thermal analysis indicates that the gold-, gallium-, and iron-containing precipitates present as the most thermodynamically stable structures at room temperature, while the tin-containing structure does not. Computational modeling established that the precipitation process is thermodynamically driven, with ion exchange calculations matching the observed experimental selectivity ordering. Calculations also show that the stretched ligand conformation seen in the X-ray crystal structure of the gold-containing precipitate is more strained than in the structures of the other metal precipitates, indicating that intermolecular interactions likely dictate the selectivity ordering. This was confirmed through a combination of Hirshfeld, noncovalent interaction (NCI), and quantum theory of atoms in molecules (QTAIM) analyses, which highlight favorable halogen···halogen contacts between metalates and pseudo-anagostic C-H···metal interactions in the crystal structure of the gold-containing precipitate.

DFT-D3 and TD-DFT Studies of the Adsorption and Sensing Behavior of Mn-Phthalocyanine toward NH3, PH3, and AsH3 Molecules.

This study employs density functional theory (DFT) calculations at the B3LYP/6-311+g(d,p) level to investigate the interaction of XH3 gases (X = N, P, As) with the Mn-phthalocyanine molecule (MnPc). Grimme's D3 dispersion correction is applied to consider long-range interactions. The adsorption behavior is explored under the influence of an external static electric field (EF) ranging from -0.514 to 0.514 V/Å. Chemical adsorption of XH3 molecules onto the MnPc molecule is confirmed. The adsorption results in a significant decrease in the energy gap (Eg) of MnPc, indicating the potential alteration of its optical properties. Quantum theory of atoms in molecules (QTAIM) analysis reveals partially covalent bonds between XH3 and MnPc, and the charge density differenc (Δρ) calculations suggest a charge donation-back donation mechanism. The UV-vis spectrum of MnPc experiences a blue shift upon XH3 adsorption, highlighting MnPc's potential as a naked-eye sensor for XH3 molecules. Thermodynamic calculations indicate exothermic interactions, with NH3/MnPc being the most stable complex. The stability of NH3/MnPc decreases with increasing temperature. The direction and magnitude of the applied electric field (EF) play a crucial role in determining the adsorption energy (Eads) for XH3/MnPc complexes. The Eg values decrease with an increasing negative EF, which suggests that the electrical conductivity (σ) and the electrical sensitivity (ΔEg) of the XH3/MnPc complexes are influenced by the magnitude and direction of the applied EF. Overall, this study provides valuable insights into the suggested promising prospects for the utilization of MnPc in sensing applications of XH3 gases.

The future of drug Monitoring: Highly selective ratiometric sensing of mefenamic acid by simple AIEE active probe supported through Extensive fluorometric and DFT studies

Over intake of mefenamic acid (MA) cause morbidity, mortality, liver damage, and hepatic necrosis. For this reason, it is of great importance to discover novel methodologies that provide sharp detection timing, improved sensing efficiency, and profound reproducibility in MA detection. In our current research, we synthesized a naphthalic anhydride based probe PPN which revealed excellent sensing potential towards MA. Probe PPN exhibited ratiometric fluorescence against MA based on complex formation and photoinduced electron transfer (PET) process. Detection mechanism was verified through Density functional theory (DFT) calculations and 1H NMR titration experiments. The type of interaction between probe PPN and MA was investigated through quantum theory of atoms in molecules (QTAIM) analysis and noncovalent interaction (NCI) analysis and was further evaluated via spectroscopic analysis. Moreover, the probe PPN was practically employed to the sensing of MA in artificial urine, pharmaceutical wastewater, and blood samples. Probe PPN is the most streamlined probe designed ever for the sensing of MFA in complex environments with extreme selectivity and sensitivity.

Interaction between hydroxymethanesulfonic acid and several organic compounds and its atmospheric significance

The interactions of the micro-mechanism of hydroxymethanesulfonic acid (HMSA) with the typical small organic molecule in atmospheric (X = methanol, formaldehyde, formic acid, methyl formate, dimethyl ether, acetone) has been investigated by density functional theory (DFT), quantum theory of atoms in molecules (QTAIM), Generalized Kohn-Sham Enery Decomposition Analysis (GKS−EDA) and the atmospheric clusters dynamic code (ACDC). The results of DFT show that the stable six− to eight−membered ring structures are easily formed in HMSA−X clusters. According to the topological analysis results of the AIM theory and the IRI method, a strong hydrogen bonding interaction is present in the complex. GKS−EDA results show that electrostatic energy is the main contributor to the interaction energy as it accounts for 51 %–55 % of the total attraction energy. The evaporation rates of HMSA−HMSA and HMSA−HCOOH clusters were much lower than those of the other HMSA complexes. In addition, the Gibbs energy of formation (ΔG) of HMSA−X dimers is investigated under atmosphere temperature T = 217–298 K and p = 0.19–1.0 atm, the ΔG decreased with decreasing of the atmosphere temperature and increased with the decrease of atmospheric pressure, indicating that the low temperature and high pressure may significantly facilitate to the formation of dimers.

Structural and electronic assessments of Thiamazole adsorption on the transition metal doped fullerenes as a potential smart drug delivery platform

Adsorption of Thiamazole (TZOL, a medication to treat hyperthyroidism) on the transition metal (TM) doped fullerenes (MF) is investigated to gain insight into the potential development of a smart drug delivery platform. In this computational study, molecular models of adsorbed TZOL on TM-doped and undoped fullerenes were optimized and their structural and electronic features were evaluated using density functional theory (DFT) and the quantum theory of atoms in molecules (QTAIM). The TM-doped models were created by substituting a carbon atom of the original fullerene (F) with a metal atom of the first row of transition metals, yielding ten different MF models. TZOL adsorbate (TZOL@MF) showed stronger interaction through its sulphur group binding to the doped metal in comparison to the original carbon fullerene, i.e. TZOL@F. Our calculations indicate that the most stable conjugate system was TZOL on the vanadium-doped fullerene (TZOL@VF) with a free energy of −37.78 kcal/mol followed by Mn-doped fullerene (−36.86 kcal/mol) while that of all undoped fullerene is −9.18 kcal/mol. The impact of water on the stability of TZOL@MFs was investigated and results show that aqueous phases are even more stable than the gaseous phase, again, with TZOL@VF being the most stable of the conjugate adsorbate/adsorbent pair. Frontier molecular orbital analysis showed significant changes of electronic environment from the MF adsorbent to the TZOL@MF conjugated models. HOMO and LUMO levels and their gap energy detected the variations of electronic environment upon adsorption of TZOL, making this system a potential drug delivery platform capable of detection of loaded and released drug molecules.

Bond analysis in meta- and para-substituted thiophenols: overlap descriptors, local mode analysis, and QTAIM.

This study delves into the chemical nuances of thiophenols and their derivatives through a comprehensive computational analysis, moving beyond traditional energetic perspectives such as bond dissociation enthalpy and S-H dissociation dynamics. By employing the overlap model along with its topological descriptors (OP/TOP), quantum theory of atoms in molecules (QTAIM), and local vibrational mode (LVM) theories, the research provides a deeper understanding of the S-H and C-S bonding scenarios in substituted thiophenols. The investigation follows the electron-donating capacity of S-H substituent variation with the nature and positioning of other ring substituents. Energy profile analyses indicate distinct stability differences in the cis and trans conformations of meta- and para-PhSH systems, influenced by the electron-donating strength of these substituents. The study also uncovers significant variations in S-H bond distances and descriptor values, particularly in para-substituted PhSH, reflecting the influence of electron-donating or withdrawing substituents. In contrast, alterations at the meta-position show minimal effects on C-S bond descriptors, while para-substitutions markedly influence C-S bond characteristics, demonstrating a clear correlation with the electron-donating or withdrawing capabilities of the substituents. This research sheds light on the intricate bond dynamics in aromatic systems with diverse substituents, highlighting the complex interaction between electronic effects and molecular conformation. The study employs the B97X-D/Def2TZVP level of theory for molecular geometries, ensuring accurate characterization of structures as true minima via analytical harmonic frequency determination. The electronic properties of S-H and C-S bonds in variously substituted thiophenols were analyzed using OP/TOP, QTAIM, and LVM methodologies. Computational processes, including conformational scans, geometry optimizations, and vibrational frequency calculations, were conducted using Gaussian 09, with ultra-fine integration grids and tight convergence criteria for the SCF procedure. Bond descriptors were computed utilizing ChemBOS, Multiwfn, and LModeA software, providing a robust and detailed examination of bond properties.

Synthesis and Structural Studies of peri-Substituted Acenaphthenes with Tertiary Phosphine and Stibine Groups.

Two mixed peri-substituted phosphine-chlorostibines, Acenap(PiPr2)(SbPhCl) and Acenap(PiPr2)(SbCl2) (Acenap = acenaphthene-5,6-diyl) reacted cleanly with Grignard reagents or nBuLi to give the corresponding tertiary phosphine-stibines Acenap(PiPr2)(SbRR') (R, R' = Me, iPr, nBu, Ph). In addition, the Pt(II) complex of the tertiary phosphine-stibine Acenap(PiPr2)(SbPh2) as well as the Mo(0) complex of Acenap(PiPr2)(SbMePh) were synthesised and characterised. Two of the phosphine-stibines and the two metal complexes were characterised by single-crystal X-ray diffraction. The peri-substituted species act as bidentate ligands through both P and Sb atoms, forming rather short Sb-metal bonds. The tertiary phosphine-stibines display through-space J(CP) couplings between the phosphorus atom and carbon atoms bonded directly to the Sb atom of up to 40 Hz. The sequestration of the P and Sb lone pairs results in much smaller corresponding J(CP) being observed in the metal complexes. QTAIM (Quantum Theory of Atoms in Molecules) and EDA-NOCV (Energy Decomposition Analysis employing Naturalised Orbitals for Chemical Valence) computational techniques were used to provide additional insight into a weak n(P)→σ*(Sb-C) intramolecular bonding interaction (pnictogen bond) in the phosphine-stibines.

Theoretical Spectroscopic Study of Normal Raman and Charge Transfer Surface-Enhanced Raman Scattering (SERS) Spectra of the Adsorbed l- and d-Cysteine on the Chiral Au34 and Ag4@Au30 Nanoclusters: Chirality Discrimination.

In this work, the discrimination of the enantiomers of cysteine (l- and d-CYS) using the chiral Au34 and Ag4@Au30 clusters was theoretically investigated in the gas phase and water. Two modes were considered for the interaction of each enantiomer with the clusters (via only its S atom or its S atom and NH2 group, simultaneously). The interaction energy (Eint) and adsorption energy (Ead) for the complexation of each enantiomer with the clusters for each interaction mode were calculated. Considering the calculated interaction energies, the interaction of d-CYS with Au34 is stronger than that of l-CYS with the same cluster. Also, it was observed that the substitution of the Au4 core of the Au34 cluster with the Ag4 cluster caused the increase of the interaction energy of l-CYS with the Ag4@Au30 cluster compared to the Au34 cluster, while the reverse trend was observed for d-CYS. Quantum theory of atoms in molecules (QTAIM) analysis was employed to calculate the interaction paths and their related bond critical points (BCPs) between the CYS enantiomers and the clusters to explain the difference between the interaction energy of the enantiomers with the clusters. The IR, normal Raman (NR), and surface-enhanced Raman scattering (SERS) spectra of the enantiomers interacting with the Au34 and Ag4@Au30 clusters were calculated, and the discrimination between l-CYS and d-CYS using the calculated spectra was explained. It was found that the discrimination of the enantiomers based on their interaction with the clusters is controlled by the charge transfer between the enantiomers and the clusters.

Comparison of Cu3, Cu5, and Cu7 clusters as potential antioxidants: A theoretical quest.

Herein, we compare and contrast the dual roles of Cun clusters (n = 3, 5, and 7 atoms) in scavenging or generating RO• free radicals from ROH at the theoretical levels (where R = H, methyl, ethyl, n-propyl, i-propyl, n-butyl, t-butyl, and phenyl). This investigation is performed in water media to mimic the actual environment in the biological system. In the presence of the Cun clusters, bond dissociation energy (BDE) of RO-H and R-OH is reduced. This is clear evidence for the increased possibility of both the RO-H and R-OH bonds breakage and scavenging of RO• radicals. The nature of anchoring bonds responsible for the interaction of Cun clusters with ROH and RO• are interpreted using the quantum theory of atoms in molecules (QTAIM) and the natural bond orbital (NBO) analysis. The DFT results indicate that the O•⋅⋅⋅•Cu bond is stronger and has more covalent character in RO•⋅⋅⋅•Cun radical complexes than in ROH⋅⋅⋅•Cun. Therefore, the interactions of Cun clusters with RO• radicals (antioxidant) are more pronounced than their interactions with ROH non-radicals (pro-oxidant). The GAMESS software package was utilized in this paper. The B3LYP and M06 functions with the 6-311 + + G(d,p), and LANL2DZ/SDD basis sets was used to perform the important geometrical parameters of RO•⋅⋅⋅•Cun and ROH⋅⋅⋅•Cun, binding energy (Eb), and bond dissociation energy (BDE).

Structural, theoretical and biological studies on Cu2+ and Co2+ complexes of new thiosemicarbazone ligands

Two sets of Cu2+, and Co2+ complexes of two 4 – Pyridyl thiosemicarbazone derivatives ligands symbolized by (H3L1), and (H3L2), were synthesized and examined utilizing different analytical, and spectroscopic techniques such as (FT-IR, Elemental Analysis, Magnetic studies, PXRD, UV–Vis, and GCMS–). Thermal stability along with kinetic parameters of both Co2+ complexes were studied. 1H NMR technique was used to confirm the structures of both ligands. The proposed geometries of complexes were recognized by density function theory (DFT) calculations using Material software. Additionally, Quantum theory of atoms in molecules (QTAIM) topological analyses for both ligands were obtained using Multiwfn software. The cyclic voltammogram revealed that copper ions are electroactive and exhibited two reduction waves. Fluorescence studies for both ligands showed a direct increase in the intensity of emissions because of increasing Co2+ concentration in solution. Moreover, several biological evaluations were carried out for all six compounds to evaluate their potential use as biological agents, including antioxidant activity using 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radical scavenging approach, anti-microbial activity against Staphylococcus aureus, Escherichia coli, and Candida albicans, DNA degradation activity, in addition to anticancer activity, along with molecular docking theoretical study against MCF-7 breast cancer cell line to determine the compounds ability to act as antitumor. It was found that the investigated compounds (especially the free ligands) have beneficial effects such as antimicrobial, antitumor, and DNA degradation agents. Furthermore, Co2+ complex (2) has the highest ABTS scavenging activity.

Selective Synthesis of Functionalized 3(2H)‐Furanones via Tandem Michael Addition/Rearrangement/Cyclization Reaction of Aliphatic Alkynones: A Combined Experimental and Theoretical Study

AbstractA novel catalyst‐ and solvent‐controlled dimerization of aliphatic alkynones through tandem Michael addition/rearrangement/cyclization sequence has been developed. The elaborated protocol provides a convenient chemo‐, regio‐ and stereoselective access to rare 3(2H)‐furanones decorated with 2‐exo‐methylene and 4‐ethenyl functionalities. A comprehensive density functional theory (DFT) study of possible reaction mechanism including ab initio molecular dynamics (AIMD) simulations and quantum theory of atoms in molecules (QTAIM) analysis of various substrate/catalyst/solvent complexes has revealed the Janus‐like behavior of the employed sodium tert‐butoxide/toluene system that is responsible both for the chemoselectivity of the initial addition step and the inhibition of the final cyclization step.

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.