Design, Transport/Molecular Scale Electronics, Electric Properties, and a Conventional Quantum Study of a New Potential Molecular Switch for Nanoelectronic Devices.

In this study, we examined the influence of an external electric field applied in two directions: horizontal (X-axis) and vertical (Y-axis) on the electronic and vibrational properties of a field-effect molecular switch, denoted as M. We employed density functional theory and quantum theory of atoms in molecules for this analysis. The current-voltage (I-V) characteristic curve of molecular switch system M was computed by applying the Landauer formula. The results showed that the switching mechanism depends on the direction of the electric field. When the electric field is applied along the X-axis and its intensity is around 0.01 au, OFF/ON switching mechanisms occur. By utilizing electronic localization functions and localized-orbital locator topological analysis, we observed significant intramolecular electronic charge transfer "back and forth" in Au-M-Au systems when compared to the isolated system. The noncovalent interaction revealed that the Au-M-Au complex is also stabilized by electrostatic interactions. However, if the electric field is applied along the Y-axis, a switching mechanism (OFF/ON) occurs when the electric field intensity reaches 0.008 au. Additionally, the local electronic phenomenological coefficients (Lelec) of this field-effect molecular switch were determined by using the Onsager phenomenological approach. It can also be predicted that the molecular electrical conductance (G) increases as Lelec increases. Finally, the electronic and vibrational properties of the proposed models M and Au-M-Au exhibit a powerful switching mechanism that may potentially be employed in a new generation of electronic devices.

Antiplatelet activity and toxicity profile of novel phosphonium salts derived from Michael reaction.

In this work, five novel phosphonium salts derived from the Michael reaction were screened for their antiplatelet activity. Our findings revealed that compounds 2a, 2b, 2c, and 2d significantly inhibit platelet aggregation triggered by ADP or collagen (P < 0.001). Notably, compound 2c inhibited the arachidonic acid pathway (P < 0.001). Moreover, the selected compounds reduce CD62-P expression and inhibit GPIIb/IIIa activation. The interactions of the active compounds with their targets, ADP and collagen receptors, P2Y12 and GPVI respectively were investigated in silico using molecular docking studies. The results revealed a strong affinity of the active compounds for P2Y12 and GPVI. Additionally, cytotoxicity assays on platelets, erythrocytes, and human embryonic kidney HEK293 cells showed that compounds 2a, 2c and 2d were non-toxic even at high concentrations. In summary, our study shows that phosphonium salts can have strong antiplatelet power and suggests that compounds 2a, 2c and 2d could be promising antiplatelet agents for the management of cardiovascular diseases.

Structures and stability of K+ cation solvated in Arn clusters.

The solvation of K+ cation plays an important role in various phenomena such as biological procedures, geological time, and archaeological properties. Monte Carlo (MC) simulation and DFT method are employed to study the structural and energetic characteristics of the K + Arn (n = 1-14) clusters. The potential model (PM) and the Basin-Hopping (BH) method are the foundation of the MC simulation. The pairwise PM (PW-PM) is improved by introducing the N-body interactions via the polarizable potential model (PPM). On the other side, the DFT functional M05-2X, combined with the 6-311++G(3d2f,2p) basis set, and the Grimme dispersion correction GD3 was used to deeply investigate the geometrical properties and the relative stability of the K + Arn clusters. Starting from n = 12, a structural transition from square antiprism (SA) to icosahedron (ICOS) form is detected. Additionally, the PPM allows us to examine the largest sizes (n = 15-54). Herein, the first ICOS layers are found for n = 12 and 54 cluster sizes, respectively. The binding energy and the second energy difference as a function of cluster size are used to evaluate the relative stability of K + Arn clusters. The obtained data are in concordance with the available results in the literature.

Design, synthesis, and density functional theory studies of a new selective chemosensor for Pb2.

Herein, we have focused on a new colorimetric ligand synthesized from the reaction of 2-hydroxy-5-methylbenzene-1,3-dialdehyde with 2-amino-thiophenol, and investigated its activity as a sensor. In this regard, the sensory activity of the ligand towards different ions (Mn2+, Cu2+, Co2+, Fe2+, Fe3+, Zn2+, Ni2+, Cd2+, Ag+, Na+, Cs+, Mg2+, Al3+, Ba2+, K+, and Pb2+) was studied. The specificity of ion bindings is discussed through UV-Vis analysis. The ligand that was synthesized showed remarkable sensitivity, with a detection limit of 0.001 ppb. Additionally, the presence of Pb2+ ions can be visually detected through a color change from colorless to yellow. In the last part of this work, we seek to predict the available experimental measurements. Density functional theory (DFT) and quantum theory of atoms in molecules (QTAIM) are employed to examine the bonding between the ligand and the Pb2+ ion. The effect of water solvent was thoroughly examined for all the steps via the conductor-like Polarizable Continuum Model (CPCM). The theoretical findings revealed that electronic properties, including energy gap, adsorption energy, charge/energy transfer, and optical characteristics, undergo significant changes when Pb2+ cations are present. Hence, it can be inferred that the newly synthesized chemosensor (NC) is highly efficient in detecting Pb2+.

Copper-Catalyzed Asymmetric Hydroboration Reaction of Novel Methylene Isoindolinone Compounds through Microwave Irradiation and Their Antileishmanial and Antitoxoplasma Activities.

The aim of this study was devoted into molecular docking calculations to discover the potential antileishmania and antitoxoplasma activities of newly synthesized compounds obtained by applying a practical and simple method under microwave irradiation. All these compounds were tested in vitro for their biological activity against Leishmania major promastigotes, amastigotes, and Toxoplasma gondii tachyzoites. Compounds 2a, 5a, and 5e were the most active against both L. major promastigotes and amastigotes, with IC50 values of less than 0.4 µM mL-1. Compounds 2c, 2e, 2h, and 5d had a strong antitoxoplasma activity of less than 2.1 µM mL-1 against T. gondii. We can conclude that aromatic methyleneisoindolinones are potently active against both L. major and T. gondii. Further studies for mode of action evaluation are recommended. Compounds 5c and 5b are the best drug candidates for antileishmania and antitoxoplasma due to their SI values being over 13. The docking studies of compounds 2a-h and 5a-e against pteridine reductase 1 and T. gondii enoyl acyl carrier protein reductase reveal that compound 5e may be an effective antileishmanial and antitoxoplasma drug discovery initiative.

Effective Synthesis and Biological Evaluation of Dicoumarols: Preparation, Characterization, and Docking Studies.

A series of 3,3-arylidene bis (4-hydroxycoumarins) 2 were synthesized by the reaction of aromatic aldehydes with 4-hydroxycoumarin using dodecylbenzenesulfonic acid as Brønsted acid-surfactant catalyst in aqueous media and under microwave irradiation. The present method is operationally simple and the use of water as the reaction medium makes the process environmentally benign. The epoxydicoumarins 5 were then obtained with a good yield by heating 3,3'-arylidenebis-4-hydroxycoumarins 2 in acetic anhydride. Techniques such as elemental analysis, 1H, 13C-1H NMR, and infrared spectroscopy were employed to characterize these compounds. The synthesized compounds displayed good antibacterial potential against Escherichia coli (ATCC 25988), Pseudomonas aeruginosa (ATCC 27853), Klebsilla pneumonia (ATCC 700603), Staphylococcus aureus (ATCC 29213), methicillin-resistant Staphylococcus aureus (ATCC 43300) and Candida albicans (ATCC 14053). The MIC values of 23 mg/mL for compound 5e against Escherichia coli (ATCC 25988) and 17 mg/mL for 2a were observed. Furthemore, a molecular docking simulation has been performed to evaluate the antibacterial activities and the probable binding modes of the studied compounds 2a-f and 5a-g toward the active sites of a series of well known antibacterial targets. Among the investigated compounds, the binding modes and docking scores demonstrate that 2a has the most antibacterial and antifungal activities. Additionally, DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS has been tested for their ability to scavenge hydrogen peroxide and free radicals. According to our results, these compounds exhibit excellent radical scavenging properties. Furthermore, compounds 2-5 were evaluated for anti-inflammatory activity by indirect haemolytic and lipoxygenase inhibition assays and revealed good activity.

Novel 3-phenyl-1- (alkylphenyl)-9-oxa-4-azaphenanthren-10-ones as inhibitors of some enzymes: synthesis, characterization, biological evaluation and molecular docking studies.

A series of novel 3-phenyl-1-(alkylphenyl)-9-oxa-4-azaphenanthren-10-ones and (E)-1-phenyl-3-(aryl)prop-2-en-1-ones were synthesized and characterized by IR, 1H NMR, 13C spectroscopy and elemental analysis. The synthesized Compounds 5a-f were subjected to molecular docking simulation with three proteins, namely, tyrosyl-tRNA synthetase, heme oxygenase 1 and acetylcholinesterase to evaluate the antibacterial, antioxidant and acetylcholinesterase inhibition, respectively. Moreover, the docked poses of all compounds inside the proteins were subjected to further dynamic simulation through the calculation of the binding free energy using MM-GBSA analysis. Compound 5d exhibits high potential inhibition against antibacterial, antioxidant and acetylcholinesterase activities. Compounds 3d, 3f, 5a and 5d recorded an important scavenging activity in DPPH and ABTS assays. Investigation of the anti-acetylcholinesterase activity of the synthesized compounds showed that Compounds 5a and 3d are the most potent inhibitors against AchE, with percent inhibition values of 38 and 30%, respectively.Communicated by Ramaswamy H. Sarma.

Microsolvation of lithium cation in xenon clusters: An octahedral growth pattern.

The structural and energetic proprieties for the Li + Xen (n = 1-18) clusters are investigated using both Basin-Hopping combined with Potential Model description (BH-PM) and DFT methods. A structural transition from tetrahedral (4 coordination) form to octahedral (6 coordination) one is observed for n = 6. Above this size, all structures have an octahedral core. The cubic-face-centered arrangement for xenon atoms is detected for Li + Xe14. To the best of our knowledge, the Li + Xen (n = 1-18) clusters are studied in the present work for the first time using the DFT theoretical approach. The M062X functional combined with aug-cc-pVDZ (for Li) and def2-TZVP (for Xe) basis sets reproduces accurately the CCSD(T) potential energy curve of Li + Xe system. Atom-Centered Density Matrix Propagation (ADMP) molecular dynamic calculations have been carried. Moreover, we investigate the larger sizes n = 31-35, 44, and 55 for the first time using the BH-PM theoretical approach. The closing of the first and second octahedron shells are proved for the n = 6 and 34 sizes, respectively. The relative stabilities of the Li + Xen molecules are also studied by computing the total energy, the binding energy per atoms for each size n. Then, the second energy difference between the size n and its two near neighbors allows identifying the magic number series. Our present data are analyzed, discussed and compared with the available theoretical and experimental data.

Solvation of potassium cation in helium clusters: Density functional theory versus pairwise method.

Microsolvation of a cation in helium quantum solvent is an attractive phenomenon leading generally to the formation of a strongly packed structure known as 'Snowball' feature. Here, the lowest energy structures and the relative stability of the solvated potassium cation K+ in helium clusters K+Hen up to the size n = 20 are investigated employing Density Functional Theory (DFT) and pairwise methods. The DFT calculations showed that M05-2X/6-311++G (3df, 2p) level of theory can reproduce properly the experimental data of K+He diatomic potential, whereas, in the pairwise method, the Basin-Hopping Monte Carlo (BHMC) algorithm was applied for the global optimization. The remarkable differences in the lowest energy structures computed in the frame of both methods are shown for K+He11 and K+He12 clusters. The BHMC optimization converged to an icosahedral geometry for n = 12, corresponding to the highest value of the binding energy per atom. For both methods, we have concluded that the first solvation shell is completed at the size n = 15, despite the maximum packing structure obtained at n = 17. Finally, the stability of the potassium doped helium cluster is discussed based on the Density Of States (DOS) curves.

Molecular docking studies, structural and spectroscopic properties of monomeric and dimeric species of benzofuran-carboxylic acids derivatives: DFT calculations and biological activities.

Structural optimization, molecular docking analysis, electronic and vibrational properties have been investigated for the 1-benzofuran-2-carboxylic acid (2BF) and 1-benzofuran-3-carboxylic acid (3BF) using DFT/B3LYP/6-311++G(d,p) level of theory. The theoretical parameters have a very good consistency with the experimental ones. The weak intermolecular interactions were analyzed by different tool such as: Hirshfeld surfaces, topological analysis and natural bond orbital studies. The nonlinear optical properties have been investigated. Molecular electrostatic potential and frontier molecular orbitals (FMOs) analysis have been carried out to understand the reactivity of the molecule. In addition, TD-DFT calculation is initiated to simulate the UV-vis absorption spectrum and to determine several important electronic properties like HOMO-LUMO gap energy and electronic transitions. The complete vibrational assignments and the force constants were reported for monomer and dimers of both acids. The biological activities of the tow acids have been studied via molecular docking analysis. The later calculations prove that the studied acids have an inhibitor effect against cancer and microbial diseases.

Host-guest complexation studies of NO3, NO2, CO2, and N2 gas with the calix[4]arene molecule.

Calix[n]arenes (abbreviated as CX[n]) are the macro-molecules based on phenol groups with a hydrophobic cavity to encapsulate a gas or small molecules. They are used as molecular vehicles. For instance, these molecules are used in the activation of the solubility of monomers in the specific media and in pharmaceutical drug delivery. The limit of the development of gaseous pollutants will be a vital subject in the future. The polluting gases NO3, NO2, CO2, N2, etc., need cage molecules, such as CX[4], to be encapsulated. In this report, the red shift of the H-bonding interactions of the CX[4]-gas (by adding the gas inside or outside the cavity) is clearly explained by the vibrational analysis. The electronic spectra of the complexes of CX[4] with NO3, NO2, CO2, and N2) exhibit a blue-shift pick in comparison with the ones observed for the CX[4] molecule. The electrophilic and nucleophilic sites of the stable host-guest have been investigated. Additionally, the non-covalent interactions have been calculated based on the reduced density gradient RDG and QTAIM theory.

Solvation of lithium ion in helium clusters: Structural properties and relative stabilities.

Structural study and relative stabilities of Li+-doped helium clusters Li+Hen (n = 1-18) has been reported in this work using two theoretical protocols. The first one is based on the basin-hopping optimization technique, where the total energy of each cluster is described by an additive model describing Li+-He and He-He interactions. The second one is the DFT calculations, in which the initial structures are generated by ABCluster algorithm and CALYPSO software. The CSA shape was found where the first solvation shell is completed at n = 10. The relative stabilities of Li+Hen (n = 1-18) clusters have been discussed based on the variation of the binding energy, second-order difference in energy, fragmentation energy and HOMO-LUMO energy gap as a function of the cluster size. The results showed that Li+He10 is the most stable cluster. The dipole moment is calculated and showed the polar character of the Li+Hen clusters. Finally, the interatomic interactions have been examined topologically by the means of AIM and non-covalent reduced density gradient (NC-RDG) analyses.

Role of hydrogen bonding interactions within of the conformational preferences of calix[n = 4,6,8]arene: DFT and QTAIM analysis.

Understanding the interactions of the cage molecules with a variety of invited molecules is getting very important. But, the hydrogen bonds can also play a crucial role in the interaction phenomenon. In this work, natural population analysis (NPA), chemical shifts, and atom in molecules (AIM) analysis have been used to identify the role of hydrogen bonds in the stability of CX[n] molecules. According to our calculation, the 13C NMR spectra are also sensitive to the nature of hydrogen bonds. We note that the DFT calculations have reproduced with a very good agreement, the experimentally observed chemical shifts of CX[4].

Intermolecular associations in an equimolar formamide-water solution based on neutron scattering and DFT calculations.

In the present work, we have investigated the intermolecular associations of formamide with water in an equimolar formamide-water solution (FA-Water) by means of neutron scattering in combination with density functional theory calculations. The neutron scattering data were analyzed to deduce the structure factor SM(q) and the intermolecular pair correlation function gL(r). By considering different hydrogen bonded FA-Water associations, it has been shown that some of them describe well the local order in the solution. Natural bond orbital and atoms in molecules analyses have been performed to give more insight into the properties of hydrogen bonds involved in the more probable models.

Molecular structure, vibrational spectra, AIM, HOMO-LUMO, NBO, UV, first order hyperpolarizability, analysis of 3-thiophenecarboxylic acid monomer and dimer by Hartree-Fock and density functional theory.

In this work, the molecular structure, harmonic vibrational frequencies, UV, NBO and AIM of 3-thiophenecarboxilic acid (abbreviated as 3-TCA) monomer and dimer has been investigated. The FT-IR and FT-Raman spectra were recorded. The ground-state molecular geometry and vibrational frequencies have been calculated by using the Hartree-Fock (HF) and density functional theory (DFT)/B3LYP methods and 6-311++G(d,p) as a basis set. The fundamental vibrations were assigned on the basis of the total energy distribution (TED) of the vibrational modes, calculated with VEDA program. Comparison of the observed fundamental vibrational frequencies of 3-TCA with calculated results by HF and DFT methods indicates that B3LYP is better to HF method for molecular vibrational problems. The difference between the observed and scaled wavenumber values is very small. The theoretically predicted FT-IR and FT-Raman spectra of the title compound have been constructed. A study on the Mulliken atomic charges, the electronic properties were performed by time-dependent DFT (TD-DFT) approach, frontier molecular orbitals (HOMO-LUMO), molecular electrostatic potential (MEP) and thermodynamic properties have been performed. The electric dipole moment (µ) and the first hyperpolarizability (ß) values of the investigated molecule have been also computed.

Theoretical investigation of the relative stability of Na⁺He(n) (n = 2-24) clusters: many-body versus delocalization effects.

The solvation of the Na(+) ion in helium clusters has been studied theoretically using optimization methods. A many-body empirical potential was developed to account for Na(+)-He and polarization interactions, and the most stable structures of Na(+)He(n) clusters were determined using the basin-hopping method. Vibrational delocalization was accounted for using zero-point energy corrections at the harmonic or anharmonic levels, the latter being evaluated from quantum Monte Carlo simulations for spinless particles. From the static perspective, many-body effects are found to play a minor role, and the structures obtained reflect homogeneous covering up to n = 10, followed by polyicosahedral packing above this size, the cluster obtained at n = 12 appearing particularly stable. The cationic impurity binds the closest helium atoms sufficiently to negate vibrational delocalization at small sizes. However, this snowball effect is obliterated earlier than shell completion, the nuclear wavefunctions of (4)He(n)Na(+) with n = 5-7, and n > 10 already exhibiting multiple inherent structures. The decrease in the snowball size due to many-body effects is consistent with recent mass spectrometry measurements.

Many-body effects on the structures and stability of Ba²âºXe(n) (n = 1-39, 54) clusters.

The structures and relative stabilities of mixed Ba(2+)Xe(n) (n = 1-39, 54) clusters have been theoretically studied using basin-hopping global optimization. Analytical potential energy surfaces were constructed from ab initio or experimental data, assuming either purely additive interactions or including many-body polarization effects and the mutual contribution of self-consistent induced dipoles. For both models the stable structures are characterized by the barium cation being coated by a shell of xenon atoms, as expected from simple energetic arguments. Icosahedral packing is dominantly found, the exceptional stability of the icosahedral motif at n = 12 being further manifested at the size n = 32 where the basic icosahedron is surrounded by a dodecahedral cage, and at n = 54 where the transition to multilayer Mackay icosahedra has occurred. Interactions between induced dipoles generally tend to decrease the Xe-Xe binding, leading to different solvation patterns at small sizes but also favoring polyicosahedral growth. Besides attenuating relative energetic stability, many-body effects affect the structures by expanding the clusters by a few percents and allowing them to deform more.

A complete assignment of the vibrational spectra of 2-furoic acid based on the structures of the more stable monomer and dimer.

The structural and vibrational properties of cyclic dimer of 2-furoic acid (2FA) were predicted by combining the available experimental infrared and Raman spectra in the solid phase and ab initio calculations based on density functional theory (DFT) with Pople's basis sets. The calculations show that there are two cyclic dimers for the title molecule that have been theoretically determined in the gas phase, and that only one of them, cis conformer, is present in the solid phase. The complete assignment of the 66 normal vibrational modes for the cis cyclic dimer was performed using the Pulay's Scaled Quantum Mechanics Force Field (SQMFF) methodology. Four strong bands in the infrared spectrum at 1583, 1427, 1126 and 887 cm(-1) and the group of bands in the Raman spectrum at 1464, 1452, 1147, 1030, 885, 873, 848, 715 and 590 cm(-1) are characteristic of the dimeric form of 2FA in the solid phase. In this work, the calculated structural and vibrational properties of both dimeric species were analyzed and compared between them. In addition, three types of atomic charges, bond orders, possible charge transfer, topological properties of the furan rings, Natural Bond Orbital (NBO) and Atoms in Molecules (AIM) theory calculations were employed to study the stabilities and intermolecular interactions of the both dimers of 2FA.

Adiabatic ab initio study of the BaH(+) ion including high energy excited states.

An adiabatic study of 1-34 (1,3)Σ(+) electronic states of barium hydride ion (BaH(+)) is presented for all states dissociating below the ionic limit Ba(2+)H(-). The 1-20 (1,3)Π and 1-12 (1,3)Δ states have been also investigated. In our approach, the valence electrons of the Ba(2+) ion described by an effective core potential (ECP) and core polarization potential (CPP) with l-dependent cutoff functions have been used. The ionic molecule BaH(+) has been treated as a two-electron system, and the full valence configuration interaction (CI) is easily achieved. The spectroscopic constants Re, De, Te, ωe, ωexe, and Be are derived. In addition, vibrational level spacing and permanent and transition dipole moments are determined and analyzed. Unusual potential shapes are found and also accidental quasidegeneracy in the vibrational spacing progression for various excited states. The (1)Σ(+) states exhibit ionic charge transfer avoided crossings series which could lead to neutralization or even H(-) formation in collisions of H(+) with Ba.

Explaining the structure of the OH stretching band in the IR spectra of strongly hydrogen-bonded dimers of phosphinic acid and their deuterated analogs in the gas phase: a computational study.

We present a simulation of the OH stretching band in the gas-phase IR spectra of strongly hydrogen-bonded dimers of phosphinic acid and their deuterated analogs [(R(2)POOH(D), with R = CH(2)Cl, CH(3)], which is based on a model for a centrosymmetric hydrogen-bonded dimer that treats the high-frequency OH stretches harmonically and the low-frequency intermonomer (i.e., O···O) stretches anharmonically. This model takes into account the following effects: anharmonic coupling between the OH and O···O stretching modes; Davydov coupling between the two hydrogen bonds in the dimer; promotion of symmetry-forbidden OH stretching transitions; Fermi resonances between the fundamental of the OH stretches and the overtones of the in- and out-of-plane bending modes involving the OH groups; direct relaxation of the OH stretches; and indirect relaxation of the OH stretches via the O···O stretches. Using a set of physically sound parameters as input into this model, we have captured the main features in the experimental OH(D) bands of these dimers. The effects of key parameters on the spectra are also elucidated. By increasing the number and strength of the Fermi resonances and by promoting symmetry-forbidden OH stretching transitions in our simulations, we directly see the emergence of the ABC structure, which is a characteristic feature in the spectra of very strongly hydrogen-bonded dimers. However, in the case of the deuterated dimers, which do not exhibit the ABC structure, the Fermi resonances are found to be much weaker. The results of this model therefore shed light on the origin of the ABC structure in the IR spectra of strongly hydrogen-bonded dimers, which has been a subject of debate for decades.