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The structural and energetic proprieties for the Li

Herein, we have investigated the key functions of the calix[4]arene, abbreviated as CX [1], and designed its several derivatives by substitution of the functional groups. Molecular geometry provides an intuitive understanding of the effect of functional groups on various physical properties. The addition of the N-beta -ketoimine (n=1-4) ligands has a direct effect on the stretching vibration of the H-bonding interaction. The results showed that all molecules possess absorption bands at 190 nm and in the range between 200 and 300 nm assigned to pi-pi* and n-pi* transitions. HOMO-LUMO energy gap of the CX[4]-N-beta -ketoimine, one with chemical hardness of 1.62 eV, has been found to be 3.24 eV calculated at B3LYP/6-31+G(d) level of theory. This finding explains the good kinetic stability of this compound. The large values of electrophilicity make the current molecules as a good electrophilic species. The atom in molecule (AIM) and the reduced density gradient (RDG) analyses showed the type and the strength of the interactions taking place between Cu2+ and the beta -ketoimine ligands. Tunisian's Ministry of high education and scientific research The authors acknowledge financial support from the Tunisian's Ministry of high education and scientific research. WOS:000608022300002 2-s2.0-85098997128 PubMed: 33409596

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.

Density Functional Theory (DFT) calculations was performed to highlighted the effects of Carbon nanospheres (CNSs) on the properties of Poly (N-vinylcarbazole) (PVK) as well as the charge transfer between them. This study is based on the diameter and number of CNSs as well as the distance between PVK and CNSs. First, a charge transfer between the PVK and the CNSs is observed and the properties of the obtained composites depend strongly not only on the diameter of CNSs but also on the distance between PVK and CNSs. Theoretical absorption spectra and charge transfer of modeling composites configurations have shown a decrease and a redshift whenever the number of CNSs is increased. Non covalent interaction governed by Van Der Waals interaction have making evidence by NBO, AIM and RDG analysis.

International audience; 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.

The lowest energy structures and relative stabilities of pure and sodium-doped helium clusters Na+Hen have been determined using DFT calculations. Firstly, a series of DFT functionals have been tested by the calculation of the potential energy curve of the Na+–He system in order to find the most suitable and reliable method for studying the Na+Hen clusters. The calculations showed that the M05-2X functional combined with the extended polarized and diffused Pople basis set 6-311++G(d,p) reproduce correctly the experimental Na+–He potential energy curve. Hence, the most stable geometries of Na+Hen clusters up to n = 20 have been optimized at M05-2X/6-311++G(d,p) level. An icosahedral geometry is obtained for the Na+He12 ensuring the closure of the first solvation shell and forming the so-called ‘Snowballs’ feature. The relative stabilities of the Na+Hen clusters are discussed on the basis of the dependence of the binding energy, fragmentation energy and second-order difference of energy as well as the HOMO–LUMO energy gap with the size of the clusters. The clusters Na+He8, Na+He9 and Na+He12 are found to be relatively more stable than their neighbors. The snowball formation was explained through natural population analysis. The non-covalent interaction NCI analysis was performed on the basis of the reduced density gradient RDG. Finally, binding enthalpy, entropy and Gibbs free energy are calculated and showed that the formation process of Na+Hen clusters is endothermic.

Van der Waals interactions between the valence electrons of the barium atom and the closed-shell cores have been studied using ab initio methods with a combination of pseudopotentials and core polarisation potential. We have reported the potential energy curves, the spectroscopic constants, the vibrational levels as well as the electric dipole moments for the ground and several excited states of Ba+Kr and BaKr complexes. Interesting behaviour has been observed in the potential energy curves, particularly for Σ+ states. This can show the strong repulsive interactions between Rydberg electrons and the Krypton atom.

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].

The structural properties and relative stabilities of the Na+Nen clusters, with n = 1–16, have been investigated by using pairwise and density functional theory (DFT) methods. The DFT calculations have been carried out using the M06-2X functional combined with the augmented aug-cc-pVTZ basis sets. For both methods, the high stability is obtained for Na+Ne12 cluster with an icosahedral structure, and the twelve Ne atoms complete the first solvation shell around the Na+ cation. Therefore, the icosahedral Na+Ne12 structure will be considered as the core for the larger sizes. The relative stabilities have been studied in terms of the binding energies, second-order difference of energies, fragmentation energies and HOMO–LUMO energy gaps. The Na–Ne interactions within the Na+Nen clusters in relation to the relative stabilities have been discussed through topological atom-in-molecules and reduced density gradient analyses. Finally, the relative stabilities of the Na+Nen clusters have been discussed topologically.

The shape, size and diameter of the cavities are one of the main factors which control the interactions of the calix[n]arene molecules with cation, anion or neutral guests in sensor applications. In this work, vibrational spectroscopy analysis, molecular electrostatic potential (MEP) surface, atom in molecules (AIM) and thermochemical properties were used to check the reorganizations of hydrogen bonds in such cavity shape for the improvement of physical proprieties of CX[n] molecules. We have demonstrated that the hydrogen bonds O···H and the angles O–H···O of CX[n = 4, 6, 8] play the role of the moderator or modifier of the cavity. MEP topography reveals that the cavity form of CX[8] is less hydrophilic as compared to those of CX[4] cavity. The QTAIM theory showed that CX[4] and CX[8] has a more symmetric and well-organized cavity than CX[6]. It was also shown that the hydrogen bond enhanced the topographic parameters in CX[n] at the lower edge levels.

In the present work, we reported a structural investigation of liquid ethylene glycol (EG) at 298 K and atmospheric pressure via neutron scattering and DFT calculation. Original scattering data at large scattering wave vectors were analyzed to deduce the structure factor SM(q), the molecular form factor F1(q) and the intermolecular pair correlation function gL(r). A large variety of hydrogen-bonded dimers and trimers has been considered in order to describe the intermolecular arrangement of the liquid EG. Natural bond orbital (NBO) and atoms-in-molecules (AIM) analyses have been performed to get insight about the nature of hydrogen bond between EG molecules. Complete vibrational assignments and analysis of fundamental modes of the more probable clusters were performed on the basis of potential energy distribution (PED) calculations and the available experimental infrared and Raman spectra in the liquid phase.

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.

In this work, electronic properties of alkali atoms interacting with helium rare gas (CsHe and RbHe) are studied through a full configuration interaction calculation, in cooperation with a pseudopotential approach and core polarization potential. The adiabatic potential energy curves for the ground state and numerous excited states of CsHe and RbHe systems are investigated. The corresponding spectroscopic constants such as equilibrium distance Re, well depth De, vibrational constant ωe, anharmonic constant, rotational constant Be, and transition energy Te as well as the vibrational levels of all electronic states are computed. Finally, permanent and transition dipole moment curves for the sigma states are determined and analyzed.

Density functional theory (DFT) calculations are performed to study the conformations, hydrogen-bonding network, and the stabilities of all possible molecular associations, urea–(H 2 O) n , ( n = 1–5) in aqueous solutions of urea. The B3LYP functional and the basis set 6-311++G(d, p) are used through the calculations. Natural bond orbital (NBO) theory and atoms in molecule (AIM) analysis are applied to quantify the relative strength of hydrogen bond interactions and to account their effect on the stabilities of molecular arrangements. The charge transferred from lone pair of the hydrogen bond acceptor to antibonding orbital of the donor provides the substantial stabilizing component of the hydrogen bond. The energy analyses prove that O H⋯O interactions between water molecules give more stability of the clusters. The hydrogen bonded structure is found to be slightly influenced by the presence of urea molecules.

This study is interested in the illustration of ab initio potential energy curves for Ba+Arn (n = 1–4) clusters. The electronic structures of these molecules are calculated using [Ba2+] and [Ar] non-empirical core pseudo-potentials complemented by the core polarisation operators for both atoms, which allow the consideration of core valence correlation effects. The structure and stabilities of Ba+Arn (n = 1–4) clusters are investigated. These molecules are treated as one-electron active system. Spectroscopic constants and vibrational energy levels have been derived from their potentials. The analysis of the geometric forms, basing on the potential energy curves and the spectroscopic constants, clearly shows the importance of rare gas induced dipole. We also show that the dipolar interactions can influence the coupling between atoms.

In this work, theoretical studies on the structure, molecular properties, hydrogen bonding, and vibrational spectra of the N-methylformamide–water (NMF···3H2O) complex will be presented. The molecular geometry was optimised by using Hartree–Fock (HF), second Moller–Plesset (MP2), and density functional theory methods with different basis sets. The harmonic vibrational frequencies are computed by using the B3LYP method with 6-311++G(d,p) as a basis set and then scaled with a suitable scale factor to yield good coherence with the observed values. The temperature dependence of various thermodynamic functions (heat capacity, entropy, and enthalpy changes) was also studied. A detailed analysis of the nature of the hydrogen bonding, using natural bond orbital (NBO) and topological atoms in molecules theory, has been reported.

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.

A wide adiabatic study has been performed for numerous electronic states of CaLi+ molecular ion. The adiabatic potential energy curves and their spectroscopic constants (R-e, D-e, omega(e) and T-e) have been calculated using an ab initio approach including a nonempirical pseudo-potential for the Ca and Li cores with the core polarisation potentials operator through full configuration interaction (FCI). Thereafter, the energies of vibrational levels and their spacing for all these states have been reported. In addition, the electric dipole moment curves have been investigated for the (1-19) Sigma, (1-12) Pi and (1-8) Delta electric states. Moreover it lets us check the extreme transition dipole moments (TDM). These behaviours of TDM are more accustomed to estimate the radiative lifetimes for all vibrational levels in 2(1)Sigma(+) and 3(1)Sigma(+) states. Also, the bound-bound and the bound-free contribution have been calculated precisely and by employing a Franck-Condon (FC) approximation

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.

This work presents a theoretical simulation of νOH and νOD band shapes in the polarized infrared spectra of 2-furoic acid dimer crystals measured at liquid-nitrogen temperature. The line shapes are studied theoretically within the framework of the anharmonic couplings between low-frequency hydrogen-bond vibrations and degenerate excited states of high-frequency hydrogen vibrations in hydrogen-bonded dimers and the anharmonic coupling between the first excited state of the fast mode and the harmonics or band combinations of some low-frequency bending modes, which lead to Fermi resonances.This approach takes into account the adiabatic approximation, the intrinsic anharmonicity of the low-frequency mode through a Morse potential, Davydov coupling triggered by resonance exchange between the excited states of the fast modes of the two hydrogen bonds involved in the cyclic dimer, and the direct and indirect damping of the fast-stretching modes of the hydrogen bonds and of the bending modes. The infrared spectral density was calculated within the linear response theory by Fourier transform of the autocorrelation function of the transition dipole moment operator of the fast mode. Numerical results show that mixing of all these effects allows satisfactory reproduction of the main features of the experimental IR line shapes of crystalline H- and D-bonded 2-furoic acid at liquid-nitrogen temperature and for different polarizations. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012

Polarized IR spectra of the hydrogen bond in 2-thiophenic acid crystals, isotopically neat and of mixed H/D isotopic content, are measured at 298 and 77 K in the "residual" nuO-H and nuO-D band frequency ranges. This crystalline system provides spectra in these band frequency ranges that differ considerably in intensity distribution from the spectra of other H-bonded centrosymmetric dimeric species. This change in the spectral properties of the crystals is probably due to the influence of the sulfur atoms from the thiophene aromatic rings, which are directly linked to the (COOH)2 or (COOD)2 cycles. The magnitude of this effect correlates with the net electronic charge distribution at the 2- and 3-positions of substituted thiophene rings, which in a different way influences the electron charge density in the hydrogen bonds of the two thiophenic acid isomers. The experimental results for spectral structures are compared to predictions obtained with theoretical calculations involving the combined effects of anharmonicities, Davydov coupling, Fermi resonances, and direct and indirect relaxations within the framework of the linear response theory. Numerical results show that mixing of all these effects allows satisfactory reproduction of the main features of the experimental IR line shapes of crystalline H- and D-bonded 2-thiophenic acid at room and liquid-nitrogen temperatures.

The paper presents extension of a quantum non-adiabatic treatment of H-bonds in which effects of anharmonicities of the high frequency XH→⋯Y and the low frequency X←H⋯Y→ modes on the υX–H infrared lineshapes of H-bonds systems are considered. The anharmonic coupling between the high frequency XH→⋯Y and the low frequency X←H⋯Y→ modes is treated within strong anharmonic coupling theory and the relaxation is included following quantum treatment of Rosch and Ratner. The intrinsic anharmonicity of the fast frequency mode is described by a double well potential and of the slow frequency mode by Morse potential. IR spectral density is obtained within the linear response theory by the Fourier transform of the autocorrelation function of the X–H transition dipole moment operator. The main feature brought by the anharmonicity of the H-bond bridge X←H⋯Y→ is the increase of the average frequency of the υX–H IR band with temperature for asymmetrical H-bonds, and decrease for symmetrical and weakly asymmetrical H-bonds. The numerical results are in fairly good agreement with the experimental behaviour of the first and the second moment of the X–H bands, observed when varying the temperature.

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.

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.

International audience; 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.

Anomalous isotopic effects on the position and the shape of the υ s ( X – H → … Y ) stretching vibration bond of hydrogen-bonded systems have been studied theoretically by applying a previous model [N. Rekik, N. Issaoui, H. Ghalla, B. Oujia, M.J. Wojcik, J. Mol. Struct. (Theochem) 821 (2007) 9–29]. The study of this effect is undertaken for weak to medium-strong H-bonded systems. Numerical results show that the relation between the isotopic frequency ratio, 〈 ω 〉 H / 〈 ω 〉 D and ω ° H / 〈 ω 〉 H , derived in this paper is confirmed by published experimental data.

The paper presents extension of a quantum non-adiabatic treatment of H-bonds involving intrinsic anharmonicity of the fast mode [Rekik et al. Chem. Phys. 273 (2001) 11] by accounting for quadratic dependence of both the angular frequency and the equilibrium position of the X H → ⋯ Y stretching mode on the X ← H ⋯ Y → motion, in order to account for stronger H-bonds. Attention is focused on the study of effects induced by incorporation of such dependence on the IR spectral density of the high frequency stretching mode. The spectral density is obtained, within the linear response theory, by Fourier transform of the direct damped autocorrelation function of the dipole moment of the fast stretching mode. The anharmonic coupling between the high frequency X H → ⋯ Y and the low frequency X ← H ⋯ Y → modes is treated by the strong anharmonic coupling theory. Intrinsic anharmonicity of the fast mode is described by a double well potential, whereas the slow mode is considered to be harmonic. The relaxation of the fast mode (direct damping) is considered.