Ab Initio Hartree-Fock Research Articles

FT-IR, FT-raman and UV spectra and ab initio HF and DFT study of conformational analysis, molecular structure and properties of ortho- meta– and para–chlorophenylboronic acid isomers

In this study, the FT-IR, FT-Raman, and UV–Vis spectroscopic properties of three monosubstituted phenylboronic acid derivatives: ortho-chlorophenylboronic acid (o-ClPhBA), meta-chlorophenylboronic acid (m-ClPhBA) and para-chlorophenylboronic acid (p-ClPhBA) molecules are investigated both experimentally and theoretically using Density Functional Theory (B3LYP) and Hartree Fock (HF). In order to find the stable possible conformations of the compounds, the conformational analysis was carried out by running potential energy surface (PES) scan by means of rotation of two structural parameters, the dihedral angles indicated as φ2 (C6–B–O1–H1A) and φ3 (C6–B–O2–H2A), varying from −180° to 180° with an increment of 10° using B3LYP/6-31G level of theory. Also, to determinate the most stable conformer for all the molecules, potential energy curve (PEC) the stable possible conformations on PES scan were investigated as a function of φ1 (C1-C6–B–O1) dihedral angle from 0° up to 180° with an increment of 10° using B3LYP/6–311++G(d,p) and HF/6–311++G(d,p) level of theory. For all the studied compounds, two conformational structures (conformer anti-anti, syn-syn) that did not have imaginary frequency values outside the equilibrium state (conformer anti-syn) were detected theoretically at the both methods.Due to their conformational flexibility, the relative stabilities of the anti-syn, anti-anti, and syn-syn conformers of o-ClPhBA, m-ClPhBA, and p-ClPhBA are 0.0, 4.66, and 6.76 kcal/mol, respectively, at the B3LYP/6–311++G(d,p) level of theory. For the HF/6–311++G(d,p) level of theory, the relative stabilities are 0.00, 4.54, and 6.11 kcal/mol for o-ClPhBA; 0.00, 3.98, and 1.51 kcal/mol for m-ClPhBA; and 0.00, 4.10, and 1.44 kcal/mol for p-ClPhBA, respectively. Some of the determined stable conformations of these molecules are different in symmetry groups. It was observed that the increase in the symmetry was effective in the of molecular properties, especially for vibrational frequencies. The structural parameter, dipole moments (μ), vibrational frequencies, polarizability (α), hyperpolarizability (β), the highest occupied molecular orbital (HOMO), and the lowest unoccupied molecular orbital (LUMO) of the stable conformers were calculated by using Ab initio HF/6–311++G(d,p) and DFT/B3LYP/6–311++G(d,p) level of theory. The assignments of fundamental vibrational modes of the studied molecule were performed based on total energy distribution (TED) analysis.

State-to-state rovibrational transition rates for CO2 in the bend mode in collisions with He atoms.

Modeling environments that are not in local thermal equilibrium, such as protoplanetary disks or planetary atmospheres, with molecular spectroscopic data from space telescopes requires knowledge of the rate coefficients of rovibrationally inelastic molecular collisions. Here, we present such rate coefficients in a temperature range from 10 to 500K for collisions of CO2 with He atoms in which CO2 is (de)excited in the bend mode. They are obtained from numerically exact coupled-channel (CC) calculations as well as from calculations with the less demanding coupled-states approximation (CSA) and the vibrational close-coupling rotational infinite-order sudden (VCC-IOS) method. All of the calculations are based on a newly calculated accurate abinitio four-dimensional CO2-He potential surface including the CO2 bend (ν2) mode. We find that the rovibrationally inelastic collision cross sections and rate coefficients from the CSA and VCC-IOS calculations agree to within 50% with the CC results at the rotational state-to-state level, except for the smaller ones and in the low energy resonance region, and to within 20% for the overall vibrational quenching rates except for temperatures below 50K where resonances provide a substantial contribution. Our CC quenching rates agree with the most recent experimental data within the error bars. We also compared our results with data from Clary et al. calculated in the 1980s with the CSA [A. J. Banks and D. C. Clary, J. Chem. Phys. 86, 802 (1987)] and VCC-IOS [D. C. Clary, J. Chem. Phys. 78, 4915 (1983)] methods and a simple atom-atom model potential based on abinitio Hartree-Fock calculations and found that their cross sections agree fairly well with ours for collision energies above 500 cm-1, but that the inclusion of long range attractive dispersion interactions is crucial to obtain reliable cross sections at lower energies and rate coefficients at lower temperatures.

Cavity Born-Oppenheimer Hartree-Fock Ansatz: Light-Matter Properties of Strongly Coupled Molecular Ensembles.

Experimental studies indicate that optical cavities can affect chemical reactions through either vibrational or electronic strong coupling and the quantized cavity modes. However, the current understanding of the interplay between molecules and confined light modes is incomplete. Accurate theoretical models that take into account intermolecular interactions to describe ensembles are therefore essential to understand the mechanisms governing polaritonic chemistry. We present an ab initio Hartree-Fock ansatz in the framework of the cavity Born-Oppenheimer approximation and study molecules strongly interacting with an optical cavity. This ansatz provides a nonperturbative, self-consistent description of strongly coupled molecular ensembles, taking into account the cavity-mediated dipole self-energy contributions. To demonstrate the capability of the cavity Born-Oppenheimer Hartree-Fock ansatz, we study the collective effects in ensembles of strongly coupled diatomic hydrogen fluoride molecules. Our results highlight the importance of the cavity-mediated intermolecular dipole-dipole interactions, which lead to energetic changes of individual molecules in the coupled ensemble.

A comparative investigation for identification of N-(4-dimethylamino 3,5-dinitrophenyl)maleimide

This study has identified the characteristic behaviors of N-(4-dimethylamino 3,5-dinitrophenyl)maleimide molecule using ab initio Hartree-Fock (HF) and density functional theory (DFT) based on Becke’s three-parameter hybrid exchange functional combined with Lee-Yang-Parr non-local correlation function (HF/B3LYP and DFT/B3LYP) at 6-311G++(d,p) level of theory for the first time. On this basis, the optimized molecular structures, some thermodynamic features at 300 K, function groups of structures, charge distributions-dipole moments, molecular charge transfer regions, spectroscopic characteristic properties, vibrational frequencies, nuclear magnetic resonance chemical shifts of 13C-NMR and 1H-NMR spectra, and corresponding vibrational assignments have been investigated in detail. Comparisons between some experimental findings and theoretical results are performed to test the reliability of the calculation method preferred in the study. The comparison results in high correlation parameters such as R2 =0.976 and R2 =0.985 for the molecular structures and vibrational frequencies in the DFT and HF calculation levels, respectively. Moreover, the obtained vibrational frequencies and calculated results are in good agreement with the experimental data. Additionally, the simulations of highest/lowest occupied/unoccupied molecular orbital (HOMO and LUMO), molecular electrostatic potential (MEP), and electrostatic potential (ESP) maps have shown that there appear strong non-uniform intra-molecular charge distributions (ICT), electron engagements, lone pairs of electrons, π-π* conjugative effects based on the bond weakening, and intermolecular hydrogen bonding in the compound. Correspondingly, the molecule with the electrophilic reactive and nucleophilic regions has been noted to exhibit kinetical chemical stability. All the discussions have been confirmed by means of the findings of optimized molecular structures and vibrational frequencies belonging to the molecule.

Encapsulating Ne inside C20H20. A molecular dynamics study on the stability of the endohedral system

The central collision between a neon atom and a dodecahedrane cage has been investigated within the framework of ab initio Hartree-Fock molecular dynamics simulations for various initial velocities of the incident atom. Four scenarios regarding the interaction’s outcome have been identified. A reaction channel involving the encapsulation of the projectile inside the molecular cage has been studied for a simulation time of 4.8 ps. The analysis is focused on: the rate of energy exchange between Ne and C20H20, the mechanical oscillation frequencies of the atom and the cage, and also, on the frequency with which the dipole moment changes. The results suggest that inside the molecular cage, neon is a stable atomic vibrator, which oscillates with the highest peak frequency of 16 THz. Furthermore, the same frequency characterizes the dipole moment oscillation, suggesting a strong coupling between the atom and the cage, making the endohedral system suitable for a wide range of applications in nano-electronics.

Molecular dynamics of He encapsulation in the C20H20 cage at the threshold energy

The encapsulation of He inside C20H20 cage has been investigated in the framework of molecular dynamics for incident atom energy in a range close to the threshold value, corresponding to the projectile passing through the pentagonal carbon ring. The entrance of He atom into dodecahedrane is analyzed in terms of static and dynamic potential barriers. The details of helium capture inside the molecular box is revealed by using geometric and energetic parameters, being associated with the response of the atomic configuration near the collision site on the C20H20 cage. The energy transferred from the incident atom to deformation, vibrations, and recoil of the molecule target, was calculated as a function of the distance between the projectile and the collision site on C20H20 cage. The calculations show that the noble gas atom, encapsulated at the threshold of 315.62 Å/ps, oscillates across the void of the dodecahedrane with frequencies of 2.5, 22.5, and 25.0 THz, monitored for a time interval of 10 ps starting at helium penetration into C20H20. Molecular dynamics calculations are based on ab-initio Hartree-Fock method, considering an adiabatic process. This study reveals advantageous features of helium encapsulation in dodecahedrane molecules in designing super-molecular structures for advanced nano sensors in the field of THz detectors.

Carbon supports for the oxidative cleavage of oleic acid: Influence of textural properties

Microporous oxidized activated carbon (ACO) and macroporous oxidized carbon black (CBO) were assessed in the complexation of Ru for the oxidative cleavage of oleic acid. This reaction breaks carbon-carbon double bond to produce azelaic and pelargonic acids (highly demanded in pharmacology). Both carbon materials were treated with HNO3 prior Ru deposition by wet impregnation method. Carbon supports were characterized by FTIR, Boehm's titration and N2 physisorption, while Ru complexation was determined by ICP and XPS spectroscopy. Activated carbon catalyst displayed a low conversion (∼53%) in comparison to carbon black catalyst (>99%). The reason is related to the molecular length of oleic acid (2.2 nm), estimated by ab initio Hartree-Fock calculation, which is larger than micropores from activated carbon (∼0.7 nm). Despite Ru losses during the catalytic tests, CBO was more active and stable than ACO, confirming that a macroporous support is more suitable to perform the oxidative cleavage of oleic acid.

Spectroscopic Investigations, Computational Studies and Molecular Properties of Naphthalene Derivatives

Theoretical studies have been carried out on bio active molecules such as Naphthalene (npa) and its derivatives naphthalene-2-sulfonic acid (nsa) and 1-nitroso-2-naphthol (nnol) using both Ab initio HF and DFT-B3LYP methods with 6-311++G(d,2p) basis sets. The geometrical parameters, molecular properties and vibrational spectra of nsa, nnol and npa were calculated and analyzed. Geometrical optimizations of the nsa, nnol and npa molecules were done by Density Functional Theory (DFT) using the B3LYP function and Hartree-Fock (HF) level with 6-311++G(d,2p) basis set. The optimized molecular geometry and computed vibrational spectra are compared with experimental results which show significant agreement. DFT and HF global chemical reactivity descriptors (chemical hardness, total energy, electronic chemical otential and electrophilicity) are calculated for the title molecules and used to predict their relative stability and reactivity.

Structural and spectroscopic study of neutral dioxides MO2 (M = B, Al, Ga, In, Tl)

Both ab initio Hartree-Fock self consistent field (HF-SCF) with Cluster Coupled (CCSD(T)) and Density Functional Theory with B3LYP functional, high level theories are adopted for structural study of different dioxides MO2 (M = B, Al, Ga, In and Tl). A geometry optimization is performed using the avtz, aug-cc-pwcvnz (nz = tz; qz; 5z), 6–311++G** and Lanl2DZ basis sets. Vibration frequencies are reported for optimized geometries. We also report calculated M-O and O-O bond lengths, O-M-O and M-O-O, bond angles for stable isomers. Our calculations indicate that there are five possible isomers with linear or folded shapes. Some discrepancies with previous results are noted, on the other hand, according to our CCSD(T) calculations, MO2 molecule (M = B, Al and Ga) is in ground state when it is linear and symmetric O-M-O (2Πg), then in a higher energy state with the cyclic isomer (2A2, or 2A1) and in more higher state when it is dissymmetric M-O-O (2A’, 2∑+), B3LYP and CCSD(T) results agree on energetic ordering of various isomeric forms for BO2, AlO2,InO2 and TlO2 systems, while there is disagreement for GaO2, molecule. HOMO-1, HOMO, LUMO and LUMO + 1 molecular orbitals for the most stable structures are given as well. NBO analysis is performed to study the superoxide 2A2 and its stability which evolves according to electropositivity of metal along the 13th column of periodic table.

Mechanism study of Cd(II) ion adsorption onto resins with sulfonic/phosphonic groups using electronic structure methods

Cadmium is a persistent bio-accumulative toxic metallic element causing hazardous impacts on environment. Through adsorption tests, it was found that Dowex G-26 resin with sulfonic group and Puromet™ MTS9570 resin with both sulfonic and phosphonic groups had excellent performance for Cd (II) ion removal from aqueous solution. To understand the adsorption mechanism of Cd(II) ion onto Dowex G-26 and Puromet™ MTS9570 resins, a density functional theory (DFT) B3LYP (Becke, 3-parameter, Lee–Yang–Parr) method and an ab initio Hartree-Fock (HF) method were employed to calculate the electronic structure properties including Mulliken population analysis, Mulliken charges of atoms, the energies of frontier orbitals, total electronic energy Ɛ0, enthalpy ΔH°f, and free energy ΔG°f of fourteen possible structural units with sulfonic or phosphonic group in these two resins and their interaction with Cd(II) ion. The hydration of Cd(II) ion was considered during the simulation of the interaction of Cd(II) ion with the structural units. The calculation results of the electronic properties were of more reasonable significance of physics when simulating with HF method compared to B3LYP DFT method. HF method is a more suitable and reliable electronic structure theory for analyzing metal ion adsorption systems. The major reaction of Cd(II) ion adsorption onto G-26 and MTS9570 resins was presented.

Theoretical treatment of IO-X (X = N2, CO, CO2, H2O) complexes.

Iodine monoxide (IO) is an important component of the biogeochemical cycle of iodine. For instance, it is present in the troposphere, where it plays a crucial role in the physical chemical processes involving iodine containing compounds. Here, we present a theoretical study on a series of atmospherically relevant complexes of IO with N2, CO, CO2 and H2O, where their structural and spectroscopic properties and their interaction energies are computed. Calculations are carried out by means of ab initio post Hartree-Fock (RCCSD(T) and RMP2) methods and density functional theory DFT (PBE0 and M05-2X) based approaches with and without the inclusion of dispersion correction. After comparison to RCCSD(T), we highlight the good performance of M05-2X(+D3) DFT in describing the bonding between IO and X (X = N2, CO, CO2, H2O). Moreover, we found that the IO-X (X = N2, CO, CO2, H2O) complexes are formed by non-covalent interactions between the two monomers. In sum, we characterized two types of complexes: I-bonded and O-bonded, where the former is more stable. The atmospheric implications of the present findings are also discussed such as in the formation of the iodine oxide particles (IOPs).

Cis boron hydrogen chains: Theoretical calculations

Ab initio quantum Hartree-Fock and Møller–Plesset approximations used to study cis boron hydrogen cis-(BH)n chains. The ground-state energies, binding energies, Mulliken population and the optimal geometrical configurations of cis-(BH)n are reported in terms of the chain size n. The calculated ground-state energies in terms of chain dimerization un showed two phases cis-transoid and Trans-cisoid. The energies of these two phases at MP2 fitted into the modified Su-Schrieffer-Heeger (SSH) model in order to determine the corresponding parameters. According to this model, the dimerization induces a band gap around 0.12 eV for cis-transoid phase and 0.11 eV for the trans-cisoid one.

Extended analysis of the free ion spectrum of Er[formula omitted](Er IV)

The analysis of the vacuum spark spectrum of erbium in the wavelength region 705 - 2460 Å has been extended. A total of 1022 spectral lines are newly identified as transitions between the low lying configurations 4f11, 4f105d, 4f106s and 4f106p of the Er3+ ion (Er IV), in addition to the confirmed previously identified 582 ones. The extended analysis has led to the determination of 168 new energy levels in Er3+, in addition to the 120 previously known ones. Energy values have been optimised by a least-squares procedure based on an increased number of measured wavelengths, resulting in a reduction of their uncertainties. Parametric calculations have been performed using the Cowan codes, in which radial integrals are parameters fitted by least-squares minimisation of the differences calculated - experimental energies. The increased number of experimentally known levels leads to better defined parameters and improved predictions of unknown energy levels and electric dipole transition probabilities. Fitted parameters are compared with ab initio Hartree-Fock integrals including relativistic corrections (HFR). The mean errors of the fits are respectively 51 cm−1 for 65 known levels of the odd configurations 4f11 + 4f106p with 9 free parameters, and 53 cm−1 for 223 known levels of the even configurations 4f105d + 4f106s with 17 free parameters.

Infrared Spectrum for the New Nanomolecules ASi, CSi, TSi and Gsi

The core of the work is based on the replacement of carbon atoms by silicon atoms, on the basis of four standard bases of DNA: A, C, G and T (adenine, cytosine, guanine, thymine). Determining with minimum computational methods via ab initio Hartree-Fock methods, infrared spectrum and their peak absorbance frequencies. The option for simple replacement of carbon by silicon is due to the peculiar characteristics between both. Atomic interactions under non-carbon conditions were studied, with only the Hydrogen, Silicon, Nitrogen and Oxygen atoms, in CNTP, for the four standard bases of DNA, A, C, G and T, thus obtaining by quantum chemistry four new compounds, named here as: ASi, CSi, GSi and TSi. Computational calculations admit the possibility of the formation of such molecules, their existence being possible via quantum chemistry. Calculations obtained in the ab initio Unrestricted and Restrict Hartree-Fock method, (UHF and RHF) in the set of bases used Effective core potential (ECP) minimal basis, UHF CEP-31G (ECP split valance) and UHF CEP-121G (ECP triple-split basis), CC-pVTZ (Correlation-consistent valence-only basis sets triple-zeta) and 6-311G**(3df, 3pd) (Gaussian functions quadruple-zeta basis sets).

Infrared Spectrum for the New Exobiological Nanomolecules Asi, Csi, Tsi and Gsi

The core of the work is based on the replacement of carbon atoms by silicon atoms, on the basis of four standard bases of DNA: A, C, G and T (adenine, cytosine, guanine, thymine). Determining with minimum computational methods via ab initio Hartree-Fock methods, infrared spectrum and their peak absorbance frequencies. The option for simple replacement of carbon by silicon is due to the peculiar characteristics between both. Atomic interactions under non-carbon conditions were studied, with only the Hydrogen, Silicon, Nitrogen and Oxygen atoms, in CNTP, for the four standard bases of DNA, A, C, G and T, thus obtaining by quantum chemistry four new compounds, named here as: ASi, CSi, GSi and TSi. Computational calculations admit the possibility of the formation of such molecules, their existence being possible via quantum chemistry. Calculations obtained in the ab initio Unrestricted and Restrict Hartree-Fock method, (UHF and RHF) in the set of basis used Effective core potential (ECP) minimal basis, UHF CEP-31G (ECP split valance) and UHF CEP-121G (ECP triple-split basis), CC-pVTZ (Correlation-consistent valence-only basis sets triple-zeta) and 6-311G**(3df, 3pd) (Gaussian functions quadruple-zeta basis sets).

Development of a Cyclic Periodic Wave Function Approach for the Study of Infinitely Periodic Solid-State Systems.

The ab initio cyclic periodic wave function (CPWF) approach is developed for the treatment of infinitely periodic systems. Using the full infinite Hamiltonian operator, as well as symmetrically identical basis set wave functions that preserve the translational symmetry of the electron density of the system, this approach can be applied at the Hartree–Fock level, or correlation can be directly included by the usual modes. In this approach, all many-body interactions are included, and no edge effects occur. Initial test calculations of the CPWF method at the ab initio Hartree–Fock level are performed on the chains of hydrogen fluoride molecules.

Theoretical Studies on The Structural, Vibrational, Conformational Analysis and Nonlinear Optic (NLO) Property of 4-(Methoxycarbonyl) Phenylboronic Acid

In this paper, the structural, electronic, non-linear optical (NLO) properties and vibrational frequencies of 4-(methoxycarbonyl) phenylboronic acid has been examined theoretically using ab initio Hartree-Fock (HF) and Density Functional Theory (DFT/B3LYP) methods applying the standard 6-311++G(d,p) basis set. 1H- and 13C-chemical shifts were calculated by employing the direct implementation of the gauge including-atomic-orbital (GIAO) method at the B3LYP/6-311++G(d,p) and HF/6-31G(d) levels of the theory. There are two conformers, (cis-trans = ct) and (trans-cis = tc) for title molecule. The energy difference between ct and tc conformers of studied molecule are of 0.126 kcal/mol with B3LYP/6-311++G(d,p) and 0.138 kcal/mol with HF/6-311++G(d,p), respectively. The conformer ct is more stable than the conformer tc. Also, the energy gap (ΔΕg) differences between the highest occupied (HOMO) and lowest unoccupied molecular orbitals(LUMO), dipole moment, polarizability and first static hyperpolarizability were calculated as a function of both dihedral angle (C3-C4-C7-O3), between methoxycarbonyl group (CH3-O-CO-) and benzene ring, and dihedral angle (C2-C1-B-O1), between boronic acid group (-B(OH)2) and benzene ring. In the change of the energy gap and polarizability depending on dihedral angles, it was shown that the polarizabilities were follow inverse relationship the energy gaps.

Molecular spectroscopic investigation, quantum chemical, molecular docking and biological evaluation of 2-(4-Chlorophenyl)-1-[3-(4-chlorophenyl)-5-[4-(propan-2-yl) phenyl-3, 5-dihydro-1H-pyrazole-yl] ethanone

2-(4-Chlorophenyl)-1-[3-(4-chlorophenyl)-5-[4-(propan-2-yl)phenyl-3, 5-dihydro-1H-pyrazole-yl] ethanone (CCPPE) has been studied experimentally and theoretically. The structure of CCPPE was characterized by X-ray diffraction (XRD), and determined theoretically by the ab initio Hartree-Fock (HF) method and by the density functional theory(DFT) method B3LYP using the 6-311++G (d, p) basis set. Theoretical topological analysis of the electron density, according to the Quantum Theory of Atoms in Molecule (AIM), electron localization function (ELF) and the localized orbital locator (LOL) have been performed. Fourier Transform Infrared (FTIR) and Fourier Transform Raman (FT-Raman) vibrational spectra were recorded and the observed frequencies were compared to those obtained from B3LYP/6-311G (d, p) and B3LYP/6-311++G (d, p) calculations. The HOMO and LUMO energy results show that good exchange of charge happened inside the molecule. Molecular electrostatic potential was also performed. From the MEP it is evident that the negative charges cover the C=O group, the region having the positive potential are over the phenyl rings and the remaining species are surrounded by zero potential. Theoretical (TD-DFT) and experimental UV-Vis absorption wavelengths (λ) were compared with each other. The stability of the molecule arising from hyper-conjugative interaction and charge delocalization has been analyzed using NBO analysis. The antimicrobial activity of the CCPPE was determined against bacterial strains such as Bacillus subtilis,Staphylococcus aureus, E.coli, Pseudomonas and fungal strains such as Candida albicans and A.niger. The obtained results show that the compound exhibited good to moderate antimicrobial activity. Molecular docking studies were executed to understand the inhibitory activity of CCPPE against antibacterial, antifungal, anti-inflammatory, antioxidant, antiviral activities.

Theoretical and experimental assesment of structural, spectroscopic, electronic and nonlinear optical properties of two aroylhydrazone derivative

Two aroylhydrazone, N'-(pyridine-4-ylmethylene)nicotic acid hydrazide (1) and N'-(pyridine-3-ylmethylene)nicotic acid hydrazide (2), were synthesized and their structures were determined by single-crystal X-ray diffraction analysis. The X-ray analysis indicated that the compound 1 was crystallized in triclinic crystal system with P -1 space group a = 8.7899 (2) Å, b = 10.8983 (3) Å, c = 11.7726 (3) Å, α= 89.952 (3)°, β = 88.684 (3)°, γ= 75.293 (2)°, V = 1090.50 (5) Å3 and Z = 4 and compound 2 was crystallized in monoclinic crystal system with P21/c space group, a = 11.9239 (3) Å, b = 8.6495 (2) Å, c = 11.1021 (3) Å, α= 90 (3)°, β = 111.664 (3) (3)°, γ= 90°, V = 1064.14 (5) Å3 and Z = 4. Intermolecular interactions of the compounds were determined by Hirhfeld Surface Analysis. The H ··· H interactions with 37.9% (for compound 1) and 37.5% (for compound 2) contributions are the most important interactions to the overall crystal packings. FT-IR, Raman, 1H and 13C NMR and UV–Vis spectroscopy methods were used for spectroscopic characterization of the compounds. The spectroscopic properties of the compounds were calculated theoretically by using Density Functional Theory (DFT) with B3LYP and ab initio Hartree-Fock (HF) methods at different basis sets. A correlation was found between the theoretical and experimental values for the spectroscopic results. Moreover, the highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO), electric dipole moment (μ), polarizability (α) and hyperpolarizability (β) of the compounds were computed both DFT/B3LYP/6–311++G(d,p) and ab initio HF/6–311++G(d,p) methods. The calculated first hyperpolarizability value at the DFT/B3LYP/6–31++G (d,p) level of compound 1 with dimer structure is 18.14 times larger than urea, the standard nonlinear optical material. So, this value implies that compound 1 considered have potential candidates for designing high quality nonlinear optical materials. The energy gap (ΔEgap) and Molecular Electrostatic Potential (MEP) of the compounds were investigated. The structural and vibration frequency values calculated theoretically were compared with the experimental values.

Ortorombik metaborik asit molekülünün moleküler yapısı ve elektronik özellikleri üzerindeki konformasyonel etkinin teorik olarak incelenmesi

In the present study, conformational analysis, Nonlinear Optical (NLO) behavior, vibrational spectra, electronic and the molecular structure of orthorhombic metaboric acid have been investigated comprehensively by using ab initio Hartree Fock (HF) and Density Functional Theory DFT at the B3LYP level with 6-311++G(d, p) basis set. The conformational analysis was performed in detail for the first time as a function of both the φ (B1-O1-H) bond angle and the ψ (O6-B1-O1-H) dihedral angle. The results of calculated potential energy curves show that the molecule has two conformers (C-I and C-II Conformer) with minimum energies in a stable form. C-I conformer is a more stable form than C-II conformer. Linear and nonlinear optical properties of conformer C-I and C-II of the orthorhombic metaboric acid molecule are examined by the determination of the electric dipole moment μ, the polarizability α, and the hyperpolarizability β both methods. The optimized molecular structures of C-I and C-II conformer of the molecule belong to C3h and Cs symmetry, respectively. The dipole moment values for conformer C-II with Cs symmetry obtained using B3LYP/6-311++G(d, p) and HF/6-311++G(d, p) methods were found to be 2.95 and 3.07 Debye, Whereas, for C-I conformer with C3h symmetry, the values obtained using the same methods are found equal (0.0 Debye). Total energy distributions (TED) were calculated to find assignments of calculated vibration modes of both conformers by using VEDA 4f program. It was observed that there is a good agreement between the experimental data in the literature and the calculated structural parameters.