DFT Quantum Chemical Calculations Research Articles

Quantum chemical studies of mechanisms of organic reactions: VI. Reaction of ethane-1,2-dithiol with vinylidene chloride

A theoretical mechanism has been proposed for the reaction of vinylidene chloride with ethane-1,2-dithiol in the system hydrazine hydrate–potassium hydroxide on the basis of DFT quantum chemical calculations at the B3LYP/6-311++G(d,p) level of theory. The reaction includes two consecutive stages: dehydrochlorination of vinylidene chloride to chloroacetylene and nucleophilic addition of one thiol group of ethane-1,2-dithiol to the β-carbon atom of chloroacetylene, followed by closure of 2,3-dihydro-1,4-dithiine ring via nucleophilic substitution of chlorine by sulfur atom of the second thiol group.

Terpenoids from Curcuma wenyujin increased glucose consumption on HepG2 cells

Thirty four terpenoids, including two new cadinane-type sesquiterpenoids containing conjugated aromatic-ketone moieties, curcujinone A (1) and curcujinone B (2), were isolated from 95% ethanol extract of the root tubers of Curcuma wenyujin. Their structures were determined by spectroscopic methods, especially 2D NMR and HRMS techniques. The relative and absolute configurations of 1 and 2 were identified by quantum chemical DFT and TDDFT calculations of the 13C NMR chemical shifts, ECD spectra, and specific optical rotations. All compounds and extracts were evaluated for their anti-diabetic activities with a glucose consumption model on HepG2 Cells. The petroleum fraction CWP (10μg/mL) and compounds curcumenol (4), 7α,11α-epoxy-5β-hydroxy-9-guaiaen-8-one (5), curdione (17), (1S, 4S, 5S 10S)-germacrone (18), zederone (20), a mixture of curcumanolide A (25) and curcumanolide B (26), gajutsulactone B (27), and wenyujinin C (30) showed promising activities with over 45% increasing of glucose consumption at 10μM.

Synthesis, characterization, spectroscopic properties and DFT study of a new pyridazinone family

Nitrogen compounds are widely investigated due to their pharmacological properties such as antihypertensive, antinociceptive, antibacterial, antifungal, analgesic, anticancer and inhibition activities and lately even as pesticide. In this context, we present the synthesis of new compounds: (E)-6-(3,4-dimethoxyphenyl)-3-(3-(3,4-dimethoxyphenyl)acryloyl)-1-(4-R-phenyl)- 5,6-dihydropyridazin-4(1H)-one (with R = H(1), -Cl(2), -Br(3), I(4) and COOH(5)) that was carried out by reaction of (1E, 6E)-1,7-bis(3,4-dimethoxyphenyl)hepta-1,6-diene-3,5-dione with a substituted phenylamine with general formula p-R-C6H4NH2 (R = H (1), Cl (2), -Br(3), I(4) and COOH(5)). This is the first synthesis report of a pyridazinone using as precursors a curcuminoid derivative and a diazonium salt formed in situ. All compounds were characterized by EA, FT-IR, UV–Vis, Emission,1H- and13C-NMR spectroscopy and the crystalline and molecular structure of 4 was solved by X-rays diffraction method. DFT and TD-DFT quantum chemical calculations were also employed to characterize the compounds and provide a rational explanation to the spectroscopic properties. To assess the biological activity of the systems, we focused on pesticide tests on compound 2, which showed an inhibitory effect in plant growth of Agrostis tenuis Higland.

3-hydroxy-4-hydroxyiminomethyl-5-hydroxymethyl-1,2-dimethylpyridinium iodide molekülünün geometrik yapısının incelenmesi

In this study, the ground state of 3-hydroxy-4-hydroxyiminomethyl-5-hydroxymethyl-1,2-dimethylpyridinium iodide [ C 9 H 13 IN 2 O 3 ] (1A) molecule of the theoretical molecular structure were performed by using Gaussian 09 program. B3LYP levels of density functional theory with the LanL2DZ basis set have been used to perform above-mentioned calculations. The molecular structure of 1A molecule was determined and the vibrational properties were investigated. In addition, the molecular frontier orbital ( HOMO-LUMO) energies, the electronic properties (total energy, dipole moment, electronegativity, chemical hardness and softness), nonlinear optical (the mean polarizability (<α>) and the anisotropy of the polarizability (Δα)) properties, Mulliken atomic charges and thermodynamic parameters were investigated using DFT quantum chemical calculations.

Synthesis, X-ray single crystal structure, likelihood of occurrence of intermolecular contacts, spectroscopic investigation and DFT quantum chemical calculations of zwitterionic complex: 1-Ethylpiperaziniumtrichlorozincate (II)

The synthesis and the X-ray structure of the Zn(II) zwitterionic complex:1-ethylpiperaziniumtrichlorozincate (II) are described. In the atomic arrangement, the ZnCl3N entities, grouped in pairs, are deployed along the b-axis to form layers. The organic entities are inserted between these layers through NH⋯Cl and CH⋯Cl hydrogen bonds to form infinite three-dimensional network. The 3D Hirshfeld surfaces were investigated for intermolecular interactions. The optimized geometry, Mulliken charge distribution, molecular electrostatic potential (MEP) maps and thermodynamic properties have been calculated using the Lee-Yang-Parr correlation functional B3LYP with the LanL2DZ basis set. The HOMO and LUMO energy gap and chemical reactivity parameters were made. The 13C and 15N CP-MAS NMR spectra are in agreement with the X-ray crystal structure. The vibrational absorption bands were identified by infrared spectroscopy. DFT calculations allowed the attribution of the NMR peaks and of the IR bands.

A Blue Diketopyrrolopyrrole Sensitizer with High Efficiency in Nickel-Oxide-based Dye-Sensitized Solar Cells.

We prepared a series of four new diketopyrrolopyrroles (DPPs)-based sensitizers that exhibit high-molar extinction coefficients, extended absorption into the long wavelengths, and well-suited photoredox properties to act as sensitizers in p-type dye-sensitized solar cells (p-DSSCs). These new DPP dyes, composed of a thienyl DPP core, are substituted on one end either by a thiophene carboxylic (Th) or a 4,4'-[(phenyl)aza]dibenzoic acid as anchoring group and, on the other extremity, either by a proton or a naphthalene diimide (NDI) moiety. These new dyes were completely characterized by absorption and emission spectroscopy along with electrochemistry and they were modeled by time-dependent DFT (TD-DFT) quantum chemical calculations. The photovoltaic study in p-DSSC with iodine-based electrolyte reveals that the Th-DPP-NDI dye is particularly efficient (Jsc =7.38 mA cm-2 ; Voc =147 mV; FF=0.32; η=0.35 %) and quite active in the low-energy region of the solar spectrum (above 700 nm), where only a few NiO dyes are effective. To illustrate the potential of DPP dyes in photocathodes, we designed a highly efficient tandem DSSC composed of a TiO2 photoanode sensitized by the dye D35 and a NiO photocathode sensitized by Th-DPP-NDI. This tandem DSSC gives the highest performances ever reported (Jsc =6.73 mA cm-2 ; Voc =910 mV; η=4.1 %) and, importantly, the tandem cell outcompetes with the sub-cells.

Extraction and DFT study on complexation of the barium cation with [Gly6]-antamanide

On the basis of extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium Ba2+(aq) + 1·Sr2+(nb) ⇄1·Ba2+ (nb) + Sr2+(aq) occurring in the two–phase water – nitrobenzene system (1 = [Gly6]-antamanide; aq = aqueous phase, nb = nitrobenzene phase) was determined as log Kex (Ba2+,1·Sr2+) = 0.6 ± 0.1. Further, the stability constant of the 1·Ba2+ complex in nitrobenzene saturated with water was calculated for a temperature of 25 °C: log βnb (1·Ba2+) = 9.5 ± 0.2. Finally, by using quantum chemical DFT calculations, the most probable structure of the cationic complex species 1·Ba2+ was derived. In the resulting complex, the “central” cation Ba2+ is bound by six bonding interactions to the corresponding six carbonyl oxygen atoms of the parent ligand 1. The interaction energy of the considered 1·Ba2+ complex was found to be −943.5 kJ/mol, confirming the formation of this cationic species as well

Crystal and molecular structures, temperature dependence of the IR and Raman spectra and vibrational dynamics of aquo 4,6-dimethyl-5H-[1,2,3]triazolo[4,5-c]pyridine in a new zwitterionic form

The crystal and molecular structures of aquo 4,6-dimethyl-5H-[1,2,3]triazolo[4,5-c]pyridine in a zwitterionic form have been determined by X-ray diffraction and DFT quantum chemical calculations. The compound adopts a triclinic crystal structure, space group P-1 = Ci1 (No. 2) with Z = 2 and the unit cell parameters: a = 6.7452 Å, b = 9.5292 Å, c = 9.5554 Å and α = 69.279°, β = 73.951°, γ = 74.242°. The temperature dependence of its IR and Raman spectra have been measured and discussed in terms of proton transfer dynamics. The molecular structure and simulated vibrational spectra of the studied compound have been determined using the DFT B3LYP/6-311G(2d,2p) approach. Vibrational characteristics of a triazolo-pyridinium system in the studied compound has been proposed. A role of water molecules in stabilization of the compound space structure has been considered.

Crystal structure, vibrational, spectral investigation, quantum chemical DFT calculations and thermal behavior of Diethyl [hydroxy (phenyl) methyl] phosphonate

Single Diethyl [hydroxy (phenyl) methyl] phosphonate (DHPMP) crystal with chemical formula C11H17O4P, was synthesized via the base-catalyzed Pudovik reaction and Lewis acid as catalyst. The results of SXRD analyzes indicate that this compound crystallizes into a mono-clinic system with space group P21/n symmetry and Z = 4. The crystal structure parameters are a = 9.293 Å, b = 8.103 Å, c = 17.542 Å, β = 95.329° and V = 1315.2 Å3, the structure displays one inter-molecular O—H⋯O hydrogen bonding. The UV–Visible absorption spectrum shows that the crystal exhibits a good optical transmission in the visible domain, and strong absorption in middle ultraviolet one. The vibrational frequencies of various functional groups present in DHPMP crystal have been deduced from FT-IR and FT-Raman spectra and then compared with theoretical values performed with DFT (B3LYP) method using 6-31G (p, d) basis sets. Chemical and thermodynamic parameters such as: ionization potential (I), electron affinity (A), hardness (σ), softness (η), electronegativity (χ) and electrophilicity index (ω), are also calculated using the same theoretical method. The thermal decomposition behavior of DHPMP, studied by using thermogravimetric analysis (TDG), shows a thermal stability until to 125 °C.

Experimental and theoretical study on complexation of the calcium cation with [Gly6]-antamanide

On the basis of extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium Ca2+(aq)+1∙Sr2+(nb)⇄1∙Ca2+ (nb)+Sr2+(aq) occurring in the two–phase water–nitrobenzene system (1=[Gly6]-antamanide; aq=aqueous phase, nb=nitrobenzene phase) was determined as log Kex (Ca2+,1·Sr2+)=0.6±0.1. Further, the stability constant of the 1·Ca2+ complex in nitrobenzene saturated with water was calculated for a temperature of 25°C: log βnb (1∙Ca2+)=10.2±0.2. Finally, by using quantum chemical DFT calculations, the most probable structure of the cationic complex species 1∙Ca2+ was derived. In the resulting complex, the “central” cation Ca2+ is bound by six bonding interactions to the corresponding six carbonyl oxygen atoms of the parent ligand 1. The interaction energy of the considered 1∙Ca2+ complex was found to be −1221.2kJ/mol, confirming the formation of this cationic species as well.

Interaction of vacancies on the Cu(001) surface

The results of quantum chemical DFT calculations of energy barriers during the diffusion of vacancies on the Cu(001) surface at increased concentrations of vacant sites were described. The formation and destruction of dimers, trimers, and configuration of four vacancies were considered. For vacancies located at the neighboring sites of the surface lattice, there is effective attraction, which promotes the formation of vacancy clusters.

Synthesis, spectroscopic and single crystal X-ray studies on three new mononuclear Ni(II) pincer type complexes: DFT calculations and their antimicrobial activities

Three new mononuclear square planar Ni(II) complexes, containing pincer type tridentate Schiff base ligands, having general formula [(NiL1(4-MePy)] (1), [(NiL1(2-AzNp)] (2), and [(NiL2(4-MePy)] (3) [where L1 = anion of N-(2-hydroxy-3-methoxybenzylidene) benzoylhydrazide (HL1), L2 = anion of N-(2-hydroxy-3-methoxybenzylidene) thiosemicarbazide (HL2), 4-MePy = 4-Methylpyridine and 2-AzNp = 2-Azanapthalene] have been synthesized and fully characterized by FT-IR, UV–visible, NMR, single crystal X-ray diffraction studies and elemental analysis. All the three complexes show square planar geometry around the nickel atom. The pincer type ligand occupies three coordination sites, while the fourth site is occupied by the monodentate nitrogen containing ligand. The Quantum chemical DFT calculations have also been carried out using DFT/B3LYP method and 6-311++G(d,p) basis set. The synthesized nickel complexes were screened for antimicrobial activities by agar well diffusion method against E. coli bacteria. Out of three complexes, [(NiL2(4-MePy)] (3) only showed the antimicrobial activity against E. coli bacteria.

Molecular structure of hexatomic heteronuclear (AlFe) metal clusters as determined by the DFT quantum-chemical calculation

Geometric parameters of molecular structures of hexatomic heteronuclear (AlFe) clusters with various number of aluminum atoms (Al2Fe4 and Al3Fe3) were calculated using the density functional hybrid method in the OPBE/TZVP approximation. It was found that the first of these clusters is able to exist in nine and the second in twenty structural modifications substantially differing from each other in their stability and geometric parameters. The values of bond lengths, planar and dihedral (torsion) angles for some of these modifications are given.

Synthesis, structures, spectral properties and DFT quantum chemical calculations of (E)-4-(((4-propylphenyl)imino)methyl)phenol and (E)-4-((2-tolylimino)methyl)phenol; their corrosion inhibition studies of mild steel in aqueous HCl

Two Schiff base compounds with similar backbone, but different positions and lengths of alkyl groups, (E)-4-(((4-propylphenyl)imino)methyl)phenol (PMP) and (E)-4-((2-tolylimino)methyl)phenol (TMP) have been synthesized. Their structures were established by spectroscopic techniques which include FTIR, 1H and 13C NMR, relative molecular mass (mass spect.), and single crystal X-ray crystallography. The spectroscopic methods revealed the characteristic imine functional groups and the exact molecular masses of the compounds. Single crystal analysis revealed an orthorhombic crystal system with Pca21 space group for the two compounds; and the structure of PMP reveal that the propyl group is disordered over two positions in 0.79:0.21 ratio. The corrosion inhibition behaviour of the two Schiff bases were studied by electrochemical measurements. The results suggest that the two derivatives adsorbed onto the mild steel surface and formed hydrophobic films, which to an appreciable extent, protected the surface of the mild steel. Potentiodynamic polarization results strongly suggested that the investigated Schiff bases behave as mixed-type inhibitors with a more pronounced cathodic nature, and the adsorption isotherm basically obeys the Langmuir isotherm. Quantum chemical computations were also employed to provide further explanations on the adsorption mode, and the theoretical predictions conformed to the experimental results.

Reversible Photoisomerization among Triplet Amino Naphthylnitrene, Triplet Diimine Biradical, and Indazole: Matrix-Isolation IR Spectra of 8-Amino-1-naphthylnitrene, 1,8-Naphthalenediimine, and 1,2-Dihydrobenz[cd]indazole.

Reaction mechanisms of nitrene, one of the most famous biradicals, have been frequently studied, and many spectral data have been obtained so far. In the present study, the experimental IR spectra of triplet 8-amino-1-naphthylnitrene (3ANN), a triplet diimine biradical 1,8-dihydro-1,8-naphthalenediimine (3DND), and 1,2-dihydrobenz[cd]indazole (DBI), which are produced in the UV photolysis of 1,8-diaminonaphthalene in an Ar matrix and identified by a combination method of IR spectroscopy and DFT quantum chemical calculations, are first reported. 3ANN is found to change to DBI by hydrogen-atom migration with bond making between the two nitrogen atoms upon visible-light irradiation (λ > 580 nm) with its backward reaction caused by 350 nm irradiation. In addition, 3ANN isomerizes to 3DND by 700 nm irradiation, while its backward reaction occurs upon 500 nm irradiation. The wavelength dependences of these photoisomerizations are explained in terms of their electronic transition energies estimated by time-dependent DFT calculations. It is concluded that the novel reversible photoisomerization system among 3ANN, 3DND, and DBI is totally different from the well-known photoisomerization between phenylnitrene and a seven-membered cyclic compound.

Three-component one-pot synthesis of novel pyrido[2,3-d]pyrimidine indole substituted derivatives and DFT analysis

Pyridopyrimidines are heterocyclic aromatic compounds known by their antibacterial and medicinal properties. In this work, a series of pyrido[2,3-d]pyrimidine indole derivatives were synthesized by three-component one pot cyclocondensation Michael reaction between 2,6-diaminopirimidin-4(3H)-one, 3-(2-cyanoacetyl)indole and aromatic aldehydes in boiling acetic acid as solvent. The compounds differ with respect to the substituents of the aromatic aldehyde which are comprised by -C6H5, -4-ClC6H4, -4-NO2C6H4, -3,4-OCH2OC6H3, -3-OCH3,4-OH,5-NO2C6H2, and -3,4,5-tri-H3COC6H2, respectively. The compounds were synthesized with reasonable yields. They were characterized by and IR, mass, and NMR spectrometry. The protocol employed offers the convenient advantages of a one-step synthesis, considerable savings of solvents, and easy isolation of reaction products. In addition, DFT and TD-DFT quantum chemical calculations were used to characterize the geometry and electronic structure of the compounds.

Synthesis and photostability of 1,4-bis(5-phenyloxazol-2-yl)benzene (POPOP) structural isomers and their trimethylsilyl derivatives

In this work, a versatile synthetic method for preparation of linear phenyloxazoles and their organosilicon derivatives under mild conditions via a combination of van Leusen and direct CH arylation reactions is reported. It was used for the synthesis of a novel trimethylsilyl (TMS) derivative of blue laser dye 1,4-bis(5-phenyloxazol-2-yl)benzene (POPOP) and its structural isomer 1,4-bis(2-phenyloxazol-5-yl)benzene (isoPOPOP) with and without TMS substituents. All of the compounds demonstrated high photoluminescence quantum yields and large molar extinction coefficients, which further increased for their TMS derivatives. Measurements of accelerated photodegradation of the dyes in diluted THF solutions revealed that POPOP-type compounds are twice more stable than their isoPOPOP-type isomers, independent of the presence or absence of TMS substituents. Cyclic voltammetry (CV) investigations revealed that POPOP-type dyes are more electrochemically stable as compared to their isoPOPOP-type isomers. Quantum chemical TD DFT calculations of the frontier energy levels of the dyes were in a good agreement with the experimental data obtained by CV. Single-crystal X-ray diffraction experiments revealed significant structural differences between crystal lattices of the dyes. Due to facile synthesis and excellent optical properties as well as high photo- and thermo- stability the novel luminescent dyes may find wide application in organic photonics.

Unexpected pyrylium to pyrylium domino transformation. Synthesis of pyrano[3,4-c]pyran-7-ium cation and its recyclization to 2,7-naphthyridine derivative

4-Ethyl-3-formyl-2,6-diphenylpyrylium perchlorate was obtained from 2,6-diphenylpyrylium perchlorate in three steps. Its reaction with triethyl orthoformate was accompanied by rearrangement of the initial pyrylium ring and led to pyrano[3,4-c]pyran-7-ium perchlorate system through a domino process involving ethanol addition-elimination. A plausible mechanism of the reaction is suggested on the basis of DFT quantum-chemical calculations. Reaction of the obtained pyrano[3,4-c]pyran-7-ium perchlorate with ammonium acetate led to a 2,7-naphthyridine derivative without a skeletal rearrangement.

Structural and Spectral Properties of Photochromic Diarylethenes: Size Effect of the Ethene Bridge.

The effect of the size of the ethene bridge on the structural and spectral properties of photochromic diarylethenes, which remains a poorly understood phenomenon, was studied as applied to diarylethenes containing unsymmetrical (cyclohexenone and cyclopentenone) and symmetrical (cyclohexene and cyclopentene) ethene bridges. Thiophene, oxazole, and imidazole derivatives were used as aryl moieties. An increase in the size of the ethene bridge in the cycloalkenone series was found to be accompanied by a hypsochromic shift of the absorption maximum of the photoinduced form, whereas no difference was found for cycloalkenes. A detailed analysis of the NMR spectra (including 2D experiments) revealed previously unknown effects associated with the existence of an intramolecular hydrogen bond (CH···N) between the six-membered ethene bridge and the azole substituents. The NMR experimental data obtained were confirmed by DFT quantum chemical calculations and X-ray analysis. It was found that an intramolecular hydrogen bond favors an increase of the quantum yield of the photocyclization reaction.

Molecular structure, spectroscopic characterization, HOMO and LUMO analysis of PU and PCL grafted onto PEMA-co-PHEMA with DFT quantum chemical calculations

A newly synthesized polycaprolactone (PCL) and polyurethane (PU) polymers, which grafted onto poly (ethylmethacrylate-co-2-hydroxyethyl methacrylate) (PEMA-co-PHEMA) were characterized both theoretically and experimentally. The FTIR and 1H NMR spectra were recorded for the PCL and PU polymers and the experimental values were compared the theoretical values. The molecular structure evaluation, vibrational frequencies and 1H NMR chemical shift values, which carried out by using gauge including atomic orbital (GIAO) approach, of the PCL and PU polymers were calculated by using density functional method (DFT/B3LYP) with 6-311G (d, p) as a basis set in the ground state. The calculated data such as vibrational frequencies and chemical shift values show good agreement with experimental values. Besides, the thermodynamic properties such as rotational temperatures, rotational constants, zero-point vibrational energy, specific heat capacity, thermal energy, entropy, enthalpy, the electronic properties such as HOMO and LUMO energies, and molecular electrostatic potential (MEP) surfaces for the PCL and PU were calculated and interpreted.