DFT Study on the Heterofullerene C48O12 with Rare Th Symmetry

The molecule with T_h symmetry is rare. A novel C60-like molecule C48O12 with rare Th symmetry has been studied at the B3LYP/6-31G(d) level of theory. Its structural, electronic, vibrational, NMR, and thermodynamic properties have been calculated at the B3LYP/6-31G(d) level of theory. Vibrational modes have been assigned according to their symmetry. There are 73 independent vibrational modes: 22 IR-active modes with T u symmetry and 37 Raman-active modes with Ag , Eg and Tg symmetry, respectively. The heat of formation has been calculated by using isodesmic reactions, 765.7 kJ mol-1 . According to the heat of formation and the HOMO-LUMO gap, C48O12 with rare Th symmetry is more stable than C60 .     

DFT Study on a Heterofullerene C_(58)Sn with Odd Number of Atoms

Density functional theory calculations and structural minimization techniques have been employed to characterize the structural and electronic properties of [5,6]-heterofullerene-C58Sn-C2. Since the heterofullerene molecule CssSn has a nearly planar tetra-coordinated Sn atom on the skeleton of cage, it is a heterofullerene molecule with odd number of atoms and a novel molecule. Vibrational frequencies of the molecule have been calculated at the B3LYP/CEP-31G level of theory. The absence of imaginary vibrational frequency confirms that the molecule corresponds to a true minimum on the potential energy hypersurface, and its heat of formation was estimated in this study. Owing to the C2 symmetry of [5,6]-heterofullerene-C58Sn-C2, it is a chiral molecule.     

Reaction of C2HCl2＋O2： Combined TR-FTIR Spectroscopy and Electronic Structure

The product channels and mechanisms of the C2HC12＋O2 reaction are investigated by step-scan time-resolved Fourier transform infrared emission spectroscopy and the G3MP2// B3LYP/6-311G（d,p） level of electronic structure calculations. Vibrationally excited products of HCI, CO, and CO2 are observed in the IR emission spectra and the product vibrational state distribution are determined which shows that HCI and CO are vibrationally excited with the nascent average vibrational energy estimated to be 59.8 and 51.8 kJ/mol respectively. In combination with the G3MP2//B3LYP/6-311G（d,p） calculations, the reaction mechanisms have been characterized and the energetically favorable reaction pathways have been suggested.     

Equilibrium Structures and Isomerization Reactions of the Unsaturated Germylenoid H2C=GeLiF

The unsaturated germylenoid H2C=GeLiF has been studied by using DFT method at the B3LYP/6-311+G (d, p) level. Geometry optimization calculations indicate that H2C=GeLiF has three equilibrium configurations, in which the p-complex is the lowest in energy and the most stable structure. Two transition states for isomerization reactions of H2C=GeLiF are located and the energy barriers are calculated. For the most stable one, vibrational frequencies and infrared intensities have been predicted.     

Thermodynamic Properties and Relative Stability of Polyhydroxylated Dibenzo-p dioxins Calculated by Density Functional Theory

In this work, partial thermodynamic properties of polyhydroxylated dibenzo-p-dioxins (PHODDs) are calculated by density functional theory (DFT) with the Gaussian 03 program at the B3LYP/6-311G** level. By comparing the total energy Eθ values, it is found that two types of hydrogen bonds exist in PHODDs, one between a hydroxyl and the parent compound (dibenzop-dioxin) with bond energy of approximate 15.7 kJ/mol and the other between two ortho hydroxyl groups with higher bond energy of about 18.3 kJ/mol. Hydrogen bonds have an effect on the conformation stability. On the basis of evaluating the strength of these two types of hydrogen bonds, 75 most stable congeners are ascertained. The relations of calculated thermodynamic parameters (total energy Eθ, zero-point vibrational energy ZPE, correction value of thermal energy Ethθ, heat capacity at constant volume CVθ) with the number and position of hydroxyl substitution (NPHOS) are also discussed. The results show that the NPHOS models can be used to predict the thermodynamic properties for PHODD congeners. In addition, the values of molar heat capacities at constant pressure (Cp,m) from 200 to 1000 K for PHODD congeners are calculated, and the temperature dependence relation of Cp,m is obtained with the least-squares method.     

DFT Study on the Structural, Electronic, and Spectroscopic Properties of the Highest Epoxygenated Fullerene C36O18

Theoretical investigation on the highest epoxygenated fullerene C36O18 formed from the initial C36 fullerene with D6h symmetry has been performed at the B3LYP/6-31G(d) level. Their equilibrium structures, thermal stabilities, electronic structures, vertical ionization potentials, vertical electron affinities, vibrational frequencies and 13C NMR chemical shifts have been studied. The calculation results showed that C36O18 isomers have higher LUMO-HOMO energy gaps than the fullerene C36 and should be more stable. Compared with C36 , it is less possible for C36O18 to accept or donate electrons from reduced VEAs and enhanced VIPs. It has been found that C36O18 isomers are not aromatic at all or antiaromatic on analyzing the NICS values. The present study will encourage further theoretical and experimental analyses of this system in future.     

Quantum-chemical Investigations of Structures and Stabilities of Ethynyl-or Ethenyl-expanded [n]-Prismanes

Quantum-chemical calculations on some derivatives of [n]-prismanes expanded by ethynyl or ethenyl groups have been performed using density functional theory (DFT) method.Their geometric structures,electronic structures,vertical ionization potentials and vertical electron affinities have been obtained at the B3LYP/6-31G** level of theory.Meanwhile,the total strain energy has been investigated in detail and compared with [n]-prismane and other derivatives.The present paper has also computed the enthalpies of formation for different isomers so as to evaluate their thermal stabilities.     

FT-IR, Raman and NMR Spectra, Molecular Geometry, Vibrational Assignments, ab initio and Density Functional Theory Calculations for Diethyl Phthalate

Phthalate acid esters (PAEs) possess endocrine disruptive effects and can produce reproductive and developmental toxicities. In this paper, both experimental and theoretical studies on FT-IR, Raman and 1H NMR spectra of diethyl phthalate (DEP) have been carried out. The geometrical structure of DEP was optimized at the HF/6-31G*, HF/6-311G**, B3LYP/6-31G*, and B3LYP/6-311G** levels, respectively. The harmonic vibrational frequencies, IR intensity, Raman activity and 1H NMR chemical shifts have been computed at the B3LYP/6-31G* and B3LYP/6-311G** levels. Anharmonic corrections to frequencies were obtained by means of second-order perturbation theory (PT2) at the B3LYP/6-31G* level. Based on potential energy distribution (PED), the vibrational assignments have also been performed. The theoretical calculation values were compared with the experimental observations and the results indicate they are in excellent agreement.     

Theoretical Studies on Intermolecular Hydrogen-bond Interactions between Hexamethylenetetramine and Nitric Acid

The structures of the complexes generated by hexamethylenetetramine and nitric acid have been fully optimized by B3LYP method at the 6-311++G** and aug-cc-pVTZ levels. The intermolecular hydrogen-bonding interactions have been calculated by the B3LYP/6-311++G**, B3LYP/aug-cc-pVTZ, MP2(full)/6-311++G** and CCSD(T)/6-311++G** methods, respectively. The NBO (nature bond orbital), AIM (atom in molecule), temperature effect and solvation effect have been analyzed to reveal the origin of the interactions. The results indicate that the stable hydrogen-bonded complexes could be generated by hexamethylenetetramine and nitric acid. The interactions follow the order of (a)>>(e)>(b)>(c)>(d)>(f)>(g). The C-N bonds which are adjacent to the methylene involving the hydrogen bonds tend to break in the chemical reaction. Due to the exothermic process, low temperature is conducive to the formation of the composition, which tallies with the experimental result.     

Synthesis,Crystal Structure,Characterizationand Quantum Chemical Studies on 1N-Acetyl-3-（2,4-dichloro-5-fluorophenyl）-5-（p-methyl-phenyl）-2-pyrazoline

1N-Acetyl-3-（2,4-dichloro-5-fluoro-phenyl）-5-（p-methyl-phenyl）-2-pyrazoline has been synthesized and characterized by elemental analysis, IR, UV-Vis and X-ray single-crystal diffraction. Ab intio calculations have been carded out for the compound by using both B3LYP and HF methods at the 6-31G^＊ basis set. The calculated results show that the predicted geometry can well reproduce the structural parameters. The electronic absorption spectra calculated by B3LYP/6-31G^＊ method are approximate to the experiments and the Natural Bond Orbital （NBO） analyses suggest that the above electronic transitions are mainly assigned to n→π^＊ and π→π^＊ transitions. CIS-HF/6-31G^＊ method is not suitable to predict the electronic spectra for the title compound. The calculation of the second order optical nonlinearity was carded out, giving the value of molecular hyperpolarizability equal to 2.194^＋ 10^-30 esu. On the basis of vibrational analyses, the thermodynamic properties of the compound at different temperature have been calculated, revealing the correlation between C p, m^0, S m^0, H m^0 and temperature.     

Theoretical Study on the High Energy Density Compound Hexanitrohexaazatricyclotetradecanedifuroxan

Density functional theory （DFT） has been employed to study the molecular geometries, electronic structures, infrared （IR） spectra, and thermodynamic properties of the high energy density compound hexanitrohexaazatricyclotetradecanedifuroxan （HHTTD） at the B3LYP/6-31G^＊＊ level of theory. The calculated results show that there are four conformational isomers （α, β, γ and δ） for HHTTD, and the relative stabilities of four conformers were assessed based on the calculated total energies and the energy-gaps between the frontier molecular orbitals. The computed harmonic vibrational frequencies are in reasonable agreement with the available experimental data. Thermodynamic properties derived from the IR spectra on the basis of statistical thermodynamic principles are linearly correlated with the temperature. Detonation performances were evaluated by using the Kamlet-Jacobs equations based on the calculated densities and heats of formation. It was found that four HHTTD isomers with the predicted densities of ca. 2 g·cm^-3, detonation velocities near 10 km·s^-1, and detonation pressures over 45 GPa, may be novel potential candidates of high energy density materials （HEDM）. These results may provide basic information for the molecular design of HEDM.     

BONDING CHARACTERISTICS OF COMPLEXES[MoS4（CuCN）n]2—（n=1,2）

<正> The electronic structures and bonding properties of the Mo-Cu-S complexes with a general formula [MoS4(CuCN)n]2-(n=1,2)have been investigated by using CNDO/2 method,and the effect of electron transfer on the formation of the Mo-Cu-S complexes has been discussed based on the bonding properties and the energy of the frontier orbitals.     

Studies of Structural and Thermodynamic Properties for Polychlorinated Thianthrenes by Density Functional Theory

The structural and thermodynamic （PCTAs） in the ideal gas state at 298.15 K and 1.013 properties of 75 polychlorinated thianthrenes ×10^5 Pa have been calculated at the B3LYP/6- 31G＊ level using Gaussian 98 program. Based on the output data of Gaussian, the isodesmic reactions were designed to calculate standard enthalpy of formation （△fH^θ） and standard free energy of formation （△fH^θ） of PCTAs congeners. The relations of these thermodynamic parameters with the number and position of C1 atom substitution （Npcs） were discussed, and it was found that there exists high correlation between thermodynamic parameters （total energy （TE）, zero-point vibrational energy （ZPE）, thermal correction to energy （Eth）, heat capacity at constant volume （Cv^θ）, entropy （S^θ）, enthalpy （H^θ）, free energy （G^θ）, standard enthalpies of formation （△fH^θ） and standard Gibbs energies of formation （△fG^θ）） and Npcs. On the basis of the relative magnitude of their △fG^θ, the order of relative stability of PCTA congeners was theoretically proposed. In addition, the correlations between structural parameters and Npcs were also discussed. The good correlations were found between molecular average polarizability （α）, energy of the highest occupied molecular orbital （EHOMO）, molecular volume （Vm） and Npcs, and all R^2 values are larger than 0.95. Moreover, it was supposed that the isomer groups with higher toxicity should be Tri-CTA and TCTA.     

DFT Studies on Thermal Stabilities,Electronic Structures,and ~（13）C Chemical Shifts of C_（24）O_2 Based on Fullerene C_（24）（D_6）

Quantum chemical calculations on some possible equilibrium geometries of C24O2 isomers derived from C24 (D6) and C24O have been performed using density functional theory (DFT) method. The geometric and electronic structures as well as the relative energies and thermal stabilities of various C24O2 isomers at the ground state have been calculated at the B3LYP/6-31G(d) level of theory. And the 1,4,2,5-C24O2 isomer was found to be the most stable geometry where two oxygen atoms were added to the longest carbon-carbon bonds in the same pentagon from a thermodynamic point of view. Based on the optimized neutral geometries, the vertical ionization potential and vertical electron affinity have been obtained. Meanwhile, the vibrational frequencies, IR spectrum, and 13C chemical shifts of various C24O2 isomers have been calculated and analyzed.     

Comparative Study on Thermodynamic Properties and Stabilities of Polychloro-phenazines and Polychlorinated Dibenzo-p-dioxin

The thermodynamic properties and molecular volumes （Vm） of 76 polychlorophenazines （PCPZs） have been calculated at the B3LYP/6-31G^＊ level by using density functional theory. The isodesmic reactions were designed to calculate standard enthalpy of formation （△fH^θ） and standard free energy of formation （△fG^θ） of PCPZ congeners. According to the relative magnitude of their △fG^θ, the order of relative stability of PCPZ congeners was theoretically proposed. Comparing the results with those of polychlorinated dibenzo-p-dioxin （PCDD） isomers, it was found that S^θ, △fH^θ, △fG^θ, Vm and the order of relative stability of PCPZ congeners were quite similar to those of PCDDs.     

Quantum Chemical Study of CnAl2^± （n=1～10） Clusters： Structure and Stability

Geometries, electronic structures and vibrational frequencies of CnAl2± clusters have been investigated by using the B3LYP-DFT method in the range of n = 1～10. At the B3LYP/6-311G level, the ground state structures of CnAl2± clusters are planar or linear with terminal aluminum atom. In these structures, the C–C bonds are alternately changed between double and triple. The changing magnitude of the averaged bond length decreases with the increase of cluster size. The energetic analysis showed that CnAl2± clusters with even n are more stable than those with odd n.     

Hydrogen Bonding Character Between the Glycine and BF4^-

The hydrogen bonding character between the BF4- and glycine was theoretically studied at the level of B3LYP/6-31＋G^＊, single point energies were performed at the level of B3LYP/6-311＋＋G^＊＊. The relevant geometrical characteristics, energy properties, as well as the characters of the intramolecular hydrogen bonds have been studied. Atoms in molecule theory topological analysis indicated the （3,-1） critical points for hydrogen bonds. In addition, the electron density and Laplacian were in the range suggested for the hydrogen bonds. Especially, the changes of atomic charge, hydrogen upon hydrogen bonds formation dipole moment, enegry as well as volume of the were systemitically discussed.     

A Density Functional Theory Study on Electronic Structure and Second—order Nonlinear Optical Properties of Some Push—Pull Molecules

Time-dependent density-functional theory(TDDFT)has been applied to calculate the electronic structure and second-order nonlinear optical(NLO) properties of some organic molecules.The two-dimensional(2-D)charge transfer charateristics of calculated molecules were studied and compared with corresponding experimental results.All the theoretical results agree well with the measurement.For 2-D molecule with two-fold symmetry,the dominant charge transfer is off-diagonal,while for three-fold symmetry 2-D molecule,the dominant charge transfer is not only between branches and central group but also among branches.     

Theoretical Investigations into the Intermolecular Hydrogen-bonding Interactions between Azacyclopentane-2-one and N-Methylol Ethanone

The structures of the complexes formed between N-methylol ethanone(model molecule of ceramide) and azacyclopentane-2-one(the model molecule of azone) have been fully optimized at the B3LYP/6-311++G** level.The intermolecular hydrogen bonding interaction energies have been calculated by using the B3LYP/6-311++G**,B3LYP/6-311++G(2df,2p),MP2(full)/6-311++G** and MP2(full)/6-311++G(2df,2p) methods,respectively.The results show that strong O–H···O=C,N–H···O=C and C–H···O=C hydrogen bonds could exist between azacyclopentane-2-one and N-methylol ethanone.The formation of the complexes might change the conformation of ceramide molecule and thus cause better percutaneous permeation for the drugs.This is perhaps the origin of the permeation enhances the activity of azone for medicament,as is in accordance with the experimental results.The hydrogen-bonding interactions follow the order of(a) (c) (b) (d) (g) ≈(e) ≈(i) (h) (f).The analyses of frequency,NBO,AIM and electron density shift are used to further reveal the nature of the complex formation.In the range of 263.0~328.0 K,the complex is formed via an exothermic reaction,and the solvent with lower temperature and dielectric constant is favorable to this process.     

Effect of Zr and C Co-doping on the Optical Properties and Electronic Structure of TiO_2

The systematic trends and effect introduced by Zr and C co-doping to TiO2 of electronic structure and optical properties of anatase TiO2 have been calculated by the plane-wave ultra-soft pseudopotential density functional theory (DFT) method within the generalized gradient approximation (GGA) for the exchange-correlation potential. Through the current calculations, the density of states (DOS), energy band structure and optical absorption coefficients have been obtained for TiO2 and compared with the doped TiO2, and the influence of electronic structure and optical properties caused by Zr and C co-doping has been presented qualitatively together. The results revealed that the energy band gap has been decreased owing to the doped Zr and C, whereas the optical absorption coefficients have been increased in the region of 400～800 nm and a red shift of absorption band can be found. Accordingly, photo catalytic activity of TiO2 has been enhanced. The current calculations are in good agreement with the experimental data.