Density functional theory calculations of dynamic first hyperpolarizabilities for organic molecules in organic solvent: comparison to experiment

Against experimental values obtained from solution-phase dc electric field induced second-harmonic generation measurements at a fundamental wavelength of 1910 nm, the performance of 20 exchange-correlation functionals in density functional theory in evaluation of solvent modulated dynamic first hyperpolarizabilities of 82 organic molecules in chloroform, 1,4-dioxane, and/or dichloromethane was evaluated. The used exchange-correlation functionals consisted of generalized gradient approximation (GGA), meta-GGA, global hybrids, and range-separated hybrids. The PCM-X/6-311+G(2d,p)//PCM-B3LYP/6-31G(2df,p) level of theory was employed. The calculated results showed functionals with the exact asymptote of the exchange potential gave satisfying linear correlation with R(2) of 0.95 between experimental data and theoretical values. With a linear correction, these functionals also provided a better accuracy with mean absolute error of 5 × 10(-30) esu than other functionals. The solvent effect and solvation scheme on the calculated property were also studied.     

Exact-exchange density functional theory for hyperpolarizabilities

Time-dependent density functional theory (TDDFT) employing the exact-exchange functional (TDDFTx) has been formulated using the optimized effective potential method for the beta static hyperpolarizabilities, where it reduces to coupled-perturbed Kohn-Sham theory. A diagrammatic technique is used to take the functional derivatives for the derivation of the adiabatic second kernel, which is required for the analytical calculation of the beta static hyperpolarizabilities with DFT. The derived formulas have been implemented using Gaussian basis sets. The structure of the adiabatic exact-exchange second kernel is described and numerical examples are presented. It is shown that no current DFT functional satisfies the correct properties of the second kernel. Not surprisingly, TDDFTx, which corrects the self-interaction error in standard DFT methods and has the correct long-range behavior, provides results close to those of time-dependent Hartree-Fock in the static limit.     

Molecular first hyperpolarizabilities of retinal and its derivatives

The hyper-Rayleigh scattering technique (HRS) has been used to determine the molecular first hyperpolarizabilities β of retinal, retinoic acid, vitamin A acetate and a retinal Schiff base in its protonated and unprotonated form. The former is responsible for the linear and non-linear optical properties of bacteriorhodopsin. A previous examination of these compounds by HRS at 1064 nm yielded surprisingly high β-values. Here, we report HRS measurements performed at 1064, 1300 and 1500 nm. The derived hyperpolarizabilities are self-consistent with the two-state model for all three wavelengths, but they are one order of magnitude lower than those reported previously.     

Density function theory study on energetic nitro-triaziridine derivatives

The series of nitro-triaziridines had been studied as high-energy density compounds at B3LYP/6-311G** and MP2/6-311G** levels by means of density functional theory. The heats of formation (HOFs), bond dissociation energies, and detonation performance had been calculated in detail. It was found that all nitro-triaziridines have high position HOFs, and electron-withdrawing of nitro, the steric hindrance, and abundant N–N bond had positive effect with increasing values of HOFs. The thermodynamic stability is estimated by bond dissociation energy and available free space per molecule in unit cell. The detonation performance had been estimated via Kamlet–Jacobs equation and relative specific, However, two different consequences were obtained for detonation performance. Hence, for nitro-triaziridines derivatives, we assumed that a large number of extra oxygen was produced in combustion reaction or explosive reaction, which was negative for the energy released. Therefore, the oxygen balance must be considered for designing high-energy compounds. We also assumed that the Kamlet–Jacobs equation may not be applicable for the compounds, which was constituted of only oxygen, hydrogen, and nitrogen elements.     

磷化镍晶体结构的密度泛函理论研究

运用密度泛函理论系统地研究了已知的磷化镍晶体如Ni3P、 Ni12P5、 Ni2P、 Ni5P4、 NiP、 NiP2 和 NiP3等的结构、成键以及相关的热力学稳定性,对于结构简易化合物（Ni2P和NiP3）的弹性行为进行了预测。这些数据有助于更好的理解磷化镍的催化活性。     

Density functional theory rationalization of the substituent effects in trifluoromethyl-pyridinol derivatives

The influence of α-substitution in the structure, bonding and thermochemical properties of trifluoromethyl-pyridinol derivatives and their protonated counterparts has been studied by means of density functional theory. The geometries of the neutral and protonated species were optimized at the B3-LYP/6-311G(d,p) level of theory. Final energies were obtained through single point B3-LYP/6-311+G(3df,2p) calculations.The relative orientation of the different substituents within the heterocycle ring favours the formation of unexpected intramolecular hydrogen bonds (IHB), which have been characterized by means of the Atoms in Molecules theory of Bader. Although weak, these IHB are of great importance for understanding the gas phase structure and the thermodynamical properties of these compounds. Surprisingly, most of the substituted investigated pyridinols present proton affinities below or close to that calculated for the unsubstituted pyridine molecule. Only pyridinols bearing strong σ or π donor activating groups show proton affinities greater than that of pyridine.     

Mechanism for large first hyperpolarizabilities of phosphonic acid stilbene derivatives

This paper presents calculations of dipole moments (mu), static polarizabilities (alpha), and first hyperpolarizabilities (beta) of phosphonic acid stilbene derivatives calculated in the framework of density functional theory. These calculations were performed using a finite field approach implemented in the density functional program ALLCHEM and were of an all-electron type using local exchange-correlation functional and specially designed basis sets. The molecular structures have been fully optimized using the semiempirical program MSINDO. Some of the investigated stilbenes have been synthesized very recently while others are described for the first time. Donor and acceptor groups of these analogues have been modified and the influence of these changes on the first hyperpolarizabilities has been investigated. This work demonstrates that the nonlinear optical response beta of these compounds increases dramatically when the acceptor moiety is displaced by analogues containing alkali metal groups. A general mechanism for the design of novel nonlinear optical materials with large first hyperpolarizabilities is described.     

Density functional theory study of formaldehyde oligomers

Hydrogen‐bonded formaldehyde oligomers (dimer to pentamer) are studied using density functional theory (DFT), the B3LYP method, and the 6‐311+G* basis set. Many‐body interaction energies are obtained to study the contribution of many‐body terms to binding energy. The basis set superposition error (BSSE)‐corrected total energies are ?229.08170, ?343.61410, ?458.16660, and ?572.70901 hartrees for dimer, trimer, tetramer, and pentamer, respectively, with corresponding binding energies ?2.55, ?4.86, ?6.99, and ?9.49 kcal/mol. Two‐body energies have been found to contribute significantly to the total binding energy in dimer to pentamer, whereas higher‐order interaction energies are negligible. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

Density functional theory study of BnC clusters

B_nC clusters (n = 3–10) were studied at the density functional theory (DFT) (B3LYP)/6‐311G** level of theory. The calculations predicted that the most stable configurations of the B_nC clusters are the (n + 1)‐membered cyclic structures. For boron–carbon clusters, the configurations containing greater numbers of three‐membered boron rings are more favorable, except for the B₇C and B₉C clusters. Through molecular orbital analysis of these B_nC clusters, we have concluded that π‐electron delocalization plays a crucial role in the stability of n + 1‐membered cyclic structures. In this paper, the relative stability of each cluster is discussed based on their single atomic‐binding energies. The capability of clusters to obtain or lose an electron was also discussed, based on their vertical electron detachment energies (VDEs), adiabatic electron detachment energies (ADEs), vertical electron affinities (VEAs) and adiabatic electron affinities (AEAs). Copyright © 2011 John Wiley & Sons, Ltd.     

吲哚分子振动光谱的密度泛函理论研究

用多种密度泛函理论(DFT)方法(BLYP/6-31G^*^*,B3LYP/6-31G^*^*,B3PW91/6-31G^*^*和SVWN/6-31G^*^*)对吲哚分子的平衡几何构型进行了优化。在优化构型的基础上计算了吲哚分子的谐力场、振动基频和红外光谱强度。计算得到的振动频率与实验值比较平均偏差对四种计算方法(BLYP/6-31G^*^*,P3LYP/6-31G^*^*,B3PW91/6-31G^*^*和SVWN/6-31G^*^*)分别为16.3,40.5,45.1和26.4cm^-^1。BLYP/6-31G^*^*理论力场被用于吲哚分子的简正坐标分析计算中。根据振动率的势能分布(PEDs)对此分子的振动基频进行了理论归属。     

苯酚分子拉曼光谱的密度泛函理论研究

采用B3LYP杂化泛函,6-31++G(d,p)基组,对苯酚分子的结构进行了优化.通过频率计算,获得了苯酚分子的拉曼光谱,并利用势能函数分布(PED)对拉曼光谱进行了指认.绘制了苯酚分子的静电势分布图,讨论了苯酚分子发生化学反应的位置,同时计算了HOMO-LUMO的能级差.通过TD-DFT计算获得了苯酚分子的吸收光谱和激发态.     

Density functional theory study of vibronic structure of the first absorption Qx band in free-base porphin

Harmonic vibrational frequencies and vibronic intensities in the first S(0)-->S(1) (pipi( *)) absorption band of free-base porphin (H(2) P) are investigated by hybrid density functional theory (DFT) with the standard B3LYP functional. The S(0)-S(1) transition probability is calculated using time-dependent DFT with account of Franck-Condon (FC) and Herzberg-Teller (HT) contributions to the electric-dipole transition moments including displacements along all 108 vibrational modes. Two weak wide bands observed in the gas phase absorption spectra of the H(2) P molecule at 626 and 576 nm are interpreted as the 0-0 band of the X(1) A(g)-->1B(3u) transition and the 0-1 band with largest contributions from the nu(10)(a(g))=1610 cm(-1) and nu(19)(b(1g))=1600 cm(-1) modes, respectively, in agreement with previous tentative assignments. Both bands are induced by the HT mechanism, while the FC contributions are negligible. A number of fine structure bands, including combination of two vibrational quanta, are obtained and compared with available spectra from supersonic jet and Shpolskij matrices. Both absorption and fluorescence spectra are interpreted on ground of the linear coupling model and a good fulfillment of the mirror-symmetry rule.     

青蒿素及其衍生物抗疟活性的密度泛函理论研究

为了深入研究青蒿素及其衍生物的抗疟活性和分子结构之间的关系,运用密度泛函理论B3LYP方法,以6-31G*为基组对青蒿素及其衍生物二氢青蒿素、蒿甲醚和青蒿琥酯进行了优化计算.从分子的几何构型、NBO电荷及前线轨道能等方面分析了青蒿素及其衍生物的抗疟活性与结构之间的关系.青蒿素及其衍生物结构中的过氧桥键是其抗疟作用的活性位,O17和O_20带负电荷越多、ΔE_(LUMO-HOMO)越低、E_(HOMO)能级越高,分子的抗疟活性越强.结果表明,4种化合物的抗疟活性顺序为:青蒿素二氢青蒿素蒿甲醚青蒿琥酯,与临床实验结果相吻合.     

Density functional theory study on the interaction of catechin and cytosine

The interacting patterns and mechanism of the catechin and cytosine have been investigated using the density functional theory B3LYP method with 6-31+G* basis set.Eleven stable structures of the catechin-cytosine complexes have been found respectively.The results indicate that the complexes are mainly stabilized by the hydrogen bonding interactions.Theories of atoms in molecules(AIM) and natural bond orbital(NBO) have been utilized to investigate the hydrogen bonds involved in all the systems.The interactio...     

白藜芦醇清除自由基活性的密度泛函理论研究

采用密度泛函理论(DFT)方法,从静态与动态两大方面分析了白藜芦醇分子酚羟基在不同溶剂中清除自由基活性的能力大小.通过白藜芦醇的结构参数、前线轨道理论、3种抽氢反应机制等方面分析了分子活性位与其性质的关系.探讨了白藜芦醇分子不同位置酚羟基清除·OH和·OOH的抗氧化机理,得到了该分子与·OOH发生抽氢反应时的过渡态结构.计算结果表明,在任何溶剂中白藜芦醇分子C(4')位上酚羟基活性最高,发生抽氢反应时反应热最小,是高活性位点.     

Density functional theory study on electron and hole transport properties of organic pentacene derivatives with electron-withdrawing substituent

Attaching electron-withdrawing substituent to organic conjugated molecules is considered as an effective method to produce n-type and ambipolar transport materials. In this work, we use density functional theory calculations to investigate the electron and hole transport properties of pentacene (PENT) derivatives after substituent and simulate the angular resolution anisotropic mobility for both electron and hole transport. Our results show that adding electron-withdrawing substituents can lower the energy level of lowest unoccupied molecular orbital (LUMO) and increase electron affinity, which are beneficial to the electron injection and ambient stability of the material. Also the LUMO electronic couplings for electron transport in these pentacene derivatives can achieve up to a hundred meV which promises good electron transport mobility, although adding electron-withdrawing groups will introduce the increase of electron transfer reorganization energy. The final results of our angular resolution anisotropic mobility simulations show that the electron mobility of these pentacene derivatives can get to several cm(2) V(-1) s(-1), but it is important to control the orientation of the organic material relative to the device channel to obtain the highest electron mobility. Our investigation provide detailed information to assist in the design of n-type and ambipolar organic electronic materials with high mobility performance.     

Density functional theory study of single-wall platinum nanotubes

Single-wall platinum nanotubes (SWPtN) were studied using spin-polarized density functional theory calculations. These nanotubes consist of 5-, 6-, and 8-Pt atoms coiling around the tubular axis forming 3.54–4.73 Å in diameter and 0.7–1.4 nm and infinite in length. Two types of wall structures, square and triangular, were investigated. The results show that triangular nanotubes are more stable. Our results suggest that it is also feasible to synthesize the 5- and 8-atom triangular nanotubes as the 6-atom Pt nanotubes were found experimentally. These SWPtN may provide a new dimension in the catalytic applications of platinum.     

The chemistry of organoimido derivatives of polyoxometalates

The chemistry of organoimido derivatives of polyoxometalates (POMs) has received increasing interest. In recent decades, a great development of the synthetic chemistry of organoimido derivatives of POMs using different imido-releasing reagents has taken place, particularly the novel DCC-dehydrating protocol to prepare organoimido derivatives of POMs was developed recently by us and co-workers. Organoimido substituted POMs as valuable building blocks can construct novel nanostructured organic-inorganic hybrid molecular materials in well-developed common organic synthesis methods, such as Pd-catalyzed carbon-carbon coupling and esterification. Therefore, the reactive chemistry of organoimido derivatives of POMs stands for the fascinating future of the chemistry of organoimido derivatives of POMs.