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Alkanes are deceptively simple in their geometric structures, yet their electronic structures are a tough nut to crack. We employ two total energy partition schemes in density functional theory and the information-theoretic approach quantities to dissect the so-called isomerization problem. From our validation results, we have found theoretical methods, basis sets, dispersion corrections, and numerical integration grids all make contributions to the total energy difference. We highly recommend that PBE0-D3(BJ)/def2-QZVPP is a good choice for studying the longer alkane isomerization issue. We further find that the electrostatic potential dominates the isomerization of alkanes, provided that empirical dispersion is added. This observation contrasts the commonly held belief that electron delocalization dictates alkane isomerization. We also find that molecular polarizability can be linearly correlated with some ITA quantities (such as Shannon entropy and Fisher information), indicating that simple density-based functions can be good descriptors of molecular properties.

To better understand the effect of the interaction of dye molecules at the interface of clays on thermochromism, we report here a new preparation strategy for a clay-based reversible thermochromic material, namely a nanohybrid prepared by heavily grinding the Congo red dye with palygorskite. Firstly, the hybrid was prepared by liquid-phase adsorption–desorption method in an acidic system with a pH less than 3.5. The color of the hybrid changed from blue to red through heavy grinding, which is mainly due to such a process producing some Si–O− broken bonds, which capture H+ ions in the protonated dye molecule, thus transforming it from the ammonium and azonium forms to the neutral form, leading to color change. Furthermore, the color of the heavily ground hybrid changed from red to purple after heating, the transition point being around 110 °C. This is mainly due to the fact that both adsorbed and zeolitic water in palygorskite were removed by temperature rise. These two kinds of water can interact with the dye molecules by hydrogen bonding, the destruction of which leads to the change of the balance between the different forms of dye molecules in the hybrid, further affecting the color. The reversible desorption and adsorption of the two kinds of waters determines the reversibility of the thermochromic property in the heavily ground hybrid. A polyvinyl alcohol film prepared with the pigment exhibited an excellent thermochromic property changing color (from red to purple) at 110 °C; and no significant change in performance was observed after repeated use 30 times. This clay-based hybrid can be used as a thermochromic pigment, e.g., in the sterilization of food and medical equipment, the preparation of intelligent tires and other related fields.

Organic nanomaterials with efficient ROS generation and high photothermal conversion efficiency have emerged as a new generation therapeutic agent for PDT/PTT synergistic cancer treatment. However, most of the organic nanomaterials exhibited weak emission in water because of the aggregation-caused quenching (ACQ) effect, which seriously hampers their biological application in fluorescence bioimaging. In this study, we design and synthesize a new organic small molecule (T-BDP) with a donor–acceptor–donor (D–A–D) structure by the conjugation of boron-dipyrromethene (BODIPY) and triphenylamine (TPA). Moreover, a 1,8-naphthalenediimide (NI) structure with electron-withdrawing ability is introduced onto the core of BODIPY to further enhance the intramolecular charge transfer, leading to the redshift of absorption to the near-infrared region. T-BDP displays significant aggregation-induced emission (AIE) performance, probably due to the presence of two twisted TPA groups onto the BODIPY core. Accordingly, after self-assembly into nanoparticles, T-BDP NPs exhibit strong near-infrared emission in water. Under single 635 nm laser irradiation, T-BDP NPs could generate reactive oxygen species and heat simultaneously. The photothermal conversion efficiency of T-BDP NPs is determined to be 50.9%. The low dark toxicity and high photocytotoxicity of T-BDP NPs are verified against A549 cells using the MTT assay and the AM/PI staining method. Due to the strong emission of T-BDP NPs, their accumulation and subcellular localization in cancer cells are observed using a laser confocal fluorescence microscope. The results demonstrate that T-BDP NPs are mainly located in the lysosomes of cancer cells. Thus, the as-prepared small molecule-based AIE nanoparticles hold great potential for fluorescence imaging-guided PDT/PTT synergistic tumor therapy.

The chemoselective catalytic reduction of nitro scaffolds to value-added amine functions is desirable but challenging. We developed a combined KOtBu/BEt3 catalyst for deoxygenative reduction of nitroarenes, nitro heteroarenes and even notoriously challenging nitroalkanes using pinacolborane under mild reaction conditions. The novel transition-metal-free strategy is readily applicable to the preparation of commercially available pharmaceuticals.

The selective catalytic C–N bond cleavage of amides into value-added amine products is a desirable but challenging transformation. Molecules containing iminodibenzyl motifs are prevalent in pharmac...

The condensation of 4-diethylaminosalicylaldehyde and 3,5-di-tert-butyl-salicylaldehyde with 3,4-diaminobenzoic acid afforded two salophen type Schiff base ligands, L1 and L2, respectively. Subsequently, their corresponding platinum(II) and zinc(II) salophen complexes (PtL1, PtL2, ZnL1 and ZnL2) were synthesized through the reaction of the two salophen ligands with potassium tetrachloroplatinate(II) and zinc(II) acetate, respectively. The structures of the metallosalophen complexes were characterized by 1H NMR, infrared spectroscopy and high-resolution mass spectrometry. Their photophysical properties and cyclic voltammetry behaviours were investigated in detail. Using these complexes as photosensitizers, the dye-sensitized solar cells (DSSCs) were prepared and inferior performances were recorded due to their planar structures and significant aggregations. Upon the addition of chenodeoxycholic acid (CDCA) as co-adsorbents, the aggregation behaviours could be effectively inhibited and the cell performances could be enhanced with the highest power conversion efficiency up to 2.57% for PtL1. Considering the simplicity in the preparation and the structure variability, these metallosalophen complexes represent a new class of photosensitizers for DSSC applications.

Three types noncovalent interactions (type I, II and III) between pyrazine (C

Except σ-type and π-type halogen bond, a new type of the parallel halogen bond interactions between pyrazine (C4H4N2) and XF (X=F,Cl,Br and I) have been discovered at the MP2/aug-cc-pVTZ level. Through comparing the calculated interaction energy,we can know that the π-type halogen bonding interactions are weaker than the corresponding σ-type halogen bonding interactions, and parallel halogen-bond interactions are weaker than the corresponding π-type halogen bonding interactions in C4H4N2-XF complexes. SAPT analysis shows that the electrostatic energy are the major source of the attraction for the σ-type halogen bonding interactions while the parallel halogen-bond interactions are mainly dispersion energy. For the π-type halogen bonding interactions in C4H4N2-XF(X=F and Cl) complexes, electrostatic energy are the major source of the attraction, while in C4H4N2-XF(X=Br and I) complexes the electrostatic term, induction and dispersion play equally important role in the total attractive interaction.NBO analysis, AIM theory and Conceptual DFT are also be utilized.

The condensation of 3,3′-diaminobenzidine with different substituted salicylaldehyde afforded three dimeric salophen ligands H4L1-H4L3. Subsequently, their corresponding dimeric salophen platinum(II) complexes Pt2L1-Pt2L3 were prepared through the metallation of ligands with K2PtCl4. The ligands and complexes were characterized by 1H NMR, infrared spectroscopy, mass spectrometry and elemental analysis and their thermal stabilities, photophysical properties, and electrochemical behavior were further investigated in detail. Using Pt2L1 as phosphorescent emitting materials, deep red light-emitting devices were fabricated with moderate efficiency. The maximum current efficiency, power efficiency, and brightness for the 3.0 wt % Pt2L1 doped OLED are 1.39 cd A−1, 0.74 lm·W−1 and 1774 cd m−2, respectively. Given the synthetic simplicity and ease of structural variation, the preliminary results here indicate that these dimeric salophen complexes are good candidates for phosphorescent OLED.

The selective catalytic C-N bond cleavage of amides into value-added amine products is a desirable but challenging transformation. Molecules containing iminodibenzyl motifs are prevalent in pharmaceutical molecules and functional materials. Here we established a combined KOH/BEt

This work reports an efficient co-catalyst of AgRu nanoparticles supported on γ-Al2O3 for highly selective hydrogenation of the C=C bond of cinnamaldehyde (CAL) at 443 K, uncovering a catalytic route for selective hydrocinnamaldehyde production from the CAL. This kind of chemo-selectivity of AgRu/γ-Al2O3 catalyst seems unique since any competitive hydrogenation at the conjugated C=O bond was significant.

The solubility of sodium 1-naphthalenesulfonate and sodium 2-naphthalenesulfonate in pure organic solvents of acetone, 1,4-dioxane, cyclohexanone, ethanol, ethyl acetate and isopropanol were measured by using the isothermal saturation method at temperature ranging from (278.15 to 323.15) K under 101.3 kPa. The mole fraction solubility of sodium 1-naphthalenesulfonate and sodium 2-naphthalenesulfonate in the selected pure solvents increased with the increase in temperature. The maximum mole fraction solubility of sodium 1-naphthalenesulfonate was observed in ethanol (2.767 × 10 − 3 at 323.15 K), followed by that in 1,4-dioxane (2.028 × 10 − 3 at 323.15 K), cyclohexanone (1.522 × 10 − 3 at 323.15 K), isopropanol (1.094 × 10 − 3 at 323.15 K), acetone (5.997 × 10 − 4 at 308.15 K) and ethyl acetate (3.111 × 10 − 4 at 323.15 K); For sodium 2-naphthalenesulfonate + solvents systems, the maximum mole fraction solubility was observed in ethanol (1.178 × 10 − 3 at 323.15 K), followed by that in 1,4-dioxane (1.027 × 10 − 3 at 323.15 K), ethyl acetate (6.197 × 10 − 4 at 323.15 K), cyclohexanone (3.233 × 10 − 4 at 323.15 K), isopropanol (1.058 × 10 − 4 at 323.15 K) and acetone (9.683 × 10 − 5 at 323.15 K). The measured solubility data were correlated and calculated by using the modified Apelblat equation, λh equation and NRTL model. The calculated solubilities agreed better with the experimental values by using the modified Apelblat equation than the other two models. Moreover, the mixing properties including the mixing Gibbs energy, mixing enthalpy, mixing entropy, activity coefficient at infinitesimal concentration ( γ 1 ∞ ) and reduced excess enthalpy ( H 1 E , ∞ ) were calculated by NRTL model.

The condensation of different groups substituted salicylaldehydes with aniline and 2,4,5-trifluoroaniline, afforded five one-armed Schiff base ligands HL 1 , HL 2 , HL 3 , HL 4 and HL 5 . And their platinum(II) complexes Pt(L 1 ) 2 , Pt(L 2 ) 2 , Pt(L 3 ) 2 , Pt(L 4 ) 2 , Pt(L 5 ) 2 and PtL 5 · DMSO were prepared through the metallation of ligands with K 2 PtCl 4 . All ligands and complexes were characterized by 1 H NMR, infrared spectroscopy, mass spectrometry and single crystal X-ray diffraction. And their thermal stability, photophysical properties, and electrochemical behaviors were investigated in detail. Using these complexes as phosphorescent emitting materials, blue to orange light-emitting devices were fabricated with moderate efficiencies. The maximum current efficiency, power efficiency, and brightness for the 3.0 wt % Pt(L 3 ) 2 doped OLED are 1.12 cd A −1 , 0.62 l m W −1 and 1521 cd m −2 , respectively. Given the synthetic simplicity and ease of structural variation, the results here indicate that these platinum(II) Schiff base complexes are good candidates for phosphorescent OLEDs.

The oxidation state, also called oxidation number, of atoms in molecules is a fundamental chemical concept. It is defined as the charge of an atom in a molecule after the ionic approximation of its heteronuclear bonds is applied. Even though for simple molecules the assignment of oxidation states is straightforward, redundancy and ambiguity do exist for others. In this work, we present a density-based framework to determine the oxidation state using the quantities from the information-theoretic approach. As a proof of concept, we examined six elements for a total of 49 molecules. Strong linear correlations were obtained with Shannon entropy, Ghosh-Berkowitz-Parr entropy, information gain, relative Renyi entropy of orders 2 and 3, and Hirshfeld charge. We also discovered that the crystal radius of elements plays the key role in rationalizing the system dependent nature of these strong linear correlations. The validity and effectiveness of our results were demonstrated by the examples of molecules containing elements with two or more oxidation states. Our results should be applicable to more complicated systems in assigning different oxidation states.

The equilibrium solubility of sodium 2,4-diaminobenzene sulfonate in liquid mixtures (methanol + water, isopropanol + water, and 1,2-propanediol + water) were determined at temperatures ranging from (273.15 to 323.15) K. The solubility of sodium 2,4-diaminobenzene sulfonate increased with temperature increment but decreased with the concentrations of methanol, isopropanol or 1,2-propanediol in liquid mixtures. The obtained solubility data were correlated by Apelblat equation and Sun model. On the base of the measured solubility, the dissolution enthalpy ( Δ H sol o ) of the dissolution process were calculated.

2,4-Dibromopyridines reacted with arylacetylenes, catalyzed by Pd(CF 3 COO) 2 /CuI/PPh 3 in the presence of i -Pr 2 NH in CH 3 CN at reflux for 24 h, to afford 2-alkynylpyridines in good to high yields, while 2,3- and 2,5-dihalopyridines reacted with arylacetylenes, catalyzed by Pd(OAc) 2 /CuI/PPh 3 in the presence of i -Pr 2 NH in CH 3 CN at reflux for 24 h, to afford 2-alkynylpyridines in good to high yields.

As far as we know, the adsorption behavior of coordination complex on metal-supported oxide film has never been systematically investigated before, which obstructs the rational design and functional application of inverse composite catalyst toward chemisorbing substances with coordination bonds. In clinical practice and experiments, magnesia has been used together with cisplatin for intravenous magnesium supplementation, to reduce the side effects of cisplatin. In this contribution, interaction profile between cisplatin anticancer drug with magnesia and gold-supported magnesia is elucidated for the first time utilizing periodic density functional theory (DFT) calculations with dispersion corrections. Equilibrium geometries, translation potential profile, differential charge density contour, particular occupied orbitals, projected density of states and electron localization function are characterized to reveal the structural features and electronic properties of cisplatin chemisorption on magnesia-gold hybrid structure. It is anticipated that the interaction mechanism of cisplatin with inert and nontoxic magnesia film could provide useful clue for novel application of oxide-metal composite constructed by depositing oxide film on metallic slab toward chemisorbing and treating coordination compounds.

The pnicogen and halogen bonding interactions in the PH2X---BrCl(X = H, F, OH, OCH3 and CH3) complexes have been studied at the MP2/aug-cc-pVTZ level. Analysis of interaction energies shows that the pnicogen-bonded structures are less stable than the corresponding halogen-bonded structures. The pnicogen and halogen bonds were also studied by conceptual DFT reactivity indices. Noncovalent interaction (NCI) and SAPT analysis reveals that the dispersion interactions dominate the pnicogen-bonded complexes of PH2X---BrCl in nature, while the halogen-bonded complexes are dominantly electrostatic energy.

The pnicogen and halogen bonding interactions in the PH

The equilibrium solubilities of sodium 3-nitrobenzenesulfonate and sodium 4-nitrobenzenesulfonate in ethanol, acetone, 1-butanol, ethyl acetate, cyclohexanone, and tetrahydrofuran were measured experimentally by using a steady-state method at temperatures ranging from 283.15 to 323.15 K under 101.3 kPa. The solubilities of sodium 3-nitrobenzenesulfonate increased faster in ethanol than in the other solvents as the temperature increase. The order of the solubility values from high to low was: ethanol > acetone > tetrahydrofuran > 1-butanol > ethyl acetate > cyclohexanone. For the systems of sodium 4-nitrobenzenesulfonate + solvents, the sequence of the mole fraction solubility data was: acetone > ethanol > (cyclohexanone, 1-butanol) > (ethyl acetate, tetrahydrofuran). The experimental solubility data were correlated with the modified Apelblat equation and λh equation. The results indicated that the calculated values via the modified Apelblat equation agreed well with experimental results for sodium 3/4-nit...

Not too much is known about the beryllium bonding interactions. Here, the total energy partition schemes as well as DFT-SAPT are used to explore the origin and nature of the beryllium bonds from an energetic point of view. In addition, Shannon entropy and Fisher information, which are based upon the electron probability density, rather than the shape function, are adopted to dissect the impact resulted from a wavefunction perspective. Results reveal that the electrostatic potential largely causes the formation of beryllium bonds. Moreover, there are strong linear relationships between atomic Shannon entropy and Fisher information of Be atoms, which can aid to distinguish the different sources of noncovalent weak interactions.

Molecular acidity is one of the important physiochemical properties of a molecular system, yet its accurate calculation and prediction are still an unresolved problem in the literature. In this work, we propose to make use of the quantities from the information-theoretic (IT) approach in density functional reactivity theory and provide an accurate description of molecular acidity from a completely new perspective. To illustrate our point, five different categories of acidic series, singly and doubly substituted benzoic acids, singly substituted benzenesulfinic acids, benzeneseleninic acids, phenols, and alkyl carboxylic acids, have been thoroughly examined. We show that using IT quantities such as Shannon entropy, Fisher information, Ghosh-Berkowitz-Parr entropy, information gain, Onicescu information energy, and relative Rényi entropy, one is able to simultaneously predict experimental pKa values of these different categories of compounds. Because of the universality of the quantities employed in this work, which are all density dependent, our approach should be general and be applicable to other systems as well. © 2017 Wiley Periodicals, Inc.

Phenylpropanoids comprise a broad spectrum of biologically active natural products. As part of our ongoing research on antiepileptic active compounds from traditional Chinese herb, Acorus calamus var. angustatus Besser, three undescribed phenylpropanoids and twenty-two known ones were isolated. All the undescribed structures were determined by a combination of 1D and 2D NMR, HRMS. In addition, γ-asaronol was identified as racemates and its absolute configuration were determined by the modified Mosher's method and ECD spectral data. Furthermore, some selected isolated compounds were evaluated for their cell viability and neuroprotective activities in H2O2-induced SH-SY5Y cells. α-Asaronol, β-asaronol, 3-(2,4,5-trimethoxyphenyl)propan-1-ol and 1,2,4-trimethoxy-5-(3-methoxypropyl)benzene exerted potential protective activity from neuronal oxidative stress in all test concentrations ranging from 0.01 to 100 μM, in which the neuroprotective activity of β-asaronol was the best.

The optimizations geometries and the intermolecular interactions between C 5 H 5 N and C 4 H 4 Y(Y = O, S) with LiNH 2 have been investigated with the MP2 method and various density functional theory (DFT) including B3LYP, M06 and M06-2X. After comparing the results using the benchmark CCSD(T)/aug-cc-pVDZ approach we found that the M06 and B3LYP functionals provided the accurate and reliable results for the lithium bond. The results revealed that the complexes of C 5 H 5 N have only σ-type lithium bond complexes. The complexes of C 4 H 4 O have σ-type and π-type lithium bond complexes, while the complexes of C 4 H 4 S have only π-type lithium bond complexes. The Li–N stretch vibration has a red shift in the σ-type lithium bond complexes. However, it exhibits a blue shift in the π-type lithium bond complexes. The nature of lithium bond has been analyzed with natural bond orbital (NBO), atoms in molecules (AIMs) and symmetry adapted perturbation theory (SAPT) methods. The results indicate that σ-type lithium bond complexes interactions are predominantly electrostatic in nature, while the induction forces dominate the π-type lithium bond complexes.

Proton coupled electron transfer (PCET) and hydrogen atom transfer (HAT) mechanisms are fundamental to reactions of biological and solar energy conversion processes. We employ the descriptors including dual descriptor and electrophilic Fukui function calculated from density functional reactivity theory (DFRT) to characterize the propensity difference between the proton transfer and electron transfer. These reactivity descriptor schemes have been applied to several systems, getting conclusions in agreement with experiments in studying the PCET and HAT mechanisms.

The nature and origin of the π–H interaction in the borazine with the first-row hydrides (BH3, CH4, NH3, H2O and HF) has been investigated by carrying out high level ab initio calculations. The results indicate that the strength of the π–H interaction is enhanced as one progresses from CH4 to HF of the borazine complexes, with the exception of that of BH3. The symmetry adapted perturbation theory (SAPT) calculations were carried out to decompose the binding energy of these complexes into individual interaction energy components. Both electrostatic and dispersive energies are important in the description of these interactions.

We established two good linear relationships between pKa and acidic atom’s electrostatic potential (MEP) in the gas phase by DFT methods at B3LYP/6-31+G(d, p) level of theory. We studied 13 experimentally well-characterized singly substituted benzoic acids to determine the best level of theory. A good linear relationship between MEP and the experimental pKa data has been revealed (standard deviation (STD) = 0.081, R2 = 0.937 for model 1; STD = 0.081, R2 = 0.934 for model 2), better than the computational results in the literatures. Our models also showed that it is reliable to estimate the pKa values of multiply substituted benzoic acids.

The formation mechanism and photochromic property of a novel solid state Schiff base compound (E-isomer, C 21 H 18 I 2 N 3 O 2) derived from 4-aminoantipyrine and 3,5-diiodosalicylaldehyde is investigated in this work using density functional theory at the B3LYP/6-31l++G** level with and without solvent water presence. Our computational results show that the conversion in the gas phase is unlikely to occur and the solvent water is involved in the reaction to decrease the barrier height. We considered one to three water molecule participations in the water-catalyzed mechanism to produce the E-isomer. Time-dependent density functional theory (B3LYP/6-311+G*) is employed to examine the photochromic property of the molecule. A large Stokes shift between absorption and emission has been attributed to the intramolecular H-transfer ( O – H ⋯ N to O ⋯ H – N ) following photoexcitation of the enol species, suggesting that the keto form of the photoproduct structure plays the key role, in agreement with the experimental finding of stereoselectivity. Conceptual DFT reactivity indices are employed to rationalize the findings from the present study.

Porphyrin and pincer complexes are both important categories of compounds in biological and catalytic systems. The idea to combine them is computationally investigated in this work. By employment of density functional theory (DFT), conceptual DFT, and time-dependent DFT approaches, structure, spectroscopy, and reactivity properties of porphyrin pincers are systematically studied for a selection of divalent metal ions. We found that the porphyrin pincers are structurally and spectroscopically different from their precursors and are more reactive in electrophilic and nucleophilic reactions. A few quantitative linear/exponential relationships have been discovered between bonding interactions, charge distributions, and DFT chemical reactivity indices. These results are implicative in chemical modification of hemoproteins and understanding chemical reactivity in heme-containing and other biologically important complexes and cofactors.

Using ferric-S-methyl-porphyrin as the prototype of heme-containing complexes, we address how to accurately and efficiently carry out density functional studies for systems of biological importance. Our results indicate that GGA and meta-GGA functionals bias the lower spin state by producing levitated frontier orbitals and often fail to provide a correct description of the ground spin state. Also, we propose composite double and triple zeta quality basis sets with polarization functions applied only to the transition metal and electronegative atoms. Accurate structural and electronic properties including DFT reactivity indices have been obtained and significant gain in computational efficiency has been achieved.

Validity and interpretation of Hund's multiplicity rule for one molecular system, boron hydride, is investigated from the density functional framework in the present work. Performance of a number of approximate exchange-correlaton energy denstiy functionals from LDA, GGA and hybrid models have been examined. It has been shown that all approximate functionals are able to predict the correct energy order, both adiabatically and vertically, for different spin states of the molecule, reproducing that a higher spin state from the same electronic configuration possesses a lower total energy. It is only the hybrid functionals, however, that render the picture derived for the exact density functionl theory of excited states and multiplets, that is, the validity of Hund's rule can be interpreted by the sole contribution from the outmost orbital (i.e. HOMO) of the spin states. Systematic discrepancy between the total and HOMO energy differences have been observed for both LDA and GGA forms, indicating that they are not as good in simulating the same-spin electron correlation effect as the Hartree–Fock method. We also show that it is the same as what we have found from the Hartree–Fock theory, and justification via either the nuclear-electron attraction or the exchange energy alone is not adequate to interpret the validity of the rule.

The anomeric effect (the tendency of heteroatomic substituents adjacent to a heteroatom within the cyclohexane ring to prefer the axial orientation instead of the sterically less hindered equatorial position) is traditionally explained through either the dipole moment repulsion or the hyperconjugation effect. In this work, by employing our recent work in density functional steric analysis, we provide a novel two-component explanation, which is consistent with the common belief in chemistry that the effect has a stereoelectronic origin. With α-D-glucopyranose as the prototype, we systematically explore its conformational space and generate 32 isomers, leading to a total of 80 axial-equatorial conformation pairs. The energy difference analysis of these pairs shows that while statistically speaking the tendency is valid, the anomeric effect is not always true and can be violated. Three energy components, exchange-correlation, classical electrostatic, and density functional steric, are found to be directly proportional to the total energy difference between axial and equatorial isomers. We also found that the total dipole moment change, not the hyperconjugation effect, is a reasonable indicator of the total energy difference. However, all these correlations alone are not strong enough to provide a compellingly convincing explanation for the general validity of the effect. With the help of strong correlations between energy components, an explanation with two energy components, steric and electrostatic, was proposed in this work. We show that the axial-equatorial energy difference in general, with the anomeric effect as a special case, is dictated by two factors of the stereoelectronic origin, steric hindrance and classical electrostatic interactions, synchronously working together. Another explanation in terms of exchange-correlation and electrostatic interactions has also been obtained in this work.

Structural and dynamic properties of the building block of silica nanowires, (SiO 2)6, are investigated by BornOppenheimer quantum molecular dynamics simulations. Thirteen conformers have been identified, seven of which have not been reported before. The energy component analysis shows that the lower electrostatic interaction differentiates the global minimum from the other structures. We also observe that the maximum hardness principle can be employed to justify the molecular stability for this system. Time profiles of a few density functional reactivity indices exhibit correlations of dynamic fluctuations between HOMO and LUMO and between chemical potential and hardness. Electrophilicity, nucleaofugality, and electrofugality indices are found to change concurrently and significantly, indicating that the nanostructures sampled during the dynamic process are exceedingly reactive and rich in chemistry.

Density functional theory has been widely used to investigate the structural and electronic properties of heme-containing proteins such as cytochrome P450. Nevertheless, recent studies have shown that approximate exchange-correlation energy density functionals can incorrectly predict the stability order of spin states in, for instance, iron-containing pyridine and imidazole systems. This raises questions about the validity of earlier theoretical studies. In this work, we systematically investigate a few typical inorganic and organic iron-containing complexes and try to understand the performance difference of various density functionals. Two oxidation states of iron, Fe(II) and Fe(III), with different spin states and both adiabatic and vertical structures are considered. A different description of the outmost molecular orbital is found to play the crucial role. Local density and generalized gradient based functionals bias the lower spin state and produce a more localized frontier orbital that is higher in energy than the hybrid functionals. Energy component analysis has been performed, together with comparison of numerous structural and electronic properties. Implications of the present work to the theoretical study of heme-containing biological molecules and other spin-related systems are discussed.

A theoretical study on the formation mechanism of bisaryl oxime ether from benzaldehyde and phenoxyamine at the B3LYP/6-31++G** level indicates that the water-assisted acid-catalyzed mechanism is m...