Toward the Rational Design of Conjugated Oligomers and Polymers: Systematic Study of the Substituent Effect in Oligothiophenes

A systematic study of substituent electronic effects on a number of oligothiophene properties was performed using well-defined oligothiophenes of various chain lengths that were monosubstituted with classical electron-withdrawing or -donating groups. The main focus was to understand how the effect of a substituent on one thiophene ring was transmitted through the other thiophene rings in the oligomer. The physical and electrochemical properties were studied by optical absorption and emission spectroscopy and by cyclic voltammetry. The experimental data were complemented with theoretical calculations of HOMO LUMO gaps, charge distribution, bond length alternations, and ¹³C NMR spectra. We show that substitution has a significant electronic effect on the substituted ring; however, the effect decreases strongly over conjugation. A semiquantitative evaluation of the substituent effect in a well-defined long conjugated system was obtained for the first time using the Hammett equation.     

Organocatalysts for the Synthesis of Poly(ethylene terephthalate‐co‐isosorbide terephthalate): A Combined Experimental and DFT Study

Organocatalysts are assessed for the insertion of isosorbide, a rigid, biobased diol monomer, into poly(ethylene terephthalate). A sulfonic acid (p‐toluenesulfonic acid—APTS), an amidine base (1,8‐diazabicyclo [5.4.0] undec‐7‐ene—DBU) and a guanidine base (1,5,7‐triazabicyclo[4.4.0]dec‐5‐ene—TBD) successfully catalyze the polymerization. The reaction mechanisms are studied by density functional theory. A bifunctional activation is observed in the presence of the sulfonic acid, the carbonyl moiety being activated via the acidic proton of APTS and the alcohol via the basic oxygen. Regarding DBU, a mechanism based on a basic activation of the alcohol rather than a nucleophilic attack of the catalyst is evidenced. The difference observed between TBD and DBU is attributed to a better H‐bonding ability of the former versus the latter.     

Study of the Electrochemical Behavior of N-Substituted-4-Piperidones Curcumin Analogs: A Combined Experimental and Theoretical Approach

The electrochemical behavior of N-methyl- and N-benzyl-4-piperidone curcumin analogs were studied experimentally and theoretically. The studied compounds present different substituents at the para position in the phenyl rings (-H, -Br, -Cl, -CF₃, and -OCH₃). We assessed their electrochemical behavior by differential pulse and cyclic voltammetry, while we employed density functional theory (DFT) M06 and M06-2x functionals along with 6-311+G(d,p) basis set calculations to study them theoretically. The results showed that compounds suffer a two-electron irreversible oxidation in the range of 0.72 to 0.86 V, with surface concentrations ranging from 1.72 × 10⁻⁷ to 5.01 × 10⁻⁷ mol/cm². The results also suggested that the process is diffusion-controlled for all compounds. M06 DFT calculations showed a better performance than M06-2x to obtain oxidation potentials. We found a good correlation between the experimental and theoretical oxidation potential for N-benzyl-4-piperidones (R² = 0.9846), while the correlation was poor for N-methyl-4-piperidones (R² = 0.3786), suggesting that the latter suffer a more complex oxidation process. Calculations of the BDEs for labile C-H bonds in the compounds suggested that neither of the two series of compounds has a different tendency for a proton-coupled electron transfer (PCET) oxidation process. It is proposed that irreversible behavior is due to possible dimerization of the compounds by Shono-type oxidation.     

单层器件分子的设计与密度泛函理论研究

设计了含咔唑、三苯基硼烷的可用来制作单层器件的简单分子9-（4-（diphenylboryl）phenyl）-9H-carbazole（DPPC）,并采用基于第一性原理的密度泛函理论对其基态和激发态以及光谱性质进行了系统研究,结果表明,在DPPC中HOMO、LUMO轨道分布良好,具有良好的空穴传输与电子传输特性。     

含能材料分子N8H8结构与性质的理论研究

采用密度泛函理论的b3lyp方法在6-311＋＋G＊＊基组上对30种N8H8链状异构体进行了理论计算,并应用分子中的原子理论（Atoms In Molecules,AIM）和自然键轨道理论（Nature Bond Orbital,NBO）分析了这些化合物相对稳定性和成键特征,G3MP2方法计算了各异构体的能量及生成热。结果表明：N8H8链状异构体中,含有N=N双键特征的异构体稳定性较好,影响氮氮键键长变化的主要因素是N原子孤对电子到相邻的氮氮键的超共轭作用;所有异构体中α3的生成热最大,β15的密度最大。     

A Theoretical and Experimental Study on Solubility of Curatives in Rubbers

The current study provides indications for improving the properties of dissimilar rubber blends. As solubility is a key factor for the distribution and a driving force for the migration of curatives in dissimilar rubber blends, it is of importance to have precise data of their solubilities. The solubilities of (insoluble) sulfur and the accelerators CBS, MBT and DCBS are measured at RT and at 60 °C, in lightly crosslinked SBR, NBR and EPDM. The experimental results correlate well with calculated solubility parameters, as determined using the method of Hoftijzer and van Krevelen.

     

活性炭吸附二苯并噻吩过程中酚羟基作用的分子模拟和实验研究

采用密度泛函方法研究了酚羟基与二苯并噻吩的作用机理,根据"分子内原子理论"计算酚羟基与二苯并噻吩络合吸附体系的电荷密度及其拉普拉斯值,用"自然键轨道理论"计算酚羟基与二苯并噻吩之间的电荷转移,结果表明:酚羟基的反键轨道σ*O33-H34与二苯并噻吩的π体系πC1=C2存在交互作用(C1=C2σ*O33-H34);二苯并噻吩的π电子体系中约有5.29×10 22C的电荷转移至酚羟基(O-H)的反键轨道σ*O33-H34,H34与C1=C2之间形成了O-H...π芳香氢键,其结合能为7.97 kJ mol 1。实验测定了不同酚羟基含量的活性炭对二苯并噻吩的平衡吸附量,结果表明:活性炭对二苯并噻吩吸附量随着表面酚羟基含量增加而增强,当活性炭表面酚羟基含量从0.14 mmol g 1AC增加到0.38mmol g 1AC时,活性炭对DBT吸附量从9.3 mg S g 1AC增加到14.1 mg S g 1AC,提高了52%。这与分子模拟计算及分析结论一致,提高活性炭表面酚羟基含量,使得活性炭与二苯并噻吩有更多机会形成芳香氢键,利于提高活性炭对二苯并噻吩的吸附容量。     

Electrochemistry as a Tool to Monitor Lewis Acid-Base Reactions between Methacrylonitrile and Metallic Surfaces: A Theoretical and Experimental Proposal

This paper presents a tentative extension of the Lewis acid-base concept to the case of an organic molecule interacting with a polarized metallic surface. Towards this aim, we make use of the Density Functional Theory (DFT) viewpoint on Lewis acid-base interactions. This theory has been shown to be relevant to describe adhesion processes at a molecular scale. It allows the introduction of three key parameters, for the molecule as well as for the metallic surface. These are the DFT chemical potential, μ, the absolute hardness, η and the Fukui function, f(inag hear). In the present paper, we show that the DFT chemical potential, μ, of the metallic surface is linearly related to the electrode potential drop, Δε, imposed between this surface and a reference electrode in an electrochemical cell. Thus, while the chemical potential of the molecule is only determined by its chemical structure, that of the metallic surface can be monitored continuously. This means that the Lewis acidic or basic character of the metallic surface towards the molecule can, in principle, be chosen. We present experimental results arguing in the sense of this model by studying the interaction of 2-methyl 2-propenenitrile (methacrylonitrile) alternatively with a metallic cathode and with a metallic anode. The two different transient molecule surface interactions are frozen thanks to an anionic electropolymerization of the monomer on the cathode and to a (first reported) cationic electropolymerization of the monomer on the anode. A detailed analysis of the molecular structures of the two resulting polymer/metal interfaces shows results which are in agreement with the theoretical predictions.

This paper is dedicated to Professor Jacques Schultz as an acknowledgement of his constant interest in our work.     

HF Formation through Dissociative Electron Attachment—A Combined Experimental and Theoretical Study on Pentafluorothiophenol and 2-Fluorothiophenol

In chemoradiation therapy, dissociative electron attachment (DEA) may play an important role with respect to the efficiency of the radiosensitizers used. The rational tailoring of such radiosensitizers to be more susceptive to DEA may thus offer a path to increase their efficiency. Potentially, this may be achieved by tailoring rearrangement reactions into the DEA process such that these may proceed at low incident electron energies, where DEA is most effective. Favorably altering the orbital structure of the respective molecules through substitution is another path that may be taken to promote dissociation up on electron capture. Here we present a combined experimental and theoretical study on DEA in relation to pentafluorothiophenol (PFTP) and 2-fluorothiophenol (2-FTP). We investigate the thermochemistry and dynamics of neutral HF formation through DEA as means to lower the threshold for dissociation up on electron capture to these compounds, and we explore the influence of perfluorination on their orbital structure. Fragment ion yield curves are presented, and the thermochemical thresholds for the respective DEA processes are computed as well as the minimum energy paths for HF formation up on electron capture and the underlying orbital structure of the respective molecular anions. We show that perfluorination of the aromatic ring in these compounds plays an important role in enabling HF formation by further lowering the threshold for this process and through favorable influence on the orbital structure, such that DEA is promoted. We argue that this approach may offer a path for tailoring new and efficient radiosensitizers.     

BrONO_2与Br(~2P_(3/2))气相反应的密度泛函理论研究

采用密度泛函理论计算方法B3LYP和基组6 31G(d),对BrONO2+Br(2P3/2)的反应机理进行了理论计算,得到各种可能反应途径的过渡态,并经过频率振动分析和内禀反应坐标(IRC)分析加以确认。结果表明:该反应是3通道反应,其中BrONO2+Br→Br2+NO3的反应活化能(5.25kJ/mol)最低,是反应主通道。     

[Fe(O)OH]~⊕活化甲烷反应的理论研究

采用密度泛函理论研究了气相中[Fe(O)OH]⊕与甲烷的反应机理。用B3LYP方法优化了势能面上各反应路径的过渡态和中间体等各驻点的结构,并通过振动分析和内禀反应坐标法对过渡态和中间体进行了确认,计算提出了两条可能的反应路线,揭示了[Fe(O)OH]⊕与甲烷的反应机理,同时对反应中存在的势能面交叉现象进行了研究,确定了最低势能交叉点处的作用机制。     

Rapid Hydrogenation of Aromatic Nitro Compounds in Supercritical Carbon Dioxide: Mechanistic Implications via Experimental and Theoretical Investigations

An exceptionally rapid hydrogenation of nitrobenzene to aniline [TOF=252,000 h⁻¹] over palladium containing MCM‐41 (Pd/MCM‐41) with excellent yield of >99% can be achieved in supercritical carbon dioxide at 50 °C and a hydrogen pressure of 2.5 MPa. It has been observed that this promising method preferred a single phase between liquid substrate and carbon dioxide‐hydrogen system. The ascendancy of the supercritical carbon dioxide medium is established in comparison with the conventional organic solvent and solvent‐less conditions. Changes in the reaction parameters such as carbon dioxide and hydrogen pressure, temperature and the reaction time do not affect the selectivity. A combined experimental and theoretical study has elucidated the mechanism under the studied reaction condition because experimental observations revealed a direct conversion of nitrobenzene to aniline. However, density functional theory (DFT) calculation shows that the direct conversion is energetically unfavourable; hence, a stepwise mechanism has been proposed. Theoretical predictions and experimental observations suggested that the rate‐limiting step of nitrobenzene conversion is different from that of the liquid phase hydrogenation. This catalytic process can also be successfully extended to the hydrogenation of other aromatic nitro compounds with different substituents. Easy separation of the liquid product from catalyst and the use of an environmentally friendly solvent make this procedure a viable and an attractive green chemical process.     

Li‐ion conductivity in PEO‐graphene oxide nanocomposite polymer electrolytes: A study on effect of the counter anion

Graphene oxide (GO) has been prepared by modified Hummer's method for their incorporation as nanofiller in designing nanocomposite polymer electrolytes (NCPEs). Prior to use the GO nanofillers has been characterized by TEM, FTIR, and Raman studies to elucidate their nanostructure, functionality, and purity. The various poly(ethylene oxide) (PEO)‐based NCPEs has been prepared by incorporating GO nanofillers in presence of three different lithium salts, viz., CF₃SO₃Li, LiTFSI, and LiNO₃ as the source of Li‐ions and then casted into free standing polymeric films. The change in PEO crystallinity has been studied considering their full width half maximum values of respective diffraction peaks in the XRD spectra. The Li‐ion conductivity of various NCPEs has been studied from impedance spectroscopy. All the NCPE films show optimum value of Li‐ion conductivity with 0.3% GO nanofiller content irrespective of the source of Li‐ions used. But, variation of the Li‐ion conductivity values is occurred for all the three studied lithium salts. Both LiTFSI and LiNO₃ salts display Li‐ion conductivity in the order of 10^?4 S cm^?1 whereas CF₃SO₃Li in the order of 10^?6 S cm^?1, all in presence of 0.3% GO nanofillers. The change in conductivity values of the NCPEs has been explained by correlating with Argand plots and also with change in PEO crystallinity, which occurs due to various relaxation processes. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46336.     

二苯并-18-冠-6及其配合物结构的理论研究

在捕获和输送碱金属离子时,冠醚的分子构型起着重要作用。利用密度泛函理论B3LYP方法,在6-31G(d)水平上对二苯并-18-冠-6及其配合物进行构型优化、频率、相互作用能等计算,得出了最稳定结构。研究表明,直径的匹配,配体的构象变化以及溶剂化效应都影响着二苯并-18-冠-6对离子的选择。     

水化在18-冠醚-6对K+和Na+选择过程中作用的理论研究

A combination of molecular dynamics (MD) and density functional theory (DFT) calculations were used to study the hydration structures of K+ and Na+ ions under the confinement of 18-crown-6 in order to identify the role of water in the selectivity of 18-crown-6 towards K+. The radial distribution functions, coordination numbers, orientation structures and interaction energies were analyzed to investigate the hydration of K+ and Na+ in 18-crown-6/cation complexes. All calculations of K+ and Na+ in bulk water were also conducted for comparison. The simulation results show that the orientation distributions of the water molecules in the first coordination shell of K+ are more sensitive to the confinement of 18-crown-6 than those of Na+. It is more favorable to confine a K+ in 18-crown-6 than a Na+ in terms of interaction energy. Good agreement is obtained between MD results and DFT results.     

杂环轮烯类化合物密度泛函理论研究

运用量子化学中的密度泛函和含时密度泛函理论法,计算了四种加共轭环的脱氢苯[15]轮烯衍生物的几何构型、电子结构、前线分子轨道和电子光谱性质。计算结果表明当脱氢苯[15]轮烯分子(M)被杂环取代或增加分子的共轭性,对轮烯的键长和键角等结构参数的影响不大,这与轮烯具有较强的共轭性有关。当母体中的苯环被嘧啶环取代时,最大吸收波长蓝移;当母体中的苯环被萘取代时,最大吸收波长与母体中的苯被吡嗪取代时的最大吸收波长相近。     

Tautomerism and Magnesium Chelation of HIV‐1 Integrase Inhibitors: A Theoretical Study

The tautomerism and corresponding transition states of four authentic HIV‐1 integrase (IN) inhibitor prototype structures, α,γ‐diketo acid, α,γ‐diketotriazole, dihydroxypyrimidine carboxamide and 4‐quinolone‐3‐carboxylic acid, were investigated at the B3LYP/6‐311++G(d,p) level in vacuum and in aqueous solvent models. To study the possible chelating modes of these tautomers with two magnesium ions—a process important for inhibition—we modeled an assembly of three formic acids, four water molecules and two Mg²⁺ ions as a template mimicking the binding site of IN. The DFT calculation results show that deprotonated enolized or phenolic hydroxy groups of specific tautomers in water lead to the most stable complexes, with the two magnesium ions separated by a distance of approximately 3.70 to 3.74 Å, and with each magnesium ion at the center of an octahedron. The drug candidate GS‐9137 (Gilead), based on the 4‐quinolone‐3‐carboxylic acid scaffold, and its analogues form similar but different chelating modes. When one water molecule in the complex is replaced by a methanol molecule, which mimics the terminal 3′‐OH of viral DNA, a good chelating complex is retained. This supports the hypothesis that, in the binding site of IN after 3′‐processing, the terminal 3′‐OH of viral DNA interacts with one Mg²⁺ by chelation.     

Experimental and Theoretical Study of N2 Adsorption on Hydrogenated Y2C4H− and Dehydrogenated Y2C4− Cluster Anions at Room Temperature

The adsorption of atmospheric dinitrogen (N₂) on transition metal sites is an important topic in chemistry, which is regarded as the prerequisite for the activation of robust N≡N bonds in biological and industrial fields. Metal hydride bonds play an important part in the adsorption of N₂, while the role of hydrogen has not been comprehensively studied. Herein, we report the N₂ adsorption on the well-defined Y₂C₄H_0,1⁻ cluster anions under mild conditions by using mass spectrometry and density functional theory calculations. The mass spectrometry results reveal that the reactivity of N₂ adsorption on Y₂C₄H⁻ is 50 times higher than that on Y₂C₄⁻ clusters. Further analysis reveals the important role of the H atom: (1) the presence of the H atom modifies the charge distribution of the Y₂C₄H⁻ anion; (2) the approach of N₂ to Y₂C₄H⁻ is more favorable kinetically compared to that to Y₂C₄⁻; and (3) a natural charge analysis shows that two Y atoms and one Y atom are the major electron donors in the Y₂C₄⁻ and Y₂C₄H⁻ anion clusters, respectively. This work provides new clues to the rational design of TM-based catalysts by efficiently doping hydrogen atoms to modulate the reactivity towards N₂.     

苦味酸含能离子盐的结构、生成热及爆炸性能理论研究

运用密度泛函理论DFT-B3LYP方法对5种苦味酸系列含能离子盐:苦味酸铵、苦味酸氨基脲、苦味酸碳酰肼、苦味酸氨基胍和苦味酸1,5-二氨基四唑进行了几何结构优化及红外振动分析,计算出生成热,并在此基础上,运用Kamlet-Jacobs方程估算出该类离子盐的爆速和爆压.