氰基乙烯基苯胺衍生物的电化学行为

本文利用循环伏安法研究了电子给-受体模型化合物——氰基乙烯基苯胺衍生物的电化学行为,并对推电子取代基团—NH_2和—N(CH_3)_2与吸电子取代基团氰基乙烯基对化合物电化学行为的影响进行了较为详细的讨论.提出了这些化合物的电氧化态和电还原态的结构,通过分析比较叔、仲和伯自由基对化合物电化学行为的影响,探讨了电极反应机理.     

同一电子给体与名种电子受体电荷转移配合作用的研究

本文测定了八种电子受体与十五种电子给体间的电荷转移(CT)光谱.利用文献中根据极谱还原电位求得之受体的亲合势,论证了同一电子给体与各种电子受体相作用时,其CT光谱也符合MULLIKEN公式;公式中的C为变化不大的数,可近似地认为是常数.本文还用电子吸收光谱首次研究了同系列电子受体(TCNE,n=0.2,3,4)与六种电子给体的CT配合作月,实验表明其CT吸收光谱也近似地服从同系线性规律;随着同系序数的增加,CT光谱发生紫移,而不象同系列给体与同一受体作用那样发生红移.用差示脉冲极谱法测定了此受体系列的还原峰电位,求得其电子亲合势;并用EHMO法计算了它们的前线分子轨道的能量.结果表明,随着同系序数的增加,亲合势减小,最低空轨道能量升高,从而解释了CT光谱紫移现象.     

同一电子给体与各种电子受体电荷转移配合作用的研究

本文测定了八种电子受体与十五种电子给体间的电荷转移(CT)光谱.利用文献中根据极谱还原电位求得之受体的亲合势,论证了同一电子给体与各种电子受体相作用时,其CT光谱也符合Mulliken公式;公式中的C为变化不大的数,可近似地认为是常数.本文还用电子吸收光谱首次研究了同系列电子受体(TCNE,n=0,2,3,4)与六种电子给体的CT配合作用,实验表明其CT吸收光谱也近似地服从同系线性规律;随着同系序数的增加,CT光谱发生紫移,而不象同系列给体与同一受体作用那样发生红移.用差示脉冲极谱法测定了此受体系列的还原峰电位,求得其电子亲合势;并用EHMO法计算了它们的前线分子轨道的能量.结果表明,随着同系序数的增加,亲合势减小,最低空轨道能量升高,从而解释了CT光谱紫移现象.     

三发色基团体系分子内激基复合物形成的环境效应

芳香烃的荧光可以被电子给体如叔胺化合物淬灭,这一现象早为人们所熟知.随着芳烃分子荧光的淬灭出现一个向红移无结构的新荧光峰,它被认为是激发态芳香烃分子A与电子给体D相互作用形成的激基复合物(exciplex)DA所发射的荧光.将两个、三个或更多个发色基团用非共轭链连接起来,受光激发后则可以形成分子内激基复合物.通过这些体系我们可以研究电子给体和电子受体相互作用的机制,研究在复杂的氧化、还原体系(如光合作用)     

对立统一规律在氧化还原反应中的体现

氧化还原反应是化学反应中一个十分重要的内容。运用辩证唯物主义观点,正确理解和掌握氧化还原反应,对生产实践很有好处。氧化还原反应体现了事物对立统一的法则氧化还原反应,就是体系内有关各种物质的元素原子参与电子得失过程所引起的化学变化。得电子的过程叫还原,失电子的过程叫氧化。在氧化还原反应中,得电子与失电子是一对矛盾。没有失电子,就无所谓得电子;一物质失去电子的同时,必有另一物质获得电子。假如没有氧化剂存在,还原剂就不会无的放矢地把电子释放出来;没有还原剂放出电子,氧化剂就不可能获得电子。在 S~(2-)离子变成 S 的反应中失去了两个电子,但这仅仅是反应的一半,必须有另一物质获得     

电化学反应及其腐蚀

氧化―还原反应是普遍存在的一类重要的反应。冶金、锈蚀及许多化工生产都涉及到氧化―还原反应。氧化―还原反应的本质是电子得失或偏移,如何通过化学能转变为电能,使氧化―还原反应获得或失去电子等,是化学教学中的重点和难点。文章介绍了氧化―还原反应中电化学的概念和原电池的原理,利用电化学的知识来解释一些电化学腐蚀现象。     

左旋多巴在单层碳纳米管修饰电极上的电化学行为

单层碳纳米管修饰电极对左旋多巴的电化学氧化还原具有很高的催化活性.在pH 4.6的0.1 mol/L HAc-NaAc缓冲溶液中,可得到一对峰形很好的氧化还原峰.电极反应受扩散控制,反应过程中电子的得失伴随着等量的质子参与.氧化峰电流与左旋多巴浓度在2.1×10-4～5.0×10-6 mol/L范围内成线性关系,检测限为2.0×10-6 mol/L.     

纳米Ni(OH)_2微萃取和电催化敌草隆的循环伏安和量子化学法研究

电沉积纳米氢氧化镍于碳糊电极表面上实现了原位修饰,以循环伏安和PM7量子化学方法研究了敌草隆在纳米氢氧化镍表面形成的络合物,具有固相微萃取和电化学催化功能。循环伏安结果表明,氢氧化镍与敌草隆络合后,与在KCl溶液中的结果相比,还原峰电流增大,还原峰负移,氧化峰正移,与在NaOH溶液中的结果相比,氧化峰电流增大。表明敌草隆与镍配位形成的络合物有利于萃取富集,具有一定的氧化还原催化作用,提高峰电流。PM7量子化学半经验分子轨道方法计算络合物的热力学参数、分子轨道能量与组成。通过热力学原理分析计算所得数据,表明该络合物稳定性更大,络合作用可以自发形成,形成络合物分子的可移动电子数增加,更有利于电子转移。理论计算结果与实验结果趋于一致。     

推拉电子取代基对二茂铁衍生笺性质及电子结构的影响

根据前线轨道理论分析３种具有推拉电子取代基的二茂铁衍生物循环伏安曲线，电子上光谱衣光谱电子化学行为，为给出了分子轨道能级图。实验结果表明，ＰⅡ有两对可逆氧化还原峰，Ｅ＾ｏｘ１，Ｅ＾ｏｘ２分别为０．３３，０．５９Ｖ，第一氧化态ＰⅡ＾＋（Ｄ－Ｆｃ＾＋－Ｒ）在６１３ｎｍ有强的ＬＭＣＴ（ｌｉｇａｎｄ－ｔｏ－ｍｅｔａｌ－ｃｈｇａｒｇｅ－ｔｒａｎｓｆｅｒ）带，是一种良好的光学特性氧化还原开关。ＰⅡ在３５４ｎｍ     

异构的蒽乙烯单钌配合物:合成与表征、电化学、光谱性质及理论计算

通过9-蒽乙炔基及2-蒽乙炔基分别与有机金属氢化物羰基氯氢三(三苯基膦)钌(Ⅱ)[Ru HCl(CO)(PPh_3)_3]反应,再使用三甲基膦(PMe_3)交换配体,合成并表征了具有同分异构结构的蒽乙烯单钌配合物1和2,其中配合物2的结构还经X射线单晶衍射的确证,结合理论计算研究了其电学及光学性质。密度泛函理论(DFT)优化配合物1和2的电子结构显示,在两个异构体中钌乙烯基与蒽配体呈现明显不同的构型,前线分子轨道图显示最高已占分子轨道(HOMO)上电子离域于整个分子骨架,其中以配体蒽乙烯基所占比例为90%,表明蒽乙烯基配体参与该配合物氧化进程的比例很大。电化学实验结果表明,配合物1的氧化还原可逆性明显低于配合物2。配合物1和2及前体分子1b和2b的电子吸收光谱结果表明,配合物与前体分子相比光谱性质呈现明显变化,其在紫外区域的强吸收峰明显减弱,而在长波长方向均出现了弱而宽的吸收峰,该吸收峰已经通过含时密度泛函理论(TDDFT)计算将其归属于π→π*以及金属配位电荷转移(MLCT)跃迁吸收,均来自于HOMO→LUMO跃迁产生。荧光发射光谱揭示金属配位之后其荧光强度和荧光量子产率明显降低。CCDC:1488284,2。     

Theoretical Study on the Structures and Electronic Spectra of the Derivatives of C_(60)-P-2,4,6-Triphenyl Borazinc

1 INTRODUCTION The electron-transfer reaction of C60 derivatives, especially light-induced electron-transfer reaction, has been an active research field for a long time. Many researches are focused on the long-live charge- separated state caused by electron-transfer[1]. And several electron-transfers between electron donor and C60 or intramolecular electron-transfer have been confirmed. As an example, TTF-C60 is proved to be a short-live charge-separated compound[2].Due to the excelle…     

二苯二硫和二苄二硫润滑性能的量子化学研究

The molecular geometries optimization and electronic structures of diphenyl disulfide (DPDS) and dibenzyl disulfide (DBDS) compounds were investigated by density functional theory (DFT) and ab initio method at the 6-31G basis set level. The active atoms and bonds of reaction were provided by frontier molecular orbital theory. The molecular orbital parameters of DPDS and DBDS compounds and iron atom cluster were calculated by using density functional theory. The interaction pattern between the organic disulfide compounds and iron atom cluster was discussed based on the approximate rule of orbital energy. Some parameters characterizing the action strength between the organic disulfide compounds and iron atom cluster, including the bonding strength, reactive strength and static action strength, were analyzed by using frontier electron density, super de-localizability, net atomic charge and the interaction energy of chemical adsorption as criteria. The results indicate that S-S chemical bond and C-S chemical bond of the compounds are inclined to be broken when DPDS and DBDS interact with the metal. The anti wear ability order of DPDS and DBDS compounds is DPDS>DBDS, and the extreme pressure ability order of DPDS and DBDS compounds is DBDS>DPDS, and the prediction results based on quantum chemistry calculations are in good accordance with the friction and wear test results.     

Orbital views of molecular conductance perturbed by anchor units

Site-specific electron transport phenomena through benzene and benzenedithiol derivatives are discussed on the basis of a qualitative Hu?ckel molecular orbital analysis for better understanding of the effect of anchoring sulfur atoms. A recent work for the orbital control of electron transport through aromatic hydrocarbons provided an important concept for the design of high-conductance connections of a molecule with anchoring atoms. In this work the origin of the frontier orbitals of benzenedithiol derivatives, the effect of the sulfur atoms on the orbitals and on the electron transport properties, and the applicability of the theoretical concept on aromatic hydrocarbons with the anchoring units are studied. The results demonstrate that the orbital view predictions are applicable to molecules perturbed by the anchoring units. The electron transport properties of benzene are found to be qualitatively consistent with those of benzenedithiol with respect to the site dependence. To verify the result of the Hu?ckel molecular orbital calculations, fragment molecular orbital analyses with the extended Hu?ckel molecular orbital theory and electron transport calculations with density functional theory are performed. Calculated results are in good agreement with the orbital interaction analysis. The phase, amplitude, and spatial distribution of the frontier orbitals play an essential role in the design of the electron transport properties through aromatic hydrocarbons.     

Molecular orbital analysis of chemical carcinogens

Simple molecular orbital calculations are employed in searching electronic parameters which may characterize the chemical carcinogens. Using frontier orbitals, the carcinogen-DNA bond formation is described as an electron transfer from the highest occupied molecular orbital (HOMO) of DNA to the lowest unoccupied molecular orbital (LUMO) of the carcinogen. Analysis of the DNA bases units shows that the electron donation occurs preferentially at the guanine site. The calculated low LUMO energy of several carcinogens indicate correctly the electrophilic character of these compounds. The difference between the carcinogen and the ultimate carcinogen is analyzed. Epoxides, free radicals, alkylating agents, and other metabolite forms are studied. A reasonable correlation is found between the LUMO energy and the carcinogenic function. © 1997 John Wiley & Sons, Inc.     

Theoretical insights into the 1D‐charge transport properties in a series of hexaazatrinaphthylene‐based discotic molecules

Discotic liquid crystal (DLC) materials have attracted considerable attention mainly due to their high charge carrier mobilities in quasi‐one‐dimensional columns. In this article, five hexaazatrinaphthylene‐based DLC molecules were investigated theoretically, and their frontier molecular orbital energy levels, crystal structures, and electron/hole drift mobilities were calculated by combination of density functional theory (DFT) and semiclassical Marcus charge transfer theory. The systems studied in this work include three experimentally reported molecules ( 1 , 2 , and 3 ) and two theoretically designed molecules ( 4 and 5 ). Compared with the 1 – 3 compounds, 4 and 5 have three more extended benzene rings in the π‐conjugated core. The present results show that the orders of the frontier molecular orbital energy levels and electron drift mobilities agree very well with the experiment. For 4 and 5 , the electron/hole reorganization energies are lower than those of compounds 1 – 3 . Furthermore, the calculated electron/hole transfer integral of 5 is the largest among all the five systems, leading to the highest electron and hole mobilities. In addition, the hydrophobicity and solubility were also evaluated by DFT, indicating that compound 5 has good hydrophobicity and good solubility in trichloromethane. As a result, it is expected that compound 5 can be a potential charge transport material in electronic and optoelectronic devices. © 2017 Wiley Periodicals, Inc.     

Synthesis, electronic properties, and electrochemiluminescence of donor-substituted phenylethynylanthronitriles

A new series of pi-conjugated donor-acceptor compounds (1-6) with inherent redox centers have been prepared and studied with respect to their electronic properties. The photophysical characteristics of these compounds have been studied in relation to their structures. Cyclic voltammetry and UV-vis spectroelectrochemistry were used to probe the ground-state electronic properties of the neutral and charged species. The observed electronic absorption properties of the neutral and charged molecules are explained with the help of frontier orbital structures and electrostatic potential maps obtained from density functional theory (DFT, B3LYP/6-31G) calculations. Electrochemiluminescence (ECL) of this series of donor-substituted phenylethynylanthronitriles with different donors was also studied. The structure-property relationship of all of the compounds is discussed.     

Molecular orbital studies on some 4-substituted pyridine N-oxides and 4-nitroquinoline N-oxide

The electronic structures of a series of 4-substituted pyridine N-oxides and 4-nitroquinoline N-oxide are investigated using the simple Pariser-Parr-Pople (PPP), a modified PPP, IEH and MINDO/2 methods. The electronic absorption band maxima and dipole moments are calculated and compared with experimental values. The photoelectron spectra of these compounds are assigned. The nature of the N-oxide group is characterized using the orbital population distributions. The antifungal activity exhibited by some of these compounds is discussed in terms of the nucleophilic frontier electron densities, superdelocalizabilities and electron acceptor properties. The effect of the electron releasing as well as the electron withdrawing substituents on the physico-chemical properties is explained.     

Negative-ion mass spectra of diterpene alkaloids with the keto group in the 6- or 7-position

Processes resulting in the formation of negative ions by molecules of some diterpene alkaloids via resonance electron capture have been studied. The mass spectra of these compounds have a small number of lines represented largely by intense peaks in the thermal electron energy region and are due to electron capture onto the lower unoccupied molecular orbital, which is π*-C=O or π*-Ph-C=O in character.     

Fiber-optic infrared reflectance spectroelectrochemical studies of osmium and ruthenium nitrosyl porphyrins containing alkoxide and thiolate ligands

We have examined the redox behavior of the osmium and ruthenium compounds (OEP)M(NO)(OEt) and (OEP)M(NO)(SEt) (OEP = octaethylporphyrinato dianion; M = Os, Ru) by cyclic voltammetry and infrared spectroelectrochemistry. The compound (OEP)Os(NO)(OEt) undergoes a single reversible oxidation process in dichloromethane. In contrast, the thiolate compound (OEP)Os(NO)(SEt) undergoes a net irreversible oxidation resulting in formal loss of the SEt ligand. Extended Hückel calculations on crystal structures of these two compounds provide insight into the nature of their HOMOs. In the case of the alkoxide compound, the HOMO is largely metal centered, with 70% of the charge located in the metal's orbital and approximately 25% on the porphyrin ring. However, the HOMO of the thiolate compound consists of a pi bonding interaction between the metal dxz orbital and the px orbital on the sulfur, and a pi antibonding interaction between the metal d orbital and a pi* orbital on NO. The redox behavior of the Ru analogues have been determined, and are compared with those of the Os compounds.     

Triple a

Many biological compounds exhibit irreversible redox behavior as a result of slow heterogeneous electron transfer at electrode surfaces. In order to study the electrochemical behavior of these biocomponents, redox mediators are used to facilitate the electron transfer process. In this review the characteristics of ideal mediators are discussed and structural information on previously reported mediator compounds is provided. The electrochemical literature has been extensively surveyed to provide an up-to-date compilation of mediators suitable for use in potentiometric and coulometric titrations and in various types of voltammetric studies of biological redox systems. The compilation provides information on the formal potentials of the mediators as well as their previous applications and references. This review is intended to provide a current survey of compounds having suitable redox mediation characteristics.