聚磷氮烯及其衍生物电子结构的理论研究

用分子轨道和晶体轨道方法,对聚磷氮烯及其衍生物的电子结构进行了研究,以期更深入地了解聚磷氮烯的结构和性能.研究发现,链状聚磷氮烯和环状三聚磷氮烯为平面结构,其它的环状聚磷氮烯则为巢式结构,吸电子基团取代有使环状聚磷氮烯主链环取平面结构的倾向.研究还发现,无论是链状还是环状聚磷氮烯,都表现为半导体.取代基效应表明,吸电子基团-F和-CN的取代,使聚合物的电子亲和势(EA)和电离能(IP)均增大,能隙减小,给电子基团-CH₃和-OCH₃的取代,使聚合物的IP减少;吸电子基团取代有利于n-型掺杂,给电子基团取代有利于p-型掺杂,但都不改变其半导体的特性.     

Diazo liquid crystals for potential infrared applications

Nine series of liquid crystals containing an electron-donating group at one end of a conjugated system and an electron-withdrawing group at the other end have been synthesized. The electron-donating group is 4-n-alkylpiperazine and the electron-withdrawing group is the nitro group; and the conjugated system is diphenyldiazene with zero, one or two substituents on the phenyl ring not containing the nitro group. The substituents are-F,-Cl, and-CH₃. Most of the compounds synthesized are nematogenic and exhibit rather broad liquid crystalline ranges. The effects of the lateral substituents on the optical absorption and phase transition temperatures are correlated with their nature and position of substitution. Dielectric anisotropy and birefringence measurements were made using mixtures containing 10 wt % of synthesized liquid crystals dissolved in commercial mixture E7.     

Picolinoxy group, a new leaving group for anti SN2' selective allylic substitution with aryl anions based on Grignard reagents

The picolinoxy group was found to be an extremely powerful leaving group for allylic substitution with aryl nucleophiles derived from ArMgBr and CuBr*Me2S. The substitution proceeds with anti SN2' pathway and with high chirality transfer. The electron-withdrawing effect of the pyridyl group and chelation to MgBr2 are likely the origin of success. Results suggesting these effects were obtained.     

Diazo liquid crystals for potential infrared applications

Nine series of liquid crystals containing an electron-donating group at one end of a conjugated system and an electron-withdrawing group at the other end have been synthesized. The electron-donating group is 4-n-alkylpiperazine and the electron-withdrawing group is the nitro group; and the conjugated system is diphenyldiazene with zero, one or two substituents on the phenyl ring not containing the nitro group. The substituents are-F,-Cl, and-CH₃. Most of the compounds synthesized are nematogenic and exhibit rather broad liquid crystalline ranges. The effects of the lateral substituents on the optical absorption and phase transition temperatures are correlated with their nature and position of substitution. Dielectric anisotropy and birefringence measurements were made using mixtures containing 10 wt % of synthesized liquid crystals dissolved in commercial mixture E7.     

Kinetic enolate formation by lithium arylamide: effects of basicity on selectivity

Five ketones R1COCH2R2 (1a-e) were enolized in tetrahydrofuran solvent employing lithium arylamides with different electron-withdrawing and -donating substituents on the phenyl ring (4a-e). Enolate selectivity is unaffected by a moderate electron-releasing or -withdrawing group, but significantly enhanced by strong electron-withdrawing substituents to yield predominantly Z-enolate. Outstanding selectivity was achieved with lithium trichloroanilide (5) and lithium diphenylamide (6). The results are rationalized in terms of electronic effects on the tightness of the transition states.     

Sulfonyl: a new application of electron-withdrawing substituent in highly efficient photovoltaic polymer

A strong electron-withdrawing group, sulfonyl, was firstly introduced to a semiconducting polymer, PBDTTT-S. The PCE of the PBDTTT-S device reached 6.22% with a high open-circuit voltage of 0.76 V. The sulfonyl group is thus a promising candidate as a strong electron-withdrawing group applied to high-efficiency PSCs.     

取代基结构-活性关系对电化学降解取代苯胺的影响

以Na2SO4为支持电解质, 使用Ti/PbO2电极, 研究了带有推电子基(—CH3)和吸电子基(—NO2, —Cl)的邻或对位取代基苯胺类化合物的电催化氧化降解过程. 研究结果表明, 带有取代基苯胺类化合物的氧化降解是在羟基自由基进攻下生成氨基酚类化合物, 然后在电极表面失去电子生成苯醌继续氧化的过程. 带有推电子基团苯胺的电催化降解速度比带有吸电子基团的苯胺降解速度快, 这是因为推电子基团使苯环电子云密度提高, 有利于羟基自由基的进攻; 吸电子基团使苯环电子云密度降低, 不利于羟基自由基的进攻. 由于阴极还原反应的作用, 化学反应活性和电化学反应活性并不完全一致. 氯代苯胺在羟基自由基进攻下—Cl离去, 以Cl-离子形式进入溶液中, 被氧化生成有效氯, 加快降解反应速度. 硝基虽然是强吸电子基, 但是可以转化为对苯二胺, 进一步活化苯环, 其降解速度较快.     

羟基卟啉衍生物的电喷雾多级串联质谱研究

研究了3种单羟基卟啉的电喷雾多级串联质谱，对其可能的裂解途径进行了归纳；结果表明，仅仅在苯环上无取代基的卟啉HPTPP中才能观察到失去活性的羟基或羟苯基的裂解碎片，苯环具有拉电子取代基的卟啉比具有推电子取代基的卟啉更容易裂解；由此可见，苯环上取代基性质对羟基卟啉的裂解方式有一定的影响。     

Synthesis of new hetarylazoindole dyes from some 2-aminothiazole derivatives

A new series of heterocyclic disperse dyes were prepared by diazotization of some 2-aminothiazole derivatives and subsequent coupling with indole compounds. The dyes were characterized by UV-Vis, FT-IR, ¹H NMR, and mass spectra (LC-MS). Solvent effects on their visible absorption spectra were estimated. The color of the dyes is discussed with respect to the substituent therein. The effects of acids and bases on the visible absorption maxima of the dyes are also reported. Replacement of methyl group in the 4-position of the thiazole ring by phenyl group leads to red shift of the absorption maximum due to π-electron-donating properties of the phenyl group, while weak electron-withdrawing chlorine or bromine atom in the para-position of the phenyl group in the 2-amino-4-phenylthiazole fragment induce a small blue shift relative to 2-amino-4-phenylthiazole derivatives. Introduction of an electron-withdrawing 4-nitrophenylsulfonyl group into the thiazole ring produces bathochromic shift of the absorption maximum in all solvents. Published in Russian in Zhurnal Organicheskoi Khimii, 2008, Vol. 44, No. 4, pp. 592–599. The text was submitted by the authors in English.     

A Density Functional Study of Substituent Effects on the O-H and O-CH(3) Bond Dissociation Energies in Phenol and Anisole

The substituent effects on O-H and O-CH(3) bond dissociation energies for a series of 18 para-substituted phenols (p-XC(6)H(4)OH) and 11 para-substituted anisoles have been studied using the density functional method in order to understand the origin of these effects. The calculated substituent effects agree well with experimental measurements for phenols but are substantially larger than the reported values for anisoles. Both ground-state effect and radical effect contribute significantly to the overall substituent effect. An electron-donating group causes a destabilization in phenols or anisoles (ground-state effect) but a stabilization in the phenoxy radicals (radical effect), resulting in reduced O-R bond dissociation energy. An electron-withdrawing group has the opposite effect. In most cases, the radical effect is more important than the ground-state effect. There is a good correlation between the calculated radical effects and calculated variations in charge and spin density on the phenoxy oxygen. This supports the concept that both polar and spin delocalization effects influence the stability of the phenoxy radical. While almost every para-substituent causes a stabilization of the phenoxy radical by spin delocalization, electron-donating groups stabilize and electron-withdrawing groups destabilize the phenoxy radical by the polar effect.     

Acidity inversions of alpha-NO2 and alpha-SO2CF3 activated carbon acids as a result of contrasting solvent effects on transfer from water to dimethyl sulfoxide solutions

Measurements of pK(a) values for the ionization of alpha-X-substituted ethyl acetates (1, X = NO(2); 2, X = CN; 3, X = SO(2)CF(3)) in H(2)O[bond]Me(2)SO mixtures and pure Me(2)SO show a unique response of the acidity of the SO(2)CF(3) derivative to the solvent changes, thereby resulting in a remarkable inversion in the acidifying effects of the strongly electron-withdrawing NO(2) and SO(2)CF(3) groups on going from H(2)O to Me(2)SO. Overall, the results obtained provide strong evidence that the powerful electron-withdrawing effect of the SO(2)CF(3) group is by far the result of polarization effects rather than other factors such as negative hyperconjugation.     

A selective,tin-free radical mediated synthesis of indoles based on a sulfonate template

A synthesis of indoles based on a vinyl sulfonate template is described. The approach employs a sulfonate group which plays three discrete roles in the synthetic sequence. Firstly the highly electron-withdrawing sulfonate group behaves as an activating group for a 1,4-addition of an aniline to the unsaturated system. Secondly, the electron-withdrawing nature of the same group also allows it to behave as a radical stabilising group which facilitates radical cyclisation to an aromatic ring to yield a transient indoline. Finally, the pendant sulfonate group behaves as a leaving group to yield the indole.     

顺[1-溴-2-羟基-2-(对-甲氧基苯基)乙基]膦酸二异丙酯的羟基反应性能的研究

研究了顺[1-溴-2-羟基-2-(对-甲氧基苯基)乙基]膦酸二异丙酯羟基的反应性能。由于膦酸酯基和电负性的溴原子的吸电子作用,羟基氧原子周围的电子云密度降低．从而增强了羟基上质子的酸性并减弱了碱性条件下相应的烷氧基负离子的亲核能力,因而得到了有关羟基与酚进行Mitsunobu脱水反应和酯化反应的特殊反应性能。同时,由于氢键的作用和膦酸酯基团的空问障碍作用,羟基与酰氯的反应活性较低。     

Studies on 4,7-di-substitution effects of one ligand in [Ru(phen)3]2+ with DFT method

Studies on the complex [Ru(phen)3]2+ (phen = 1,10-phenanthroline) and its derivatives with 4,7-di-substitution on one ligand(phen) were carried out using the DFT method at the B3LYP/LanL2DZ level of theory. The trends in the substituent effects caused by the electron-pushing group (OH) and the electron-withdrawing group (F), on the electronic structures and the related properties, for example, the energies and the components of some frontier molecular orbitals, the spectroscopy properties, and the net charge populations of some main atoms of the complexes, etc., have been investigated. The computational results show that the substituents have some interesting effects on the electronic structures and the related properties of the complexes. First, according to the analysis of components of LUMO of the complexes, the electron-withdrawing group (F) can activate the main ligand (the substituted ligand, i.e., 2R-phen) and passivate the coligands, on the contrary, the electron-pushing group (OH) can activate the coligands and passivate the main ligand in the first electronic excited states of complexes. Second, both the electron-pushing group (OH) and the electron-withdrawing group (F) can cause a red shift in the electronic ground bands. Third, the characteristics of the atomic net charge populations on the main ligand can also be analyzed in detail by means of a schematic map expressed by several series of arrowheads based on the law of polarity alternation and the idea of polarity interference. The most negative charges are populated on N1, the next most net negative charges are populated on C3 among the skeleton atoms for the three complexes, etc. The computational results can be better used to explain some experimental phenomena and trends.     

Selective reduction of the nitro group in the presence of the azoxy group. Synthesis of 2-(alkyl-NNO-azoxy)anilines

Tin(ii) chloride selectively reduces the aromatic nitro group to the amino group, the azoxy group remaining intact. This allows the preparation of 2-(R-NNO-azoxy)anilines from 2-(R-NNO-azoxy)nitrobenzenes bearing electron-donating or weak electron-withdrawing substituents (Me or Br) in the benzene ring and alkyl substituents at the distal N atom of the azoxy group. The presence of electron-withdrawing substituents at the azoxy group (for example, CO₂Et) leads to a change in the direction of the reaction resulting in selective reduction of the azoxy group to the hydrazo group.     

Hybrid silica materials derived from Hoveyda-Grubbs ruthenium carbenes. Electronic effects of the nitro group on the activity and recyclability as diene and enyne metathesis catalysts

The preparation of several organic-inorganic hybrid materials by sol-gel process derived from Hoveyda-type monomers is described. One of them presents a nitro group at the para position with respect to the alkoxy moiety. These materials were treated with Grubbs catalysts to generate the corresponding Hoveyda-Grubbs carbene ruthenium complexes covalently bonded to the silica matrix, which were tested as recyclable catalysts for diene and enyne RCM. Electronic effects of the nitro group resulted in enhanced activity of the catalyst. Whereas the recyclability decreased in RCM of dienes, the presence of this electron-withdrawing group was highly advantageous for the RCM of enynes, the reusability being greatly improved.     

含羧基双氮席夫碱配体对甲基三氧化铼催化烯烃环氧化反应的影响

摘要: 以2-吡啶甲醛与氨基苯衍生物缩合制备了3个双氮席夫碱配体,对其结构进行了表征。将这些席夫碱配体用作甲基三氧化铼(MTO)催化30% H2O2环氧化烯烃反应的添加物,研究了席夫碱结构对MTO催化性能的影响。结果表明,含有吸电子的羧基的双氮席夫碱配体由于具有适宜的配位能力和酸性,可显著提高MTO催化烯烃环氧化反应选择性,而反应速率没有明显降低,并且在低温下对MTO催化性能的改进更好;不具吸电子基羧基的双氮席夫碱配体尽管可以提高环氧化物的选择性,但同时却降低了MTO的催化活性。     

Substituents on quinone methides strongly modulate formation and stability of their nucleophilic adducts

Electronic perturbation of quinone methides (QM) greatly influences their stability and in turn alters the kinetics and product profile of QM reaction with deoxynucleosides. Consistent with the electron-deficient nature of this reactive intermediate, electron-donating substituents are stabilizing and electron-withdrawing substituents are destabilizing. For example, a dC N3-QM adduct is made stable over the course of observation (7 days) by the presence of an electron-withdrawing ester group that inhibits QM regeneration. Conversely, a related adduct with an electron-donating methyl group is very labile and regenerates its QM with a half-life of approximately 5 h. The generality of these effects is demonstrated with a series of alternative quinone methide precursors (QMP) containing a variety of substituents attached at different positions with respect to the exocyclic methylene. The rates of nucleophilic addition to substituted QMs measured by laser flash photolysis similarly span 5 orders of magnitude with electron-rich species reacting most slowly and electron-deficient species reacting most quickly. The reversibility of QM reaction can now be predictably adjusted for any desired application.     

Structure dependent prototropy in 4-hydroxy-3-formylideneamino-1-methyl/phenylquinolin-2-ones

The electronic absorption spectra of 4-hydroxy-3-formyl quinolin-2-ones and their Schiff bases were investigated in various solvents of varying polarity. The three aromatic transitions of napthalene in quinolin-2-one are shifted to longer wavelength on their transformation to anils. Electron-donating group in the anils lead to enolimine form, while electron-withdrawing group leads to an equilibrium mixture of enolimine and ketoamine forms and the Schiff base derived from alkyl amine exist in ketoamine form. The prototropic interconversion of enolimine and ketoimine forms in the anils with the electron-withdrawing substituted anils is further supported by proton NMR studies. The spectral shifts are solvent dependent. Dipolar aprotic solvents bring bathochromic shift while polar protic solvents cause blue shift in the longer wavelength absorption maxima. In the case of Schiff bases substituted by electron-donating group the bathochromic shift is directly related to the polarity of the solvents.     

Electronic effect on the optical properties and sensing ability of AIEgens with ESIPT process based on salicylaldehyde azine

Two novel AIE-active salicylaldehyde azine(SAA) derivatives with a typical excited-state intramolecular proton transfer(ESIPT) process are prepared by introducing electron-withdrawing and donating groups at para-position of phenolic hydroxyl group(CN-SAA and TPA-SAA). The effect of the proton activity in SAA framework on their optical behaviors is investigated spectroscopically. The results from NMR and solvation measurements show that the proton of phenolic hydroxyl group has higher activity when there are electron-withdrawing groups, and the absorption and fluorescence spectra in buffers with different pH also provide the same results. After inviting F. as a nucleophilic probe, this proton activity difference in CN-SAA and TPA-SAA becomes more obvious. The potential application of both molecules is investigated. TPA-SAA exhibits good quantitative sensing ability towards F. with a fluorescence "turn-on" mode, whereas the aggregates of TPA-SAA can selectively and sensitively detect Cu2+ in aqueous solution. From these results, a structure-property relationship is established: the occurrence of ESIPT process will become much easier when linking electron-withdrawing groups at the para-position of phenolic hydroxyl group(e.g., CN-SAA),and it is better to introduce electron-donating groups to enhance the sensing ability towards ions(e.g., TPA-SAA). This work will provide guidance for further design and preparation of AIE-active luminogens with ESIPT process for sensing applications.