带不同推电子基团二聚苯撑乙烯的电子结构与发光性能

用Wittig路线合成了一系列带不同推电子取代基的二聚苯撑乙烯,用紫外光谱和循环伏安方法测定其电子结构,并用量子化学计算方法对齐聚物的电子能级进行模拟.讨论了吸收光谱、发射光谱与生色团的电子结构的关系.     

Synthesis and self-association properties of functionalized C3-symmetric hexakis(p-substituted-phenylethynyl)triindoles

A number of differently substituted phenylethynyl triindoles has been synthesized by 6-fold Sonogashira coupling in a key step. This new series of hexaalkynyl triindoles self-associate through arene-arene interactions in solution. The electronic communication of the external substituents with the central electron-rich triindole core has been demonstrated by means of cyclic voltammetry and optical absorption. A study of the effect of the electronic character of peripheral substituents on their self-association behavior is presented in an effort to shed light on the nature of the pi-stacking interactions.     

取代基物化参数及其在药物定量构效关系中的应用

把取代基电性、立体及疏水性物化参数组合建立一种新取代基描述方法, 对环尿素类和N,N-二甲基-2-溴苯乙胺类衍生物进行结构表征. 对训练样本集通过逐步回归筛选变量, 所建多元线性回归方程R2分别为0.853和0.960, 留一法交互检验Rcv2分别为0.723和0.901；用预测集样本作外部预测, 所得Qext2分别为0.7617和0.7653. 结果显示：环尿素类化合物结构中苯环邻位立体、间位疏水、对位疏水及立体因素对该类药物抗HIV活性产生阻抑作用； N,N-二甲基-2-溴苯乙胺类苯环上取代基立体因素及对位给电子效应有利于提高肾上腺素能阻断活性.     

The electronic structure and energy of acyloxy and dioxacyclopropyl cations

The electronic structure and heats of formation of several acyloxy cations and the isomeric dioxacyclopropyl cations have been determined by MINDO/2 calculations. The potential energy surface shows the cyclic isomer to represent the least energy species. The stabilizing effect of alkyl substituents in the latter has been traced to strong hyperconjugative interaction.     

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.     

Si-H键伸缩振动频率与结构关系的研究

本文研究了开链及环状硅氢化合物中硅原子上取代基的电子效应和立体效应对Si-H键伸缩振动频率的影响。     

Substituent effects of phosphonate groups electronic repartition of π-conjugated ferrocene analogues of stilbene

The synthesis of para-substituted ferrocene analogues of stilbene was performed by using the Heck reaction, starting from vinylferrocene. The variation of the electronic density of these compounds with the electronic withdrawing strength of the substituents was studied using ¹³C NMR spectroscopy, absorption spectra and cyclic voltammetry. The correlation of Hammett constants with the redox properties of the substituted compounds using Nagy's method allowed us to revisit the determination of the Hammett constants of diethyl phosphonate ester and phosphonic acid substituents. Our measurements were in agreement with the literature except for the diethyl phosphonate group.     

Quantum Chemical Study Aimed at Modeling Efficient Aza-BODIPY NIR Dyes: Molecular and Electronic Structure,Absorption, and Emission Spectra

A comprehensive study of the molecular structure of aza-BODIPY and its derivatives, obtained by introduction of one or more substituents, was carried out. We considered the changes in the characteristics of the electronic and geometric structure of the unsubstituted aza-BODIPY introducing the following substituents into the dipyrrin core; phenyl, 2-thiophenyl, 2-furanyl, 3-pyridinyl, 4-pyridinyl, 2-pyridinyl, and ethyl groups. The ground-state geometries of the unsubstituted Aza-BODIPY and 27 derivatives were computed at the PBE/6-31G(d) and CAM-B3LYP/6-31+G(d,p) levels of theory. The time-dependent density-functional theory (TDDFT) together with FC vibronic couplings was used to investigate their absorption and emission spectra.     

Synthesis of polyformals from nitro- and fluordiols. Substituent and chainlength effects

A series of primary and secondary diols carrying nitroalkyl, nitro, and fluoro substituents was reacted with formaldehyde under conditions of acid catalysis. Short-chain primary diols gave cyclic formals while predominantly linear polymers were obtained beginning with pentane-1,5-diols and hexane-1,6-diols, depending upon the nature of the substituents. No polymers were formed from secondary diols with 1-nitroalkyl substituents. The effect of monomer structure on polymer formation is discussed. The polymers obtained were characterized by GPC and end group analysis.     

Quantum-Chemical Study of Electronic Structure and Reactivity of Diphospha-1,3-Butadienes

Abstract

Quantum-chemical calculations of the electronic structure of 1,3-, 1,4- and 2,3-diphospha-1,3-butadienes (DPB) and their derivatives with different substituents were performed. The MNDO method was used to describe the electronic structure of phosphaalkenes. The frontier orbitals of all unsubstituted DPB are of π-type. The highest occupied molecular orbital (HOMO) is delocalized through both double phosphorus-carbon bonds; the next occupied MO is a combination of two phosphorus lone pairs (n-MO). The HOMO of 2,3-DPB differs markedly from those of 1,3- and 1,4-isomers: the contributions of phosphorus and carbon p-orbitals are nearly equal, and the energy gap between HOMO and n-MO is very small (0.008 eV). The introduction of the electron-withdrawing substituents results in the reverse order of these MO's. In contrast with 1,3- and 1,4-isomers, the double bonds of 2,3-DPB are almost non-polar. Effect of substituents upon the electron density distribution are considered. The results indicate that orbitally controlled 1,4-additions should be characteristic for the derivatives of 1,3- and 1,4-DPB, similar to 1,3-butadiene. In case of 2,3-DPB, tendency to 1,4-addition should be lower; for its derivatives the reaction type depends greatly upon the electronic effects of substituents. In particular, reactions involving phosphorus lone pairs should be typical for the derivatives of 2,3-DPB with electron-withdrawing substituents.     

Synthesis and peripheral substituent effects of bay-annulated indigo derivatives

In this study, indolo-naphthyridine-6,13-diones (5a–d) with four different peripheral substituents were prepared via bay-annulation reactions of indigo. The resulting compounds (5a–d) exhibited fluorescence in the red to near-IR region, while the parent indigo molecule showed no fluorescence. Although the peripheral substituents were oriented to the exterior of the π-conjugated system, the electronic structure affected the absorption and fluorescence spectra. Moreover, calculated molecular orbitals and absorption spectra successfully reproduced the experimental absorption spectra and cyclic voltammograms.     

Electronic structure of oxovanadium IV complexes of alpha-hydroxycarboxylic acids

A series of V(IV)O bis chelated complexes of alpha-hydroxycarboxylic acids with a 2(COO(-), O(-)) coordination set was analyzed by electronic absorption and EPR spectroscopy in aqueous solution. All the complexes exhibit a square-pyramidal geometry distorted toward trigonal bipyramid. The influence of the distortion of the geometry, as deduced from the steric hindrance produced by the substituents at the alpha-carbon atom of the ligands, on the spectroscopic parameters has been studied. The observed trends were related to the electronic structure of the metal ion in the distorted geometry.     

Chiral Macrocycles Having C3 Symmetry Resulting from Orientation of Thiophene Rings

An chiral Rh^II-catalyzed cyclooligomerization reaction of thiophenes having triazolyl and vinyl substituents at the 2- and 4-positions was studied. Structurally interesting cyclic trimers, having chirality that is ascribed only to the orientation of the 2,4-disubstituted thiophene rings, are obtained. The 2,4-disubstitution of the starting thiophene monomer allows production of each of the enantiomers. The observed electronic circular-dichroism spectra are in accord with those simulated by density-functional theory calculations.     

Characterization of peptide-pyrazole interactions in solution by low-temperature NMR studies

Complexation of the amino- and carboxyl-protected tripeptide Piv-L-Val-L-Val-L-Val-tBu with 3-methylpyrazole and 3-amino-5-methylpyrazole was studied by low-temperature NMR experiments in a freonic solvent. The peptide forms an extended beta-type structure at all temperatures and associates through hydrogen bonding with the two pyrazole-based beta-sheet ligands. A detailed structural characterization of the formed complexes by one- and two-dimensional NMR experiments under slow exchange conditions was made possible by employing very low temperatures. The tripeptide associates to stable antiparallel dimers that are symmetrically capped on both sides by two pyrazole receptors to form 2:2 complexes. Amide groups of two neighboring residues in an extended conformation are involved in cyclic hydrogen bonds to the pyrazole. Based on amide chemical shift changes, the relative strength of intermolecular hydrogen bonds can be assessed and correlated with the electronic effects of the substituents on the pyrazole.     

Studies on antiallergic agents. II. Quantitative structure-activity relationships of novel 6-substituted N-(1H-tetrazol-5-yl)-2-pyrazinecarboxamides

The effect of structural modifications of 6-substituted N-(1H-tetrazol-5-yl)-2-pyrazinecarboxamides on their anti-allergic activity was analyzed quantitatively by means of the Hansch-Fujita method. The activity of these compounds was correlated with hydrophobic (pi) and steric (molecular refractivity and STERIMOL B1) effects of the 6-substituent on the pyrazine ring. The 6-substituents with a length greater than n-propylamino possess an extra effect enhancing the activity. Moreover, the activity increased progressively from 6-non-amino via alkylamino- to dialkylamino-substituted compounds, other factors being equal. This could be attributable to an electronic effect of substituents. Electron-donating small and yet symmetric substituents with high hydrophobicity longer than n-propylamino seemed to be favorable to the activity. By compromising these contradictory requirements, small dialkylamino (including cyclic amino) groups were decided to be the most favorable substituents. This analysis was in agreement with the observation that the most effective compounds were the 6-dimethylamino (I-27) and 6-(1-pyrrolidinyl) (I-34) derivatives.     

Ab initio calculations on 5α-androstane

The electronic structure of 5α-androstane, the parent hydrocarbon of the hormonal steroids, has been computed by ab initio SCF methods in an STO -3G basis. The results are compared with existing MNDO computations and are used to discuss long-range electronic interactions between distant substituents that might be appended to rings A and D of 5α-androstane. It is thought that these interactions are mediated by the ribbonlike MO 'S of the parent molecule.     

Synthesis,structure, electrochemistry,and photophysics of 2,5-dibenzylidenecyclopentanones containing in benzene rings substituents different in polarity

A series of cross-conjugated dienones was synthesized to study the dependence of physicochemical characteristics on the nature of substituents in the aromatic groups of symmetric cyclopentanone dibenzylidene derivatives. The structure of compounds was established by electronic, IR, and NMR spectroscopy and X-ray diffraction study. All the compounds obtained possess the E,E-geometry. In the crystalline state, the arrangement of the dienone molecules is unfavorable for the intermolecular [2+2] photocycloaddition to take place. The low-temperature phases transition for unsubstituted diphenyl derivative of cyclopentanone was detected using variable-temperature X-ray diffraction and differential scanning calorimetry. Oxidation and reduction potentials of the dienones were measured by cyclic voltammetry. Their dependence on the nature and placement of substituents in the benzene rings was demonstrated. A linear correlation (R = 0.9343) between the difference of electrochemical oxidation and reduction potentials and the energy of the long-wavelength absorption maximum was found, that allows us to recommend the use of the data obtained in the correlation analysis of other compounds of this class.     

双二茂铁基吡咯衍生物电荷交互通道

以二茂铁炔烃为原料通过“一锅法”环加成反应合成了一系列2,5-双二茂铁基-1-苯基-吡咯衍生物, 包括: 2,5-双二茂铁基-1-(3-三氟甲基苯基)-吡咯(1), 2,5-双二茂铁基-1-(4-氟苯基)-吡咯(2), 2,5-双二茂铁基-1-苯基-吡咯(3), 2,5-双二茂铁基-1-(4-乙基苯基)-吡咯(4)和2,5-双二茂铁基-1-(4-乙氧基苯基)-吡咯(5), 使用元素分析, 傅里叶变换红外(FTIR)光谱, 质谱(MS)和核磁共振(NMR)等手段对化合物进行了结构表征. 采用循环伏安法(CV), 密度泛函理论(DFT)模拟计算研究了苯基上取代基对双二茂铁间电荷交互的影响. 研究发现第一氧化电位(E_a1), 峰电位差(ΔE)与取代基的哈米特常数(σ), 吡咯¹H NMR的化学位移(δ), 吡咯N原子自然轨道(NBO)电荷之间存在显著线性关联; 同时发现, N原子电荷密度升高, 双二茂铁间电荷交互能力减弱, N原子电荷密度降低, 双二茂铁间电荷交互能力提高. 因此这类双二茂铁基吡咯衍生物中N原子电荷密度对双二茂铁间电荷交互起着关键的影响作用.     

Étude des interactions intramoléculaires dans les bimétallophtalocyanines par électrochimie et par spectroélectrochimie

Study of intramolecular interactions in bimetallophthalocyanines by electrochemistry and spectroelectrochemistry. We have prepared and isolated in solid form a series of zinc–phthalocyanine (Pc) complexes (ZnPc, F₈ZnPc, biZnPc, F₁₂biZnPc). These compounds have been studied by means of cyclic voltammetry and spectroelectrochemistry. The results evidence a dependency relation between the electronic structure and the peripheral substituents in the binuclear species.     

Substituent effects on nitrosyl iron corrole complexes Fe(Ar3C)(NO)

A series of nitrosyl tris(5,10,15-aryl)corrolate complexes of iron(III) Fe(Ar3C)(NO) with different substituents on the aryl groups have been prepared, and certain spectroscopic and reaction properties were compared. The cyclic voltammetric analysis of the various Fe(Ar3C)(NO) complexes demonstrated that both the one-electron oxidation and one-electron reduction potentials respond in systematic and nearly identical trends relative to the electron-donor properties of the substituents. A similar pattern was seen in the nitrosyl stretching frequency, nu(NO), which modestly decreased with the stronger donor substituents. Flash photolysis of Fe(Ar3C)(NO) solutions in toluene leads to NO dissociation followed by rapid [NO]-dependent decay of the transients formed (presumably Fe(Ar3C)) to regenerate the original spectra. As was seen in an earlier flash photolysis study of Fe(TNPC)(NO) (TNPC3- = 5,10,15-tris(4-nitro-phenyl)corrolate; Joseph, C.; Ford, P. C. J. Am. Chem. Soc. 2005, 127, 6737-6743), the second-order rate constants, k(NO), are all much faster ((1-9) x 10(8) M(-1) s(-1) at 298 K) than those for analogous iron(III) complexes of porphyrins. However, on a more microscopic level there is no obvious pattern in these rates with respect to the donor properties of the aryl ring substituents. The high reactivity of the ferric triarylcorrolates with NO data is interpreted in terms of the strongly electron-donating character of the Ar3C3- ligand and the quartet electronic configuration of the Fe(Ar3C) intermediate.