推拉电子取代基与二茂铁基的前线轨道相互作用

根据5种二茂铁衍生物R-Fc-A_1(PⅠ)、A_1-Fc-A_1(PⅡ)、D-Fc-R(PⅢ)、D-Fc-A_1(PIV)、D-Fc-A_2(PV)(其中R=CH_2OH,A_1=CHO,A_2=CH=C(CN)_2,D=(C_(18)H_(37))_2N-C_6H_4-CH=CH)的电化学、电子吸收光谱及光谱电化学实验结果,分析了二茂铁基与推拉电子取代基之间前线轨道相互作用.发现吸电子取代基因其LU-MO(π_A)与(C_p~-)_2的e_(2u),e_(2g)能级相近,与二茂铁的e_(2u)((?)_(4u),(?)_(5u))和le_(2g)(d_(x~2-y~2),d_(xy))之间的强相互作用不仅使成键轨道(PⅠ,PⅡ,PⅣ,PⅤ的π_A+[(?)_(4u)]、d_(x~2-y~2)+[π_A])能级大幅度下降,而且也使非键轨道d_(xy)能级下降.推电子取代基因其HO-MO(π_D)与(C_p~-)_2的e_(lu)能级相近,与二茂铁的le_(lu)((?)_(2u),(?)_(3u))之间的强相互作用产生反键轨道(PⅢ,PⅣ,PⅤ的π_D-[(?)_(3u)])和成键轨道(?)_(3u)+[π_D].     

青蒿素及其衍生物抗疟活性的密度泛函理论研究

为了深入研究青蒿素及其衍生物的抗疟活性和分子结构之间的关系,运用密度泛函理论B3LYP方法,以6-31G*为基组对青蒿素及其衍生物二氢青蒿素、蒿甲醚和青蒿琥酯进行了优化计算.从分子的几何构型、NBO电荷及前线轨道能等方面分析了青蒿素及其衍生物的抗疟活性与结构之间的关系.青蒿素及其衍生物结构中的过氧桥键是其抗疟作用的活性位,O17和O_20带负电荷越多、ΔE_(LUMO-HOMO)越低、E_(HOMO)能级越高,分子的抗疟活性越强.结果表明,4种化合物的抗疟活性顺序为:青蒿素二氢青蒿素蒿甲醚青蒿琥酯,与临床实验结果相吻合.     

N-2-亚甲基-呋喃-二茂铁芳胺衍生物的合成与晶体结构及电化学性质

以邻、间、对-二茂铁苯胺为原料,合成了新的含呋喃二茂铁苯基席夫碱衍生物,还原得到N-2-亚甲基-呋喃-二茂铁芳胺衍生物,通过元素分析,IR,1H NMR和X-射线单晶衍射等分析手段,确证了标题化合物的组成和结构,化合物2 c单晶结构解析表明,2 c属于单斜晶系,P2/n空间群;其HOMO轨道主要由Fe原子及茂环上C的原子轨道组成,LUMO主要由O、N和苯环上C原子构成;电化学实验证明:邻、间、对化合物的电化学性质相似,苯环上取代基位置的不同,对化合物在电极表面的扩散系数影响不大,但对反应速率常数有较大的影响.     

共轭性对7-吡啶吲哚类衍生物的结构与电子光谱性质的影响

运用密度泛函理论(DFT)方法对7-吡啶吲哚衍生物的结构及电子光谱性质进行了理论研究.在B3LYP/6-31G(d)水平上得到了7-吡啶吲哚(M)以及5种共轭衍生物(a-e)的几何构型、电子布局以及前线分子轨道;应用含时密度泛函理论(TD-DFT)在B3LYP/6-31+G(d)水平上计算了5种衍生物的电子光谱性质.结果表明,共轭体系的π键成分增大,能级差减小,激发能降低,分子的最大激发波长向长波方向移动,即发生红移.但是,如果分子中的空间位阻增大,则共轭程度降低,发生蓝移.前线分子轨道分析表明该类化合物吸收光谱主要对应分子中的HOMO→LUMO电子跃迁,且为π-π*跃迁.为新型含吲哚基团的光电功能材料的设计合成提供了理论参考.     

二聚(2,5-噻吩乙烯撑)基态和激发态的电子结构: 桥基和芳环取代的影响

采用密度泛函理论(DFT)和含时密度泛函理论(TD-DFT)方法, 在B3LYP/TZVP水平下, 研究了一系列给电子基团(—NH2, —OCH3和—CH3)和吸电子基团(—CCH, —CN和—NO2)在二聚(2,5-噻吩乙烯撑)(2TV)的桥基和芳环上取代对基态和激发态电子结构的影响. 结果表明, 取代基的给/吸电子能力和取代位置对衍生物的几何结构以及吸收发射光谱均有重要影响, 其中氨基(—NH2)和硝基(—NO2)取代对2TV电子结构的影响较为显著. 此外, 对于桥基和芳环取代, 随着取代基吸电子能力的增强, 衍生物的前线分子轨道HOMO和LUMO的能级均呈逐渐降低的趋势.     

线型和星型平面噻吩类低聚物衍生物分子结构及光电性质研究

运用密度泛函DFT B3LYP／6-31G(d)方法对线型(a)和星型(b)平面噻吩类低聚物衍生物分别进行了几何构型优化,并采用含时密度泛函TD-DFT B3LYP／6-31G(d)方法计算了其紫外吸收光谱．计算结果表明:用TD-DFT．方法计算体系的紫外吸收光谱值与实验数据吻合;通过对噻吩类低聚物衍生物分子几何结构和前线分子轨道能级的分析,并从理论上解释了线型(a)和星型(b)衍生物光谱性质的差异:后者与前者相比较吸收光谱发生红移,这是由于星型结构使其相应HOMO能级升高,电离能(IP)降低,成为很好的电子给体和空穴传输材料．     

半花菁衍生物分子非线性光学性质的理论研究

采用有限场(FF)/PM3方法对半花菁衍生物的第一超极化率和分子前线轨道性质进行了计算.结果表明,半花菁衍生物分子的第一超极化率主要与D-π-A结构有关,σ-烷基链对分子第一超极化率的影响很小,并且分子第一超极化率与分子前线轨道HOMO和LUMO能级差ΔEHL呈较好的线性关系.     

呋喃查尔酮结构与电子光谱的密度泛函理论研究

在密度泛函理论的PBE1PBE/6-31G(d)水平上对呋喃查尔酮及其衍生物的几何结构进行优化计算.在获得基态稳定结构的基础上,应用含时密度泛函理论计算其电子吸收光谱,探讨了取代基和溶剂对电子吸收光谱的影响,计算结果与实验结果吻合很好,平均绝对偏差仅为3.3nm(0.04eV).结果表明,取代基的引入和溶剂极性的增大均使光谱发生红移.通过前线轨道分析,揭示了该类化合物的主要吸收峰均源自分子中HOMO→LUMO电子跃迁.     

推/拉电子取代基对PCBM结构及光谱性质影响的理论研究

应用密度泛函理论(DFT)方法计算[6,6]-苯基-C₆₁-丁酸甲酯(PCBM)及其苯环对位取代得到的4种衍生物的几何和电子结构. 采用第一激发能校正了分子的最低未占据分子轨道(LUMO)能级, 探讨了推/拉电子基团对分子前线轨道的影响. 在全优化几何构型的基础上, 采用含时密度泛函理论(TD-DFT)方法研究了电子吸收光谱特征和电荷转移态性质, 并讨论了推/拉电子基团对体系电子吸收光谱性质的影响. 通过对重组能和电子亲和势的计算, 预测了PCBM与4种衍生物的电子能力及电子迁移率大小的关系. 结果表明, 在PCBM中, 在苯环的对位引入推电子基团可以提高分子的前线轨道能级, 改变前线轨道电子云分布, 明显增强可见光范围内的吸收强度, 增加可见光范围内的电荷转移吸收, 且激发态的电荷转移随着引入基团推电子能力的增加而增强. 化合物5的激发态分子内电荷转移性质最强, 且具有较独特的光伏性质. 而在同样位置引入拉电子基团, 则降低了分子前线轨道能级对电子吸收光谱的影响.     

8-羟基喹啉铍及其衍生物电子光谱性质的含时密度泛函理论研究

运用密度泛函理论(DFT)B3LYP方法和abinitioHF单激发组态相互作用(CIS)法分别优化了有机金属配合物8-羟基喹啉铍(BeQ₂)及其3种衍生物分子的基态及最低激发单重态几何结构.系统分析了分子结构、前线分子轨道特征和能级分布规律以探索电子跃迁机理.应用含时密度泛函理论(TD-DFT)计算分子的电子光谱,揭示了BeQ₂及其衍生物的发光源于配体中π→π^*电子跃迁,指出通过配体修饰可以有效地影响配合物前线分子轨道分布,调整发光波段,并有效提高电荷转移量.     

Synthesis,Characterization, and Electron-Transfer Properties of Ferrocene–BODIPY–Fullerene Near-Infrared-Absorbing Triads: Are Catecholopyrrolidine-Linked Fullerenes a Good Architecture to Facilitate Electron-Transfer?

A series of covalent ferrocene–BODIPY–fullerene triads with the ferrocene groups conjugated to the BODIPY π-system and the fullerene acceptor linked at the boron hub by a common catecholpyrrolidine bridge were prepared and characterized by 1D and 2D NMR, UV/Vis, steady-state fluorescence spectroscopy, high-resolution mass spectrometry, and, for one of the derivatives, X-ray crystallography. Redox processes of the new compounds were investigated by electrochemical (CV and DPV) methods and spectroelectrochemistry. DFT calculations indicate that the HOMO in all triads was delocalized between ferrocene and BODIPY π-system, the LUMO was always fullerene-centered, and the catechol-centered occupied orbital was close in energy to the HOMO. TDDFT calculations were indicative of the low-energy, low-intensity charge-transfer bands originated from the ferrocene–BODIPY core to fullerene excitation, which explained the similarity of the UV/Vis spectra of the ferrocene–BODIPY dyads and ferrocene–BODIPY–fullerene triads. Photophysical properties of the new triads as well as reference BODIPY–fullerene and ferrocene–BODIPY dyads were investigated by pump-probe spectroscopy in the UV/Vis and NIR spectral regions following selective excitation of the BODIPY-based antenna. Initial charge transfer from the ferrocene to the BODIPY core was shown to outcompete sub-100 fs deactivation of the excited state mediated by the catechol bridge. However, no subsequent electron transfer to the fullerene acceptor was observed. The initial charge separated state relaxes by recombination with a time constant of 150–380 ps.     

Electrochromism based on the charge transfer process in a ferrocene-BODIPY molecule

A new type of donor-acceptor molecule DiFc-B combined ferrocene and BODIPY unit has been synthesized, and the NMR spectra, photophysical property, and electrochemical property were studied. The in situ spectro-electrochemical experiment was carried out, a notable absorption change had been observed under oxidative potential, and a recovery could happen under reductive potential and this process could repeat for several times. Such a phenomenon also happened when oxidative metal ion was added into the solution of DiFc-B. In order to study the mechanism of the electrochromism, the theoretical calculation was performed, and the result shows a D (ferrocene)-π-A (BODIPY) system. The energy gap between the HOMO and LUMO had a good consistence with the electrochemical experiment and UV-vis data. The calculation of the frontier orbital belonging to the cation state of DiFc-B shows the directional change of the D-π-A system, which supplied a theoretical basis of the electrochromism.     

Theoretical Studies on Structural and Spectroscopic Properties of Photoelectrochemical Cell Ruthenium Sensitizers-the Derivatives of N3

A series of dye molecules was designed theoretically. Particularly, azoles and their derivatives were chosen as the modifying groups linking to ancillary ligands of [Ru(dcbpyH₂)₂(NCS)₂](N3, dcbpy=4,4′-dicarboxy- 2,2′-bipyridine; NCS=thiocyanato). Density functional theory(DFT) based approaches were applied to exploring the electronic structures and properties of all these systems. The dye molecule with 1,2,4-triazole groups which exhibits a very high intensity of absorption in visible region, was obtained. Time-dependent DFT(TD-DFT) results indicate that the ancillary ligand dominates the molecular orbital(MO) energy levels and masters the absorption transition nature to a certain extent. The deprotonation of anchoring ligand not only affects the frontier MO energy levels but also controls the energy gaps of the highest occupied MO(HOMO) to the lowest unoccupied MO(LUMO) and LUMO to LUMO+1 orbital. If the gap between LUMO-LUMO+1 is small enough, the higher efficiency of dye-sensitized solar cell(DSSC) should be expected.     

Electrochemical and Spectral Studies on Ferrocene Derivatives with Electron Pushing and Drawing Substituents

Three ferrocene derivatives, P Ⅰ: R-Fc-A, P Ⅱ:D-Fc-R and P Ⅲ: D-Fc-A(R:CH₂OH, A: CH＝C(CN)CONH₂, D:(C₁₈H₃₇)₂-C₆H₄-CH=CH), were studied by means of cyclic voltammetry and absorption spectroscopy. Compound P Ⅰ shows MLCT transition,P Ⅱ D shows strong LMCT and P Ⅲ shows both strong LMCT and π→π^* CT transitions. Based on these data, frontier orbital interactions of electron pushing and drawing substituents with ferrocene group were analyzed. It was found that a drawing substituent would lower the π^* orbital energy level and a pushing, substituent would raise the π orbital level.     

N-2-亚甲基-噻酚-二茂铁基芳胺衍生物的合成、晶体结构及电化学性质

以邻、间、对-二茂铁苯胺为原料, 合成了含噻酚的二茂铁苯基席夫碱衍生物并还原得到N-2-亚甲基-噻酚-二茂铁基芳胺衍生物，通过元素分析，IR，UV，¹H NMR和X-射线单晶衍射等分析手段，确证了标题化合物的组成和结构，单晶结构解析表明，化合物2c属于单斜晶系，P2/n空间群。量化计算结果证明，化合物2c在晶体中的结构并不是它的最稳定结构；其HOMO轨道主要由Fe原子及茂环上C的原子轨道组成的；电化学实验证明所得邻、间、对化合物的电化学性质相似，氧化还原峰对应于二茂铁的氧化还原过程，Fc⁺ + e^-←→Fc；说明化合物中的二茂铁基所处的化学环境相同，苯环上取代基位置的不同，对化合物在电极表面的扩散系数影响不大, 但对反应速率常数则有较大的影响。     

New Conjugated Oligothiophenes Containing the Unique Arrangement of Internal Adjacent [All]‐S,S‐Oxygenated Thiophene Fragments

The quest for obtaining conjugated oligothiophene‐containing molecules with narrower HOMO–LUMO gaps and higher oxidation and reduction potentials is the subject of this study. Molecules containing the bithiophene tetraoxide ( 2 ) and the terthiophene hexaoxide ( 3 ) moieties were prepared and studied. They were obtained by transferring oxygen atoms to the corresponding dibromo oligothiophenes with the HOF ? CH₃CN complex and then cross‐coupling them with either thiophene‐ or acetylene tin derivatives. The photophysical and electrochemical studies of the products revealed that this particular class of mixed thiophenes is characterized by significantly smaller frontier orbital gaps and higher oxidation and reduction potentials compared with any other arrangement of oligothiophenes including various [all]‐S,S‐oxygenated thiophene derivatives.     

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…     

Synthesis and properties of novel fluorinated subnaphthalocyanines for organic photovoltaic cells

Novel fluorinated subnaphthalocyanine derivatives were newly designed and synthesized as donor materials for low molecular organic photovoltaic cells using fullerene as an acceptor. They were designed to have the low-lying HOMO energy levels for improvement of open circuit voltage without any expense of short-circuit current density. The HOMO/LUMO energy levels of hexafluoro-, heptafluoro-, dodecafluoro-, tridecafluoro- and the parent subnaphthalocyanine estimated based on the photoelectron spectroscopy were −5.69/−3.93, −5.67/−3.90, −5.96/−4.19, −5.92/−4.11 and −5.30/−3.58 eV, respectively, showing that frontier orbital energy levels can be effectively tuned by fluorination.