取代基对2-脲基-4(1H)-嘧啶酮衍生物聚集行为的影响

2-脲基-4(1H)-嘧啶酮(UPy)结构上的6位取代基会影响UPy的离域π电子云的密度,6位取代基的给电子诱导效应越强,π电子云的密度越大,四重氢键的作用越强。脲基嘧啶酮结构即UPy结构的二聚体的势能最低,表明该结构在体系内最为稳定。随着嘧啶环上的电子云密度增加,离域π键间的电子斥力增强,(001)晶面间距逐渐增大。异氰酸酯结构的空间位阻增大会阻碍UPy中氢原子与相邻嘧啶酮之间的接触,使得氢键作用强度减弱;同时,较大的空间位阻会阻碍嘧啶环间的π-π相互作用,使得(001)晶面间距增大。     

取代基对2-脲基-4(1H)-嘧啶酮衍生物聚集行为的影响

UPy结构上的6位取代基会影响UPy结构上的离域π电子云的密度,6位取代基的给电子诱导效应越强,π电子云的密度越大,四重氢键的作用越强。脲基嘧啶酮结构即UPy结构的二聚体存在着最低的势能,表明该结构在体系内最为稳定。随着嘧啶环上的电子云密度增加,离域π键间的电子斥力增强,(001)晶面间距d逐渐增大。异氰酸酯结构的空间位阻的增大会阻碍UPy中的氢原子与相邻的嘧啶酮之间的接触,使得氢键作用强度减弱,同时较大的空间位阻会阻碍嘧啶环间的π–π相互作用,使得(001)晶面间距增大。     

不对称双二茂铁脲衍生物的合成、表征及电子传递性质

以二茂铁为原料,通过多步反应,首先合成了对称的桥联双二茂铁脲(5),再将其与胱胺反应,合成了一种新的不对称桥 联双二茂铁脲衍生物MeOOC-Fc-NH-CO-NH-Fc-CO-NH-(CH₂)₂-S-S-(CH₂)₂-NH₂ (7)(Fc：二茂铁)。对目标产物进行了红外、紫外、¹H NMR和MS表征;由于目标化合物7含有不对称的二茂铁脲这一特殊结构,采用循环伏安(CV)方法对化合物7的电子迁移特性进行了研究。结果表明2个二茂铁之间通过脲键传递电子,从而使2个二茂铁基团可以分别被氧化,它们的氧化电位差ΔE_o^?为181 mV,它们之间的稳定常数Kc为1 145。相对于对称的二茂铁脲(5)(ΔE_o^?=140 mV,K_c=207),这种不对称结构分子中2个二茂铁之间电子间的相互作用增强。     

β位取代基对咔咯锰(Ⅴ)氧配合物电子吸收光谱的影响

采用含时密度泛函理论(TDDFT)和B3LYP方法对一系列β位咔咯锰(Ⅴ)氧配合物的几何结构、前线轨道、自然键轨道和电子吸收光谱进行了计算。并探讨了β位取代基对咔咯锰(Ⅴ)氧配合物电子吸收光谱的影响。结果显示β位取代基效应中的空间效应是能导致该体系电子吸收光谱Soret带和Q带红移。β位取代基的空间位阻大时,导致配合物的咔咯环产生严重扭曲,引起Soret带和Q带吸收峰的ΔE能隙减小,导致Soret带和Q带发生红移。     

基于二茂铁的两个查尔酮衍生物的合成及超快三阶非线性光学响应

二茂铁是合成新颖有机功能材料的基本单元之一。 本文设计并合成了两个基于二茂铁的同分异构查尔酮衍生物:1-二茂铁基-3-(噻吩-2-基)丙烯酮(a)和1-二茂铁基-3-(噻吩-3-基)丙烯酮(b)。 采用超快激光Z-扫描技术(脉宽180 fs,波长532 nm)测定了化合物a和b的三阶非线性光学性质。 结果表明,化合物a吸收系数β=-2.1×10^-12 m/W,折射率n₂=1.9×10^-19 m²/W,分子超极化率γ=5.37×10^-32 esu;化合物b:β=-1.2×10^-13 m/W,n₂=2.0×10^-19 m²/W,γ=4.48×10^-32 esu。 说明在飞秒激光激发下,电荷转移能够在化合物a和b分子内部快速进行,二者均具有优异的超快三阶非线性光学响应。 在B3LYP/6-311+G(d,p)理论水平下,计算了化合物a和b分子轨道能量、极化率和各基团在前线分子轨道中的占有率。 理论计算结果显示,二茂铁基团在化合物a和b前线分子轨道中占有率分别为97%和98%,对两化合物的非线性光学性能起主导作用。     

基于四重氢键作用的相变保温聚氨酯

以一种新型含四重氢键脲基嘧啶酮单元（2-脲-4[1H]-嘧啶酮,UPy）的二元醇为扩链剂,扩链异氰酸酯基封端的1,6-己二异氰酸酯（HDI）与聚乙二醇（PEG）合成的聚氨酯预聚物,成功合成了含四重氢键单元的相变保温聚氨酯。通过DSC、XRD、黏度测试及拉伸力学性能测试对聚氨酯进行了性能分析。结果表明：该聚氨酯具有较好的...     

O6-鸟嘌呤和O4-胸腺嘧啶甲基化与DNA碱基异常氢键作用的理论研究

用密度泛函B3LYP方法在6-311＋G**基组水平上对顺(cis-)、反式(anti-)O⁶-甲基鸟嘌呤(O⁶-MeG)和O⁴-甲基胸腺嘧啶(O⁴-MeT)与DNA碱基(腺嘌呤A、鸟嘌呤G)的非Watson-Crick氢键二聚体进行了优化. 在MP2/cc-pVXZ (X＝D,T)//B3LYP/6-311＋G**水平上, 采用完全基组外推方法校正了氢键二聚体的相互作用能, 并用完全均衡校正法(CP)校正了基组重叠误差(BSSE). 此外, 在B3LYP/6-311＋G**水平上计算了各氢键碱基对的全电子波函数, 并用分子中的原子理论(AIM)和电子密度拓扑方法分析了碱基间的弱相互作用. 计算结果显示, 甲基化使碱基对间的氢键作用模式发生了明显的扭转和不同程度的位移, 碱基间的电子密度分布和氢键作用能明显减小, 甲基化对O⁶-MeG和O⁴-MeT与DNA碱基间的氢键作用是去稳定化的, 这种影响主要来自于大体积的甲基的空间效应和给电子效应, 且对顺式的影响明显大于反式. 计算结果与文献给出的实验结论基本一致.     

含甲氧基偶氮苯液晶基元超分子的相行为研究

氢键是分子聚集和识别过程中的重要相互作用,利用分子间氢键,可设计并制备各种超分子体系材料,1989年,Kato等报道了吡啶基和羧酸基通过分子间氢键相互作用形成扩展液晶基元,得到了液晶稳定性增强的超分子液晶复合体系及侧链超分子液晶聚合物;同时,Lehn等报道了带脲嘧啶基和2,6-二酰胺吡啶基两种互补官能团的分子通过三重氢键缔合形成的主链超分子液晶。从此,迅速而广泛的开展利用氢键组装的超分子液晶体系的研究,并已组装合成出低分子型、     

新型二茂铁茚基化合物的设计、合成及电化学性质研究

利用Sonogashira偶联反应,以1,1¢-二碘二茂铁(I-C₅H₄FeC₅H₄-I),1,1¢-二碘联二茂铁(I-C₅H₄FeC₅H₄-C₅H₄FeC₅H₄-I)和2-乙炔茚(Ind-C≡CH)为原料,设计合成了6种新型二茂铁茚基化合物I-C₅H₄FeC₅H₄-C≡C-Ind(1,Ind为茚基), Ind-C≡C-C₅H₄FeC₅H₄-C≡C-Ind(2), I-C₅H₄FeC₅H₄-C₅H₄FeC₅H₄-C≡C-Ind(3), Ind-C≡C-C₅H₄FeC₅H₄-C₅H₄FeC₅H₄-C≡C-Ind(4), C₅H₅FeC₅H₄-C≡C-C₅H₄FeC₅H₄-C≡C-Ind(5), Fc-C≡C-C₅H₄FeC₅H₄-C₅H₄FeC₅H₄-C≡C-Ind(6,Fc为二茂铁基),其结构经¹H NMR, ¹³C NMR, MS(ESI)和X-射线单晶衍射表征,其中化合物1~3的晶体结构为首次报道。采用循环伏安法研究了化合物1~6的电化学性质。结果表明：取代基对调控二茂铁茚基衍生物二茂铁基之间的电子交互作用显著。单二茂铁茚基衍生物1和2中分别引入不对称和对称的共轭取代基团后,二茂铁基的氧化电位值升高。联二茂铁茚基衍生物3和4二茂铁基之间的电子交互作用基本不受取代基的影响。在乙炔桥相连接的取代二茂铁茚基衍生物5中,受金属-金属间距增加的影响,两个二茂铁基之间的电子交互作用减弱。不对称地引入二茂铁乙炔和乙炔茚取代基后,联二茂铁茚基衍生物6的两个二茂铁基之间的电子交互作用明显减弱。      

两种取代二茂铁基三甲基硅烷基氰醇醚的合成及晶体结构

通过两种取代的乙酰基二茂铁与三甲基氰硅烷的加成反应, 得到两种取代二茂铁基三甲基硅烷基氰醇醚的晶体: 1-(1-氰基-1-三甲基硅烷氧基乙烷基)二茂铁(1), 1,1'-二(1-氰基-1-三甲基硅烷氧基乙烷基)二茂铁(2), 用X射线单晶衍射、元素分析、红外光谱和核磁共振氢谱对分子结构进行了表征. 测试结果表明: 晶体1属正交晶系, Pbca空间群, a＝1.1995 nm, b＝1.2441 nm, c＝2.2183 nm, Z＝8, R₁＝0.0456, wR₂＝0.0880; 晶体2属正交晶系, Pna2(1)空间群, a＝2.0715 nm, b＝0.6440 nm, c＝1.8411 nm, Z＝4, R₁＝0.0485, wR₂＝0.0866. 晶体结构表明, 分子中都存在超共轭效应.     

Efficient electronic communication between two identical ferrocene centers in a hydrogen-bonded dimer

A novel ferrocene derivative that contains a donor-donor-acceptor-acceptor (DDAA) hydrogen bonding motif forms highly stable, noncovalent dimers in chloroform and dichloromethane solutions. Its voltammetric behavior and the observation of an intervalence charge-transfer band reveal that the two equivalent ferrocene centers in the hydrogen-bonded dimer exhibit a surprisingly efficient level of electronic communication.     

Unusually Strong Long‐Distance Metal–Metal Coupling in Bis(ferrocene)‐Containing BOPHY: An Introduction to Organometallic BOPHYs

The first organometallic BOPHY (BOPHY=bis(difluoroboron)‐1,2‐bis{(pyrrol‐2‐yl)methylene}hydrazine) containing two ferrocene substituents was prepared through a Knoevenagel condensation between tetramethyl substituted BOPHY and ferrocene carboxaldehyde. An unprecedentedly strong long‐range (≈17.2 Å) metal–metal coupling in this new complex was investigated using electrochemical, spectroelectrochemical, and chemical oxidation methods. Electrochemical data is indicative of a 200 mV separation between the first and the second ferrocene‐centered oxidation processes. Formation of the mixed‐valence states and appearance and disappearance of two NIR bands were observed during stepwise oxidation of the first organometallic BOPHY. The electronic structure and the nature of the excited states in this new chromophore were studied by DFT and TDDFT calculations.     

Electron transfer from cresols to N3, BrO2, ClO2, NO2 and SO4 radicals: correlation between rate constants and one-electron reduction potentials

The rate constants of oxidation of phenol and the cresol isomers to phenoxyl or methylphenoxyl radicals by inorganic radicals (R√) were studied in aqueous solutions at pH=5.8 and 11.5 using pulse radiolysis. The oxidation was due to electron transfer. Using the Marcus theory the electron transfer data were evaluated on the basis of the energy difference, ΔE, between the one-electron reduction potential of the inorganic couple and the mid-point potential of the half-cell of the phenoxyl/phenolate(phenol) couple. The standard reduction potentials of (o-CH₃PhO√/o-CH₃PhO⁻) and (m-CH₃PhO√/m-CH₃PhO⁻) couples (vs. NHE) were determined as 760 and 800 mV, respectively. The electron transfer was found to be diffusion limited when ΔE500 mV independently of the inorganic radical, type of phenol or pH. Between 0ΔE500 mV the rate constants showed good correlation with ΔE. The rate constants were dependent on the isomeric position of the methyl substituent.     

Synthesis and characterization of a ferrocene-linked bis-fullerene[60] dumbbell

A new [60]fullerene dumbbell consisting of two fulleropyrrolidines connected to a central ferrocene unit by amide linkages has been prepared and fully characterized by elemental analysis, (1)H NMR, UV/Vis, fluorescence and mass spectrometry. The electrochemical properties as determined by cyclic voltammetry show ground state electronic communication between the ferrocene and the fullerene units. In addition, the preparaton of a ferrocene building block for an alternative linking approach is presented.     

通过增强电荷转移激发态构建激发态下稳定的基于氰基二苯乙烯的E/Z构型

The E/Z isomerization reaction is found extensively in most organic molecules containing double bond unit. This limits their practical application as luminescent materials partly, especially under photoirradiation. Therefore, it is important to obtain E/Z isomers with stable configuration in the excited state after photoirradiation. It is well known that cyanostilbene and its analogues play an important role in the development of organic opto/electronic materials. The substituted cyano group on C＝C double bonds has strong electron-withdrawing ability and large steric hindrance, which benefits the formation of donor-acceptor (D-A) structures and formation of intramolecular charge transfer. In our previous work, we reported a triphenylamine-cyanostilbene molecule (TPNCF) formed by modifying the cyanostilbene structure with triphenylamine, which maintained a stable E/Z configuration as a film and in high polar solvents. According to solvatochromism mechanisms and the results of theoretical calculations, we proposed that the charge transfer (CT) excited state between the triphenylamine donor and cyanostilbene acceptor groups induced the stable configuration of the E- and Z- isomers under photoirradiation. Under irradiation, the E/Z isomerization process occurring at a higher energy locally excited (LE) state was suppressed by a rapid internal conversion process from the LE to CT state. This work inspired us to provide a universal and effective molecular design strategy by modifying D-A substituents on double bonds that can successfully stabilize E/Z isomers. To further confirm that the CT excited state induced stable E- and Z- isomers in the cyanostilbene structure under photoirradiation, we designed and synthesized a donor-acceptor phenoxazine-cyanostilbene molecule (PZNCF) and successfully characterized its two E/Z isomers. In comparison with the reported TPNCF molecule, the in-situ NMR and UV spectra of E- and Z- isomers of PZNCF demonstrated that the E/Z isomerization rate became slower under photoirradiation, which indicated that the stronger electron-donating group of phenoxazine substituted in the cyanostilbene structure induced a more stable E/Z isomer configuration in its excited state. DFT calculations and photophysical results indicated that a stronger CT state was generated in both E- and Z- isomers of PZNCF. This further confirmed our hypothesized mechanism where the stable E/Z configuration can be obtained under photoirradiation by forming a suitable donor-acceptor structure to suppress the E/Z isomerization reaction in the LE state by a rapid internal crossing process from the LE to CT state. This molecular design strategy is of great significance to organic photochemistry and photoelectronics for molecules with double bond units.     

单壁AlAs(111)纳米管结构和电子性质的密度泛函理论研究

通过卷曲立方AlAs(111)单层片(sheets)构造了一系列(n,0)和(n,m)一维单壁纳米管。用周期性密度泛函理论(DFT)计算并比较了不同类型AlAs纳米管在几何结构、能量及电子性质等方面的差别。计算结果表明锯齿型和椅型纳米管应变能均为负值,并随着管径变大而逐渐变小。然而,它们的带隙相当不同:椅型纳米管为间接带隙,随着管径的增大而带隙减小;锯齿型纳米管为直接带隙,管径为1.87 nm时存在着一个极大带隙值(2.11 eV)。这种不同主要源于锯齿型纳米管铝原子间3p轨道的耦合贡献。     

Redox-assisted ring closing reaction of the photogenerated cyclophanediene form of bis(ferrocenyl)dimethyldihydropyrene with interferrocene electronic communication switching

We synthesized ferrocene-attached dimethyldihydropyrene (DHP) derivatives and investigated their photochemical and redox behaviors. For bis(ferrocenylethynyl)dimethyldihydropyrene (1), reversible photoisomerization between the closed DHP form (1c) and the open CPD form (1o) occurred in high yields upon alternate irradiation of visible (578 nm) light and UV (303 nm) light, whereas no photoisomerization proceeded for bis(pentamethylferrocenylethynyl)dimethyldihydropyrene (2). 1 exhibited reversible switching of electronic communication between the ferrocene (Fc) moieties by photoisomerization of the DHP moiety and demonstrated a novel ring closing reaction induced by oxidation of the Fc moieties. The magnitude of electronic communication, deltaE0' (the difference between the redox potentials of two Fc's), was 63 mV in 1c and 16 mV in 1o, indicating that the electronic communication through the spacer is enhanced in the more developed pi-conjugation of the DHP moiety. The rate constants of the ring closing reaction from 1o+ to 1c+ and from 1o2+ to 1c2+ were estimated at 3.7 and 0.50 s(-1), respectively, by the simulation of cyclic voltammograms.     

Novel linear and tribranched polymers with redox-active end groups via W(CO)6-initiated metathesis polymerization

[reaction: see text] Synthesis, characterization, and electrochemistry of linear and tribranched polyphenylacetylenes having redox-active ferrocene and/or (arene)chromiumtricarbonyl as end groups are reported in this study. The methodology adopts polymerization of phenylacetylene by a metathesis pathway, initiated by W(CO)(6) when photolyzed. A distance-dependent electronic communication between the metal centers is demonstrated in these polymers by means of cyclic voltammetry.     

Host-guest complexation of a fluorescent and electrochemical chemsensor for fluoride anion

Host-guest complexation of a ferrocenenylphalene dyad 1, 1,1'-diaceylferrocenyl-3-hydroxyl-2-naphthoylhydrazone, as a fluorescent and electrochemical chemosensor for fluoride anion, was investigated. Crystal structure analysis revealed that the two naphthyl arms of compound 1 positioned in the same side about the ferrocene moiety and interacted through pi-pi stacking interactions. The intermolecular pi-pi stacking interactions and the C-H...pi interactions between the ferrocene moieties and the naphthalene rings linked the molecules together featuring a two-dimensional layered structure. Fluorescence titrations of compound 1 indicated that in the presence of F- and H2PO4-, the emission intensities enhanced significantly. Electrochemical titrations revealed that compound 1 sensed the F- anion in high selectivity with a cathodic shift of 120 mV, and had no sense in recognizing H2PO4- anion. 1H NMR titrations demonstrated that while compound 1 hydrogen-bonded to H2PO4- forming simple 1 : 1 host-guest complex, further addition of F- induced the deprotonation of compound 1.     

The synthesis of novel chiral N,O-ferrocenyl ligands and their application in the addition of diethylzinc to aldehydes

Novel chiral N,O-ferrocenyl ligands, in which N and O groups were attached to two different Cp rings of ferrocene, were synthesized from easily available ferrocene, and applied to the asymmetric diethylzinc addition to aldehydes. High chemical yields and good enantioselectivities (up to 90.9% ee) were obtained by using ferrocene ligand 6.