The Radical Anion of 1,2-Diphenylcyclopentene

ESR. and ENDOR. studies are reported for the radical anions of 1,2-diphenylcyclopentene ( 3 ) and its di(pe+deuteriophenyl)-derivative (3-D₁₀). Comparison of the coupling constants of the phenyl protons in 3 \documentclass{article}\pagestyle{empty}\begin{document}$ ^{\ominus \atop \dot{}} $\end{document}. with the analogous values for the radical anions of 1,2-diphenyl substituted cyclopropene ( 1 ) and cyclobutene ( 2 ) reveals regular changes in the sequence 1 \documentclass{article}\pagestyle{empty}\begin{document}$ ^{\ominus \atop \dot{}} $\end{document}, 2 \documentclass{article}\pagestyle{empty}\begin{document}$ ^{\ominus \atop \dot{}} $\end{document}, 3 \documentclass{article}\pagestyle{empty}\begin{document}$ ^{\ominus \atop \dot{}} $\end{document}, which are caused by an increasing twist of the phenyl groups about the C(1), C(1′)- and C(2), C(1″)-bonds linking them to the ethylene fragment. Such a twist is shown to be also responsible for the large difference in the coupling constants of the methylene β-protons in 3 \documentclass{article}\pagestyle{empty}\begin{document}$ ^{\ominus \atop \dot{}} $\end{document}. (0.659 and 0.293 mT). It is suggested that - in order to minimize the losses caused by this twist in the π-delocalization energy - the 2 p_z-axes at the centres 1 and 2 deviate from a perpendicular orientation to the mean plane of the cyclopentene ring. A deviation by 19° from such an orientation is required to account for the observed β-proton coupling constants in terms of their conventional cos²-dependence on the dihedral angles θ.     

The Complexed Triphosphaallyl Radical,Cation, and Anion Family

Radically complex : The photolytic reaction of [Cp*P{W(CO)₅}₂] (Cp*=C₅Me₅) with a diphosphene produces, via a radical intermediate, an air‐stable complexed triphosphaallyl radical, in which the unpaired electron is evenly distributed over both terminal P atoms. Oxidation of the radical leads to a triphosphaallyl cation, which is only stable at low temperatures in solution, whereas the stable triphosphaallyl anion is formed by reduction (see picture, Mes*=2,4,6‐tri‐tert‐butylphenyl).

     

The Radical Anion of trans-10b, 10c-Dihydropyrene

The radical anion of trans-10b, 10c-dihydropyrene (V), which is formed upon reduction of the isomeric [2.2]metacyclophane-1,9-diene (III) with solvated electrons, has been identified by its ESR.-spectrum. The large coupling constant (19.1 Gauss), due to the two equivalent β-protons in the alkyl bridge, gives evidence of an important hyperfine interaction between the σ-MO's of the C(sp³)-H bonds and the singly occupied π-MO of the fourteen-membered perimeter. This finding supports the assumption that the unexpected energy sequence of the lowest antibonding perimeter MO's in the dihydropyrene V and its 10b, 10c-dimethyl derivative (VI) is determined by hyperconjugation rather than by the inductive effect of the alkyl bridge. When the solution of V^○ in 1,2-dimethyoxyethane (DME) is brought in contact with an alkali metal mirror, an immediate conversion of V^Φ into the radical anion of pyrene (IV) occurs. The anion IV^Φ also results from reduction of [2.2.2](1,3,5)cyclophane-1,9,17-triene (VIII) with potassium in DME, whereas the radical anions of 4,5,9,10-tetrahydropyrene (II) and its 2,7-dimethyl-derivative (IX) are obtained by corresponding reactions of [2.2]metacyclophane (I) and [2.2.2](1,3,5)cyclophane (VII), respectively.     

The Radical Anion and Dianion of Tetraazapentacene

The mono‐ and bis‐reduction of 6,13‐bis((triisopropylsilyl)ethynyl)quinoxalino[2,3‐b]phenazine ( 1 ) with potassium anthracenide in THF is reported. Both the radical anion 1 ^.? and the dianion 1 ^2? were isolated and characterized by optical and structural (single‐crystal X‐ray diffraction) methods. Solutions of the radical anion 1 ^{. ?} were stable in air for several hours and characterized by EPR spectroscopy. Dianion 1 ^2? is highly fluorescent and photostable.     

Molecular Orbital Studies of the Protonation of Diazomethane

CNDO/Z, MINDO/3 and ab initio molecular orbital calculations indicate that C-protonated diazomethane is more stable than N(end)-protonated diazomethane. Extrapolation of these results to solution chemistry as well as the kinetic references of protonation of diazomethane are discussed.     

The Radical Anion,Dianion and Electron Transport Properties of Tetraiodotetraazapentacene

Tetraiodotetraazapentacene I₄TAP , the last missing derivative in the series of halogenated silylated tetraazapentacenes, was synthesized via condensation chemistry from a TIPS-ethynylated diaminobenzothiadiazol in three steps. Single and double reduction furnished its air-stable monoanion and relatively air-stable dianion, both of which were characterized by crystallography. All three species are structurally and spectroscopically compared to non-halogenated TAP and Br₄TAP . I₄TAP is an n-channel material in thin-film transistors with average electron mobilities exceeding 1 cm² (Vs)⁻¹.     

The ESR. Spectrum of the Diphenylcyclopropenone Radical Anion

The ESR. spectrum of the relatively unstable radical anion of diphenylcyclo-propenone (II) has been observed upon electrolytic reduction of II in N,N-di-methylformamide and 1,2-dimethoxyethane. Simple MO models account well for the π-spin distribution and for the restricted rotation of the phenyl substituents in II\documentclass{article}\pagestyle{empty}\begin{document}$ ^{\ominus \atop \dot{}} $\end{document}. A rather facile loss of a CO molecule by II\documentclass{article}\pagestyle{empty}\begin{document}$ ^{\ominus \atop \dot{}} $\end{document} results in formation of the radical anion of tolane (diphenylacetylene; III). No ESR. spectra could be obtained for the radical anions of dialkylcyclopropenones which are even shorter-lived than II\documentclass{article}\pagestyle{empty}\begin{document}$ ^{\ominus \atop \dot{}} $\end{document}, although decay by decarbonylation seems to be less favoured with them than with II\documentclass{article}\pagestyle{empty}\begin{document}$ ^{\ominus \atop \dot{}} $\end{document}. In presence of air, electrolytic reduction of either II or its dimethyl and di-t-butyl analogues yields the correspondingly disubstituted semidione anions.     

The Radical Anion of Cyclopentasilane‐Fused Hexasilabenzvalene

The radical anion of cyclopentasilane‐fused hexasilabenzvalene was synthesized by the reduction of the corresponding neutral compound. X‐ray crystallographic analysis showed a more trans‐bent structure of the disilene moiety than the neutral compound. Theoretical calculations showed that the highly trans‐bent structure is attributed to the hexasilabenzvalene structure. The EPR spectrum showed that an unpaired electron exists mainly at the disilene moiety. In the UV/Vis spectrum, a large bathochromic shift was observed compared with the neutral compound.     

自组装中的苯二甲酸阴离子形貌及质子化效应

在高效合成大环主体化合物环[2][2,6-二（1H-咪唑基）]吡啶[2]（1,4-二亚甲基苯）[cyclo[2]（2,6-bis（1H-imidazol-1-yl）pyridine）[2]（1,4-dimethylenebenzene）;1⁴⁺]的基础上,通过溶液中核磁¹H谱、扩散排序核磁共振谱（Diffusion Ordered NMR Spectroscopy;DOSY）、二维核磁欧沃豪斯效应增强谱（Nuclear Overhauser Effect Spectroscopy;NOESY）波谱方法,气相中质谱（ESI-MS）及固相中X射线单晶衍射方法,详细考察1⁴⁺与一系列苯二甲酸阴离子客体的相互作用. 发现苯二甲酸阴离子客体的形貌与质子化因素对主客体的作用模式、相互作用的化学计量比以及形成超分子自组装复合物的结合常数均起着决定性的作用. 本文结果将有助于指导后继新型大环主体化合物与多羧酸阴离子构筑的自组装体系的设计和研究.     

Protonation effects on the inclusion complexation of 6-deoxy-6-diethylamino-beta-cyclodextrin with 2-anthracenesulfonate, 2-naphthalenesulfonate, 2,6-naphthalenedisulfonate, and 2,7-naphthalenedisulfonate in aqueous solutions

At pH values 5.5 and 10.3, 6-deoxy-6-diethylamino-beta-cyclodextrin (DD-beta-CD) as well as beta-CD forms 1:1 inclusion complexes with 2-anthracenesulfonate (2AS), 2-naphthalenesulfonate (2NS), 2,6-naphthalenedisulfonate (2,6NDS), and 2,7-naphthalenedisulfonate (2,7NDS). The equilibrium constants (K) for the formation of the 1:1 inclusion complexes have been evaluated from the absorbance and/or fluorescence intensity changes. With respect to the beta-CD inclusion complexes of 2AS, 2NS, 2,6NDS, and 2,7NDS, the K values at pH 5.5 are nearly the same as the corresponding ones at pH 10.3. In the case of the DD-beta-CD inclusion complexes, the K values of 2AS and 2NS similarly do not depend on the pH value. However, the K values of 2,6NDS and 2,7NDS for DD-beta-CD at pH 5.5 have been found to be more than two times greater than the corresponding ones at pH 10.3, suggesting the electrostatic attraction between the protonated diethylamino group of DD-beta-CD and the sulfonato group of the NDSs.     

Radical Anion of Azuleno[5.6.7-cd]phenalene,a Failure of the Simple HMO Model

Hyperfine proton coupling constants are reported for the radical anions of azuleno-[5.6.7-cd]phenalene (I), 6-phenylazulene (II) and the corresponding 1,3-dideuterio-derivatives (I-d₂ and II-d₂). The singly occupied orbitals of both I^? and II^? are found to be symmetric with respect to the mirror plane perpendicular to the plane of the molecule. In the case of I, surprisingly, such an orbital corresponds not to the first, but to the second lowest antibonding HMO. A correlation diagram for the relevant orbitals of I and II indicates that the correct energy order in the HMO model of I can be achieved by a decrease in the absolute value of the parameter β_μν for the bonds 4a–5, 6–6a, 9a–10 and 11–11a.     

氯化硝基四氮唑蓝显色检测超氧阴离子自由基的研究

将超氧化钾(KO2)溶解于二甲基亚砜(DMSO)和十八冠醚混合溶剂中可以制备稳定的超氧阴离子自由基(O2-·)的溶液,在该溶液体系中O2-·与氯化硝基四氮唑蓝(nitroblue tetrazolium,NBT)可以定量反应生成蓝色的单甲腊(monoformazan),用分光光度法进行检测.研究证实:单甲臢在DMSO溶液中的最大吸收波长为680 nm;反应时间和反应温度对测定结果有一定的影响.NBT与O2-·反应5 min较为适宜;由于低温条件下O2-·较为稳定,故测定温度维持在20℃左右.反应后体系吸光度与O2-·量之间的线性方程为:A680=(-0.071±0.015) (2.607±0.037)X,r=0.999 8,其中x为O2-·的量,标准偏差为1.4%.抗坏血酸对O2-·清除效果的验证实验表明,该方法可应用于实验室抗氧化剂的筛选与研究.