稀土有机光→电、电→光转换器件

198 6年Ｔａｎｇ发表双层有机光伏电池[1] 与无机光伏电池相比 ,以重量轻 ,材料经济并可以沉积在柔性衬底上等潜在优势正在引起人们注意。目前对有机光伏效应的研究多集中在聚苯乙炔 (ＰＰＶ)及其衍生物上[2 ,3 ] ,能量转换效率在 10ｍＷ·ｃｍ- 2 紫外光照下可超过 4 % [4 ] ;以小分子有机物制成的光伏器件也得到研究人员的关注[5,6] 。但是采用稀土配合物作为电子给体层的有机光伏器件还未见报道。我们研究组一直对以稀土有机配合物为发光层的有机ＥＬ器件进行研究[7,8] 。在研究ＥＬ器件特性过程中 ,我们发现稀土有机电致发光器件在紫外…     

Electrophilic 1,3-C→N− and-N→C− migrations in saturated systems

A new type of intramolecular electrophilic rearrangements involving the shift of COOAlk groups from carbon to an N-anionic center is considered. Carbanionic species with COOAlk groups at anionic centers containing no acidic hydrogen react unusually with alkyl(aryl) iso(thio)cyanates giving carbamates as a result of insertion of RNCX into the C−C bond. The kinetics and mechanism of insertion of aryl isocyanates into the C−C bond of the phosphonium zwitterion obtained from triisopropylphosphine and ethyl 2-cyanoacrylate are discussed. The reaction of α-carbanions derived fromN,N-disubstituted amides with methyl trifluoromethanesulfonate results inO-methylation. Some possibilities of back N→C⁻ migrations are considered. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1643–1648, September, 1999.     

F Cl_2→ClF Cl和Cl′F Cl→Cl′ ClF的反应机理

用密度泛函理论(DFT)B3LYP方法,取6-311G基组,计算研究了F＋Cl2→ClF＋Cl的反应机理.求得1个线形和2个三角形过渡态,反应能垒分别为1.24、46.37和105.09kJ·mol－1;同时发现F以∠FClCl为10～20°（或120～160°）进攻Cl2时,反应无能垒.此外,求得对称反应Cl′F＋Cl→Cl′＋ClF的能垒为40.57kJ·mol－1的1个过渡态.     

C60的激发态光谱S1→Sn,T1→Tn与反饱和吸收

用ＩＮＤＯ／ＣＴ方法研究了Ｃ６０分子的电子结构及基态和激发态光谱（Ｓ０→Ｓｎ，Ｓ１→Ｓｎ，Ｔ１→Ｔｎ），激发态分子动态学和反饱和吸收的微观机制，用动态模型解速率方程，实现反饱和吸收的必要条件是激发态对激光的吸收截面，在波长５３２ｎｍ的激光作用下，Ｃ６０满足该条件，故Ｃ６０呈现反饱合吸收特征，理论分析与实验结果一致。     

Synthesis of Analogues of the Antitumor （1→6）-Branched （1→3）-Glucohexaose

β-D-Glcp-(1→）3-[β-D-Glcp-(1→6)-]α-D-Manp-(1→3)-β-D-Glcp-(1→3)-[β-D-Glcp(1→6)-]D-Glcp(18)and β-D-Glcp(1→3)-[β-D-Glcp(1→6)-]α-D-Manp-(1→3)-β-D-Glcp(1→3)-[β-D-Glcp(1→6)-]β-D-Glcp-D-(1→3)-Glcp-1→OM3(29)were synthesized as the analogues of the immunomodulator β-D-Glcp-(1→3)-[β-D-Glcp(1→6)-]α-D-Glcp(1→3)-β-D-Glcp(1→63)-[β-D-Glcp(1→6)-]D-Glcp through coupling of trisaccharide donors 9 with trisaccharide acceptor 16 and tetrasaccharide acceptor 27 followed by deprotection,respectively.     

Intramolecular O→Te and N→Te coordination bonds in molecules of β-tellurocyclohexenals and their nitrogen analogs

The structures of -tellurocyclohexenals and their nitrogen analogs, viz., -methyltellurocyclohexenal (6), -(4-ethoxyphenyltelluro)cyclohexenal (7), di(2-formylcyclohexen-1-yl) telluride (8), -(4-ethoxyphenyltelluro)cyclohexenylidene(4"-methylaniline) (9), -bromotellurenylcyclohexenylidene(4"-methylaniline) (10), and -bromotellurenylcyclohexenal (4-methylbenzoyl)hydrazone (11), were studied by X-ray diffraction analysis. Compounds 6—11 have a Z configuration at the double bond, which provides the formation of intramolecular OTe or NTe coordination bonds. The bonds about the Te atom have a T-shaped configuration. There is only one of two possible OTe coordination bonds in dialdehyde 8 and, consequently, this compound belongs to the 10-Te-3-tellurane structural type. Hydrazone 11 possesses both NTe and OTe intramolecular coordination bonds. Taking into account these interactions, the coordination polyhedron of the tellurium atom can be considered as a trigonal bipyramid. The intramolecular OTe or NTe coordination bond lengths in compounds 6 (2.692 ), 7 (2.657 ), 8 (2.657 ), and 9 (2.690 ) are 0.9—1.0 smaller than the sums of the van der Waals radii of the corresponding atoms. These bond lengths in compounds 10 (2.170 ) and 11 (2.203 ) are almost equal to the standard covalent bond length.     

CNF→FCN异构化反应的LMO研究

采用定域分子轨道（ＬＭＯ）理论研究了异构化反应ＣＮＦ→ＦＣＮ的反应机理。反应的能量过渡态（ＴＳ）是在６－３１Ｇ基组下用Ｐｏｗｅｌｌ方法优化得到的。结果表明体系中的孤对电子对于反应的进行起着重要的桥梁作用。     

A pentiptycene-derived molecular brake: photochemical E→Z and electrochemical Z→E switching of an enone module

The synthesis and brakelike performance of a new molecular system (1) consisting of a pentiptycene rotor and a 2-methyleneindanone brake are reported. The rotation kinetics of the rotor was probed by both variable-temperature (1)H and (13)C NMR spectroscopy and DFT calculations, and the switching between the brake-on and brake-off states was conducted by a combination of photochemical and electrochemical isomerization. Because of the greater steric hindrance between the rotor and the brake units in the Z form ((Z)-1) than in the E form ((E)-1), rotation of the rotor is slowed down 500-fold at room temperature (298 K) on going from (E)-1 to (Z)-1, corresponding to the brake-off and brake-on states, respectively. The (E)-1→(Z)-1 photoisomerization in acetonitrile is efficient and reaches an (E)-1/(Z)-1 ratio of 11:89 in the photostationary state upon excitation at 290 nm, attributable to a much larger isomerization quantum efficiency for (E)-1 versus (Z)-1. An efficient (Z)-1→(E)-1 isomerization (96%) was also achieved by electrochemical treatment through the radical anionic intermediates. Consequently, the reversibility of the E-Z switching of 1 is as high as 85%. The repeated E-Z switching of 1 with alternating photochemical and electrochemical treatments is also demonstrated.     

Synthesis of an antimetastatic tetrasaccharide β-D-Gal-(1→4)-β-d-GlcpNAc-(1→6)-α-D-Manp-(1→6)-β-D-Manp-OMe

An antimetastatic tetrasaccharide T₁,β-D-Gal-（1→4）-β-D-GlcpNAc-（1→6）-α-D-Manp-（1→6）-β-D-Manp-OMe,was synthesized with two approaches.The first approach was a conventional method employing thioglycoside and Koenigs-Knorr glycosylation reaction in 24%overall yield.The second one was a novel route through the azidoiodo-glycosylation strategy by using 2-iodo-2-deoxylactosyl azide as the donor in 36%overall yield.     

5F3 → 5I7 and 5F5 → 5I8 luminescence transitions of HoCl63−

Under 488 nm excitation, the positions and intensities of bands between 640–690 nm in the luminescence spectrum of HoCl₆³⁻ change, depending upon the cubic elpasolite host lattice. In neat Cs₂NaHoCl₆ the ⁵F₅ → ⁵I₈ transition is observed in this spectral region, whereas in Cs₂NaYbCl₆:HoCl₆³⁻ this transition is absent and the ⁵F₃ → ⁵I₇ transition is observed instead. Both transitions are apparent in the spectra of Cs₂NaLCl₆HoCl₆³⁻ (L = Y, Gd). Decay measurements enable the luminescence behaviour to be explained and detailed analyses of the 20 K spectra permit all ⁵I₇, ⁵I₈ crystal-field levels to be located. The assignments are in agreement with those from analysis of the ⁵I₇ → ⁵I₈ luminescence spectrum. New assign- ments are made for the crystal-field components of ⁵F₃.     

T → S Energy Transfer in Some Molecular Complexes

Calculations on the bimolecular complexes of acetophenone or benzophenone with anthracene and its substituted derivatives were carried out using a standard quantum-chemical approach to molecular systems. The deactivation pathways for lower triplet excited states of acetophenone and benzophenone were established. The probability of energy transfer from the energy donor to acceptor in the complexes was considered. The analysis of calculation results showed that the T S transfer of electronic excitation energy in these complexes is feasible only in the case of a small distance between the molecules, and the efficiency of this transfer is higher in the acetophenone rather than benzophenone complexes.     

DNAB→Z构象转换的扭转角变化特征

选择鸟嘌呤脱氧单核苷酸（Ｇ）作为模型,在一定范围内改变确定ＤＮＡ分子构象的８ 个扭转角,对Ｂ→Ｚ转换过程中的不同构象进行量子化学计算。通过能量分析,可将转换中扭转角的作用分为三类：从Ｂ型到Ｚ型,随扭转角γ的变化,势能曲线呈现两个能垒,与８ 个扭转角同时变化一致,说明γ是最重要的。α角和δ角的变化使能量升高对Ｚ构象的形成有显著影响,而β、ε、χ、ν０、ν４ 的变化使能量基本保持不变对新构象的生成影响不大。     

FNC→FCN IRC途径中化学键的变化

利用电子密度分布函数的拓朴分析方法,研究化学反应中键的断裂与生成的变化过程,是理论化学的新课题。本文作者利用CNDO/2方法计算了若干基态分子体系,对其电子密度分布进行拓扑分析,所得结论与Bader等人精确从头算的结果定性一致。本文用CNDO/2及Abinitio(STO-3G)计算了FNC→FCN IRC途径上的若干点。一方面讨论这一反应过程中化学键特性的变化,一方面比较上述两种计算方法所得电子密度的拓扑性质的导同。     

HCO＋HCN→HCHO＋CN反应机理研究

用ａｂｉｎｉｔｉｏ方法在ＵＨＦ／６－３１Ｇ基组上研究了ＨＣＯ　＋ＨＣＮ→ＨＣＨＯ＋ＣＮ　反应的反应机理。经寻找反应的过渡态和计算内禀反应坐标（ＩＲＣ）表明，该反应经一过渡态而形成产物，具有较宽的位垒，并属于后位垒反应。用ＵＭＰ２∥６－３１Ｇ方法计算的活化位垒为１４９．６０２ｋＪ／ｍｏｌ，与实验值（１４３．００１ｋＪ／ｍｏｌ）相当一致。     

Synthesis of (1→5)-β-d-galactofuranan and cyclo[(1→5)-β-d-galactofurano]oligosaccharides

Synthesis of a linear (1→5)-β-d-galactofuranan was accomplished by trityl-cyanoethylidene polycondensation. On 10-fold reduction in the monomer concentration, the condensation products are cyclic oligosaccharides; the formation of 1,5-anhydro-α-d-galactofuranose was also demonstrated.     

Synthesis ofα-D-GlcpNAc-（1→2）-[α-D-ManpNAc-（1→3）-]α-L-Rhap-（1→2）-α-L-Rhap-（1→3）-α-L-Rhap,the repeating unit of O10 antigen from Acinetobacter baumannii

An efficient synthesis ofα-D-GlcpNAc-（1→2）-[α-D-ManpNAc-（1→3）-]α-L-Rhap-（1→2）-α-L-Rhap-（1→3）-α-L-Rhap（1）, the repeating unit of the O10 antigen from Acinetobacter baumannii was achieved via sequential assembly of the building blocks,p- methoxylphenyl 2,4-di-O-benzoyl-α-L-rhamnopyranoside（2）;2-O-allyloxycarbonyl-3,4-di-O-bcnzoyl-α-L-rhamnopyranosyl tri- chloroacetimidate（3）;4-methoxylphenyl 3-O-allyloxycarbonyl-4-O-benzoyl-α-L-rhanmopyranoside（4）;2-azido-3-O-benzoyl-2- deoxy-4,6-O-isopropylidene-α-D-mannopyranosyl trichloroacetirnidatc（5）;2-azido-3,4,6-tri-O-benzoyl-2-deoxy-α,β-D-glucopyr- ano syl trichloroacetimidatc（6）.The total yield of 1 from 4 was 4.7%.     

Z→E Photoisomerization of Homoactivated Carbon Carbon Double Bonds

Z-configured 1,4-diene or β,γ-unsaturated carbonyl systems are readily available by the Wittig reaction. Isomerization required for access into the E-series can easily be accomplished by irradiation using an ordinary tungsten lamp and diphenyl disulphide sensitizer. There is very little formation of conjugated isomers (less than 1%).     

Ionization-induced π→ H site switching dynamics in phenol-Ar3

Electronic excitation spectra of the S(1)← S(0) transition obtained by resonance-enhanced two-photon ionization (REMPI) are analysed for phenol-Ar(n) (PhOH-Ar(n)) clusters with n≤ 4. An additivity rule has been established for the S(1) origin shifts upon sequential complexation at various π binding sites, which has allowed for the identification of two less stable isomers not recognized previously, namely the (2/0) isomer for n = 2 and the (2/1) isomer for n = 3. Infrared (IR) spectra of neutral PhOH-Ar(n) and cationic PhOH(+)-Ar(n) clusters are recorded in the vicinity of the OH and CH stretch fundamentals (ν(OH), ν(CH)) in their S(0) and D(0) ground electronic states using IR ion dip spectroscopy. The small monotonic spectral redshifts Δν(OH) of about -1 cm(-1) per Ar atom observed for neutral PhOH-Ar(n) are consistent with π-bonded ligands. In contrast, the IR spectra of the PhOH(+)-Ar(n) cations generated by resonant photoionization of the neutral precursor display the signature of H-bonded isomers, suggesting that ionization triggers an isomerization reaction, in which one of the π-bonded Ar ligands moves to the more attractive OH site. The dynamics of this isomerization reaction is probed for PhOH(+)-Ar(3) by picosecond time-resolved IR spectroscopy. Ionization of the (3/0) isomer of PhOH(+)-Ar(3)(3π) with three π-bonded Ar ligands on the same side of the aromatic ring induces a π→ H switching reaction toward the PhOH(+)-Ar(3)(H/2π) isomer with a time constant faster than 3 ps. Fast intracluster vibrational energy redistribution prevents any H →π back reaction.