Intramolecular Alkyne Coupling in the Reaction of 1,8-bis(phenylethynyl)naphthalene with Pt2Ru4(CO)18

The reaction of Pt₂Ru₄(CO)₁₈, 1 with 1,8-bis(phenylethynyl)naphthalene, 2 has yielded two metal carbonyl cluster complexes: Ru₂(CO)₆[- ²-C₁₀H₆C₄Ph₂], 3 (60% yield) and Ru₂Pt(CO)₆[- ²-C₁₀H₆C₄Ph₂]₂, 4 (8% yield). Both compounds were characterized by a single crystal X-ray diffraction analysis. Both products were formed as a result of fragmentation of the Pt₂Ru₄ cluster of 1. Compound 3 contains two ruthenium atoms. They are bridged by a tricyclic C₁₀H₆C₄Ph₂ ligand formed by the coupling of the two -carbon atoms of the alkyne groups. The -carbon atoms of the alkynes are -bonded to one of the ruthenium atoms to form a metallacycle and this entire group is -bonded to the second ruthenium atom. Compound 4 contains two ruthenium atoms with a platinum atom between them. This molecule contains two tricyclic C₁₀H₆C₄Ph₂ ligands similar to that in 3, and two metallacycles formed by coordination of the -carbon atoms of both ligands to the platinum atom. One ligand is -bonded to each of the ruthenium atoms.     

从能源产业发展和人才需求浅谈“能源化学”新工科改造

Based on building emerging engineering education of "energy chemistry", we investigated the state key petro-chemical enterprises according to the industrial development and the demand of professional talents. The research report summarizes, analyzes and discusses the current priority development fields of industry, the talent training status, curriculum structure and education program of the chemistry and chemical engineering in universities. The ideas on emerging engineering education of "energy chemistry" have been proposed, and it will be beneficial to building a novel education program for talents training, which integrates the principle of chemistry, energy conversion and information science, etc.     

Examination of the statistical method in the conjugated circuit theory

Summary The recently proposed statistical method for the calculation of resonance energies in the conjugated circuit theory is tested on the example of polyacenes. It is found that for the estimation of the resonance energy with a 10% average error, the method requires a sample consisting of about 20 (randomly chosen) Kekulé structures. Further increase of the sample size gives no significant gain in the accuracy of the method.

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Überprüfung der statistischen Methode in der Konjugierten-Ring-Theorie

Zusammenfassung Die unlängst vorgeschlagene statistische Methode in der Konjugierten-Ring-Theorie (conjugated circuit theory) wird am Beispiel der Polyacene getestet. Es wurde festgestellt, daß für die Abschätzung der Resonanzenergien bei einem mittleren Fehler von 10% für diese Methode ungefähr 20 (willkürlich gewählte) Kekulé-Strukturen nötig sind. Weitere Erhöhung dieser Anzahl bringt keine signifikante Verbesserung der Genauigkeit der Methode.

     

Theoretical Study on the Hetero-Diels-Alder Reactions between 3-Pyridinedithioesters and 1-Phenylsulfanylbutadiene

The mechanism, catalytic effect and solvent effect of the hetero-Diels-Alder reac- tions between 3-pyridinedithioesters and 1-phenylsulfanylbutadiene have been studied theoretically using density functional theory (DFT) at the B3LYP/6-31G(d) level. The results show that all of these reactions proceed in a concerted but asynchronous way. In some reactions the formation of C-S bond is prior to that of C-C bond and the opposite results are found in other reactions. The BF3 catalyst may lower the activation barriers by changing the energies of LUMO for 3-pyridine- dithioester. THF solvent has trivial influence on the potential energy surface of these reactions. With the BF3-catalyzed reactions, regioselectivity and stereoselectivity observed experimentally were predicted correctly by calculations and these results originate probably from C-H···F interaction in two transition states.     

Theoretical Study of the Low-Lying Excited States of Butoxy Radicals and Non-Radiative Decay Routes

The potential energy surfaces for the butoxy radical dissociation into R·＋O on the six low-lying electronic states have been determined with the combined CASSCF and MR-CI methods. The isomerization reactions between the different conformers of 1- and 2-butoxy radicals at the X and B states have been also investigated with the MP2, B3LYP, and CASSCF methods. The non-radiative decay mechanisms of butoxy radicals at the B state have been characterized with the computed potential energy surfaces and intersections. Supported by recent LIF experimental results, it was predicted that the t-butoxy radical would predissociate via the B/C intersection. As to 1- and 2-butoxy radicals, the relative energies of the transition states for the isomerization reactions between conformers at the B state are much lower than those of the B/C intersections, resulting in the predominance of the isomerization in the decay of the B state for 1- and 2-butoxy radicals.     

Synthesis and spectroscopic analysis of tetraphenylporphyrinatoantimony(V) complexes linked to boron-dipyrrin chromophore on axial ligands

Tetraphenylporphyrinatoantimony(V) complexes, linked to boron-dipyrrin chromophores on axial ligands, were synthesized. The fluorescence spectra of 1a, 1b and 1c (3-[4-(N,N′-difluorobornyl-5-dipyrrinyl)phenyl]propoxo(methoxo)antimony(V) tetraphenylporphyrin bromide (1a); 6-[4-(N,N′-difluorobornyl-5-dipyrrinyl)phenyl]hexyloxo(methoxo)antimony(V) tetraphenylporphyrin bromide (1b); bis{3-[4-(N,N′-difluorobornyl-5-dipyrrinyl)phenyl]propoxo}antimony(V) tetraphenylporphyrin bromide (1c)) were analyzed under the excitations of N,N′-difluorobornyl-5-dipyrrinylphenyl (Bdpy) and tetraphenylporphyrinatoantimony(V) (Sb(TPP)) chromophores. Under the irradiation of Bdpy chromophore, the excitation energy was transferred from Bdpy chromophore to the Sb(TPP) moiety at 0.13–0.40 of the quantum yields, even in a polar solvent. On the other hand, the emission of Sb(TPP) chromophores was quenched by Bdpy chromophores at rate constants of 10⁸–10⁹ s⁻¹, independent of on the solvent polarity. Under the excitation of the Bdpy chromophore of 1d (3-[4-(N,N′-difluorobornyl-5-dipyrrinyl)phenyl]propoxo(phenyloxo)antimony(V) tetraphenylporphyrin bromide) involving both the Bdpy and the phenoxy chromophores on the axial ligands, the excited singlet state of the Sb(TPP) chromophore generated by the energy transfer from the Bdpy chromophore was quenched by the phenoxy ligand via non-radiative processes involving electron transfer. However, rapid back electron-transfer may occur because no absorption of the anion radical of Sb(TPP) was observed by nanosecond laser photolysis.     

Design of highly active heterogeneous palladium catalysts for the activation of aryl chlorides in Heck reactions

In situ generation of highly active palladium species by intermediate dissolution of Pd from solid supported catalysts has been demonstrated to be a very successful approach for the activation of aryl chlorides in Heck reactions. The new ‘heterogeneous’ Pd catalysts act as reservoir for molecular Pd species with unsaturated coordination sphere in solution. Crucial Pd leaching and re-deposition onto the support can be controlled by optimization of reaction conditions and by the properties of the catalysts. Pd is re-deposited onto the support at the end of the reaction. The catalysts, palladium supported on activated carbon, on various metal oxides or fluorides and Pd complexes in zeolites, are easy to prepare, though the preparation conditions are crucial. The catalysts convert all aryl bromides completely within minutes (TON 100,000). Aryl chlorides (even deactivated ones) are converted with high yields, within 2-6 h. The catalysts belong to the most active ones in Heck reactions at all (including best homogeneous systems) and fulfill all relevant requirements for practical applications in laboratory and industry.     

Spin–orbit coupling in oxygen containing diradicals

Intermediate diradicals which occur in the Paterno–Büchi photocycloaddition and in the Norrish type I photoreactions have been calculated taking into account the spin–orbit coupling (SOC) between the singlet (S) and triplet (T) states. Reaction paths for the photocycloaddition of formaldehyde to ethene and the diradical products of the α-cleavage of cyclohexanone have been optimized by the MNDO CI method for a number of different singlet and triplet states. SOC integrals are calculated by an effective one-electron approximation. Intermediate diradicals in the Paterno–Büchi reaction and the SOC effects are also studied ab initio with CAS SCF geometry optimization in a TZV basis set. Both methods predict a large SOC matrix element between the S and T states in the course of the C–C attack, while the SOC integral is two orders of magnitude smaller for the diradical produced in the C–O attack. In the Norrish type I photoreaction the oxygen atom also produces some nonzero contribution to the SOC integral which governs intersystem crossing in a ·C–C· diradical. For the diradicals produced by the α-cleavage of cyclohexanone a vibronic interaction is responsible for the SOC mixing between the lowest S and T states. The importance of one-center versus two-center SOC contributions in diradicals is briefly discussed.     

Analysis of critical points on the potential energy surface

A simple classification scheme is proposed for critical points, based only on rankr and signatures of the (n,n)-matrixG of harmonic force constants. The determination ofr ands, e.g. by the well-known factorizationG=L ^T gL (L: triangular matrix,g: diagonal matrix), has several theoretical as well as practical (computational) advantages over the inspection of eigenvalues ofG, so far used in quantum chemistry. The eigenvalues are sufficient butnot necessary for a classification whereas rank and signature are the only necessary and sufficient prerequisites for solving the task. For the purpose of presenting a working example, by calculating only a 2×2 torque constant matrix, it is shown that the coplanar ethylbenzene is unstable in the CNDO/2 picture.     

2-芳基吲哚的敏化光氧化偶合反应

本文研究了十七种2-芳基吲哚(1a-1q)在甲醇-乙酸介质中的亚甲基蓝(MB)敏化光氧化反应, 发现有十五种吲哚(1a-1o)以85%-95%的产率给出2,2'-二芳基-[2,3'-联-1H-吲哚]-3(2H)-酮(2a-2o), 而2-(4-硝基苯基]吲哚(1p)和2-联苯基吲哚(1q)则分别生成2-甲氧基-2-(4-硝基苯基)-1,2-二氢-3H-吲哚-3-酮(7p)和2-联苯基-4H-3,1-苯并恶嗪-4-酮(11q), 其中7p在分离过程中失去甲醇分子给出2-(4-硝基苯基)-3H-吲哚-3-酮(10p)。