C77N+异构体的稳定性和电子光谱研究

All of the possible 21 isomers for C77N+, an isoelectronic molecule of C78, were investigated by the INDO methods based on C78(C2V). It indicates from optimization that the most stable isomer is that the nitrogen atom substitutes C(78) located at the C(78)-C(73) bond passed through by the Y shortest axis and the atoms near the Z longest axis are also easy to substitute, whereas the atoms near the X shortest axis are relatively difficult to substitute. At the same time, C78 was compressed a little and ready to perform the further reaction to form C77 NR at the location of substitution. Electronic spectra of C77N+ were calculated by INDO/SCI method and electronic transition was theoretically assigned. The red shift of absorption peaks for electronic spectra of C77N+ took place compared with that of C78(C2V) because of its narrower LUMO HOMO energy gap. There are great differences in characteristic absorptions among C77N+ isomers, which can be considered as evidence of the formation for each isomer.     

OH+ C2H2N←C2H3 + NO→CH3 + NCO反应机理的密度泛函理论研究

应用密度泛函理论研究了反应通道(a)C2H3 NO→CH3 NCO和(b)C2H3 NO→OH C2H2N的反应机理．在B3LYP／6-31G(d)水平上优化了反应物、中间体、过滤态、产物的几何构型，通过频率分析确定了11个中间体和10个过渡态．所有的反应物、中间体、过渡态、产物都在CCSD／6-311 G(d，P)水平上进行了单点能较正．并讨论了反应的异构化过程．计算结果表明10是能量最低的中间体，比反应物的能量低308．479kJ／mol；过渡态1／3，2／5，3／4，4／8比反应物的能量高，其中3／4是能量最高的过渡态，比反应物的能量高91．894kJ／mol．通道(a)和(b)的理论放热值分别为111．059和96．619kJ／mol．     

C3H+与N反应的理论研究

用密度泛函方法在QCISD(T)／6—311 G^**//B3LYP／6—311G^*水平上研究了气相反应C3H^ N的反应机理．得到了不同能量产物的可能的反应通道，获得反应势能面．整个反应为多通道反应，经过多个步骤完成，共找到9个中间体和11个过渡态，产物C3H^ N(P2)为能量较低的产物，通道3：IM5→TS4→IM6→TS5→IM7→TS7→IM8→P2为较为可行的反应通道．     

C75N+位置异构体的电子结构和光谱研究

杂原子的介入可改变纯碳笼的电子结构, 使其在超导、光电子器件及有机铁磁体等方面得到应用, 还可改善其氧化还原性能, 提高反应活性, 因而引起人们的研究兴趣[1～3]. Averdung[1]研究了C59N+与H的反应, 用质谱检测到C59NH和C59NH+2, 并用AM1方法优化其结构; Lamparth[2]以双氮杂富勒烯为前体, 合成了C59N+和C69N+, 测定中间体的 1H NMR谱、 UV谱及产物的FAB质谱, 并用 15N标记法证实了最强的碎片峰是N原子进入母体碳笼骨架所致. Diederich[3]观察到C76氮化物的FAB质谱信号, 但未给出进一步信息. 本文用INDO系列方法对氮杂富勒烯C75N+位置异构体的结构和稳定性进行理论研究, 找出最稳定的异构体, 计算其电子吸收光谱, 为实验室合成分离提供理论依据.     

Hyperfine coupling constants of the azafullerenes C19N, C59N, C69N, and C75N

The isomers of the nitrogen-substituted fullerenes (azafullerenes) C19N, C59N, C69N, and C75N are examined using all-electron Gaussian atomic orbital basis density functional theory, to determine the doublet radical geometries and hyperfine coupling constants. We find that the inaccuracy of previously calculated hyperfine coupling constants of C59N resulted from a poor treatment of the geometry optimization. We find that UB3LYP minimization of the radical geometry in the 6-31G basis, followed by single-point evaluation of the hyperfine constants in which an expanded basis is used on the atomic sites of interest, forms an efficient compromise between computational cost and accuracy with respect to experimental hyperfine constants. Using this approach, we assign the hyperfine signals observed in experiments on the C69N radical by calculating the hyperfine coupling constants for all five of the isomers and examine the electron spin density distribution. Finally, we present predicted hyperfine coupling constants for the isomers of C19N and C75N for use in the interpretation of future experiments.     

Stereoselective cascade reactions for construction of polyfunctionalised octahydroquinolines via [2C+2C+1C,1N] cyclisation

A conceptually unifying approach for a highly enantio- and diastereoselective synthesis of polyfunctionalised octrahydroquinolines incorporating three contiguous chiral centres is reported. The synthesis involves diphenylprolinol silyl ether-catalysed Michael addition of 1,3-cyclohexanedione to nitroalkenes followed by potassium carbonate-promoted aza-Henry reaction with N-tosyl aldimines, intramolecular hemiaminalisation and dehydration reaction cascade in a one-pot operation.     

Diode laser spectroscopy of the fundamental bands of 12C14N, 13C14N, 12C15N, 13C15N free radicals in the ground 2 Sigma+ electronic state

Rotationally resolved spectra of the fundamental band of the CN free radical in four isotopic forms have been measured using tunable diode laser absorption spectroscopy. The source of the radical was a microwave discharge in a mixture of isotopically selected methane and nitrogen diluted with argon. The lines were measured to an accuracy of 5 x 10(-4) cm(-1) and fitted to the formula for the vibration rotation spectrum of a diatomic molecule, including quartic distortion constants. The band origins of each of the isotopomers from the five parameter fits were found to be 12C14N: 2042.42115(38) cm(-1), 13C14N: 2000.08479(23) cm(-1), 12C15N: 2011.25594(25) cm(-1), 13C15N: 1968.22093(33) cm(-1) with one standard deviation from the fit given in parenthesis. Some of the lines showed a resolved splitting due to the spin rotation interaction. This was averaged for fitting purposes. The average equilibrium internuclear distance derived from the upsilon = 0 and 1 rotational constants of the four isotopomers is 1.171800(6) A which is in good agreement with the value determined from microwave spectroscopy.     

Simultaneous electron capture and target ion excitation in collisions of C4+ and N5+ on He

Cross sections for simultaneous electron capture and target ion excitation have been measured for impact of slow He-like C⁴⁺ and N⁵⁺ ions on He. The energy of the primary ion beams has been varied over more than two orders of magnitude: 0.05–7 keV/amu. The results are discussed on basis of a slightly modified version of the dynamic classical over-barrier model for multiple electron capture. The differences in the energy dependences of the experimental results of C⁴⁺ and N⁵⁺ — He can be explained qualitatively by assuming that for N⁵⁺ binding energy sharing between the two participating electrons is of importance, particularly at the lower impact energies.     

Crystalline Inclusions Formed in C+N+BF2 Coimplanted on Silicon (111)

In the present work, high-doses (10¹⁷–10¹⁸cm^–2) of carbon, nitrogen, and boron (BF₂⁺) ions were coimplanted on silicon (111) substrates at 21, 25 and 77keV, respectively. Two series of samples have been implanted (series A and B) and subsequently annealed. Series A samples have been implanted at room temperature and treated one minute by rapid thermal annealing (RTA) and 3 hours at 1200°C. Series B samples have been implanted at 600°C and subsequently annealed at 1200°C during 3 hours. The annealing in both series has been carried out in N₂ at atmospheric pressures.The structure of the buried layers has been determined by conventional and high resolution transmission electron microscopy (CTEM and HRTEM). Polycrystalline silicon and new crystalline phases are observed by electron diffraction patterns. The polycrystalline silicon inclusions have been confirmed from analysis of HRTEM images.     

石墨型C3N4的固态合成及嵌锂性能研究

采用固态反应方法制备了石墨型C3N4. 采用XRD, FTIR, XPS对产物的组成和结构进行了表征. 研究了石墨型C3N4的电化学行为, 并将其用作负极材料组装成锂离子电池进行测试, 发现该材料具有一定的嵌锂能力, 但比容量低, 循环寿命短. 采用少量嵌入Mg2＋, Al3＋的方法对石墨型C3N4进行改性, 结果发现石墨型C3N4的充放电性能得到一定改善.     

Synthesis of the C59N+ carbocation. A monomeric azafullerene isoelectronic to C60

A heterofullerene isoelectronic to C60 is reported. The azafullerenium cation C59N+ can be isolated in good yield as a carborane salt via the two-electron oxidation of the C-C bond of (C59N)2 dimer. [C59N][Ag(CB11H6Cl6)2] has been characterized by electronic, IR, Raman, and 13C NMR spectroscopies, MALDI spectrometry, DFT calculations, and X-ray crystallography.     

Pulsed field-ionization photoelectron-photoion coincidence study of the process N2+hnu-->N++N+e-: bond dissociation energies of N2 and N2+

We have examined the dissociative photoionization reaction N2+hnu-->N++N+e- near its threshold using the pulsed field-ionization photoelectron-photoion coincidence (PFI-PEPICO) time-of-flight (TOF) method. By examining the kinetic-energy release based on the simulation of the N+ PFI-PEPICO TOF peak profile as a function of vacuum ultraviolet photon energy and by analyzing the breakdown curves of N+ and N2+, we have determined the 0-K threshold or appearance energy (AE) of this reaction to be 24.2884+/-0.0010 eV. Using this 0-K AE, together with known ionization energies of N and N2, results in more precise values for the 0-K bond dissociation energies of N-N (9.7543+/-0.0010 eV) and N-N+ (8.7076+/-0.0010 eV) and the 0-K heats of formation for N (112.469+/-0.012 kcal/mol) and N+ (447.634+/-0.012 kcal/mol).     

Structural isomers of C2N+: a selected-ion flow tube study

Reactivities of the structural isomers CCN+ and CNC+ were examined in a selected-ion flow tube at 300 +/- 5 K. The less reactive CNC+ isomer was identified as the product of the reactions of C(+) + HCN and C(+) + C2N2; in these reactions only CNC+ can be produced because of energy constraints. Rate coefficients and branching ratios are reported for the reactions of each isomer with H2, CH4, NH3, H2O, C2H2, HCN, N2, O2, N2O, and CO2. Ab initio calculations are presented for CCN+ and CNC+; a saddle point for the reaction CCN+ --> CNC+ is calculated to be 195 kJ mol-1 above the CNC+. The results provide evidence that the more reactive CCN+ isomer is unlikely to be present in measurable densities in interstellar clouds.     

双电荷离子[C12H12N2O]2+和[C12H12N2S]2+的气相单分子分解反应研究

The unimolecular dissociation reactions of doubly charged ions were reported,which resulted from a tandem mass spectrometer and a reversed geometry double focusing mass spectrometer by electron impact.Mass analyzed ion kinetic energy spectrometry(MIKES) was used to obtain the kinetic energy releases in charge separation reactions of doubly charged ions.The intercharge distances between the two charges at transition states can be calculated from the kinetic energy releases.Transition structures of unimolecular dissociation reactions were infered from MIKES and MS/MS.     

Theoretical investigation of the heterofullerenes C59N and C69N and their dimers

The heterofullerenes C₅₉N and C₆₉N and their dimers are examined by the intermediate neglect of differential overlap (INDO/1 and INDO/S) models. The results confirm the stability of the (C₅₉N)₂ and (C₆₉)₂ (C_2h) isomers with a 6–6 closure fusion link between the two monomers. The nearest neighbor C of nitrogen, at the hexagon–hexagon fusion in C₅₉N and in C₆₉N where the N replaces one C in the pentagon of the fullerene has the largest electronic spin density, and this is where the two radicals of C₅₉N or C₆₉N link to form dimers. Also the dimers readily dissociate to free radical monomers to react regioselectively with other reagents. The electronic spectra of the radicals are similar to those of the dimers, which suggest essentially identical electronic structures. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 78: 422–436, 2000