预测[Si, C, S]＋和[Si, C, S]－体系的稳定异构体

采用DFT, QCISD及CCSD(T)方法分别对二重态的[Si, C, S]＋和[Si, C, S]－体系势能面进行理论计算, 用QCISD/6-311＋G(d)方法, 在[Si, C, S]＋和[Si, C, S]－体系中, 我们分别得到了2个过渡态连接的3个稳定体和2个过渡态连接的4个稳定体, 经热力学及动力学分析发现, [Si, C, S]＋体系只有二重态线性的离子[Si—C—S]＋可能稳定存在, 而[Si, C, S]－体系有二重态线性的离子[Si—C—S]－和三元环c-[SiCS]－可能稳定存在.     

互连式硼烷neo-B20H182-同分异构体的构型稳定性研究

富硼化合物的构型稳定性研究对其应用具有重要作用,通过设计9个独立的neo-B20H182-同分异构体,应用密度泛函方法G96PW91方法,结合SHC基组,对其几何结构进行优化,获得总能和电子性质,区分了它们的稳定性差异,并与分子前沿轨道能差得到的稳定性结论一致。其中(ae1,e1a)-C2h、(e12,e22)-D2、(e12,e2a)-C1、(a2,e2)-C2v和(e12,e22)-C2h等5个同分异构体稳定性相当,均属稳定分子构型;(e12,e1e2)-C1和(e12,ae1)-C1稳定性相当,为较稳定的同分异构体;(e12,e12)-C2h和(e12,e12)-C2v的总能和互连能都与前7个相差很大,属不稳定的同分异构体。论文还就影响互连键强度和分子稳定性的因素进行了讨论。     

Relativistic coupled cluster calculation of Mössbauer isomer shifts of iodine compounds

ABSTRACT

Mössbauer isomer shifts of ¹²⁹I and ¹²⁷I in the ICl, IBr and I₂ molecules are studied. Filatov's formulation is used, based on calculating the electronic energy change of the two systems involved in the Mössbauer γ transition, the source and absorber. The energy difference between the transitions in the two systems determines the shift. The effects of relativity and electron correlation on the shifts are investigated. The exact two-component (X2C) and the four-component relativistic schemes give virtually identical results; the non-relativistic approach yields about 50% of the relativistic shifts. Electron correlation is included by coupled-cluster singles-and-doubles with perturbative triples [CCSD(T)]; it reduces Hartree–Fock shifts by 15%–20%. Basis sets are increased until the isomer shifts converge. The final results, calculated with the converged basis in the framework of the X2C Hamiltonian and CCSD(T) correlation, give an agreement of 10% or better with experimental data.     

十一钨锆杂多配合物位置异构体的合成表征及催化性能

过渡元素取代的杂多配合物由于其独特的催化活性和抗病毒性受到人们的重视 ,由于缺位 β位的介稳定性和异构化 ,给合成带来了一定的困难。我们发现 ,某些单取代金属衍生物中 β异构体具有良好的催化活性[1 ,2 ] 。本文报道了通式为α ,βi K6[SiW1 1 ZrO40 ]·XH2 O( βi=β1 ,β2 ,β3)的四种异构体 (简记作α ,β SiW1 1 Zr)的合成、表征及四种异构体对烯烃环氧化反应的催化活性 ,为研究Zr杂多化合物的应用提供选择。1　实验部分1 1　仪器与试剂日本岛津IR 40 8红外光谱仪 (KBr压片 ) ,美国PE公司产λ 35型紫外分光光谱仪 ;384B…     

Isomer separation and measurement of nuclear moments with the ISOLDE RILIS

Short-lived radioisotopes are element selectively ionized by the resonance ionization laser ion source (RILIS) of the on-line isotope separator ISOLDE (CERN). The relative production of low and high spin isomers can be significantly changed when a narrow-bandwidth laser is used to scan through the atomic hyperfine structure. This allows the assignment of gamma ray transitions to the decay of the individual isomers. Moreover, the measurement of the hyperfine splitting provides a very sensitive method for the determination of magnetic moments of exotic isotopes. The technical developments are discussed for the example of copper. This revised version was published online in August 2006 with corrections to the Cover Date.     

Temperature Dependence of Photoinduced Birefringence in Polystyrene Doped with Disperse Red‐1

A theoretical model on the basis of the free‐volume concept is presented explaining the temperature dependence of photoinduced birefringence in polystyrene films that contain Disperse Red‐1. Birefringence increases with temperature up to 180 K as the free volume for isomerization increases, and then decreases as thermally activated processes dominate. The fast process of birefringence decay has a time constant that increases with temperature at low temperatures, due to the change in photoisomerization.

Temperature dependence of the birefringence amplitude measured at 300 s. The amplitude increases with temperature up to 180 K and then decreases. The solid line is for guiding the eye.     

计算饱和醇异构体标准生成焓的新方法

基于极性叠加原理,在成功设计烷烃异构体和多氯代烷烃生成焓计算新方法的基础上,设计了一种计算多元醇异构体生成焓的新方法,并合理地假定任一异构体的原子化焓等于三种键（C-C、C-H和C-O-H键）的键能、极性叠加能项以及氢键能项的加和。用这一模型拟合24种原子化粹数据,得到了标准生成焓的估算公式。为了检验预测的精确性,又设计了一种预测方法,使用在排除液预测的化合物条件下回归得到的参数,预测该化合物的生成焓。按这种方法,预测了24种异构体的生成焓。通过该5参数预测的相对于实验值的各种误差（平均绝对误差、均方根误差和最大绝对误差）不仅比7参数的基团法预测的对应误差小得多,而且比相应实验数据的误差还要小。与键加和法比较,该方法的模型包含了极性叠加能和氢键能量,该两项代表了主要的非键相互作用能,表征了不同异构体的结构差异,并大大减少了参数。     

C_(70)PH可能异构体的结构与稳定性的理论研究

分别用半经验的AM1, PM3及MNDO方法研究了富勒烯衍生物C_(70)PH的12种可能异构体的结构和稳定性。计算结果表明: -PH基团加成在4种6-6键上的稳定构型中,非赤道带6-6键加成的三个异构体为闭环结构,赤道带6-6键加成的一个异构体为开环结构;-PH基团加成在4种6-5键上均可产生开环和闭环2种稳定构型。加成在6-5双键的异构体其闭环构型更稳定,加成在6-5单键的异构体其开环构型更稳定。闭环异构体中-PH基团加成在碳球极处6-6键上的构型1,2最稳定,开环异构体中-PH基团加成在赤道带6-6键上的构型8最稳定。     

四取代酞菁金属配合物异构体~1HNMR的表征

概述了近年来用1 HNMR表征一些四取代酞菁金属配合物异构体的研究进展情况。四取代酞菁配合物存在 4种异构体和 8种磁不等价的异吲哚基。这些磁不等价的异吲哚基对苯环上以及取代基的质子的1 HNMR谱均有所影响 ,因此可以通过测定这些质子的1 HNMR谱来确定异构体。