聚磷阴离子的立体构型和稳定性

聚磷阴离子的种类繁多, 存在于过渡金属盐、稀土金属盐、有机物、氢化物和以配位体形式生成的金属络合物等化合物中, 聚磷阴离子是磷烷、聚磷金属盐以及聚磷有机物的组成和结构核心。在形成聚磷化物时, 稳定的聚磷阴离子扮演着重要的中间体角色。从大量聚磷化物的实验结构和理化性质出发, 用从头算(ab initio)RHF/6-311++G(d)和MPW1PW91/G96PW-91/6 -311++G(d)方法, 就其中独立聚磷阴离子P33～P213的稳定性、笼型结构和成键特点、溶剂化形成的稳定性等进行了定量的描述, 得到符合实验事实的独立离子优化立体构型、组成聚阴离子的主要结构单元、μ2P原子对聚阴离子独立稳定性的影响等多方面的结论。由此指出聚磷阴离子是路易斯碱, 并与各种路易斯酸化合组成一大类化合物。最后, 讨论了笼型结构特征频率的振动模式, 对实验谱峰进行了归属。论文绘出了14个离子的结构图, 以及普遍存在的结构单元P33、P73 和P113的简正振动模式图。 33     

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。     

LEWIS碱对聚丙烯构型的影响

用~(13)C-NMR技术研究了Lewis碱对聚丙烯等规和无规构型、立规度和数均序列长度的影响。     

异核金属多重键配合物Cp_2MM'(μ-C_8H_8)的理论研究

研究了双核金属多重键配合物Cp2MM'(μ-C8H8)(MM'=ScMn,TiCr,ScCo,TiFe,VMn,VV,CrCr)的结构和成键模式.计算结果表明,对于28价电子体系,Cp2V2(μ-C8H8)基态为含V-V三重键的三态构型,其等电子体Cp2TiCr(μ-C8H8)为Ti-Cr四重键的单态,等电子体Cp2ScMn(μ-C8H8)为Sc-Mn三重键的单态.对于30价电子体系,Cp2Cr2(μ-C8H8)基态为含Cr-Cr三重键的单态,等电子体Cp2VMn(μ-C8H8)为含V-Mn单键的三态,等电子体Cp2ScCo(μ-C8H8)和Cp2TiFe(μ-C8H8)为含Sc-Co和Ti-Fe双键的单态.在三态Cp2MM'(μ-C8H8)中,两个金属原子多为17电子构型,而单态结构中两种金属原子多分别为16和18电子构型.     

磷酸二氢铵水溶液构型能删和径向分布函数的分子动力学模拟

采用分子动力学模拟对不同温度下磷酸二氢铵水溶液的构型能和径向分布函数进行了研究．磷酸二氢根被看作七节点模型,铵离子被看作五节点模型,而水分子则被看作简单点电荷模型．在饱和温度附近,体系局域粒子数密度有波动．373-400K的溶液势能增长缓慢表明磷酸二氧铵部分分解．磷酸二氢根中的氧原子与铵离子中氢原子的径向分布函数在三种不同温度下呈现明显不同,表明溶液中平均氢键数目随温度的变化明显改变．温度对磷酸二氢根中的氧原子和氧原子的结合有一定的影响,而在饱和溶液中有更多的生长基无产生．     

磷原子团簇同分异构体的理论研究I:P5+、P5-和P5的预测

由激光产生的磷原子团簇正离子的质谱图中呈现很强的 P5 和 P5- 谱峰。使用分子图形学方法设计出 9种可能的同分异构体 ,对其中性及正负离子分子进行了分子力学、PM3半经验量子化学和 ADF密度泛函优化。在磷原子团簇模型中 ,磷原子采用 2、3或 4配位方式成键。从各异构体成键能量的比较可得知 ,最稳定的 P5 构型是四方锥的结构 ,最稳定的 P5-构型是平面五边形的结构 ,而最稳定的 P5构型是在最稳定的 P4的增加一个 2配位原子所生成的结构     

手性化合物绝对构型确定的方法与应用

手性分子绝对构型(AC)的确定在手性化学研究与应用中至关重要.近年测定手性化合物AC的各种方法,根据其原理可主要分为三大类.第一类是在手性环境下激发手性化合物的原子核从而测定手性化合物AC的核磁共振(NMR)法,包括应用芳环抗磁屏蔽效应的NMR法和应用配糖位移效应的NMR法;第二类是基于原子共振散射的X射线衍射(XRD...     

几种过渡金属混配配合物的构型和量子化学研究

对几种五配位的过渡金属配合物晶体结构构型进行了详细讨论,通过扭曲角的计算证明它们均为正三角双锥(TBP)和正向四方锥(TP)的过渡构型。运用AM1量子化学计算方法,对混配体的一些物理化学参数,特别是配位N原子轨道对前线轨道的贡献进行了研究。结果表明,配位N原子轨道对前线轨道的贡献不大,而且也不影响配位构型的变化。计算还表明大多数以三(2-苯并咪唑亚甲基)胺为配体的过渡金属配合物均具有扭曲的三角双锥构型,而铜配合物的构型随协同配体的不同,在正三角双锥和正向四方锥之间的变化范围很大,这是由于铜离子较强的John-Teller效应造成的。     

能量分辨质谱区分与检测人参皂苷同分异构体20(S)-Rf和Rg1

将连续变化的碰撞能量与串联质谱相结合,建立了能量分辨质谱(Energy-resolved mass spectrometry,ERMS)分析方法用以区分和检测人参皂苷同分异构体20(S)-Rf和Rg₁. ERMS将子离子与母离子强度的比值定义为强度分数(Intensity fraction, IF),两个子离子强度的比值定义为强度比(Intensity ratio, IR),并通过IF和IR分别对连续变化的碰撞能量作图建立特征碎片离子的IF和IR曲线.虽然20(S)-Rf和Rg₁的串联质谱图无明显差异,但是多元统计分析结果显示其特征碎片离子[M-Glc-H]^-,[M-2Glc-H]^-和[M-2Glc-C₆H₁₂-H]^-的IF和IR曲线差异显著,有明显的区分边界,可以直接区分20(S)-Rf和Rg₁.进一步利用ERMS实时分析了原人参三醇型皂苷生物转化产物中20(S)-Rf和Rg₁的相对摩尔含...     

meso和dl 2,3-二氰基-2,3-二(p-取代苯基)丁二酸二乙酯的~1H NMR研究

测定了meso和dl 2,3-二氰基-2,3-二(p-X苯基)丁二酸二乙酯(X=OCH_3,CH_3,H,Cl,NO_2)的~1H NMR谱及X为CH_3相应二乙酯的~1H Noesy谱。在meso和dl异构体中,苯环m-~1H的化学位移与p-X的Hammett基团常数σ呈线性关系,c~1H的化学位移仅受分子构型的影响,;△δdl-meso为负值,乙氧基中CH_2和CH_3的质子化学位移也只受分子构型的影响,△δdl-meso均为正值。     

Reactions of Phosphorus Sulfides with Organophosphorus Substances

Abstract

We have found that the reactions of P4SIo and 1,3,2,4-dithiadiphosphetane-2,4-disulfides with phosphites, phosphonites, phosphinites, amidophosphonites, amidophosphinites, trithiophosphites, dithiophosphonites and thiophosphinites proceed under mild conditions via the previous formation of products containing the P(S)-S-P structural fragment which were isolated by column chromatography.     

New Acyclic Neutral Phosphorus Sulfides and Sulfide Oxides

A great number of binary neutral phosphorus sulfides was discovered and investigated. However all stable representatives of this family of compounds adopt a polycyclic structure in contrast to their lighter homologues, the nitrogen oxides. Acyclic representatives can be stabilized by adduct formation with a nitrogen base. The bis(pyridine) adduct py₂P₂S₅ of the unstable acyclic phosphorus sulfide P₂S₅ is readily obtained stirring P₄S₁₀ in pyridine at ambient temperature. X‐ray diffraction studies on single crystals of py₂P₂S₅ · 0.5 py ( 1b ) show a N₂O₅ like structure for the P₂S₅ framework. The long P–N distances of 1.86 Å indicate only weak coordination of the pyridine molecules to phosphorus. Single crystal X‐ray diffraction studies on py₂P₂S_4.34O_0.66 ( 2 ) reveal the presence of py₂P₂S₄O ( 3 ) together with py₂P₂S₅ in the crystal. Compound 3 contains the mixed phosphorus oxide sulfide molecule P₂S₄O stabilized as bis(pyridine) adduct. It is readily obtained from pyP₂S₅ by oxidation with KMnO₄ in pyridine. The oxygen atom occupies the bridging position between the two phosphorus atoms. Quantum chemical calculations at the MPW1PW91 level of theory as well as DTA/TG thermal analyses confirm the weak coordination of the pyridine molecules in py₂P₂S₅, py₂P₂S₄O, and py₂P₂S₇ to phosphorus.     

Influence of Iodine on Reactivity of Phosphorus Sulfides and Homologues of Davy's Reagent in Organic Reactions

Abstract

The use of iodine results in reactivity enhancement of phosphorus sulfides and homologues of Davy's reagent in the reactions with disulfides, aminals and thioacetals. The reactions β-diiodotetraphosphorus trisulfides with disulfides, aminals and thioacetals were studied.     

One- and Two-Dimensional 31P NMR Studies of Some Phosphorus Sulfides in the Liquid and Solid State

Abstract

The phosphorus sulfides of the type P₄S_n (3 ≤ n ≤ 10) exhibit a fascinating variety of structures with different molecular symmetries and crystal structures and the simplicity of the compounds combined with the 100% natural abundance of ³¹P (undiluted spin) makes these compounds ideal for studying the behaviour of the molecules in the liquid and solid state by NMR spectroscopy.     

Haloplumbate Nanochains Templated by Quaternary Phosphorus: Good Water Stabilities,Thermochromic Luminescence and Photocurrent Responses

Two triphenylmethylphosphonium/haloplumbate hybrids,i.e.,[(PPh_3Me)_2(Pb_2I_6)·CH_3CN]_n(1) and[(PPh_3Me)(PbBr_3)]_n(2),have been prepared,in which the(PbX_3)_n~(n-) nanochains built from face-sharing PbX_6 octahedra are surrounded by organic templates to assemble the core-shell quantum well.Besides,C-H…πinteractions among Ph_3 PMe~+ cations can also be detected,which give rise to the 2-D organic layer of 1 and 1-D chain for 2.The good water stabilities could be induced by the strong C-H…π interactions,which can deter the hydrolysis reaction.The energy band gaps of this work mainly derive from the charge transfer of organic components,but their luminescence stems from the inorganic(PbX_3)_n~(n-) nanochains with co-existence of free excitons and self-trapped excitons.At temperature lower than 117 K,strong quantum confinement will rule out the free excitons,and self-trapped excitons will dominate,resulting in red-shift luminescence.Moreover,effective and repeatable photocurrent responses can be found in these hybrids.     

Hetaryl 1,2,3-Thiadiazolyl Sulfides

The synthesis of hetaryl 1,2,4-thiadiazolyl sulfides has been carried out by nucleophilic substitution of the chlorine atom in 5-chloro-1,2,3-thiadiazole by mercaptoheterocycles.