Dynamic disorder in solid tetrakis(trimethylstannyl)methane, C(SnMe3)4, investigated by one- and two-dimensional variable-temperature119Sn and13C NMR spectroscopy

Modes of molecular reorientation in solid tetrakis(trimethylstannyl)methane, C(SnMe₃)₄, have been investigated by one- and two-dimensional¹³C and¹¹⁹Sn static and magic-angle spinning nuclear magnetic resonance spectroscopy (NMR) in the temperature range from 150 to 290 K. Spectral lineshape fitting of one- and two-dimensional¹¹⁹Sn NMR experiments shows the pseudo-fivefold disorder previously observed by single-crystal X-ray diffraction on C(SnMe₃)₄ to be dynamic disorder (activation energy E_a ? 32 kJmol^?1). A dynamic-disorder model where each tin atom in a C(SnMe₃)₄ molecule occupies the twenty sites of a nearly perfect pentagonal dodecahedron with equal probability agrees best with the experimental solid-state NMR results.     

Astrophysical S-factors from asymptotic normalization coefficients

S-factors for direct capture reactions can be found at astrophysical energies from asymptotic normalization coefficients which provide the normalization of the tail of the overlap function. For example the overlap for ⁸B → ⁷Be+p defines the S-factor for ⁷Be (p, γ)⁸B. Peripheral transfer reactions offer a technique to determine these asymptotic normalization coefficients. As a test of the technique, the ¹⁶O(³He, d)¹⁷F reaction has been used to determine asymptotic normalization coefficients for transitions to the ground and first excited states of ¹⁷F. The S-factors for ¹⁶O(p, γ)¹⁷F calculated from these ¹⁷F → ¹⁶O+p asymptotic normalization coefficients are found to be in very good agreement with recent measurements. Following the same technique, the ¹⁰B(⁷Be, ⁸B)⁹Be and ¹⁴N(⁷Be, ⁸B)¹³C reactions have been used to measure the asymptotic normalization coefficient for ⁷Be(p, γ)⁸B. This result provides an indirect determination of S ₁₇(0).     

壳聚糖膜固定生物活性短肽RGDS的研究

为改善壳聚糖对细胞的特异性吸附,采用水溶性碳二亚胺将生物活性短肽精氨酸-甘氨酸-天冬氨酸-丝氨酸(RGDS)固定到壳聚糖膜的表面,采用X射线光电子能谱检测固定多肽前后的壳聚糖膜表面,发现反应后壳聚糖膜表面氮元素含量增大,Nls和Cls曲线拟合谱中酰胺键增多,表明RGDS短肽已固定到壳聚糖膜的表面;人角膜缘上皮细胞体外培养实验表明,固定RGDS后壳聚糖膜的细胞黏附率有了明显提高,固定RGDS后的壳聚糖膜在角膜组织工程支架等方面有更好的应用潜力。     

9Mg(OH)(2)·MgCl(2)·4H(2)O, a high temperature phase of the magnesia binder system

The metastable phase 9Mg(OH)(2)·MgCl(2)·4H(2)O (9-1-4 phase) was found at the extended metastable isotherm of Mg(OH)(2) in the system MgO-MgCl(2)-H(2)O at 120 °C and occurs as intermediate binder phase during setting of magnesia cement due to temperature development of the setting reaction. The crystal structure of the 9-1-4 phase was solved from high resolution laboratory X-ray powder diffraction data in space group I2/m (C2/m) (a = 22.2832(3) ?, b = 3.13501(4) ?, c = 8.1316(2) ?, β = 97.753(1)°, V = 562.86(2) ?(3), and Z = 1). Structural and characteristical relations of the phases in the system MgO-MgCl(2)-H(2)O can be derived, with which the development of the cement or concrete qualities becomes explainable.     

Giant Enhancement of Second Harmonic Generation Accompanied by the Structural Transformation of 7‐Fold to 8‐Fold Interpenetrated Metal–Organic Frameworks (MOFs)

Interpenetration in metal–organic frameworks (MOFs) is an intriguing phenomenon with significant impacts on their properties, and functional applications. Herein, we show that a 7‐fold interpenetrated MOF ( 1 ) is transformed into an 8‐fold interpenetrated MOF by the loss of DMF in a single‐crystal‐to‐single‐crystal manner. This is accompanied by a giant enhancement of the second harmonic generation (SHG ca. 125 times) and two‐photon photoluminescence (ca. 14 times). The strengthened π–π interaction between the individual diamondoid networks and intensified oscillator strength of the molecules aid the augment of dipole moments and boost the nonlinear optical conversion efficiency. Large positive and negative thermal expansions of 1 occur at 30–150 °C before the loss of DMF. These results offer an avenue to manipulate the NLO properties of MOFs using interpenetration and provide access to tunable single‐crystal NLO devices.     

Synthesis,Crystal Structures,and Properties of Mn(NCS)2 Coordination Compounds with 4-Picoline as Coligand and Crystal Structure of Mn(NCS)2

Reaction of Mn(NCS)₂ with 4-picoline (4-methylpyridine) leads to the formation of [Mn(NCS)₂(4-picoline)₄] · 0.67 · 4-picoline · 0.33 · H₂O ( 1 - Mn ) reported in literature, Mn(NCS)₂(4-picoline)₂(H₂O)₂ ( 2-Mn/H₂O ), and of [Mn(NCS)₂(4-picoline)₂]_n ( 2-Mn/I ). 1-Mn and 2-Mn/H₂O consist of discrete complexes, in which the metal cations are octahedrally coordinated, whereas in 2-Mn/I the metal cations are linked by pairs of μ-1,3-bridging thiocyanate anions into corrugated chains. Measurements using thermogravimetry and differential scanning calorimetry as well as temperature dependent X-ray powder diffraction on 1-Mn and 2-Mn/H₂O reveal that upon heating both compounds transform into [Mn(NCS)₂(4-picoline)]_n ( 3-Mn ) via 2-Mn/I as intermediate. 3-Mn shows a very rare chain topology in which the metal cations are linked by μ-1,3,3 (N,S,S) coordinating anionic ligands which was never observed before with Mn^II. From these investigations there is no hint that a further modification of 2-Mn can be prepared as recently observed for [M(NCS)₂(4-picoline)₂]_n (M = Fe, Cd) and such a form is also not available if the metastable forms of the Fe^II or Cd^II compounds were used as template during thermal decomposition. Magnetic investigations on 2-Mn/H₂O show only paramagnetic behavior, whereas for 2-Mn/I antiferromagnetic ordering is observed. Finally, the crystal structure of Mn(NCS)₂ was determined from XRPD data, which shows that it is strongly related to that of 3-Mn .     

多谱线耦合系统辐射束缚问题的理论处理

提出一种处理多荧光谱线耦合系统辐射束缚问题的理论方法．这里的耦合包括激发态间的碰撞传能和当谱线重叠时对荧光的交叉吸收．首先将描述辐射束缚的Ｈｏｌｓｔｅｉｎ方程扩展为适用于描述多个激发能级且包括交叉耦合项的微分积分方程组，并将其纳入矢量、矩阵的形式．然后直接通过算符运算求解，给出按算符展开的级数解式．最后对级数解进行约化，导出一个只用有限项便可对系统行为进行完整描述的、远较简单截断近似优越的结果．还给出了一个双激发能级系统的计算实例