TiN_(12)团簇的制备研究

以高纯氮气为载气,通过532nm的激光轰击由Ti、BN粉末混合压制成的样品,生成了钛氮团簇,确定了最稳定钛氮团簇的组成为TiN12。以四氟化钛和三甲基叠氮硅烷为原料,在液氮冷却下开展了钛氮团簇的化学法合成,对所得产物进行了IR、NMR表征,确定其结构为Ti(N3)4。用密度泛函理论(DFT)对TiN12的结构进行了优化,发现存在一种Ti(N3)4形式的具有对称的正四面体结构的稳定构型,这与化学法合成的TiN12的IR和NMR谱相符。不过,仍需进一步确定激光轰击法和化学合成法产生的TiN12是否具有相似的结构。     

抗坏血酸包裹的铜纳米簇作为荧光探针定量测定维生素B12

以抗坏血酸(AA)为模板和还原剂,通过“一锅法”在水溶液中合成低毒性的青色荧光铜纳米簇(AA@CuNCs)。实验表明,制备的水溶性AA@CuNCs外观呈球形,有良好的分散性,粒径约为1.6 nm。维生素B₁₂(VB₁₂)能高效猝灭AA@CuNCs的荧光,猝灭机理为静态猝灭和内滤效应。在10～60μmol/L与100～120μmol/L浓度范围内,VB₁₂浓度与AA@CuNCs的相对荧光强度(F₀/F)呈较好的线性关系,检出限低至0.07μmol/L。此外,该荧光探针可以有效地应用于实际样品中VB₁₂的检测,并可将其应用于细胞成像。     

Al掺杂Sn12-团簇结构及电子性质的密度泛函理论研究

采用密度泛函理论(DFT)的B3PW91方法,在混合基组水平上对Al掺杂Sn12-团簇几何结构和电子结构进行了计算分析.结果表明,Al内掺杂Sn12-团簇能量更低更稳定,但LU-MO-HOMO能隙较小.外掺杂多面体簇中,电荷从Al原子移向Sn12-笼,趋向形成[Al+Sn122-]结构;内掺杂多面体簇中,电荷从Sn12-笼移向Al原子,趋向形成[Al-@Sn12]结构.     

Au4团簇上甲酸分解反应机理的理论研究

采用密度泛函理论方法对Au4团簇上甲酸分解反应的反应机理进行了研究,并考察了Au4团簇的两个催化活性位点。在路径Ⅰ和路径Ⅱ中,HCOOH分解的产物是CO2和H2。在路径Ⅲ和路径Ⅳ中,HCOOH分解的最终产物为CO和H2O。此外,本文研究了CO2、H2和CO、H2O两种产物的相互转化,即路径Ⅴ和路径Ⅵ。研究结果表明,路径Ⅰ和路径Ⅱ的活化自由能垒较低,即在Au4团簇上HCOOH更易分解得到CO2和H2,此外两种产物之间不容易转化。进一步研究发现团簇的大小及CeO2载体对HCOOH分解脱氢路径的活化自由能垒有一定的影响。     

C24和B12N12团簇的结构与稳定性

本文采用量子化学密度泛函理论的B3LYP/6-31G*方法,对C24和B12N12团簇的12种异构体进行了优化,并对它们的几何构型、振动频率、核独立化学位移(NICS)和结合能进行了理论探讨, 比较了C24和B12N12团簇结构的稳定性。研究表明:C24团簇的最稳定几何构型为类石墨结构d,B12N12团簇的最稳定结构为4/6笼状结构g。C24异构体的稳定性大小顺序为d > b > f > c > a > e。B12N12团簇异构体稳定性大小顺序为a > f> c> d > e >b。     

新团簇形成的动力学研究

利用紧束缚模型,通过对不同初始条件下的碱金属团簇的碰撞研究,得到形成大分子团簇的可能性.结果表明,对同一种团簇,具有空间对称性的团簇间的碰撞更易形成大团簇,而平面结构的团簇碰撞则反之,并且空间结构的团簇碰撞形成的新团簇复合体更加稳定.另一方面,团簇碰撞过程是可逆的.     

Ti8C12H8簇的理论研究

用量子化学从头计算方法, 预测了Ti8C12H8簇的几何结构、电子结构, 分析讨论了该簇的成键和化学反应性质。     

高核Ag/S纳米团簇合成的研究进展

硫醇配体保护的高核银纳米团簇具有丰富的结构和性能, 在光致发光、 生物传感、 纳米材料等方面具有广阔的应用前景. 然而, 精确控制高核Ag/S纳米团簇的尺寸和结构面临着巨大的挑战, 构建高核Ag/S纳米团簇的可行策略也一直是人们关注的焦点. 近年来, 随着合成方法和表征技术的不断发展, 高核Ag/S纳米团簇的合成和性能研究方面均取得了显著的成就. 本文总结了含20个或以上Ag原子的Ag/S纳米团簇的合成方法(直接还原法、 阴离子模板法及配体交换法), 对部分高核Ag/S纳米团簇的结构进行了探讨, 并展望了未来研究的趋势.     

Cu掺杂对Au11(dppf)4Cl2纳米团簇结构和光学性质的影响

通过一锅还原法成功制备了合金纳米团簇Au_11-xCu_x(dppf)₄Cl₂(x=1、2;dppf=1,1''-双(二苯基膦)二茂铁)。晶体结构解析表明,合金团簇具有与 Au₁₁(dppf)₄Cl₂类似的几何结构,如含有缺陷二十面体金属内核,不同之处在于 Cu原子取代了与 Cl配位的Au原子。因此,Au₁₁-_xCux(dppf)₄Cl₂可视为Cu对Au₁₁(dppf)₄Cl₂模板团簇的掺杂。Cu原子的引入并未改变模板团簇Au₁₁(dppf)₄Cl₂的框架结构,但有效调控了电子结构,进而使其光吸收发生红移。     

Cu掺杂对Au11(dppf)4Cl2纳米团簇结构和光学性质的影响

通过一锅还原法成功制备了合金纳米团簇Au_11-xCu_x(dppf)₄Cl₂(x=1、2;dppf=1,1''-双(二苯基膦)二茂铁)。晶体结构解析表明,合金团簇具有与 Au₁₁(dppf)₄Cl₂类似的几何结构,如含有缺陷二十面体金属内核,不同之处在于 Cu原子取代了与 Cl配位的Au原子。因此,Au_11-xCu_x(dppf)₄Cl₂可视为Cu对Au₁₁(dppf)₄Cl₂模板团簇的掺杂。Cu原子的引入并未改变模板团簇Au₁₁(dppf)₄Cl₂的框架结构,但有效调控了电子结构,进而使其光吸收发生红移。     

B12N12 Nano-cage as Potential Sensor for NO2 Detection

The NO₂ molecule adsorption on B₁₂N₁₂ nano-cage was investigated using density func-tional theory calculations in terms of adsorption energy, HOMO/LUMO energy gap (Eg) changes, charge transfer, structural deformation, etc. Furthermore, some aspects of stability and properties of B₁₂N₁₂ including calculation of binding electronic and Gibbs free energies, density of states, and molecular electrostatic potential surfaces are investigated. Three pos-sible configurations for NO₂ adsorption on the B₁₂N₁₂ nano-cage are energetically found. Interestingly, the results reveals that the Eg of B₁₂N₁₂ cluster is very sensitive to the pres-ence of NO₂ molecules as its value reduces from 6.84 eV in free cluster to 3.23 eV in the most stable configuration of NO₂/cluster complex. This phenomenon dramatically increases the electrical conductivity of the cluster, suggesting that the B₁₂N₁₂ nano-cluster may be potential sensor for NO₂ gaseous molecule detection.     

B12Sc4和B12Ti4团簇的储氢性质

提出了两个稳定的团簇B₁₂Sc₄和B₁₂Ti₄, 基于理论计算, 研究了它们的结构与储氢性质. 结果发现, 在这两个稳定的团簇中, 过渡金属原子不会聚合在一起而影响它们对氢气的吸附. B₁₂Sc₄最多可以吸附12个氢分子, 达到7.25% (质量分数)的储氢量. 它的平均每氢分子吸附能量为10.5 kJ·mol^-1. B₁₂Ti₄最多只能吸附8个氢分子, 储氢量为4.78%. 但平均每氢分子吸附能量可达50.2 kJ·mol^-1. 进一步计算表明, 即使在77 K,也需要很高的氢气压力才能使12个氢分子都吸附到B₁₂Sc₄上. 电子结构分析表明, B₁₂Ti₄-nH₂吸附结构中的Kubas作用要大于相应B₁₂Sc₄-nH₂结构中的Kubas作用.     

Li修饰B12N12储氢行为的密度泛函理论研究

采用基于密度泛函理论(DFT)的第一性原理投影缀加波方法, 研究了Li 修饰的B₁₂N₁₂笼子的储氢行为.计算结果表明: Li 原子吸附在B₁₂N₁₂笼子的四元环和六元环相交的B－N桥位上, 相对于其它六个高对称吸附位置更稳定, B₁₂N₁₂笼子周围最多可以吸附3 个Li 原子, 最稳定的构型是三个Li 原子同时吸附在N原子顶位(Top-N site). 每个Li 原子的周围能吸附三个氢分子, 笼子外侧还可以吸附两个氢分子, 内部最多可以吸附5 个氢分子. 考虑到笼内和笼外的吸附, B₁₂N₁₂笼子总的储氢量(氢分子)达到9.1% (w).     

[Na4(H2O)7][Fe(OH)6Mo6O18]: A new [12] metallacrown-6 structure with an octahedrally coordinated iron at the center

The reaction of an aqueous solution of sodium molybdate with iron powder at low pH (∼0.184) gives rise to the formation of a six-member Mo ring-shape cluster with an Fe (II) encapsulated at the center, [Na₄(H₂O)₇][Fe(OH)₆Mo₆O₁₈](1), which is further linked to a remarkable three-dimensional network via sodium ions.     

Crystallography of vitamin B12 proteins

This review deals with results from crystallographic studies on proteins that interact with the essential micronutrient cobalamin (vitamin B12). Both B12-dependent enzymes and B12-transport proteins are described with an emphasis on structural aspects of cobalamin and its protein environment.     

C12-s-C12•2Br和C12En混合水溶液的胶团化行为

季铵盐二聚表面活性剂C12 s C12•2Br（s=2、3、4、6）和非离子表面活性剂C12E10或C12E23在水溶液中生成混合胶团.其临界胶团总浓度cmcT值介于二元复配体系中各组分的临界胶团浓度和之间.当添加少量非离子型表面活性剂（在水溶液中的摩尔分数α2=0.1）时,混合胶团中C12E10或C12E23的摩尔分数均已超过0.35;随着溶液中非离子型表面活性剂含量的增大,混合胶团中逐渐以C12E10或C12E23成分为主.     

Ship-in-a-bottle formation of Ru3(CO)12 in zeolite NaY

A NaY zeolite entrapped Ru₃(CO)₁₂ cluster has been synthesized from RuCl₃ ionexchanged NaY, which are well characterized by IR and Raman spectroscopy and CO chemisorption. When the Ru³⁺/NaY sample is heated from 298 to 393 K for 25 h and kept for 10–20 h at 393 K, the sample color changes from dark to brown-yellow. Thein situ infrared spectrum exhibits bands at 2130, 2064, 2040, 2017, 1990, 1953 and 1925 cm⁻¹. The bands at 2064, 2040, 2017 and 1990 cm⁻¹ are assigned to Ru₃(CO)₁₂/NaY, which are close to crystalline Ru₃(CO)₁₂. Furthermore, Raman results provide the bands at 150 and 185 cm⁻¹, which are attributed to Ru-Ru bonds of crystalline Ru₃(CO)₁₂). CO chemisorption on [Ru₃]/NaY gives a CO/Ru ratio of 3.85, which is similar to the stoichiometry of Ru₃(CO)₁₂ (CO/Ru=4.0).     

Preparation and properties of antiperovskite-type nitrides: InNNi3 and InNCo3

Two antiperovskite-type ternary nitrides of InNM₃ (M=Ni, Co) have been synthesized from In₂O₃ and Ni or Co powders under NH₃ atmosphere at 600 °C. InNCo₃ is a new ternary nitride whereas InNNi₃ was previously reported as InN_0.5Ni₃ with different nitrogen content. The lattice parameters refined by Rietveld method are 3.8445(1) Å for InNNi₃ and 3.8541(7) Å for InNCo₃, respectively. Both nitrides show metallic behaviors and below 70 K the T² temperature dependence of resistivity was observed indicative of a Fermi liquid behavior. The temperature dependence of the field-cooling (FC) and zero-field-cooling (ZFC) magnetization and time decay of thermoremanent magnetization indicate the spin-glass-like behavior in InNM₃ (M=Ni, Co). The freezing temperatures for this behavior, T_f, are about 300 K for InNNi₃ and 10 K for InNCo₃, respectively.     

Peculiarities in the Raman spectra of ZrB12 and LuB12 single crystals

We have measured Raman spectra of high-quality Zr^natB₁₂, Lu^natB₁₂ and Lu¹¹B₁₂ single crystals with high resolution, and the observed strong peaks are attributed to specific vibration modes. Besides, there are a number of additional Raman peaks in spectral ranges, where only Raman-inactive vibrations of the atomic arrangement are expected. Accordingly, it is assumed, that the investigated crystals contain intrinsic structural imperfections or distortions in sufficient concentration and efficiency to initiate the observed breaking of phonon selection rules. We suppose boron vacancies, boron isotope effects and displacements of the metal atoms to be reasons for such imperfections.