On the catalytic transfer hydrogenation of nitroarenes by a cubane-type Mo3S4 cluster hydride: disentangling the nature of the reaction mechanism

Cubane-type Mo3S4 cluster hydrides decorated with phosphine ligands are active catalysts for the transfer hydrogenation of nitroarenes to aniline derivatives in the presence of formic acid (HCOOH) and triethylamine (Et3N). The process is highly selective and most of the cluster species involved in the catalytic cycle have been identified through reaction monitoring. Formation of a dihydrogen cluster intermediate has also been postulated based on previous kinetic and theoretical studies. However, the different steps involved in the transfer hydrogenation from the cluster to the nitroarene to finally produce aniline remain unclear. Herein, we report an in-depth computational investigation into this mechanism. Et3N reduces the activation barrier associated with the formation of Mo–HHOOCH dihydrogen species. The global catalytic process is highly exergonic and occurs in three consecutive steps with nitrosobenzene and N-phenylhydroxylamine as reaction intermediates. Our computational findings explain how hydrogen is transferred from these Mo–HHOOCH dihydrogen adducts to nitrobenzene with the concomitant formation of nitrosobenzene and the formate substituted cluster. Then, a b-hydride elimination reaction accompanied by CO2 release regenerates the cluster hydride. Two additional steps are needed for hydrogen transfer from the dihydrogen cluster to nitrosobenzene and N-phenylhydroxylamine to finally produce aniline. Our results show that the three metal centres in the Mo3S4 unit act independently, so the cluster can exist in up to ten different forms that are capable of opening a wide range of reaction paths. This behaviour reveals the outstanding catalytic possibilities of this kind of cluster complexes, which work as highly efficient catalytic machines

The QCD transition temperature: results with physical masses in the continuum limit II.

We extend our previous study [Phys. Lett. B643 (2006) 46] of the cross-over temperatures (T_c) of QCD. We improve our zero temperature analysis by using physical quark masses and finer lattices. In addition to the kaon decay constant used for scale setting we determine four quantities (masses of the \Omega baryon, K^*(892) and \phi(1020) mesons and the pion decay constant) which are found to agree with experiment. This implies that --independently of which of these quantities is used to set the overall scale-- the same results are obtained within a few percent. At finite temperature we use finer lattices down to a <= 0.1 fm (N_t=12 and N_t=16 at one point). Our new results confirm completely our previous findings. We compare the results with those of the 'hotQCD' collaboration.Comment: 19 pages, 8 figures, 3 table

Research and Design of a Routing Protocol in Large-Scale Wireless Sensor Networks

无线传感器网络，作为全球未来十大技术之一，集成了传感器技术、嵌入式计算技术、分布式信息处理和自组织网技术，可实时感知、采集、处理、传输网络分布区域内的各种信息数据，在军事国防、生物医疗、环境监测、抢险救灾、防恐反恐、危险区域远程控制等领域具有十分广阔的应用前景。 本文研究分析了无线传感器网络的已有路由协议，并针对大规模的无线传感器网络设计了一种树状路由协议，它根据节点地址信息来形成路由，从而简化了复杂繁冗的路由表查找和维护，节省了不必要的开销，提高了路由效率，实现了快速有效的数据传输。 为支持此路由协议本文提出了一种自适应动态地址分配算——ADAR（AdaptiveDynamicAddre...As one of the ten high technologies in the future, wireless sensor network, which is the integration of micro-sensors, embedded computing, modern network and Ad Hoc technologies, can apperceive, collect, process and transmit various information data within the region. It can be used in military defense, biomedical, environmental monitoring, disaster relief, counter-terrorism, remote control of haz...学位：工学硕士院系专业：信息科学与技术学院通信工程系_通信与信息系统学号：2332007115216

Overview of Low-Temperature Heat Capacity Data for Zn₂(C₈H₄O₄)₂^.C₆H₁₂N₂ and the Salam Hypothesis

The review presents the progress in the analysis of low-temperature heat capacity of the metal-organic framework Zn2(C8H4O4)2.C6H12N2 (Zn-DMOF). In Zn-DMOF, left-twisted D3(S) and right-twisted D3(R) DABCO molecules (C6H12N2) can transform into each other by tunneling to form a racemate. Termination of tunneling leads to a phase transition in the subsystem of twisted molecules. It is suggested that Zn-DMOF may be considered a model system to study the mechanisms of phase transitions belonging to the same type as hypothetical Salam phase transitions

The Role of Quadruple Bonding in the Electron Transport through a Dimolybdenum Tetraacetate Molecule

A dimolybdenum tetraacetate (Mo2(O2CCH3)4) molecule is embedded between two electrodes formed by semi-infinite 1D monatomic chains of lithium, aluminum, and titanium atoms. Electron transport through the Mo2(O2CCH3)4 molecule is calculated. The role of quadrupole bonding in the transport properties of the studied systems is analyzed

Chirality and Relativistic Effects in Os3(CO)12

The energy and structural parameters were obtained for all forms of the carbonyl complex of osmium Os3(CO)12 with D3h and D3 symmetries using density functional theory (DFT) methods. The calculations took into account various levels of relativistic effects, including those associated with nonconservation of spatial parity. It was shown that the ground state of Os3(CO)12 corresponds to the D3 symmetry and thus may be characterized either as left-twisted (D3S) or right-twisted (D3R). The D3S↔D3R transitions occur through the D3h transition state with an activation barrier of ~10–14 kJ/mol. Parity violation energy difference (PVED) between D3S and D3R states equals to ~5 × 10−10 kJ/mol. An unusual three-center exchange interaction was found inside the {Os3} fragment. It was found that the cooperative effects of the mutual influence of osmium atoms suppress the chirality of the electron system in the cluster

Dithiolene dimetallic molybdenum(V) complexes displaying intraligand charge transfer (ILCT) emission

Bifunctional dithiolene ligands have been coordinated to the MoV(O)(μ-S2)MoV(O) unit to afford [Mo2O2(μ-S)2(BPyDTS2)2]2− (12−) (BPyDTS2 (2-bis-(2-pyridyl)methylene-1,3-dithiolene) dianions. Reaction of the 12− molybdenum dimer with pentacarbonylchlorothenium(I) affords a tetrametallic complex of formula [Mo2O2(μ-S)2(BPyDTS2)2{Re(CO)3Cl}2]2− (22−). The monomeric (CH3)2Sn(BPyDTS2) (3) tin complex has also been prepared for comparative purposes. In the structure of (Et4N)2[1], the two metal atoms are in a square pyramidal coordination environment defined by two bridging sulfur atoms, one terminal oxygen atom and the two sulfur atoms of the bifunctional dithiolene ligand. This arrangement leaves two nitrogen atoms on each side which coordinate to two Re atoms in the 22− tetrametallic complex. Compound 3 has a distorted tetrahedral structure defined by two carbon atoms of the methyl groups and two sulfur atoms of the dithiolene ligand. The luminescence properties of all three complexes in acetonitrile have been investigated. Detailed studies supported on quantum mechanical calculations revealed that complex 12− shows photoluminescence in the 600–800 nm region with a maximum wavelength of 628 nm and an emission quantum yield of 0.092, associated with an intraligand charge transfer (ILCT) transition. Coordination of two Re(CO)3Cl fragments to 12− to afford 22− does not affect the emission spectrum and shape although it decreases the quantum yield, approximately by a factor of 4.6. Compound 3 exhibits a similar emission spectrum to those of the complexes 12− and 22− in good agreement with the ILCT assignment. The quantum yield of 3 lies between that of the 12− and 22− complexes

Synthesis, molecular and electronic structures of a paramagnetic trimetallic cluster containing an unusual Mo3(l3-Se)2(l-Se)3 core

The electron precise [Mo3(l3-Se)(l-Se)3(dppe)3Br3] + incomplete cuboidal complex, with six cluster skeletal electrons (CSE), was converted into the paramagnetic bicapped [Mo3(l3-Se)2(l-Se)3(dppe)3] + cluster (1+ ), with an unusual seven metal electron population, by treatment with elemental Ga. The cluster core consists of an almost equilateral Mo3 triangle (Mo–Mo distances are in the range 2.7583(7)–2.7748(7) Å with an average value of 2.77(3) Å), capped by two selenide ligands. The remaining selenium atoms bridge adjacent metal atoms, defining a virtually planar Mo3(l-Se)3 unit, with the capping Se atoms positioned above and below this plane. The new complex possesses a doublet ground state with the unpaired electron density delocalized over the three metal atoms. DFT calculations show that the HOMO has ‘‘a1’’ symmetry, precluding any Jahn–Teller distortion on the cluster core and giving support to EPR and structural observations