Crossed beam studies of elementary reactions of N and C atoms and CN radicals of importance in combustion

The dynamics of some elementary reactions of N(2D), C(3P,1D) and CN(X2 sigma +) of importance in combustion have been investigated by using the crossed molecular beam scattering method with mass spectrometric detection. The novel capability of producing intense, continuous beams of the radical reagents by a radio-frequency discharge beam source was exploited. From angular and velocity distribution measurements obtained in the laboratory frame, primary reaction products have been identified and their angular and translational energy distributions in the center-of-mass system, as well as branching ratios, have been derived. The dominant N/H exchange channel has been examined in the reaction N(2D) + CH4, which is found to lead to H + CH2NH (methylenimine) and H + CH3N (methylnitrene); no H2 elimination is observed. In the reaction N(2D) + H2O the N/H exchange channel has been found to occur via two competing pathways leading to HNO + H and HON + H, while formation of NO + H2 is negligible. Formation of H + H2CCCH (propargyl) is the dominant pathway, at low collision energy (Ec), of the C(3P) + C2H4 reaction, while at high Ec formation of the less stable C3H3 isomers (cyclopropenyl and/or propyn-1-yl) also occurs; the H2 elimination channel is negligible. The H elimination channel has also been found to be the dominant pathway in the C(3P,1D) + CH3CCH reaction leading to C4H3 isomers and, again, no H2 elimination has been observed to occur. In contrast, both H and H2 elimination, leading in comparable ratio to C3H + H and C3(X1 sigma g+) + H2(X1 sigma g+), respectively, have been observed in the reaction C(3P) + C2H2(X1 sigma g+). The occurrence of the spin-forbidden molecular pathway in this reaction, never detected before, has been rationalized by invoking the occurrence of intersystem crossing between triplet and singlet manifolds of the C3H2 potential energy surfaces. The reaction CN(X2 sigma +) + C2H2 has been found to lead to internally excited HCCCN (cyanoacetylene) + H. For all the reactions the dynamics have been discussed in the light of recent theoretical calculations on the relevant potential energy surfaces. Previous, lower resolution studies on C and CN reactions carried out using pulsed beams are noted. Finally, throughout the paper the relevance of these results to combustion chemistry is considered.     

From calcium interaction to calcium electrochemical detection by [(C5H5)Fe(C5H4COCH=CHC6H4NEt2)] and its two novel structurally characterized derivatives

[(C(5)H(5))Fe(C(5)H(4)COCH=CHC(6)H(4)NEt(2))] (1) has been electrochemically evaluated toward different cations in solution. Calcium sensing by this compound and its two new derivatives [(C(5)H(5))Fe(C(5)H(4)CO(CH=CH)(2)C(6)H(4)NMe(2))] (2) and [(C(5)H(5))Fe(C(5)H(4)CH=CHCOCH=CHC(6)H(4)NEt(2))] (3) that exhibit a conjugated link between the ferrocene unit and the nitrogen atom has been thoroughly examined. Compounds 2 and 3 have been structurally characterized by single-crystal X-ray diffraction studies. The three related protonated species [1H][BF(4)] (4), [2H][BF(4)] (5), and [3H][BF(4)] (6) have been isolated in a good yield. NMR experiments clearly established that calcium interaction occurs in the vicinity of the carbonyl group, and mass spectrometry studies confirmed that this interaction, which involves several ligand-Ca(2+) adducts, is complex. A combination of electrochemical and NMR experiments highlighted an original salt influence on the electrochemical calcium sensing result.     

间硝基苯胺的同步辐射光电离研究

利用同步辐射光电质谱法对间硝基苯脘进行了研究，测得了其电离势ＩＰ为９．６６０．０５ｅＶ，以及一些碎片离子出现势ＡＰ，计算出离解能Ｄ０（Ｎ２Ｏ－Ｃ６Ｈ６Ｎ＾＋）和离子生成焓ΔＨｆ（Ｃ６Ｈ６Ｎ＾＋）。给出了间硝基苯胺的同步辐射同离质谱图，并对主要碎片离子的产生过程进行了初步分析。     

Synthesis and properties of new ditertiary stibines based upon o-, m- or p-xylyl and m- or p-phenylene backbones and their complexes with tungsten, iron and nickel carbonyls

High yield syntheses for 1,2-, 1,3-, and 1,4-xylyl distibines (1,2-C6H4(CH2SbMe2)2, 1,3-C6H4(CH2SbMe2)2, 1,4-C6H4(CH2SbMe2)2, respectively) from Me2SbCl (conveniently made in situ from Me2PhSb and HClgas) and the appropriate di-Grignard are reported. The 1,3- and 1,4-phenylene distibines, 1,3-C6H4(SbMe2)2 and 1,4-C6H4(SbMe2)2, were made similarly. The new ligands have been characterised by mass spectrometry, 1H and 13C[1H] NMR spectroscopy, and by the preparation of methiodide derivatives. The crystal structures of 1,4-C6H4(CH2SbMe2)2 and [1,3-C6H4(CH2SbMe3)2]I2 have been determined. The synthesis of 1,2-C6H4(CH2SbPh2)2 has been achieved similarly in modest yield and the distibine converted into the tetra-iodo-derivative 1,2-C6H4(CH2SbPh2I2)2. The coordination modes available to these ligands have been probed by the synthesis and characterisation of complexes with nickel, iron and tungsten carbonyls. The crystal structure of [[Fe(CO)4]2[micro-1,3-C6H4(CH2SbMe2)2]] has been determined. The spectroscopic properties of these carbonyl derivatives have been compared with those of complexes of other antimony ligands, and in some cases with diphosphine and diarsine complexes, to probe the electronic properties of the new ligands.     

Ab initio molecular dynamics study of the hydrolysis reaction of diborane

The hydrolysis reaction of the diborane molecule in aqueous solution has been studied by a series of Car-Parrinello Molecular Dynamics simulations in the Blue Moon Ensemble. The total reaction has been divided into two parts: one dealing with the breaking of B(2)H(6) molecule and the formation of a BH(4)(-) ion, a H(2)BOH molecule and a H(+) ion; the second leads to the formation of two hydrogen molecules and another H(2)BOH molecule, starting from BH(4)(-), two water molecules and a H(+) ion. The total reaction studied in this work has been B(2)H(6) + 2H(2)O --> 2H(2)BOH + 2H(2). We have described both structurally and electronically the reagents and the products through the radial distribution functions and the Wannier Function Center positions calculations, with attention to the solvent effects on the compounds. The free energy barrier value for the first part of the reaction and a detailed mechanisms for both parts have been reported. An interesting behavior of BH(3) and H(2) molecules in solution has been observed. They form a quite stable three center bond between the electron pair of the hydrogen molecule and the empty orbital of the boron atom in BH(3), which has been described from both a structural and electronic point of view.     

Formation and thermodynamic properties of complexes of Ag(I) with thiourea as ligand

A potentiometric study has been made of the Ag(I)CSN(2)H(4)H(2)O system. Mathematical analysis of the formation functions reveals the existence of the complexes AgCSN(2)H(+)(4), Ag(CSN(2)H(4))(+)(4), Ag(CSN(2)H(4))(+)(3) and Ag(CSN(2)H(4))(+)(4) for which the stability constants have been calculated at different ionic strengths and temperatures. No evidence was found for the formation of polynuclear complexes.     

含氮硅烷对聚二甲基硅氧烷涂膜表面疏水性的影响

将含氮硅烷与正硅酸乙酯进行对比，研究了它们对端羟基聚二甲基硅氧烷（ＨＴＰＤＭＳ）缩合固化形成的涂膜表面疏水性的影响，发现固化剂ＮＨ２（ＣＨ２）３Ｓｉ（ＯＣ２Ｈ）３使涂膜疏水性明显下降．用ＥＳＣＡ和相差显微镜等方法证明了这种现象是由于ＮＨ２（ＣＨ２）３Ｓｉ（ＯＣ２Ｈ５）３自身固化产生的分相性引起的．     

3He NMR study of (3)He@C(60)H(6) and (3)He@C(70)H(2)(-)(10)

The (3)He NMR of (3)He@C(60)H(6), (3)He@C(70)H(2), (3)He@C(70)H(4), (3)He@C(70)H(8), and (3)He@C(70)H(10) have been investigated. A new, unidentified C(60)H(6) isomer has been found by using (3)He NMR. (3)He@C(70)H(10) shows the most downfield-shifted (3)He NMR resonance among the neutral C(70) derivatives.     

Stability and structure of Li(n)H molecules (n=3-6): experimental and density functional study

The molecules Li(3)H and Li(4)H have been identified in mass-spectrometric measurements over solutions of hydrogen in liquid Li, and the gaseous equilibria of the reactions: Li(3)H+Li=Li(2)H+Li(2), Li(3)H+Li(2)=Li(2)H+Li(3), Li(3)H+Li=LiH+Li(3), Li(3)H+LiH=2Li(2)H, and Li(4)H+Li(2)=Li(3)H+Li(3) have been measured. Density functional calculations of Li(n)H molecules (n=3-6) provide structures, vibrational frequencies, ionization energies, and free energy functions of these molecules, and these are used to estimate the enthalpies of these reactions and the atomization energies of Li(3)H (119.4 kcal/mol) and Li(4)H (151.8 kcal/mol).     

Energetic and topological analysis of the reaction of Mo and Mo2 with NH3, C2H2, and C2H4 molecules

The Density functional theory has been applied to characterize the structural features of Mo(1,2)-NH(3),-C(2)H(4), and -C(2)H(2) compounds. Coordination modes, geometrical structures, and binding energies have been calculated for several spin multiplets. It has been shown that in contrast to the conserved spin cases (Mo(1,2)-NH(3)), the interaction between Mo (or Mo(2)) and C(2)H(4) (or C(2)H(2)) are the low-spin (Mo-C(2)H(4) and -C(2)H(2)) and high-spin (Mo(2)-C(2)H(4) and -C(2)H(2)) complexes. In the ground state of Mo(1,2)-C(2)H(4) and -C(2)H(2), the metal-center always reacts with the C-C center. The spontaneous formation of the global minima is found to be possible due to the crossing between the potential energy surfaces (ground and excited states with respect to the metallic center). The bonding characterization has been performed using the topological analysis of the Electron Localization Function. It has been shown that the most stable electronic structure for a pi-acceptor ligand correlates with a maximum charge transfer from the metal center to the C-C bond of the unsaturated hydrocarbons, resulting in the formation of two new basins located on the carbon atoms (away from hydrogen atoms) and the reduction of the number of attractors of the C-C basin. The interaction between Mo(1,2) and C(2)H(4) (or C(2)H(2)) should be considered as a chemical reaction, which causes the multiplicity change. Contrarily, there is no charge transfer between Mo(1,2) and NH(3), and the partners are bound by an electrostatic interaction.     

Mechanistic studies of the ethylene trimerization reaction with chromium-diphosphine catalysts: experimental evidence for a mechanism involving metallacyclic intermediates

A system for catalytic trimerization of ethylene utilizing CrCl3(THF)3 and a diphosphine ligand PNPOMe [= (o-MeO-C6H4)2PN(Me)P(o-MeO-C6H4)2] has been investigated. The coordination chemistry of chromium with PNPOMe has been explored, and (PNPOMe)CrCl3 and (PNPOMe)CrPh3 (3) have been synthesized by ether displacement from chromium(III) precursors. Salt metathesis of (PNPOMe)CrCl3 with o,o'-biphenyldiyl Grignard affords (PNPOMe)Cr(o,o'-biphenyldiyl)Br (4). Activation of 3 with H(Et2O)2B[C6H3(CF3)2]4 or 4 with NaB[C6H3(CF3)2]4 generates a catalytic system and trimerizes a 1:1 mixture of C2D4 and C2H4 to give isotopomers of 1-hexene without H/D scrambling (C6D12, C6D8H4, C6D4H8, and C6H12 in a 1:3:3:1 ratio). The lack of crossover supports a mechanism involving metallacyclic intermediates. The mechanism of the ethylene trimerization reaction has also been studied by the reaction of trans-, cis-, and gem-ethylene-d2 with 4 upon activation with NaB[C6H3(CF3)2]4.     

Fluorescent zinc(II) complex exhibiting "on-off-on" switching toward Cu2+ and Ag+ ions

Binuclear zinc(II) and copper(II) complexes based on a new Schiff base ligand N,N'-bis(2-hydroxybenzilidene)-2,4,6-trimethylbenzene-1,3-diamine (H(2)L) have been synthesized. The ligand H(2)L and complexes under investigation have been characterized by elemental analyses, spectral (FT-IR, (1)H, (13)C NMR, ESI-MS, electronic absorption, emission), and electrochemical studies. The structures of H(2)L and complexes [{Zn(C(23)H(18)N(2)O(2))}(2)] (1) and [{Cu(C(23)H(18)N(2)O(2))}(2)]·H(2)O (2) have been determined crystallographically. Selective "On-Off-On" switching behavior of the fluorescent complex 1 has been studied. The fluorescence intensity of 1 quenches (turns-off) upon addition of Cu(2+), while enhances (turns-on) in the presence of Ag(+) ions. The mechanisms of "On-Off-On" signaling have been supported by (1)H NMR, ESI-MS, electronic absorption, and emission spectral studies. Job's plot analysis supported 1:1 and 1:2 stoichiometries for Cu(2+) and Ag(+) ions, respectively. Association and quenching constants have been estimated by the Benesi-Hildebrand method and Stern-Volmer plot. Moreover, 1 mimics a molecular keypad lock that follows correct chemical input order to give maximum output signal.     

Synthesis and reaction of fullerene C70 encapsulating two molecules of H2

New endohedral fullerene C(70) encapsulating one and two H(2) molecule(s) has been synthesized by organic reactions, the so-called "molecular surgery" method, and the first organic derivatization of H(2)@C(70) and (H(2))(2)@C(70) has been conducted. Although the interaction between inner H(2) and outer C(70) is rather weak, (H(2))(2)@C(70) exhibits smaller equilibrium constants in the Diels-Alder reaction with 9,10-dimethylanthracene than those of H(2)@C(70).     

Degree of counterion binding on water in oil microemulsions

An ion-exchange process has been used to prepare HOT from NaOT (sodium bis(2-ethylhexyl)sulfosuccinate), where the Na(+) counterion has been replaced by H(+). The acidity function, H(0), of the aqueous core of HOT-based microemulsions decreases with W from H(0) approximately 0.6 at W>20 to H(0)=-1.4 at W=2. On the basis of the H(0) acidity function of the aqueous core and the dependence of H(0) on acid concentration, we have been able to determine the degree of counterion binding (beta) in microemulsions with a value of beta approximately 0.92 which is practically independent of the water content of the system.     

Water-assisted interconversions and dissociations of the acetaldehyde ion and its isomers. An experimental and theoretical study

The gas-phase reactions of the ion [CH(3)CHO/H(2)O](+*) have been investigated by mass spectrometry. The metastable ion (MI) mass spectrum reveals that this ion-molecule complex decomposes spontaneously by the losses of H(2)O, CO, and (*)CH(3). The structures of stable complexes and transition states involved in the potential energy surface (PES) have been studied by the G3//B3-LYP/6-31+G(d) computational method. Hydrogen-bridged water complexes have been found to be the major products of the losses of CO and (*)CH(3). The CO loss produces the [(*)CH(3)...H(3)O(+)] ion and involves a "backside displacement" mechanism. The products corresponding to (*)CH(3) loss have been assigned by theory to be [OC...H(3)O(+)] and [CO...H(3)O(+)], and their 298 K enthalpy values, calculated at the G3 level of theory, are Delta(f)H[OC...H(3)O(+)] = 420 kJ/mol and Delta(f)H[CO...H(3)O(+)] = 448 kJ/mol. The PES describing the interconversions among water-solvated CH(3)CHO(+*), CH(3)COH(+*), and CH(2)CHOH(+*) have been shown to involve proton-transport catalysis (PTC), catalyzed 1,2 H-transfer, and an uncatalyzed H-atom transfer mechanism, respectively.     

The building block approach to extended solids: 3,5-pyrazoledicarboxylate coordination compounds of increasing dimensionality

A series of M(II) complexes with the ligand 3,5-pyrazoledicarboxylic acid (H3dcp) has been synthesised mainly via hydrothermal reactions and their structures have been characterised. Simple mononuclear [Ni(Hdcp)(H2O)4] (1), Na2(mu-H2O)2(H2O)8[Ni(Hdcp)2(H2O)2] (2), [M(H2dcp)2(H2O)2] x 2H2O [M = Co (3), Zn (4) and Cu (5)] and dinuclear (Et3NH)2[Cu2(dcp)2(H2O)2] (9) building blocks have been isolated and subsequently linked into 1-D chains [Mn(Hdcp)(H2O)2]infinity (6), [[Mn(H2O)4][Mn(Hdcp)2(H2O)2] x 4H2O]infinity (7), [Ni2(Hdcp)2(mu-H2O)2(H2O)2]infinity (8), [[Ni(H2O)4][Ni2(dcp)2(H2O)4]]infinity (11), or 3-D arrays [[Na2(mu-H2O)2][Cu2(dcp)2]]infinity (10), [Cu3(dcp)2(H2O)4]infinity (12), utilising novel bridging modes of the H3dcp ligand. In the unprecedented 1-D Ni(II) chain 8, rarely reported double aqua-bridges link the Ni(II) ions to form an inter-linked double stranded chain. The magnetic properties of these compounds have been measured and reveal a variety of antiferromagnetic coupling behaviours induced by the ligand bridging modes.     

Synthesis and characterization of a new bisphosphonic acid and several metal hybrids derivatives

Commercial bis-(4-bromophenyl)-ether, [BrC(6)H(4)](2)-O, has been used to prepare 4-[4'-(diethoxyphosphoryl)phenoxy]phenyl-phosphonic acid diethyl ester, [(CH(3)CH(2))(2)O(3)P-C(6)H(4)](2)-O, (I) following a slight modification of the Michaelis-Arbuzov reaction. The acid hydrolysis of I gave 4-(4'-phosphonophenoxy)phenyl phosphonic acid, [H(2)O(3)P-C(6)H(4)](2)-O (II), and both compounds have been characterized by (1)H NMR and (13)C NMR. The crystal structure of II has been determined by single-crystal X-ray diffraction. II crystallizes in an orthorhombic unit cell, space group Pbcn, with a = 7.822(3) A, b = 5.821(2) A, c = 28.982(9) A, and V = 1319.7(7) A(3). The final R factor was R1 = 0.0614. The structure is layered, being held together through a hydrogen bonding network. II has been used as precursor in the syntheses of new metal (Mn, Fe, Co, Ni, Cu, and Zn) bisphosphonates. The syntheses were carried out using a fixed metal/bisphosphonic acid molar ratio of 2.1:1 and the influence of the pH in the reactions has been studied. Nine new compounds have been isolated: Mn(2)(O(3)PC(6)H(4)OC(6)H(4)PO(3)).1.5H(2)O (III), Mn(5)(OH)(2)(O(3)PC(6)H(4)OC(6)H(4)PO(3))(2).2H(2)O (IV), Fe(HO(3)PC(6)H(4)OC(6)H(4)PO(3)).0.5H(2)O (V), Co(2)(O(3)PC(6)H(4)OC(6)H(4)PO(3)).2H(2)O (VI), Ni(2)(O(3)PC(6)H(4)OC(6)H(4)PO(3)).3H(2)O (VII), Ni(2)(O(3)PC(6)H(4)OC(6)H(4)PO(3)).2H(2)O (VIII), Cu(2)(O(3)PC(6)H(4)OC(6)H(4)PO(3)) (IX), Zn(2)(O(3)PC(6)H(4)OC(6)H(4)PO(3)) (X), and Zn(HO(3)PC(6)H(4)OC(6)H(4)PO(3)H) (XI). Compound IX crystallizes in an orthorhombic unit cell, space group Pbcn, and unit cell parameters a = 8.1012(5) A, b = 5.3109(3) A, c = 29.2595(5) A, and V = 1258.8(1) A(3). Its structure has been solved by ab initio powder diffraction and refined by the Rietveld method to R(F) = 0.042. IX has a pillared layer framework with highly distorted CuO(5) groups sharing edges to give isolated dimers. XI was indexed in a monoclinic unit cell, space group P112(1), with parameters a = 9.4991(9) A, b = 5.0445(5) A, c = 29.131(2) A, gamma = 91.945(7) degrees, and V = 1395.1(3) A(3). Its structure has been refined by the Rietveld method, R(F) = 0.054, since it is isostructural with the known compound, Zn[HO(3)P(C(6)H(4))(2)PO(3)H]. All solids were also characterized by thermal analysis and IR and UV-Vis spectroscopies.     

Dissociative recombination of H+(H2O)3 and D+(D2O)3 water cluster ions with electrons: cross sections and branching ratios

Dissociative recombination (DR) of the water cluster ions H(+)(H(2)O)(3) and D(+)(D(2)O)(3) with electrons has been studied at the heavy-ion storage ring CRYRING (Manne Siegbahn Laboratory, Stockholm University). For the first time, absolute DR cross sections have been measured for H(+)(H(2)O)(3) in the energy range of 0.001-0.8 eV, and relative cross sections have been measured for D(+)(D(2)O)(3) in the energy range of 0.001-1.0 eV. The DR cross sections for H(+)(H(2)O)(3) are larger than previously observed for H(+)(H(2)O)(n) (n=1,2), which is in agreement with the previously observed trend indicating that the DR rate coefficient increases with size of the water cluster ion. Branching ratios have been determined for the dominating product channels. Dissociative recombination of H(+)(H(2)O)(3) mainly results in the formation of 3H(2)O+H (probability of 0.95+/-0.05) and with a possible minor channel resulting in 2H(2)O+OH+H(2) (0.05+/-0.05). The dominating channels for DR of D(+)(D(2)O)(3) are 3D(2)O+D (0.88+/-0.03) and 2D(2)O+OD+D(2) (0.09+/-0.02). The branching ratios are comparable to earlier DR results for H(+)(H(2)O)(2) and D(+)(D(2)O)(2), which gave 2X(2)O+X (X=H,D) with a probability of over 0.9.     

Photodissociation of benzene under collision-free conditions: an ab initio/Rice-Ramsperger-Kassel-Marcus study

The ab initio/Rice-Ramsperger-Kassel-Marcus (RRKM) approach has been applied to investigate the photodissociation mechanism of benzene at various wavelengths upon absorption of one or two UV photons followed by internal conversion into the ground electronic state. Reaction pathways leading to various decomposition products have been mapped out at the G2M level and then the RRKM and microcanonical variational transition state theories have been applied to compute rate constants for individual reaction steps. Relative product yields (branching ratios) for C(6)H(5)+H, C(6)H(4)+H(2), C(4)H(4)+C(2)H(2), C(4)H(2)+C(2)H(4), C(3)H(3)+C(3)H(3), C(5)H(3)+CH(3), and C(4)H(3)+C(2)H(3) have been calculated subsequently using both numerical integration of kinetic master equations and the steady-state approach. The results show that upon absorption of a 248 nm photon dissociation is too slow to be observable in molecular beam experiments. In photodissociation at 193 nm, the dominant dissociation channel is H atom elimination (99.6%) and the minor reaction channel is H(2) elimination, with the branching ratio of only 0.4%. The calculated lifetime of benzene at 193 nm is about 11 micros, in excellent agreement with the experimental value of 10 micros. At 157 nm, the H loss remains the dominant channel but its branching ratio decreases to 97.5%, while that for H(2) elimination increases to 2.1%. The other channels leading to C(3)H(3)+C(3)H(3), C(5)H(3)+CH(3), C(4)H(4)+C(2)H(2), and C(4)H(3)+C(2)H(3) play insignificant role but might be observed. For photodissociation upon absorption of two UV photons occurring through the neutral "hot" benzene mechanism excluding dissociative ionization, we predict that the C(6)H(5)+H channel should be less dominant, while the contribution of C(6)H(4)+H(2) and the C(3)H(3)+C(3)H(3), CH(3)+C(5)H(3), and C(4)H(3)+C(2)H(3) radical channels should significantly increase.