Experimental and theoretical studies of neutral MgmCnHx and BemCnHx clusters

Neutral Mg(m)C(n)H(x) and Be(m)C(n)H(x) clusters are investigated both experimentally and theoretically for the first time. Single photon ionization at 193 nm is used to detect neutral cluster distributions through time of flight mass spectrometry. Mg(m)C(n)H(x) and Be(m)C(n)H(x) clusters are generated through laser ablation of Mg or Be foil into CH(4)/He expansion gas. A number of members of each cluster series are identified through isotopic substitution experiments employing (13)CH(4) and CD(4) instead of CH(4) in the expansion gas. An oscillation of the vertical ionization energies (VIEs) of Mg(m)C(n)H(x) clusters is observed in the experiments. The VIEs of Mg(m)C(n)H(x) clusters are observed to vary as a function of the number of H atoms in the clusters. Density functional theory (DFT) and ab initio (MP2) calculations are carried out to explore the structures and ionization energies of Mg(m)C(n)H(x) clusters. Many Be(m)C(n)H(x) clusters are also generated and detected in the experiments. The structures and VIEs of Be(m)C(n)H(x) clusters are also studied by theoretical calculations. Calculational results provide a good and consistent explanation for the experimental observations, and are in general agreement with them for both series of clusters.     

Cyanide-bridge Fe-Fe and Fe-Co molecular squares: structures and electrochemistry of

Cyanide-bridged iron-iron and iron--cobalt molecular squares of [Fe(II/4)(mu-CN)4(bpy)8[(PF6)4 x 4H2O (1), [Fe(II/2)Co(II/2)(mu-CN)4(bpy)8](PF6)4 x 3CHCl3 x 2CH3CN (2), and [Fe(II/2)Co(III/2)(mu-CN)4(bpy)8](PF6)6 x 2CHCl3 x 4CH3NO2 (3) (bpy =2,2'-bipyridine) were prepared. X-ray structure analyses for 1-3 were performed and their electrochemistry was studied. In 1-3, four metal ions are bridged by cyanide groups to form tetranuclear macrocycles ("molecular squares"). Each metal ion in the square is six-coordinate: four of the coordination sites are occupied by the nitrogen atoms of two of bpy ligands and the remaining cis coordination sites are occupied by cyanide-carbon or cyanide-nitrogen atoms. In 1, Fe-C (cyanide) (1.899(4)-1.927(4)A) and Fe-N(cyanide) (1.929(4)-1.950(4)A) distances are typical of low-spin Fe2+ ions. In 2, Fe-C(cyanide) and Co(2+)-N(cyanide) bond lengths are in the range 1.919(5)-1.963(5)A and 1.850(5)-2.017(5) A, respectively: in contrast, shorter bond lengths are observed for the metal to cyanide-carbon and cyanide-nitrogen (1.878(7)- 1.893(7) A) in 3. As a result, the molecular squares in 1. 2, and 3 have sides of 4.947(1)4.986(1) A, 5.001(1)-5.053(1) A, and 4.910(1)-4.918(1) A, respectively. Magnetic susceptibility measurements revealed that the Fe2+ and Co3- ions in 1 and 3 are diamagnetic, while the high-spin Co2+ ions in 2 are weakly coupled through the low-spin Fe2 ions. Cyclic voltammograms of the squares are presented, and the electrochemically generated mixed-valent species [Fe(II/2)Fe(III/2)(mu-CN)4(bpy)8]6+ was discussed in terms of the intervalence transfer band.     

Rhodium-hydrido-benzylamine-triphenylphosphine complexes: solid-state and solution structures and implications in catalyzed imine hydrogenation

The complexes cis,trans,cis-[Rh(H)(2)(PPh(3))(2)(NH(2)CH(2)Ph)(2)]PF(6) (1) and cis-[Rh(PPh(3))(2)(NH(2)CH(2)Ph)(2)]PF(6) (2) are characterized by X-ray crystallography; the structures are maintained in CH(2)Cl(2) where the species are in equilibrium under H(2). In MeOH and in acetone, loss of amine and/or H(2) can occur. Traces of 1 and 2 are present after a Rh-catalyzed H(2)-hydrogenation of PhCH=NCH(2)Ph in MeOH, where the amine is generated by hydrolysis of the imine substrate through adventitious water. The findings are relevant to catalyst poisoning in the catalytic process.     

Metal- and ligand-directed one-pot syntheses,crystal structures,and properties of novel oxo-centered tetra- and hexametallic clusters

Starting from closely related metal-ligand combinations, completely different oligomeric metal clusters are synthesized. Whereas, picoline-tetrazolylamide HL(1) (1) and zinc or nickel acetate afforded [2x2] grids [M(4)(L(1))(8)] (2), slightly different N-(2-methylthiazole-5-yl)-thiazole-2-carboxamide HL(2) (5 a) and nickel acetate yielded the monometallic complex [Ni(L(2))(2)(OH(2))(2)] (6). In contrast, reaction of 5 a with zinc acetate produced the tetrametallic zinc cluster [Zn(4)O(L(2))(4)(OAc)(2)] (7). Even more surprising, when 3-methyl-substituted HL(3) (5 b) instead of 2-methyl-substituted HL(2) (5 a) was allowed to react under identical conditions with zinc acetate, the cluster [Zn(4)O(L(3))(4)Cl(2)] (8) crystallized from dichloromethane. Clusters 7 and 8 are isostructural. As for 7, in 8 two of the edges of the tetrahedron of zinc ions are doubly bridged, two are singly bridged, and the other two are nonbridged. On the other hand, when iron(II) acetate under aerobic conditions was allowed to react with 5 a, the unprecedented complex [[Fe(3)O(L(2))(2)(OAc)(4)](2)O] (9) was isolated. Cluster 9 is composed of two trimetallic, triangular mu(3)-O(2-)-centered [Fe(3)O(L(2))(2)(OAc)(4)](+) modules, linked by an almost linear mu(2)-O(2-) bridge. The M?ssbauer spectrum together with cyclic voltammetric and square-wave voltammetric measurements of 9 are reported, and 6-9 were characterized unequivocally by single-crystal X-ray structure analyses.     

Photoelectron imaging of copper and silver mono- and diamine anions

The results of photoelectron imaging experiments of Cu and Ag mono- and diamine anions are reported. The photoelectron images were recorded at two photon energies, 800 and 527 nm. The vertical detachment energies of CuNH(2) (-) and AgNH(2) (-) are lower than those of the respective atomic metal ion and are measured to be 1.11+/-0.05 and 1.23+/-0.05 eV, respectively. By contrast, the electron detachment energies for Cu(NH(2))(2) (-) and Ag(NH(2))(2) (-) are higher than those of the corresponding metal ion and are determined to be 1.48+/-0.05 and 1.85+/-0.05 eV, respectively. Energy-dependent photoelectron anisotropy parameters are also reported. The photodetachment of the Cu and Ag mono- and diamine anions exhibit a cos(2) theta angular dependence relative to the direction of the laser polarization. The nature of the chemical bonding and the symmetry of the highest occupied molecular orbitals are discussed in relevance to the measured anisotropy parameters.     

Structures and properties of functional metal selenites and tellurites

Metal selenites and tellurites are a class of very important compounds. In this paper, the structures and properties of metal selenites or tellurites combining with transition-metal (TM) ions with the d (0) electronic configuration or tetrahedral MO 4 building blocks of post-transition main-group elements were reviewed. Most compounds in the alkali or alkaline-earth-d (0) TM-Se (IV) (or Te (IV))-O systems exhibit extended anionic architectures composed of distorted octahedra of (d (0)) TM cations and tellurite or selenite groups. The distortion of the octahedron is always away from the lone-pair cation, and some of them exhibit excellent second-order nonlinear optical properties due to the adductive effects of two types of bond polarizations. Because of the high coordination number of Ln (III) ions, most of compounds in the Ln-d (0) TM-Se (IV) (or Te (IV))-O systems are not second-harmonic-generation active; however, they are able to emit strong luminescence in the visible or near-IR region; also in most cases, the d (0) TM cations are in tetrahedral geometry and are well separated from selenite or tellurite groups. It is also interesting to note that the selenite group is normally "isolated", whereas the TeO x ( x = 3-5) can be polymerized into a variety of discrete polynuclear anionic clusters or extended architectures via Te-O-Te bridges.     

Cobalt and manganese diphosphonates with one-, two-, and three-dimensional structures and field-induced magnetic transitions

Reactions of 2-(1-Imidazole)-1-hydroxyl-1,1'-ethylidenediphosphonic acid (ImhedpH(4)) and cobalt or manganese salts under hydrothermal conditions result in three new metal diphosphonates: β-Co(3)(ImhedpH)(2)(H(2)O)(4)·2H(2)O (1), Co(3)(ImhedpH)(2)(H(2)O)(4) (2), and Mn(ImhedpH(2))·H(2)O (3). In compound 1, the columns made up of {Co1(2)O(2)} dimers and {PO(3)C} tetrahedra through corner-sharing are cross-linked through {Co2O(6)} octahedra, forming an inorganic layer. Neighboring layers are pillared by coordinated imidazole groups of ImhedpH(-) ligands, leading to a three-dimensional open framework containing two kinds of channels with sizes of 8.256 × 9.851 ? and 8.030 × 4.745 ? (van der Waals radii not accounted for). Compound 2 shows a layer structure, in which Co(3)(ImhedpH)(2)(H(2)O)(4) trimer units are connected through the corner-sharing of {Co1O(5)} trigonal bipyramids and {PO(3)C} tetrahedra, forming an inorganic layer containing 20-member rings composed of six Co atoms, two μ(3)-O1 units, and four O-P-O units. The noncoordinated imidazole groups protrude from two sides of the layer. Compound 3 shows a ladder structure, where the Mn(II) ions are bridged by ImhedpH(2)(2-) ligands through double O-P-O units to form a single chain, and two such chains are further fused together by sharing edges of {MnO(5)} trigonal bipyramids. The magnetic properties of 1-3 have been studied. Ferrimagnetism and field-induced magnetic transition from ferrimagnetism to a fully polarized state are observed in 1. Compounds 2 and 3 reveal dominant antiferromagnetic interactions between metal centers, and two-step field-induced magnetic phase transitions are found in 2.     

Adsorption and dissociation of H2O2 on Pt and Pt-alloy clusters and surfaces

The adsorption of H(2)O(2) on Pt and Pt-M alloys, where M is Cr, Co, or Ni, is investigated using density functional theory. Binding energies calculated with a hybrid DFT functional (B3PW91) are in the range of -0.71 to -0.88 eV for H(2)O(2) adsorbed with one of the oxygen atoms on top Pt positions of Pt(3), Pt(2)M, and PtM(2), and enhanced values in the range of -0.81 to -1.09 eV are found on top Ni and Co sites of the Pt(2)M clusters. Adsorption on top sites of Pt(10) yields a weaker binding of -0.48 eV, whereas on periodic Pt(111) and Pt(3)Co(111) surfaces, H(2)O(2) generally dissociates into two OH radicals. On the other hand, attempts to attach H(2)O(2) on bridge sites cause spontaneous dissociation of H(2)O(2) into two adsorbed OH radicals, suggesting that stable adsorptions on bridge sites are not possible for any of the clusters or extended surfaces that are being studied. We also found that the water-H(2)O(2) interaction reduces the strength of the adsorption of H(2)O(2) on these clusters and surfaces.     

Experimental and theoretical study of the reactions between small neutral iron oxide clusters and carbon monoxide

Reactions of small neutral iron oxide clusters (FeO(1-3) and Fe(2)O(4,5)) with carbon monoxide (CO) are investigated by experiments and first-principle calculations. The iron oxide clusters are generated by reaction of laser-ablation-generated iron plasma with O(2) in a supersonic expansion and are reacted with carbon monoxide in a fast flow reactor. Detection of the neutral clusters is through ionization with vacuum UV laser (118 nm) radiation and time-of-flight mass spectrometry. The FeO(2) and FeO(3) neutral clusters are reactive toward CO, whereas Fe(2)O(4), Fe(2)O(5), and possibly FeO are not reactive. A higher reactivity for FeO(2) [sigma(FeO(2) + CO) > 3 x 10(-17) cm(2)] than for FeO(3) [sigma(FeO(3) + CO) approximately 1 x 10(-17) cm(2)] is observed. Density functional theory (DFT) calculations are carried out to interpret the experimental observations and to generate the reaction mechanisms. The reaction pathways with negative or very small overall barriers are identified for CO oxidation by FeO(2) and FeO(3). The lower reactivity of FeO(3) with respect to FeO(2) may be related to a spin inversion process present in the reaction of FeO(3) with CO. Significant reaction barriers are calculated for the reactions of FeO and Fe(2)O(4-5) with CO. The DFT results are in good agreement with experimental observations. Molecular-level reaction mechanisms for CO oxidation by O(2), facilitated by condensed phase iron oxides as catalysts, are suggested.     

Diastereo- and Enantioselective Synthesis of syn-alpha-Vinylchlorohydrins and cis-Vinylepoxides

A new method to generate chiral syn-vinylchlorohydrins and cis-vinyloxiranes is reported. Reaction of (alpha-haloallyl)lithiums with methoxy-9-BBN or Ipc(2)BOMe followed by treatment with BF(3).OEt(2) leads to (Z)-(gamma-haloallyl)boranes which react with aldehydes to yield cis-vinylepoxides (de >/= 90%) upon oxidative workup. Alternatively, addition of ethanolamine to the allylboration product yields syn-alpha-halohydrins (de >/= 90%) that are also easily cyclized to cis-vinylepoxides. Extension of this protocol using [(Z)-gamma-chloroallyl]BIpc(2) leads to chiral syn-alpha-chlorohydrins and cis-vinylepoxides in high de (>/=90%) and ee (90-99%). Enantioselectivity of reactions of chiral (Z)-(gamma-chloroallyl)boranes with aldehydes are more sensitive to reaction conditions than enantioselectivity of reactions of other alpha-or gamma-substituted allylboranes. The effects of proportion of BF(3).OEt(2) and the relative efficacies of LiNR(2) bases on diastereo- and enantioselectivity of the chloroallylation are reported.     

Novel spectral and electrochemical characteristics of triphenylamine-bound zinc porphyrins and their intramolecular energy and electron transfer

Porphine bearing triphenylamine (TPA) pendant groups and their zinc complexes, zinc meso-tetra-p-(di-p-phenylamino)phenylporphyrin (ZnTDPAPP) and zinc meso-tetra-p-(di-p-tolylamino)phenylporphyrin (ZnTDTAPP) are synthesized and their spectral and electrochemical characteristics are studied. Zinc meso-tetraphenylporphyrin (ZnTPP) and zinc meso-tetra-p-aminophenylporphyrin (ZnTAPP) are also used as reference complexes. The B and Q bands of ZnTDPAPP and ZnTDTAPP are located at higher wavelengths and the bandwidths become broader compared with those of ZnTPP and ZnTAPP, indicating the peripheral TPA affects the electronic configuration of zinc porphyrins. Upon excitation in CH2Cl2 at room temperature, the compounds exhibit intramolecular singlet energy transfer from the TPA to the porphyrin core, and emission from the porphyrins are observed. Both ZnTDPAPP and ZnTDTAPP are easier to be oxidized and harder to be reduced than ZnTPP, in agreement with the strong electron-donating effect of the TPA groups. Extra waves corresponding to the oxidation of TPA substituents are also observed. The cation radical ZnTDTAPP+* exhibits an absorption spectrum very different from the typical spectra for porphyrin cation radicals. The NIR absorption band at 1296 nm indicates the electron transfer occurs intramolecularly. The above results evince the ability of TPA to modulate the electronic structure of zinc porphyrins.     

Synthesis and thermal characterization of new ternary chelates of piroxicam and tenoxicam with glycine and DL-phenylalanine and some transition metals

The ternary chelates of piroxicam (Pir) and tenoxicam (Ten) with Fe(II), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) in the presence of various amino acids such as glycine (Gly) or dl-phenylalanine (PhA) were prepared and characterized with different physicochemical methods. IR spectra confirm that Pir and Ten behave as a neutral bidentate ligand coordinated to the metal ions via the pyridine-N and carbonyl group of the amide moiety. Gly molecule acted as a uninegatively monodentate ligand and coordinate to the metal ions through its deprotonated carboxylic group. In addition, PhA acted as a uninegatively bidentate ligand and coordinate to the metal ions through its deprotonated carboxylic and amino groups. The solid reflectance spectra and magnetic moment measurements confirm that all the chelates have octahedral geometrical structures while Cu(II)- and Zn(II)-ternary chelates with PhA have square planar geometrical structures. Thermal behaviour of the complexes is extensively studied using TG and DTA techniques. TG results show that water molecules (hydrated and coordinated) and anions are removed in the first and second steps while Gly, PhA, Pir and Ten are decomposed in the next and subsequent steps. The pyrolyses of the chelates into different gases are observed in the DTA curves as exo- or endothermic peaks. Also, phase transition states are observed in some chelates. Different thermodynamic parameters are calculated using Coats-Redfern method and the results are interpreted.     

Experimental (FT-IR, FT-Raman) and theoretical (HF and DFT) investigation and HOMO and LUMO analysis on the structure of p-fluoronitrobenzene

FT-IR and FT-Raman spectra of p-fluoronitrobenzene (FNO(2)C(6)H(4)) have been recorded in the region 4000-100 cm(-1). In this work, the experimental and theoretical spectra of p-fluoronitrobenzene (p-FNBz) are studied. The molecular geometry and vibrational frequencies are calculated in the ground state of molecule using ab initio Hartree-Fock (HF) and DFT (B3LYP and LSDA) methods with 6-31++G(d,p) and 6-311++G(d,p) basis sets. The computed values of frequencies are scaled to yield good coherence with observed values by using suitable factor. The complete assignments are performed on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method. The observed and calculated frequencies are found to be in very good agreement. The alteration of vibration bands due to the substitutions at the first and fourth position of the skeletal ring is also investigated from their characteristic region of linked spectrum. A study on the electronic properties, such as absorption wavelengths, excitation energy, dipole moment and frontier molecular orbital energies, are performed by time dependent DFT (TD-DFT) approach. The electronic structure and the assignment of the absorption bands in the electronic spectra of steady compounds are discussed. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule. The thermodynamic properties of the title compound at different temperatures have been calculated in gas phase, revealing the correlations between standard heat capacities (C) standard entropies (S), standard enthalpy changes (H) and temperatures.     

Experimental and theoretical study of the reactions between vanadium oxide cluster cations and water

Vanadium oxide cluster cations V(x)O(y)(+) (x = 2-6) are prepared by laser ablation and are reacted with D(2)O in a fast flow reactor under room temperature conditions. A time-of-flight mass spectrometer is used to detect the cluster distribution before and after the reactions. Observation of the products (V(2)O(5))(1-3)D(+) indicates the deuterium atom abstraction reaction (V(2)O(5))(1-3)(+) + D(2)O → (V(2)O(5))(1-3)D(+) + OD. In addition, significant association products (V(2)O(5))(1-3)D(2)O(+) are also observed in the experiments. Density functional theory calculations are performed to study the reaction mechanisms of V(4)O(10)(+) with H(2)O. The calculated results are in agreement with the experimental observations and indicate that H(2)O is dissociatively rather than molecularly adsorbed in V(4)O(10)H(2)O(+) complex.     

Anion-directed self-assembly of lanthanide-notp compounds and their fluorescence, magnetic, and catalytic properties

Reactions of 1,4,7-triazacyclononane-1,4,7-triyl-tris(methylenephosphonic acid) [notpH(6), C(9)H(18)N(3)(PO(3)H(2))3] with different lanthanide salts result in four types of Ln-notp compounds: [Ln{C(9)H(20)N(3)(PO(3)H)(2)(PO(3))}(NO(3))(H(2)O)].4H2O (1), [Ln = Eu (1 Eu), Gd (1 Gd), Tb (1 Tb)], [Ln{C(9)H(20)N(3)(PO(3)H)(2)(PO(3))}(H2O)]Cl.3H2O (2) [Ln = Eu (2 Eu), Gd (2 Gd), Tb (2 Tb)], [Ln{C(9)H(20)N(3)(PO(3)H)(2)(PO(3))}(H2O)]ClO4.8H2O, (3) [Ln = Eu (3 Eu), Gd (3 Gd)], and [Ln{C(9)H(20)N(3)(PO(3)H)(2)(PO(3))}(H2O)]ClO4.3H2O (4), [Ln = Gd (4 Gd), Tb (4 Tb)]. Compounds within each type are isostructural. In compounds 1, dimers of {Ln2(notpH4)2(NO3)2(H2O)2} are found, in which the two lanthanide atoms are connected by two pairs of O-P-O and one pair of mu-O bridges. The NO3- ion serves as a bidentate terminal ligand. Compounds 2 contain similar dimeric units of {Ln2(notpH4)2(H2O)2} that are further connected by a pair of O-P-O bridges into an alternating chain. The Cl- ions are involved in the interchain hydrogen-bonding networks. A similar chain structure is also found in compounds 3; in this case, however, the chains are linked by ClO4- counterions through hydrogen-bonding interactions, forming an undulating layer in the (011) plane. These layers are fused through hydrogen-bonding interactions, leading to a three-dimensional supramolecular network with large channels in the [100] direction. Compounds 4 show an interesting brick-wall-like layer structure in which the neighboring lanthanide atoms are connected by a pair of O-P-O bridges. The ClO4- counterions and the lattice water molecules are between the layers. In all compounds the triazamacrocyclic nitrogen atoms are not coordinated to the Ln(III) ions. The anions and the pH are believed to play key roles in directing the formation of a particular structure. The fluorescence spectroscopic properties of the Eu and Tb compounds, magnetic properties of the Gd compounds, and the catalytic properties of 4 Gd were also studied.     

Effects of fluorine on the structures and energetics of the propynyl and propargyl radicals and their anions

[reaction: see text] The adiabatic electron affinity (EA(ad)) of the CH(3)-C[triple bond]C(*) radical [experiment = 2.718 +/- 0.008 eV] and the gas-phase basicity of the CH(3)-C[triple bond]C:(-) anion [experiment = 373.4 +/- 2 kcal/mol] have been compared with those of their fluorine derivatives. The latter are studied using theoretical methods. It is found that there are large effects on the electron affinities and gas-phase basicities as the H atoms of the alpha-CH(3) group in the propynyl system are substituted by F atoms. The predicted electron affinities are 3.31 eV (FCH(2)-C[triple bond]C(*)), 3.86 eV (F(2)CH-C[triple bond]C(*)), and 4.24 eV (F(3)C-C[triple bond]C(*)), and the predicted gas-phase basicities of the fluorocarbanion derivatives are 366.4 kcal/mol (FCH(2)-C[triple bond]C:(-)), 356.6 kcal/mol (F(2)CH-C[triple bond]C:(-)), and 349.8 kcal/mol (F(3)C-C[triple bond]C:(-)). It is concluded that the electron affinities of fluoropropynyl radicals increase and the gas-phase basicities decrease as F atoms sequentially replace H atoms of the alpha-CH(3) in the propynyl system. The propargyl radicals, lower in energy than the isomeric propynyl radicals, are also examined and their electron affinities are predicted to be 0.98 eV ((*)CH(2)-C[triple bond]CH), 1.18 eV ((*)CFH-C[triple bond]CH), 1.32 eV ((*)CF(2)-C[triple bond] CH), 1.71 eV ((*)CH(2)-C[triple bond]CF), 2.05 eV ((*)CFH-C[triple bond]CF), and 2.23 eV ((*)CF(2)-C[triple bond]CF).     

Ground- and excited-state diatomic bond lengths, vibrational levels, and potential-energy curves from conventional and localized Hartree-Fock-based density-functional theory

Ground- and excited-state diatomic bond lengths, vibrational levels, and potential-energy curves are determined using conventional and localized Hartree-Fock (LHF)-based density-functional theory. Exchange only and hybrid functionals (with various fractions of exchange) are considered, together with a standard generalized gradient approximation (GGA). Ground-state bond lengths and vibrational wave numbers are relatively insensitive to whether orbital exchange is treated using the conventional or LHF approach. Excited-state calculations are much more sensitive. For a standard fraction of orbital exchange, N2 and CO vertical excitation energies at experimental bond lengths are accurately described by both conventional and LHF-based approaches, providing an asymptotic correction is present. Excited-state bond lengths and vibrational levels are more accurate with the conventional approach. The best quality, however, is obtained with an asymptotically corrected GGA functional. For the ground and lowest four singlet excited states, the GGA mean absolute errors in bond lengths are 0.006 A (0.5%) and 0.011 A (0.8%) for N2 and CO, respectively. Mean absolute errors in fundamental vibrational wavenumbers are 49 cm(-1) (2.7%) and 68 cm(-1) (5.0%), respectively. The GGA potential-energy curves are compared with near-exact Rydberg-Klein-Rees curves. Agreement is very good for the ground and first excited state, but deteriorates for the higher states.     

Comparison of nickel-group metal cyanides and acetylides and their anions using anion photoelectron spectroscopy and density functional theory calculations

The photoelectron spectra of NiCN-, PdCN-, PtCN-, HNiC2H-, Ni(C2H)2(-), PdC2H-, and PtC2H- are presented along with density functional theory calculations. Linear structures are predicted for all anions and neutrals. NiCN- and NiCN are predicted to have 3delta and 2delta ground states, respectively. HNiC2H- and Ni(C2H)2(-) are predicted to have 2delta and 2delta(g) anion and 3delta and 3pi(g) neutral ground states, respectively. The palladium and platinum cyanide and acetylides have 1sigma+ anion and 2sigma+ neutral ground states. Simulations generated from the calculated parameters are compared to observed spectra, and molecular orbital diagrams are presented to compare the bonding in these species.     

Experimental and theoretical studies of reactions of neutral vanadium and tantalum oxide clusters with NO and NH3

Reactions of neutral vanadium and tantalum oxide clusters with NO, NH(3), and an NO/NH(3) mixture in a fast flow reactor are investigated by time of flight mass spectrometry and density functional theory (DFT) calculations. Single photon ionization through a 46.9 nm (26.5 eV) extreme ultraviolet (EUV) laser is employed to detect both neutral cluster distributions and reaction products. Association products VO(3)NO and V(2)O(5)NO are detected for V(m)O(n) clusters reacting with pure NO, and reaction products, TaO(3,4)(NO)(1,2), Ta(2)O(5)NO, Ta(2)O(6)(NO)(1-3), and Ta(3)O(8)(NO)(1,2) are generated for Ta(m)O(n) clusters reacting with NO. In both instances, oxygen-rich clusters are the active metal oxide species for the reaction M(m)O(n)+NO→M(m)O(n)(NO)(x). Both V(m)O(n) and Ta(m)O(n) cluster systems are very active with NH(3). The main products of the reactions with NH(3) result from the adsorption of one or two NH(3) molecules on the respective clusters. A gas mixture of NO:NH(3) (9:1) is also added into the fast flow reactor: the V(m)O(n) cluster system forms stable, observable clusters with only NH(3) and no V(m)O(n)(NO)(x)(NH(3))(y) species are detected; the Ta(m)O(n) cluster system forms stable, observable mixed clusters, Ta(m)O(n)(NO)(x)(NH(3))(y), as well as Ta(m)O(n)(NO)(x) and Ta(m)O(n)(NH(3))(y) individual clusters, under similar conditions. The mechanisms for the reactions of neutral V(m)O(n) and Ta(m)O(n) clusters with NO/NH(3) are explored via DFT calculations. Ta(m)O(n) clusters form stable complexes based on the coadsorption of NO and NH(3). V(m)O(n) clusters form weakly bound complexes following the reaction pathway toward end products N(2)+H(2)O without barrier. The calculations give an interpretation of the experimental data that is consistent with the condensed phase reactivity of V(m)O(n) catalyst and suggest the formation of intermediates in the catalytic chemistry.     

Neutral and cationic phosphoramide adducts of silicon tetrachloride: synthesis and characterization of their solution and solid-state structures

The solution and solid-state structures of hexamethylphosphoramide (HMPA) adducts of tetrachlorosilane (SiCl4) are discussed. In solution, the meridional and facial isomers of the hexa-coordinate cationic complex 3 HMPASiCl3 + Cl(-) (2) predominate at all HMPA concentrations, and are in equilibrium with the hexa-coordinate neutral trans- and cis-2 HMPASiCl4 complexes (1), as well as the penta-coordinate cationic cis-2 HMPASiCl3 + Cl(-) (3). Single crystal X-ray analyses are reported for the ionized mer-3 HMPASiCl3 + HCl2 (-) and the neutral trans-2 HMPASiCl4 complexes.