Ling Jiang

Gas-phase vibrational spectroscopy of microhydrated magnesium nitrate ions [MgNO3(H2O)(1-4)]+.

Infrared photodissociation spectra of buffer-gas-cooled [MgNO(3)(H(2)O)(n)](+) complexes with n = 1-4 are measured in the O-H stretching region. The observed bands are assigned to the excitation of the symmetric and antisymmetric stretching modes of the water molecules. The structural assignment of the spectra is aided by density functional theory calculations (B3LYP/6-311+G(d,p)) on energetically low-lying isomers, including the calculation of harmonic and anharmonic vibrational frequencies, as well as dissociation energies. The nitrate anion binds to the Mg dication in a bidentate fashion, occupying two coordination sites. The water molecules fill the remaining binding sites of the Mg cation, completing the first coordination shell at n = 4 and forming a stable six-fold-coordinated complex, the structure of which persists up to room temperature.

Structure and chemistry of the heteronuclear oxo-cluster [VPO4]•+: a model system for the gas-phase oxidation of small hydrocarbons.

The heteronuclear oxo-cluster [VPO4](•+) is generated via electrospray ionization and investigated with respect to both its electronic structure as well as its gas-phase reactivity toward small hydrocarbons, thus permitting a comparison to the well-known vanadium-oxide cation [V2O4](•+). As described in previous studies, the latter oxide exhibits no or just minor reactivity toward small hydrocarbons, such as CH4, C2H6, C3H8, n-C4H10, and C2H4, while substitution of one vanadium by a phosphorus atom yields the reactive [VPO4](•+) ion; the latter brings about oxidative dehydrogenation (ODH) of saturated hydrocarbons, e.g., propane and butane as well as oxygen-atom transfer (OAT) to unsaturated hydrocarbons, e.g. ethene, at thermal conditions. Further, the gas-phase structure of [VPO4](•+) is determined by IR photodissociation spectroscopy and compared to that of [V2O4](•+). DFT calculations help to elucidate the reaction mechanism. The results underline the crucial role of phosphorus in terms of C-H bond activation of hydrocarbons by mixed VPO clusters.

Metal–organic coordination architectures with 3-pyridin-3-yl-benzoate: crystal structures, fluorescent emission and magnetic properties

Reactions of 3-pyridin-3-yl-benzoic acid (HL) with metal nitrates under hydrothermal conditions yield seven new coordination polymers: Ni(L)2(H2O)2 (1), [Ni(L)2](H2O) (2), Co(L)2(H2O)2 (3), [Zn(L)2](H2O) (4), Cu(L)2 (5), Cd(L)2 (6) and Gd2(L)6(H2O)4 (7). A systematic investigation on coordination chemistry of the ligand and the significant function of supramolecular interactions in managing the resultant crystalline networks has been carried out. On the basis of the X-ray diffraction analysis of these complexes, the results show that complexes 1–5 and 7 form similar one-dimensional (1D) double-chain coordination arrays, among which 1 and 3, as well as 2 and 4, are isostructural. Remarkably, distinct network architectures are further constructed with the aid of weak secondary interactions. Amongst them, complexes 1, 3 and 5 exhibit the classical α-polonium networks, while complexes 2 and 4 present the (3,4)-connected two-dimensional layers. In 7, the intermolecular π–π stacking interactions lead to the formation of a double-strand structure. The CdII complex 6 assembles into a three-dimensional metal–organic framework exhibiting a unique 6-connected roa topology. The trans-configuration of L ligand is only found in the case of 6, whereas the cis-ligands are generally observed in these complexes. The fluorescent emission properties of 4 and 6 as well as the magnetic property of 7 have also been investigated.

Electron distribution in partially reduced mixed metal oxide systems: Infrared spectroscopy of cemvnoo+ gas-phase clusters

Vibrational predissociation spectra of rare-gas-tagged [(CeO(2))(VO(2))(1-2)](+) and [(Ce(2)O(3))(VO(2))](+) clusters are measured in the 400-1200 cm(-1) region. Density functional theory (DFT) is used to determine the geometric and electronic structure of low-energy isomers of the partially reduced clusters. Comparison of experimental and simulated spectra provides evidence for the larger stability of Ce(+3)/V(+5) compared to that of Ce(+4)/V(+4), which confirms that the exceptionally high reducibility of Ce(+4) accounts for the promoting role of ceria in supported vanadium oxide catalysts.

Mid- and Far-IR spectra of H5+ and D5+ compared to the predictions of anharmonic theory

H5(+) is the smallest proton-bound dimer. As such, its potential energy surface and spectroscopy are highly complex, with extreme anharmonicity and vibrational state mixing; this system provides an important benchmark for modern theoretical methods. Unfortunately, previous measurements covered only the higher-frequency region of the infrared spectrum. Here, spectra for H5(+) and D5(+) are extended to the mid- and far-IR, where the fundamental of the proton stretch and its combinations with other low-frequency vibrations are expected. Ions in a supersonic molecular beam are mass-selected and studied with multiple-photon dissociation spectroscopy using the FELIX free electron laser. A transition at 379 cm(-1) is assigned tentatively to the fundamental of the proton stretch of H5(+), and bands throughout the 300-2200 cm(-1) region are assigned to combinations of this mode with bending and torsional vibrations. Coupled vibrational calculations, using ab initio potential and dipole moment surfaces, account for the highly anharmonic nature of these complexes.

Theoretical study of the interaction of carbon monoxide with 3d metal dimers.

The interaction of carbon monoxide with 3d metal dimers (scandium through zinc) has been examined using six different exchange-correlation density functionals. Results are compared to the relevant experimental values and to other theoretical investigations when available, and the overall agreement has been obtained. The BP86 functional gives calculated C-O stretching vibrational frequencies much closer to the experimental values than the B3P86, B3LYP, mPW1PW91, and PBE1PBE functionals, and furthermore, replacing the correlation part by the Lee-Yang-Parr correlation functional yields essentially the same results. It is generally found that on going from left to right across the 3d metal series, the preference for geometrical configuration is from side-on-bonded mode to bridging, and then to terminal, whereas Ni(2)CO adopts bridging mode. Particularly, the present computation reveals a significant tendency toward four-electron donor carbonyl groups with metal-oxygen bonds with the early transition metals scandium and titanium. The C-O stretching vibrational frequencies in the ground states of M(2)CO (M=Sc to Zn) increase generally from the left to the right side of the Periodic Table. The binding energies exhibit an overall decrease trend. These general trends in the interaction of carbon monoxide with 3d metal dimers mirror the main features of CO adsorption on transition metal surfaces.

Rational assembly of a 3D metal–organic framework for gas adsorption with predesigned cubic building blocks and 1D open channels

A novel 3D metal-organic framework with predesigned cubic building blocks and 1D open channels exhibiting significant N2 adsorption has been synthesized and characterized by single crystal X-ray diffraction analysis.

Observation of the lead carbonyls, PbnCO (n=1–4): Reactions of lead atoms and small clusters with carbon monoxide in solid argon

Reactions of laser-ablated Pb atoms with CO molecules in solid argon lead to the formation of the lead carbonyls, PbnCO (n=1-4), using matrix-isolation infrared spectroscopy. Absorption at 2027.7 cm(-1) is assigned to C-O stretching mode of the PbCO product, which appears and increases on annealing, disappears on broadband irradiation, and recovers on further annealing. Small lead cluster mono-carbonyls PbnCO (n=2-4) are also observed in the present infrared spectra. Based on the results of stepwise annealing and the comparison with theoretical predictions, the absorptions at 1915.5, 1923.8, and 2042.8 cm(-1) are assigned to Pb2CO, Pb3CO, and Pb4CO, respectively. Bridging CO is found in Pb2CO or Pb3CO, whereas terminal CO in Pb4CO. The density functional theory calculations have been performed on these molecules and small naked lead clusters. The good agreement between experimental and calculated vibrational frequencies, relative absorption intensities, and isotopic shifts provides strong support for the identifications of these lead mono-carbonyls PbnCO (n=1-4). Furthermore, energetic analysis for the possible reactions of lead atoms with CO molecules is also given.

Unique Structural Trends in the Lanthanoid Oxocarbonyl Complexes

Reactions of laser-ablated lanthanoid atoms (except for radioactive Pm) with carbon dioxide molecules in solid argon have been investigated using matrix-isolation infrared spectroscopy. On the basis of isotopic shifts, mixed isotopic splitting patterns, and CCl4-doping experiments, the lanthanoid oxocarbonyl complexes have been identified. Density functional theory calculations have been performed on these products, which support the experimental assignments of the infrared spectra. Infrared spectroscopic studies of these lanthanoid complexes combined with theoretical calculations reveal that the early lanthanoid (La-Sm) oxocarbonyl complexes adopt trans configurations, the europium and ytterbium ones adopt side-on-bonded modes (Eu-(eta2-OC)O and Yb-(eta2-OC)O), and the late lanthanoid (Gd-Lu) ones adopt cis configurations. Natural bond orbital analysis indicates that the formation of the lanthanoid oxocarbonyl complexes involves the promotion of 6s and 4f electrons into the metal valence shell.

Reactions of silicon atoms and small clusters with CO: Experimental and theoretical characterization of SinCO (n=1–5), Si2(CO)2, c-Si2(μ-O)(μ-CSi), and c-Si2(μ-O)(μ-CCO) in solid argon

Reactions of silicon atoms and small clusters with carbon monoxide molecules in solid argon have been studied using matrix isolation infrared absorption spectroscopy. In addition to the previously reported SiCO monocarbonyl, Si2(CO)2 and SinCO (n=2–5) carbonyl molecules were formed spontaneously on annealing and were characterized on the basis of isotopic substitution and theoretical calculations. It was found that Si2CO, Si3CO, and Si5CO are bridge-bonded carbonyl compounds, whereas Si4CO is a terminal-bonded carbonyl molecule. The Si2(CO)2 and Si3CO molecules photochemically rearranged to the more stable c-Si2(μ-O)(μ-CCO) and c-Si2(μ-O) (μ-CSi) isomers where Si2 is inserted into the CO triple bond.Reactions of silicon atoms and small clusters with carbon monoxide molecules in solid argon have been studied using matrix isolation infrared absorption spectroscopy. In addition to the previously reported SiCO monocarbonyl, Si{sub 2}(CO){sub 2} and Si{sub n}CO (n=2-5) carbonyl molecules were formed spontaneously on annealing and were characterized on the basis of isotopic substitution and theoretical calculations. It was found that Si{sub 2}CO, Si{sub 3}CO, and Si{sub 5}CO are bridge-bonded carbonyl compounds, whereas Si{sub 4}CO is a terminal-bonded carbonyl molecule. The Si{sub 2}(CO){sub 2} and Si{sub 3}CO molecules photochemically rearranged to the more stable c-Si{sub 2}({mu}-O)({mu}-CCO) and c-Si{sub 2}({mu}-O) ({mu}-CSi) isomers where Si{sub 2} is inserted into the CO triple bond.