Reactions of laser-ablated zinc and cadmium atoms with CO: infrared spectra of the Zn(CO)x (x = 1-3), CdCO-, and Cd(CO)2 molecules in solid neon

Reactions of laser-ablated zinc and cadmium atoms with carbon monoxide molecules in solid neon have been investigated using matrix-isolation infrared spectroscopy. Based on the isotopic substitution, absorptions at 1852.2, 1901.9, 1945.9, and 1995.2 cm(-1) are assigned to the C-O stretching vibrations of the ZnCO, Zn(CO)(2), and Zn(CO)(3) molecules. Absorptions at 1735.8, 1961.3, and 2035.7 cm(-1) are assigned to the C-O stretching vibrations of the CdCO(-) and Cd(CO)(2) molecules. In contrast with the previous argon experiments, more species and more valuable information about the reaction of zinc and cadmium atoms with CO have been obtained in solid neon. Density functional theory calculations have been performed on these zinc and cadmium carbonyls. The agreement between the experimental and calculated vibrational frequencies, relative absorption intensities, and isotopic shifts substantiates the identification of these carbonyls from the matrix infrared spectrum. The present experiments also reveal that zinc is more reactive with CO than cadmium.     

Experimental and theoretical studies of the products of laser-ablated thorium atom reactions with H2O in excess argon

Reactions of laser-ablated Th atoms with H2O during condensation in excess argon have formed a variety of intriguing new Th, H, O species. Infrared absorptions at 1406.0 and 842.6 cm-1 are assigned to the H-Th and Th=O stretching vibrations of HThO. Absorptions at 1397.2, 1352.4, and 822.8 cm-1 are assigned to symmetric H-Th-H, antisymmetric H-Th-H, and Th=O stretching vibrations of the major primary reaction product H2ThO. Thorium monoxide (ThO) produced in the reaction inserts into H2O to form HThO(OH), which absorbs at 1341.0, 804.0, and 542.6 cm-1. Both HThO(OH) and ThO2 add another H2O molecule to give HTh(OH)3 and OTh(OH)2, respectively. Weaker thorium hydride (ThH1(-4)) absorptions were also observed. Relativistic DFT and ab initio calculations were performed on all proposed molecules and other possible isomers. The good agreement between experimental and calculated vibrational frequencies, relative absorption intensities, and isotopic shifts provides support for these first identifications of Th, H, O molecular species.     

Infrared spectroscopic and density functional theory studies on the CO dissociation by scandium and yttrium dimers

Reactions of laser-ablated scandium and yttrium atoms with dilute carbon monoxide molecules in solid argon have been investigated using matrix-isolation infrared spectroscopy. On the basis of the results of the isotopic substitution, the change of laser power and CO concentration and the comparison with density functional theory (DFT) calculations, the absorption at 1193.4 cm(-1) is assigned to the C-O stretching vibration of the Sc(2)[eta(2)(mu(2)-C,O)] molecule, which has a single bridging CO that is tilted to the side. This CO-activated molecule undergoes ultraviolet-visible photoinduced rearrangement to the CO-dissociated molecule, c-Sc(2)(mu-C)(mu-O). The cyclic c-Sc(2)(mu-C)(mu-O) molecule has a bridging carbon on one side of the Sc(2) unit and a bridging oxygen on the other. The analogous Y(2)[eta(2)(mu(2)-C,O)] molecule has not been observed, but the CO-dissociated c-Y(2)(mu-C)(muO) molecule has been observed in the Y + CO experiments. DFT calculations of the geometry structures, vibrational frequencies, and IR intensities strongly support the assignments. The CO activation mechanism has also been discussed. Our experimental and theoretical results schematically depict an activation process to CO dissociation.     

An ab initio investigation on (CO2)n and CO2(Ar)m clusters: geometries and IR spectra

An ab initio investigation on CO(2) homoclusters is done at MPWB1K6-31++G(2d) level of theory. Electrostatic guidelines are found to be useful for generating initial structures of (CO(2))(n) clusters. The ab initio minimum energy geometries of (CO(2))(n) with n=2-8 are T shaped, cyclic, trigonal pyramidal, tetragonal pyramidal, tetragonal bipyramidal, pentagonal bipyramidal, and pentagonal bipyramid with one CO(2) molecule attached to it. A test calculation on (CO(2))(20) cluster is also reported. The geometric parameters of the energetically most favored (CO(2))(n) clusters match quite well their experimental counterparts (wherever available) as well as those derived from molecular dynamics studies. The effect of clustering is quantified through the asymmetric C-O stretching frequency shift relative to the single CO(2) molecule. (CO(2))(n) clusters show an increasing blueshift from 1.8 to 9.6 cm(-1) on increasing number of CO(2) molecules from n=2 to 8. The energetics and geometries of CO(2)(Ar)(m) clusters have also been explored at the same level of theory. The geometries for m=1-6 show a predominant T type of the argon-CO(2) molecule interaction. Higher clusters with m=7-12 show that the argon atoms cluster around the oxygen atom after the saturation of the central carbon atom. The CO(2)(Ar)(m) clusters exhibit an increasing redshift in the C-O asymmetric stretch relative to CO(2) molecule of 0.7-5.6 cm(-1) with increasing number of argon atoms through m=1-8.     

Infrared-spectroscopic and density-functional-theory investigations of the LaCO, La2[eta2(mu2-C,O)], and c-La2(mu-C)(mu-O) molecules in solid argon

Reactions of laser-ablated lanthanum atoms with CO molecules in solid argon have been studied. The neutral lanthanum monocarbonyl (LaCO), produced upon sample deposition at 7 K, exhibits a C-O stretching frequency of 1772.7 cm(-1); to the best of our knowledge this is the lowest yet observed for a terminal CO in a neutral metal-carbonyl molecule (MCO, M = metal atom), implying anomalously enhanced metal-to-CO back-bonding. The infrared (IR) absorption band at 1145.9 cm(-1) is assigned to the C-O stretching mode of the side-on-bonding CO in the La2[eta2(mu2-C,O)] molecule. This CO-activated molecule undergoes an UV/Vis-photoinduced rearrangement to the CO-dissociated molecule, c-La2(mu-C)(mu-O). Density functional theory (DFT) calculations have been performed on these molecules, the results of which lend strong support to the experimental assignments of the IR spectra. LaCO is predicted to have a quartet ground state, corresponding to a linear geometry. Its formation involves La 6s-->4f promotion, which increases the strength of La-CO bonding by decreasing the sigma repulsion and, remarkably, by increasing the La 5d and 4f-->CO 2pi back-bonding. The observations schematically depict the whole process, starting with the interaction of CO with metal and ending with CO dissociation by the lanthanum dimer.     

Observation of anomalous C-O bond weakening on discandium and activation process to CO dissociation

Sc2[eta2(mu2-C,O)], the first homoleptic dinuclear metal carbonyl with an unprecedented bridging and side-on-bonded CO, generated from the reaction of laser-ablated Sc atoms with CO in a solid argon matrix, exhibits an unusually low C-O stretching frequency at 1193.4 cm-1, characteristic of an anomalously weakened C-O bond. This CO-activated molecule undergoes ultraviolet-visible photoinduced rearrangement to the CO-dissociated molecule, c-Sc2(mu-C)(mu-O). The infrared absorptions of the new molecules are accurately predicted by quantum chemical calculations, and the activation energy for the isomerization of Sc2[eta2(mu2-C, O)] to c-Sc2(mu-C)(mu-O) is calculated to be 15.10 kcal/mol. Our experimental and theoretical results schematically depict an activation process to CO dissociation.     

Reactions of silicon atoms and small clusters with CO: experimental and theoretical characterization of SinCO (n=1-5), Si2(CO)2, c-Si2(mu-O)(mu-CSi), and c-Si2(mu-O)(mu-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, Si(2)(CO)(2) and Si(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(2)CO, Si(3)CO, and Si(5)CO are bridge-bonded carbonyl compounds, whereas Si(4)CO is a terminal-bonded carbonyl molecule. The Si(2)(CO)(2) and Si(3)CO molecules photochemically rearranged to the more stable c-Si(2)(mu-O)(mu-CCO) and c-Si(2)(mu-O) (mu-CSi) isomers where Si(2) is inserted into the CO triple bond.     

Raman spectroscopy of uranyl rare earth carbonate kamotoite-(Y)

Raman spectroscopy at 298 and 77K has been used to study the mineral kamotoite-(Y), a uranyl rare earth carbonate mineral of formula Y(2)(UO(2))(4)(CO(3))(3)(OH)(8).10-11H(2)O. The mineral is characterised by two Raman bands at 1130.9 and 1124.6 cm(-1) assigned to the nu(1) symmetric stretching mode of the (CO(3))(2-) units, while those at 1170.4 and 862.3 cm(-1) (77K) to the deltaU-OH bending vibrations. The assignment of the two bands at 814.7 and 809.6 cm(-1) is difficult because of the potential overlap between the symmetric stretching modes of the (UO(2))(2+) units and the nu(2) bending modes of the (CO(3))(2-) units. Only a single band is observed in the 77K spectrum at 811.6 cm(-1). One possible assignment is that the band at 814.7 cm(-1) is attributable to the nu(1) symmetric stretching mode of the (UO(2))(2+) units and the second band at 809.6 cm(-1) is due to the nu(2) bending modes of the (CO(3))(2-) units. Bands observed at 584 and 547.3 cm(-1) are attributed to water librational modes. An intense band at 417.7 cm(-1) resolved into two components at 422.0 and 416.6 cm(-1) in the 77K spectrum is assigned to an Y(2)O(2) stretching vibration. Bands at 336.3, 286.4 and 231.6 cm(-1) are assigned to the nu(2) (UO(2))(2+) bending modes. U-O bond lengths in uranyl are calculated from the wavenumbers of the uranyl symmetric stretching vibrations. The presence of symmetrically distinct uranyl and carbonate units in the crystal structure of kamotoite-(Y) is assumed. Hydrogen-bonding network related to the presence of water molecules and hydroxyls is shortly discussed.     

Raman microscopy of synthetic goudeyite (YCu6(AsO4)2(OH)6 x 3H2O)

Raman microscopy has been used to study the molecular structure of a synthetic goudeyite (YCu(6)(AsO(4))(3)(OH)(6) x 3H(2)O). These types of minerals have a porous framework similar to that of zeolites with a structure based upon (A(3+))(1-x)(A(2+))(x)Cu(6)(OH)(6)(AsO(4))(3-x)(AsO(3)OH)(x). Two sets of AsO stretching vibrations were found and assigned to the vibrational modes of AsO(4) and HAsO(4) units. Two Raman bands are observed in the region 885-915 and 867-870 cm(-1) region and are assigned to the AsO stretching vibrations of (HAsO(4))(2-) and (H(2)AsO(4))(-) units. The position of the bands indicates a C(2v) symmetry of the (H(2)AsO(4))(-) anion. Two bands are found at around 800 and 835 cm(-1) and are assigned to the stretching vibrations of uncomplexed (AsO(4))(3-) units. Bands are observed at around 435, 403 and 395 cm(-1) and are assigned to the nu(2) bending modes of the HAsO(4) (434 and 400 cm(-1)) and the AsO(4) groups (324 cm(-1)).     

Raman spectroscopic study of the hydrotalcite desautelsite Mg6Mn2CO3(OH)16 x 4H2O

The structure of the hydrotalcite desautelsite Mg6Mn2CO3(OH)16.4H2O has been studied by a combination of Raman and infrared spectroscopy. Three intense Raman bands are observed at 1086, 1062 and 1055 cm(-1). A model based upon the observation of three CO3 stretching vibrations is presented. The CO3 anion may be (a) non-hydrogen bonded, (b) hydrogen bonded to the interlayer water and (c) hydrogen bonded to the brucite-like hydroxyl surface. Two intense bands at 3646 and 3608 cm(-1) are attributed to MgOH and MnOH stretching vibrations. Infrared bands at 3476, 3333, 3165 and 2991 cm(-1) are assigned to water stretching bands. Raman spectroscopy has proven a powerful tool for the study of hydrotalcite minerals.     

Structures of [(CO2)n(H2O)m]- (n=1-4, m=1,2) cluster anions. I. Infrared photodissociation spectroscopy

The infrared photodissociation spectra of [(CO(2))(n)(H(2)O)(m)](-) (n=1-4, m=1, 2) are measured in the 3000-3800 cm(-1) range. The [(CO(2))(n)(H(2)O)(1)](-) spectra are characterized by a sharp band around 3570 cm(-1) except for n=1; [(CO(2))(1)(H(2)O)(1)](-) does not photodissociate in the spectral range studied. The [(CO(2))(n)(H(2)O)(2)](-) (n=1, 2) species have similar spectral features with a broadband at approximately 3340 cm(-1). A drastic change in the spectral features is observed for [(CO(2))(3)(H(2)O)(2)](-), where sharp bands appear at 3224, 3321, 3364, 3438, and 3572 cm(-1). Ab initio calculations are performed at the MP2/6-311++G(**) level to provide structural information such as optimized structures, stabilization energies, and vibrational frequencies of the [(CO(2))(n)(H(2)O)(m)](-) species. Comparison between the experimental and theoretical results reveals rather size- and composition-specific hydration manner in [(CO(2))(n)(H(2)O)(m)](-): (1) the incorporated H(2)O is bonded to either CO(2) (-) or C(2)O(4) (-) through two equivalent OH...O hydrogen bonds to form a ring structure in [(CO(2))(n)(H(2)O)(1)](-); (2) two H(2)O molecules are independently bound to the O atoms of CO(2) (-) in [(CO(2))(n)(H(2)O)(2)](-) (n=1, 2); (3) a cyclic structure composed of CO(2) (-) and two H(2)O molecules is formed in [(CO(2))(3)(H(2)O)(2)](-).     

Synthesis, Structure, and Reactivities of [eta(2)-P(7)M(CO)(4)](3)(-), [eta(2)-HP(7)M(CO)(4)](2)(-), and [eta(2)-RP(7)M(CO)(4)](2)(-) Zintl Ion Complexes Where M = Mo, W

Ethylenediamine (en) solutions of [eta(4)-P(7)M(CO)(3)](3)(-) ions [M = W (1a), Mo (1b)] react under one atmosphere of CO to form microcrystalline yellow powders of [eta(2)-P(7)M(CO)(4)](3)(-) complexes [M = W (4a), Mo (4b)]. Compounds 4 are unstable, losing CO to re-form 1, but are highly nucleophilic and basic. They are protonated with methanol in en solvent giving [eta(2)-HP(7)M(CO)(4)](2)(-) ions (5) and are alkylated with R(4)N(+) salts in en solutions to give [eta(2)-RP(7)M(CO)(4)](2)(-) complexes (6) in good yields (R = alkyl). Compounds 5 and 6 can also be prepared by carbonylations of the [eta(4)-HP(7)M(CO)(3)](2)(-) (3) and [eta(4)-RP(7)M(CO)(3)](2)(-) (2) precursors, respectively. The carbonylations of 1-3 to form 4-6 require a change from eta(4)- to eta(2)-coordination of the P(7) cages in order to maintain 18-electron configurations at the metal centers. Comparative protonation/deprotonation studies show 4 to be more basic than 1. The compounds were characterized by IR and (1)H, (13)C, and (31)P NMR spectroscopic studies and microanalysis where appropriate. The [K(2,2,2-crypt)](+) salts of 5 were characterized by single crystal X-ray diffraction. For 5, the M-P bonds are very long (2.71(1) ?, average). The P(7)(3)(-) cages of 5 are not displaced by dppe. The P(7) cages in 4-6 have nortricyclane-like structures in contrast to the norbornadiene-type geometries observed for 1-3. (31)P NMR spectroscopic studies for 5-6 show C(1) symmetry in solution (seven inequivalent phosphorus nuclei), consistent with the structural studies for 5, and C(s)() symmetry for 4 (five phosphorus nuclei in a 2:2:1:1:1 ratio). Crystallographic data for [K(2,2,2-crypt)](2)[eta(2)-HP(7)W(CO)(4)].en: monoclinic, space group C2/c, a = 23.067(20) ?, b = 12.6931(13) ?, c = 21.433(2) ?, beta = 90.758(7) degrees, V = 6274.9(10) ?(3), Z = 4, R(F) = 0.0573, R(w)(F(2)) = 0.1409. For [K(2,2,2-crypt)](2)[eta(2)-HP(7)Mo(CO)(4)].en: monoclinic, space group C2/c, a = 22.848(2) ?, b = 12.528(2) ?, c = 21.460(2) ?, beta = 91.412(12) degrees, V = 6140.9(12) ?(3), Z = 4, R(F) = 0.0681, R(w)(F(2)) = 0.1399.     

Zerovalent titanium-sulfur complexes. Novel dithiocarbamato derivatives of Ti(CO)6: [Ti(CO)4(S2CNR2)]-

Oxidation of [Ti(CO)(6)](2-) by thiuram disulfides, (R(2)NCS(2))(2), affords the first isolable mononuclear six-coordinate titanium(0) carbonyls, [Ti(CO)(4)(S(2)CNR(2))](-), which have unusual trigonal prismatic geometries and chemical and spectral properties that are remarkably similar to those of the 18-electron and seven-coordinate anion [Ti(CO)(4)(eta(5)-C(5)H(5))](-).     

Structures of [(CO2)n(CH3OH)m](-) (n = 1-4, m = 1, 2) cluster anions

The infrared photodissociation spectra of [(CO 2) n (CH 3OH) m ] (-) ( n = 1-4, m = 1, 2) are measured in the 2700-3700 cm (-1) range. The observed spectra consist of an intense broad band characteristic of hydrogen-bonded OH stretching vibrations at approximately 3300 cm (-1) and congested vibrational bands around 2900 cm (-1). No photofragment signal is observed for [(CO 2) 1,2(CH 3OH) 1] (-) in the spectral range studied. Ab initio calculations are performed at the MP2/6-311++G** level to obtain structural information such as optimized structures, stabilization energies, and vibrational frequencies of [(CO 2) n (CH 3OH) m ] (-). Comparison between the experimental and the theoretical results reveals the structural properties of [(CO 2) n (CH 3OH) m ] (-): (1) the incorporated CH 3OH interacts directly with either CO 2 (-) or C 2O 4 (-) core by forming an O-HO linkage; (2) the introduction of CH 3OH promotes charge localization in the clusters via the hydrogen-bond formation, resulting in the predominance of CO 2 (-).(CH 3OH) m (CO 2) n-1 isomeric forms over C 2O 4 (-).(CH 3OH) m (CO 2) n-2 ; (3) the hydroxyl group of CH 3OH provides an additional solvation cite for neutral CO 2 molecules.     

Synthesis and structure of W(eta(2)-mp)(2)(CO)(3) (mp = monoanion of 2-mercaptopyridine) and its reactions with 2,2'-pyridine disulfide and/or NO to yield W(eta(2)-mp)(4), W(eta(2)-mp)(2)(NO)(2), and W(eta(2)-mp)(3)(NO)

Oxidative addition of the sulfur-sulfur bond of 2,2'-pyridine disulfide (C(5)H(4)NS-SC(5)H(4)N) with L(3)W(CO)(3) [L = pyridine, (1)/(3)CHPT; CHPT = cycloheptatriene] in methylene chloride solution yields the seven-coordinate W(II) thiolate complex W(eta(2)-mp)(2)(CO)(3) (mp = monoanion of 2-mercaptopyridine). This complex undergoes slow further oxidative addition with additional pyridine disulfide, yielding W(eta(2)- mp)(4). Reaction of W(eta(2)-mp)(2)(CO)(3) with NO results in quantitative formation of the six-coordinate W(0) complex W(eta(2)-mp)(2)(NO)(2). Reaction of W(eta(2)-mp)(2)(CO)(3) with NO in the presence of added pyridine disulfide yields the seven-coordinate W(II) nitrosyl complex W(eta(2)-mp)(3)(NO) as well as W(eta(2)-mp)(2)(NO)(2) and trace amounts of W(eta(2)-mp)(4). The complex W(eta(2)-mp)(3)(NO) is formed during the course of the reaction and not by reaction of W(eta(2)-mp)(4) or W(eta(2)-mp)(2)(NO)(2) with NO under these conditions. The crystal structures of W(eta(2)- mp)(2)(CO)(3), W(eta(2)-mp)(2)(NO)(2), and W(eta(2)-mp)(3)(NO) are reported.     

Quantum cascade laser spectroscopy and photoinduced chemistry of Al-(CO)n clusters in helium nanodroplets

Helium nanodroplet isolation and a tunable quantum cascade laser are used to probe the fundamental CO stretch bands of aluminum carbonyl complexes, Al-(CO)(n) (n ≤ 5). The droplets are doped with single aluminum atoms via the resistive heating of an aluminum wetted tantalum wire. The downstream sequential pick-up of CO molecules leads to the rapid formation and cooling of Al-(CO)(n) clusters within the droplets. Near 1900 cm(-1), rotational fine structure is resolved in bands that are assigned to the CO stretch of a linear (2)Π(1/2) Al-CO species and the asymmetric and symmetric CO stretch vibrations of a planar C(2v) Al-(CO)(2) complex in a (2)B(1) electronic state. Bands corresponding to clusters with n ≥ 3 lack resolved rotational fine structure; nevertheless, the small frequency shifts from the n = 2 bands indicate that these clusters consist of an Al-(CO)(2) core with additional CO molecules attached via van der Waals interactions. A second n = 2 band is observed near the CO stretch of Al-CO, indicating a local minimum on the n = 2 potential consisting of an "unreacted" (Al-CO)-CO cluster. The line width of this band is ～0.3 cm(-1), which is about 30 times broader than the transitions within the Al-CO band. The additional broadening is consistent with a homogeneous mechanism corresponding to a rapid vibrational excitation induced reaction within the (Al-CO)-CO cluster to form the covalently bonded Al-(CO)(2) complex. Ab initio CCSD(T) calculations and natural bond orbital (NBO) analyses are carried out to investigate the nature of the bonding in the n = 1, 2 complexes. The NBO calculations show that both π-donation (from the occupied aluminum p orbital into a π* antibonding CO orbital) and σ-donation (from CO into the empty aluminum p orbitals) play a significant role in the bonding, analogous to transition-metal carbonyl complexes. The large red shift observed for the CO stretch vibrations is consistent with this bonding 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.     

On the noble-gas-induced intersystem crossing for the CUO molecule: experimental and theoretical investigations of CUO(Ng)n (Ng = Ar, Kr, Xe; n = 1, 2, 3, 4) complexes in solid neon

Uranium atoms excited by laser ablation react with CO in excess neon to produce the novel CUO molecule, which forms distinct Ng complexes (Ng = Ar, Kr, Xe) when the heavier noble gases are added. The CUO(Ng) complexes are identified through CO isotopic and Ng substitution on the neon matrix infrared spectra and by comparison to DFT frequency calculations. The U-C and U-O stretching frequencies of CUO(Ng) complexes are slightly red-shifted from frequencies for the (1)Sigma(+) CUO ground state, which identifies singlet ground state CUO(Ng) complexes. In solid neon the CUO molecule is also a complex CUO(Ne)(n), and the CUO(Ne)(n-1)(Ng) complexes are likewise specified. The next singlet CUO(Ne)(x)(Ng)(2) complexes in excess neon follow in like manner. However, the higher CUO(Ne)(x)(Ng)(n) complex (n = 3, 4) stretching modes approach pure argon matrix CUO(Ar)(n) values and isotopic behavior, which are characterized as triplet ground state complexes by DFT frequency calculations. This work suggests that the singlet-triplet crossing occurs with 3 Ar, 3 Kr, or 4 Xe and a balance of Ne atoms coordinated to CUO in the neon matrix host.     

Effects of solvation and core switching on the photoelectron angular distributions from (CO2)n(-) and (CO2)(n)(-).H2O

Photoelectron images are recorded in the photodetachment of two series of cluster anions, (CO(2))(n)(-), n=4-9 and (CO(2))(n)(-).H(2)O, n=2-7, with linearly polarized 400 nm light. The energetics of the observed photodetachment bands compare well with previous studies, showing evidence for switching between two anionic core structures: The CO(2)(-) monomer and covalent (CO(2))(2)(-) dimer anions. The systematic study of photoelectron angular distributions (PADs) sheds light on the electronic structure of the different core anions and indicates that solvation by several CO(2) molecules and/or one water molecule has only moderate effect on the excess-electron orbitals. The observed PAD character is reconciled with the symmetry properties of the parent molecular orbitals. The most intriguing result concerns the PADs showing remarkable similarities between the monomer and dimer anion cluster-core types. This observation is explained by treating the highest-occupied molecular orbital of the covalent dimer anion as a linear combination of two spatially separated monomeric orbitals.     

Unique CO chemisorption properties of gold hexamer: Au6(CO)n- (n = 0-3)

Elucidating the chemisorption properties of CO on gold clusters is essential to understanding the catalytic mechanisms of gold nanoparticles. Gold hexamer Au(6) is a highly stable cluster, known to possess a D(3)(h) triangular ground state structure with an extremely large HOMO-LUMO gap. Here we report a photoelectron spectroscopy (PES) and quasi-relativistic density functional theory (DFT) study of Au(6)-CO complexes, Au(6)(CO)(n)(-) and Au(6)(CO)(n) (n = 0-3). CO chemisorption on Au(6) is observed to be highly unusual. While the electron donor capability of CO is known to decrease the electron binding energies of Au(m)(CO)(n)(-) complexes, CO chemisorption on Au(6) is observed to have very little effect on the electron binding energies of the first PES band of Au(6)(CO)(n)(-) (n = 1-3). Extensive DFT calculations show that the first three CO successively chemisorb to the three apex sites of the D(3)(h) Au(6). It is shown that the LUMO of the Au(6)-CO complexes is located in the inner triangle. Thus CO chemisorption on the apex sites (outer triangle) has little effect on this orbital, resulting in the roughly constant electron binding energies for the first PES band in Au(6)(CO)(n)(-) (n = 0-3). Detailed molecular orbital analyses lead to decisive information about chemisorption interactions between CO and a model Au cluster.