Showing papers by "Lester Andrews published in 2001"

Infrared Spectrum of the H3N−HCl Complex in Solid Ne, Ne/Ar, Ar, and Kr. Matrix Effects on a Strong Hydrogen-Bonded Complex

Abstract: Ammonia and hydrogen chloride vapors from thermal decomposition of NH4Cl co-deposited with excess neon at 4−5 K formed the H3N−HCl complex. Strong, broad 2084 cm-1 and strong, sharp 1060.2 cm-1 absorptions are assigned to the H−Cl stretching and symmetric NH3 bending modes and weaker 2017.4 and 708.9 cm-1 bands to the overtone of the NH3 mode and the H−Cl librational fundamental of the 1:1 complex. Complementary experiments were done with neon/argon mixtures, argon, and krypton to investigate the 1:1 complex in a range of matrix environments. Vibrational assignments are supported by 15NH4Cl, ND4Cl, and 15ND4Cl isotopic substitution. The neon matrix spectrum suggests a strong hydrogen bond, slightly stronger than in the gas-phase complex, but not as strong as found in the argon and krypton matrix hosts owing to increased solvation by the more polarizable matrix atoms.

Precious Metal−Molecular Oxygen Complexes: Neon Matrix Infrared Spectra and Density Functional Calculations for M(O2), M(O2)2 (M = Pd, Pt, Ag, Au)

Abstract: Laser-ablated palladium, platinum, silver, and gold atoms react with molecular oxygen in excess neon during condensation at 4 K. Reaction products, M-(η2-OO), M-(η2-OO)2 (M = Pd, Pt), PtO, PtO2, Au...

Infrared spectra and density functional calculations of platinum hydrides

Abstract: Laser-ablated and thermally evaporated Pt atoms react with H2 to form PtH2, which is characterized by infrared spectra of PtH2, PtHD, and PtD2 in solid argon and neon, and density functional theory calculations. The insertion reaction of Pt into dihydrogen is spontaneous on annealing solid neon to 6–8 K and solid argon to 20–30 K. This observation requires spin–orbit coupling of the ground 3D3 and excited 1S0 states of Pt in the curve-crossing region to give the stable PtH2 (1A1) molecule. Laser-ablated Pt atoms with excess energy also react with H2 to produce PtH. Further reactions of PtH with H2 or PtH2 with H atoms give evidence for a new asymmetric H2PtH molecule, which is also characterized by isotopic substitution and frequency calculations.

A Combined Theoretical and Experimental Study of the Reaction Products of Laser-Ablated Thorium Atoms with CO: First Identification of the CThO, CThO-, OThCCO, OTh(η3-CCO), and Th(CO)n (n = 1−6) Molecules

Abstract: Laser-ablated thorium atoms have been reacted with CO molecules during condensation in excess neon. Absorptions at 617.7 and 812.2 cm-1 are assigned to Th−C and Th−O stretching vibrations of the CThO molecule. Absorptions at 2048.6, 1353.6, and 822.5 cm-1 are assigned to the OThCCO molecule, which is formed by CO addition to CThO and photochemical rearrangement of Th(CO)2. The OThCCO molecule undergoes further photoinduced rearrangement to OTh(η3-CCO), which is characterized by C−C, C−O, and Th−O stretching vibrations at 1810.8, 1139.2, and 831.6 cm-1. The Th(CO)n (n = 1−6) complexes are formed on deposition or on annealing. Evidence is also presented for the CThO- and Th(CO)2- anions, which are formed by electron capture of neutral molecules. Relativistic density functional theory (DFT) calculations of the geometry structures, vibrational frequencies, and infrared intensities strongly support the experimental assignments. It is found that CThO is an unprecedented actinide-containing carbene molecule with...

A Spectroscopic and Theoretical Investigation of Charge Transfer Complexes between Silver and Nitric Oxide: Infrared Spectra and Density Functional Calculations of AgNO+,0,- and Agx(NO)y Clusters (x, y = 1, 2) in Solid Argon and Neon

Abstract: Laser-ablated silver atoms are reacted with nitric oxide, and products are isolated in solid argon and neon. The pseudo-hyponitrite complex Ag(NO)2Ag is the dominant product, with AgNOAg and AgONNO present in smaller yields. These complexes are shown using density functional theory to include significant charge transfer from silver but are not as ionic as the analogous alkali metal complexes of nitric oxide. The neutral and ionic mononitrosyls AgNO+, AgNO, and AgNO- are also observed, and qualitative trends in bond lengths and frequencies in this series are discussed.

Infrared Spectra of the H3N−HBr Complex in Solid Ne, Ne/Ar, Ar, Kr, and N2. Strong Matrix Effects on a Hydrogen-Bonded Complex

Abstract: Ammonia and hydrogen bromide vapors from the thermal decomposition of NH4Br were co-deposited with excess neon at 4−5 K to form the H3N−HBr complex. New 1208.8 and 1079.9 cm-1 infrared absorptions ...

Reactions of Laser-Ablated Platinum with Nitrogen: Matrix Infrared Spectra of Platinum Nitride, Complexes, and Anions

Abstract: Several new platinum nitride species are produced by the reaction of laser-ablated platinum with pure nitrogen, and their frequencies calculated by density functional theory in addition to the complexes observed in earlier thermal atom studies. Platinum forms PtN and a number of molecules derived from PtN including NNPtN, PtPtN, Pt2N, and PtNNPt, and PtNNN from reaction with N3 radical in pure nitrogen. The PtNN complex is characterized by the Pt−N stretching mode at 499.6 cm-1 and its combination band at 2669.6 cm-1 with the strong N−N fundamental at 2168.5 cm-1 in solid argon. Absorptions are observed for PtxNN, PtNN-, Pt(NN)2-, and Pt(NN)2 in solid argon and neon.

Infrared Spectrum of the H3N−HI Complex in Solid Ne, Ar, Ne/Ar, Kr, and N2. Comparisons of Matrix Effects on Hydrogen-Bonded Complexes

Abstract: Ammonia and hydrogen iodide vapors from the thermal decomposition of NH4I were codeposited with excess neon at 5 K to form the H3N−HI complex. New 630, 1192, and 3435 cm-1 infrared absorptions are assigned to the antisymmetric N−H−I stretching, symmetric NH3 bending, and antisymmetric NH3 stretching modes of the 1:1 complex. Vibrational assignments are supported by 15NH3, ND4I, and mixed H/D isotopic substitution. Complementary experiments were done with argon, neon/argon mixtures, krypton, and nitrogen to investigate the 1:1 complex in a range of matrix environments and to compare with previous work using the reagent gases. The above modes are shifted to 592, 1259, and 3400 cm-1 in solid argon owing to an increased interaction with the more polarizable argon matrix atoms. Neon and 2% argon mixtures gave intermediate absorptions, which evolved to the pure argon values on annealing to allow diffusion. The strong nitrogen matrix infrared absorption at 1955 cm-1 shifts approximately 4 cm-1 with 15N-substitut...

Infrared Spectrum of the Hyponitrite Dianion, N2O22-, Isolated and Insulated from Stabilizing Metal Cations in Solid Argon

Abstract: Co-deposition of laser-ablated metals with NO in excess neon at 4 K produced new 1060.8 ± 0.4 and 1052.6 ± 0.2 cm-1 absorptions, which almost disappear on annealing to 9 K and reappear in part on ultraviolet irradiation. These absorptions shift with 15N16O and 15N18O substitution as fundamental N−O vibrations and exhibit 1:2:1 triplet bands with 14N16O + 15N16O and 15N16O + 15N18O mixtures, which demonstrates the involvement of two equivalent NO oscillators. The above absorptions are assigned to N2O22- isolated and insulated from metal stabilizing cations in two solid neon matrix configurations. The blue shift from the 1028.5 cm-1 solid argon band position for this species is larger than found for most small molecules and anions, which is consistent with a dianion. The photochemistry in laser-ablated gold experiments suggests the involvement of N2O2- in electron-transfer processes to form N2O22-.

Infrared spectra of cis- and trans-peroxynitrite anion, OONO-, in solid argon.

Abstract: The peroxynitrite anion, of vast importance in biochemistry, is formed in vivo from the reaction of NO and O2-. Laser ablation of 10 different metal targets with concurrent 7 K codeposition of NO/Ar and O2/Ar mixtures gives new metal-independent infrared bands at 1458.3 and 806.1 cm-1, and at 1433.3 and 983.2 cm-1, in addition to known O4- and (NO)2- absorptions. The new bands are not observed with CCl4 added to capture electrons or in O2 and NO experiments without laser ablation to produce electrons, which identifies new product anions. Based on 15NO and 18O2 isotopic shifts, splitting patterns in mixed isotopic experiments, and comparison with DFT isotopic frequency calculations, the former absorptions are assigned to cis-OONO-, and the latter pair to trans-OONO-, which are isolated from metal cations trapped elsewhere in the matrix. The cis- and trans-peroxynitrite anion isomers are probably formed via the ion−molecule reaction between O2- and NO: the O2- anion, made by the capture of ablated electron...

Cobalt Carbonyl Nitrosyl Complexes: Matrix Infrared Spectra and Density Functional Calculations

Abstract: Reactions of laser-ablated cobalt atoms with CO and NO mixtures in excess argon during condensation at 7 K generate a series of unsaturated cobalt carbonyl nitrosyls including Co(CO)(NO), Co(CO)[NO], OCo(NCO), CO(CO)2(NO), Co(CO)2[NO], and Co(CO)(NO)2, and the saturated Co(CO)3(NO) molecule. The observed infrared bands of reaction products are identified by isotopic substitution, isotopic ratios, and isotopic distributions (13CO, 15NO, 15N18O, and mixtures). DFT/BPW91 vibrational fundamental calculations reproduced the observed frequencies and isotopic shifts very well. The isocyanate OCo(NCO) is formed from the side-bonded Co[NO] reaction with CO, which is relevant to catalytic reduction processes.

Infrared Spectra and Density Functional Calculations on Binary Unsaturated Transition Metal Carbonyl Cations, Neutrals and Anions

Abstract: The status of theory and experiment for the determination of the CO vibrational frequencies in binary unsaturated transition metal carbonyl cations, neutrals and anions is reviewed.