Infrared spectra of cyclic-O6+ and trans-O6+ in solid neon and argon

Noble Gas-Tungsten Peroxide Complexes in Noble Gas Matrixes: Infrared Spectroscopy and Density Functional Theoretical Study

The matrix isolation infrared spectroscopic and quantum chemical calculation results indicate that tungsten oxo and mono-superoxide, WO₃ and (η²-O₂)WO₂, coordinate noble gas atoms in forming noble gas-tungsten oxide complexes. The results showed that both WO₃ and (η²-O₂)WO₂ oxides can coordinate one Ar or Xe atom in solid noble gas matrixes; otherwise, tungsten mono- and dioxides cannot. Hence, the WO₃ and (η²-O₂)WO₂ molecules trapped previously in solid argon noble gas matrixes should be regarded as the WO₃(Ar) oxide and (η²-O₂)WO₂(Ar) peroxide complexes. When annealing, the lighter Ar atom can be replaced by a heavier xenon atom to form WO₃(Xe) and (η²-O₂)WO₂(Xe) complexes. What's more, upon UV photolysis, both Ar and Xe atoms can be replaced by oxygen to form a tungsten disuperoxide (η²-O₂)₂WO₂ complex. The binding energies were predicted to be 25.7, 16.6, 9.4, 14.7, and 8.1 kcal/mol for the (η²-O₂)₂WO₂, WO₃(Xe), WO₃(Ar), (η²-O₂)WO₂(Xe), and (η²-O₂)WO₂(Ar) complexes at the CCSD(T)//M06-2X-D3//def2-TZVP/DGDZVP/SDD level. The substitution law, O₂ > Xe > Ar, can be interpreted according to the chemical reaction energies calculated to be -6.6 and +11.0 kcal/mol, respectively, for the equation formulas Xe + (η²-O₂)WO₂(Ar) = (η²-O₂)WO₂(Xe) + Ar and O₂ + (η²-O₂)WO₂(Xe) = (η²-O₂)₂WO₂ + Xe at the same level.

The Oxygen-Rich Beryllium Oxides BeO4 and BeO6

Two novel isomers of BeO4 with the structures OBeOOO and OBe(O3 ) in the electronic triplet state have been prepared as well as the known disuperoxide complex Be(O2 )2 in solid noble-gas matrices. We also report the synthesis of the oxygen-rich bis(ozonide) complex Be(O3 )2 in the triplet state which has a D2d equilibrium geometry. The molecular structures were identified by infrared absorption spectroscopy with isotopic substitutions as well as quantum chemical calculations.

Pentavalent Lanthanide Compounds: Formation and Characterization of Praseodymium(V) Oxides

The chemistry of lanthanides (Ln=La-Lu) is dominated by the low-valent +3 or +2 oxidation state because of the chemical inertness of the valence 4f electrons. The highest known oxidation state of the whole lanthanide series is +4 for Ce, Pr, Nd, Tb, and Dy. We report the formation of the lanthanide oxide species PrO4 and PrO2 (+) complexes in the gas phase and in a solid noble-gas matrix. Combined infrared spectroscopic and advanced quantum chemistry studies show that these species have the unprecedented Pr(V) oxidation state, thus demonstrating that the pentavalent state is viable for lanthanide elements in a suitable coordination environment.

Formation and characterization of magnesium bisozonide and carbonyl complexes in solid argon

The reactions of magnesium atoms with dioxygen and dioxygen/carbon monoxide mixture have been investigated by matrix isolation infrared absorption spectroscopy. Magnesium atoms react with dioxygen in solid argon to form the inserted MgO(2) molecules under UV excitation, which were previously characterized. Annealing allows the dioxygen molecules to diffuse and to react with MgO(2) and form the magnesium bisozonide complex, Mg(O(3))(2), which is proposed to be coordinated by two argon atoms in solid argon matrix. The Mg(O(3))(2)(Ar)(2) complex is characterized to have two equivalent side-on bonded ozonide ligands with a D(2h) symmetry. The coordinated argon atoms can be replaced by carbon monoxide to give the magnesium bisozonide dicarbonyl complex, Mg(O(3))(2)(CO)(2), a neutral magnesium carbonyl complex with CO binding to the Mg(2+) center.

Infrared Spectroscopic Observation of the Group 13 Metal Hydroxides, M(OH)1,2,3 (M =Al, Ga, In, and Tl) and HAl(OH)2

Reactions of laser-ablated Al, Ga, In, and Tl atoms with H2O2 and with H2 + O2 mixtures diluted in argon give new absorptions in the O-H and M-O stretching and O-H bending regions, which are assigned to the metal mono-, di-, and trihydroxide molecules. Isotopic substitutions (D2O2, 18O2, 16,18O2, HD, and D2) confirm the assignments, and DFT calculations reproduce the experimental results. Infrared spectra for the Al(OH)(OD) molecule verify the calculated C2v structure. The trihydroxide molecules increase on annealing from the spontaneous reaction with a second H2O2 molecule. Aluminum atom reactions with the H2 + O2 mixtures favor the HAl(OH)2 product, suggesting that AlH3 generated by UV irradiation combines with O2 to form HAl(OH)2.

Infrared Spectra of M(OH)1,2,3 (M = Mn, Fe, Co, Ni) Molecules in Solid Argon and the Character of First Row Transition Metal Hydroxide Bonding

Reactions of laser-ablated Mn, Fe, Co, and Ni atoms with H(2)O(2) and with H(2) + O(2) mixtures in excess argon give new absorptions in the O-H and M-O stretching regions, which are assigned to metal dihydroxide and trihydroxide molecules, M(OH)(2) and M(OH)(3). Isotopic substitutions (D(2)O(2), (18)O(2), (16,18)O(2), D(2)) confirmed the assignments and DFT calculations reproduced the experimental results. The O-H stretching frequencies decreased in the dihydroxides from Sc to Zn. Mulliken and natural charge distributions indicate significant electron transfer from metal d orbitals to OH ligands that decreases from Sc to Zn, suggesting that the early transition metal hydroxides are more ionic and that the later transition metal hydroxides are more covalent.

Contrasting Products in the Reactions of Cr, Mo, and W Atoms with H2O2: Argon Matrix Infrared Spectra and Theoretical Calculations

Products in the reactions of H2O2 and H2, O2 mixtures have been observed by matrix infrared absorptions and identified through comparisons with vibrational frequencies calculated for these molecules. The chromium reactions are dominated by lower oxidation state products, whereas molybdenum and tungsten chemistry favors higher oxidation state products. For example chromium dihydroxide, Cr(OH)2, molybdenum hydride oxide, H2MoO2, and tungsten hydride oxide, H2WO2, were observed in laser-ablated metal atom reactions with H2O2, and calculations show that these are the most stable molecules for this stoichiometry. Chromium monohydroxide, CrOH, was identified through O-H and Cr-O stretching modes, while HWO was observed by W-H and W=O stretching modes. The metal oxyhydroxides, HMO(OH), were observed for all metals. However, reactions with two H2O2 molecules give OCr(OH)2, MoO2(OH)2, and WO2(OH)2. The relative stabilities of different structures for Cr, Mo, and W are due to different participations of occupied d orbitals. The reactivity of the cold metal atoms with H2O2 on annealing the solid argon matrix increases on going down the group.

Infrared Spectra of M(OH)1,2,4 (M = Pb, Sn) in Solid Argon

Infrared absorptions for the matrix-isolated lead and tin hydroxides M(OH), M(OH)2 and M(OH)4 (M = Pb, Sn) were observed in laser-ablated metal atom reactions with H2O2 during condensation in excess argon. The major M(OH)2 product was also observed with H2 and O2 mixtures, which allowed the substitution of 18O2. The band assignments were confirmed by appropriate D2O2, D2, 16O18O, and 18O2 isotopic shifts. MP2 and B3LYP calculations were performed to obtain molecular structures and to reproduce the infrared spectra. The minimum energy structure found for M(OH)2 has C(s) symmetry and a weak intramolecular hydrogen bond. In experiments with Sn, HD, and O2, the internal D bond is favored over the H bond for Sn(OH)(OD). The Pb(OH)4 and Sn(OH)4 molecules are calculated to have S4 symmetry and substantial covalent character.

Zinc and Cadmium Dihydroxide Molecules: Matrix Infrared Spectra and Theoretical Calculations

Laser-ablated zinc and cadmium atoms were mixed uniformly with H2 and O2 in excess argon or neon and with O2 in pure hydrogen or deuterium during deposition at 8 or 4 K. UV irradiation excites metal atoms to insert into O2 producing OMO molecules (M = Zn, Cd), which react further with H2 to give the metal hydroxides M(OH)2 and HMOH. The M(OH)2 molecules were identified through O-H and M-O stretching modes with appropriate HD, D2, (16,18)O2, and (18)O2 isotopic shifts. The HMOH molecules were characterized by O-H, M-H, and M-O stretching modes and an M-O-H bending mode, which were particularly strong in pure H2/D2. Analogous Zn and Cd atom reactions with H2O2 in excess argon produced the same M(OH)2 absorptions. Density functional theory and MP2 calculations reproduce the IR spectra of these molecules. The bonding of Group 12 metal dihydroxides and comparison to Group 2 dihydroxides are discussed. Although the Group 12 dihydroxide O-H stretching frequencies are lower, calculated charges show that the Group 2 dihydroxide molecules are more ionic.

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

The peroxynitrite anion, of vast importance in biochemistry, is formed in vivo from the reaction of NO and O(-2). Laser ablation of 10 different metal targets with concurrent 7 K codeposition of NO/Ar and O(2)/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 O(-4) and (NO)(-2) absorptions. The new bands are not observed with CCl(4) added to capture electrons or in O(2) and NO experiments without laser ablation to produce electrons, which identifies new product anions. Based on (15)NO and (18)O(2) 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 O(-2)and NO: the O(-2) anion, made by the capture of ablated electrons, is attested by the observation of O(-4). cis- and trans-OONO- are reversibly photoisomerized by visible and near-UV radiation. Collisional stabilization of the OONO- ion-molecule dimer complex during formation of the solid argon matrix appears to be crucial.