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Photochemistry of a polyaromatic hydrocarbon, pyrene C(16)H(10), with water has been investigated at cryogenic temperatures. Photoprocessing of this species, performed at λ > 235 nm, in argon matrices, adsorbed onto amorphous water surfaces, and trapped in solid water, led to the formation of ketonic isomers, C(16)H(10)O, and possibly quinones. These species have been identified for the first time by infrared spectroscopy with the support of isotopic substitution experiments and DFT calculations. These oxidized pyrene-like species, of atmospherical and astrochemical interest, most likely arise from a tautomeric rearrangement of their analogous hydroxylated molecules, these latter being formed by reaction of water with pyrene cations.

The mechanism of the Cu + CS2 reaction has been investigated using density functional and coupled cluster calculations. The lowest energy route on the potential energy surface corresponds to the insertion product SCuCS via the formation of intermediate coordination complexes: η1S and η2CS, which all lie below the energy of the reactants. Another path corresponding to the formation of a cyclic C2v compound η2SS leads to the same insertion product, but it involves a higher energy barrier (34.7 kcal/mol vs 26.9 kcal/mol with respect to the reactants at the CCSD(T) level). The dissociation of the insertion product SCuCS into the CuS and CS fragments is found to be endothermic by 43 kcal/mol (CCSD(T) level). Our results are related to experimental data obtained in low-temperature rare gas matrixes and in the gas phase.

The mechanism of the title reaction has been investigated using density functional and coupled cluster calculations. The results indicate that the lowest energy path corresponds to the η2CO coordination of CO2 followed by the insertion of Sc into a C−O bond. We show that two doublet state (2A‘ and 2A‘ ‘) potential energy surfaces have to be considered to describe the reaction mechanism. On the 2A‘ surface, the reaction gives a weakly bound OScCO species that can easily dissociate into ground state ScO(2Σ+) + CO products, whereas the 2A‘ ‘ state insertion complex is thermodynamically stable because it correlates to an excited state of ScO. The applicability of the B3LYP and CCSD(T) methods for the relative stability of intermediates is examined, and our results are related to available experimental findings.

The reactions of the ground-state V(s2d3) atom with CO2, CS2, and OCS molecules have been studied at the B3LYP level of density functional theory in order to compare the insertion process for these three isovalent molecules. The relative stabilities of the adduct and insertion forms are calculated. The reaction barrier between these two forms are estimated for each system from the 4A‘ ‘ and 4A‘ potential energy curves defined in terms of the C−X (X=O,S) intrinsic reaction coordinate. The barrier to metal insertion from the side-on structure is rather low (ca 4 kcal/mol) for CO2 and CS2, however, whereas V(CO2) is well above the OVCO insertion product, the V(CS2) complex is only 4.2 less stable than SVCS. Consequently, coordination of CS2 to metal centers is stronger than that of CO2. Our calculations indicate no energy barrier for the insertion of V in the CS bond of OCS, whereas the insertion in the CO bond is less favored than in CO2. We show that each insertion reaction proceeds on a single potential e...

The interaction of the CO2 molecule with nickel atoms was studied by using matrix isolation spectroscopy and density functional theory. In argon dilute matrices, no reaction occurs, even after annealing the deposit. In neat CO2 matrices, it is shown that carbon dioxide forms a 1:1 complex with nickel which is characterized by its UV−visible and FTIR absorptions, including isotopically labeled species. Theory predicts the side-on coordination mode to be the most stable. The binding energy of the side-on Ni(CO2) complex is estimated to be 18 kcal/mol. The calculated OCO angle is 145°, which is quite a large value compared to those encountered in other known CO2 complexes. In dinitrogen matrices, the yield of CO2 complexation is considerably enhanced relative to that in argon dilute and neat CO2 matrices, which is attributed to the formation of unsaturated Ni(N2)n complexes prior to CO2 coordination. The CO2 binding energies calculated for the Ni(CO2)(N2)n (n = 1, 2) complexes (respectively 32 and 4 kcal/mol...

Complete assignments of FTIR and Raman spectra are proposed for Ni(CO 2 )(PCy 3 ) 2 and its 13 CO 2 - and C 18 O 2 -labeled derivatives. Normal coordinate analysis gives a relevant force-field for side-on complexation at the solid state and shows that the complex can also exist with an «end-on» coordination mode. FTIR study in various solvents at different temperatures allows us to conclude that similar coordination modes are found in solution. Results are compared to that obtained by 13 C and 31 P NMR (including CPMAS studies) concerning the fluxionality of Ni-(CO 2 )(PCy 3 ) 2

The cocondensation products of nickel atoms with pure ethylene or ethylene-argon futures trapped at 12 K were reinvestigated by IR and UV-visible spectroscopies. The first Raman spectra were obtained. Isotopic H/D experiments and comparison of IR and Raman spectra indicate unambiguously that three complexes are formed, Ni(C 2 H 4 ) 3 , Ni(C 2 H 4 ) 2 , and Ni(C 2 H 4 ), with a normal order of increasing perturbation of ethylene vibration modes from the 1:3 to the 1:1 stoichiometries