A Combined Experimental and Theoretical Study of the Ti2 + N2O Reaction

The reactivity of diatomic titanium with nitrous oxide has been studied in solid neon. Two molecules with the same Ti2–N2O stoichiometry are identified from concentration, temperature, and irradiation effects. The more stable one is characterized by five fundamental vibrational transitions located below 1000 cm–1, the high frequency one at 946 cm–1 corresponding to a pure TiO stretching mode. Its structure, a rhombus OTiNTiN with the extra O atom fixed on one Ti, is confirmed by quantum chemical calculations, at the CCSD­(T) level, which predict a Cs structure in the singlet state with a Ti–O bond length close to 1.66 Å, two nonequivalent Ti–N distances close to 1.94 and 1.75 Å, and a OTiTi angle of 119.2°. The second Ti2–N2O molecule, only observed after annealing, is easily converted into the first one upon irradiation above 12 000 cm–1 and its kinetics of photoconversion allows vibrational transitions to be identified. The strongest one located at 2123.4 cm–1 characterizes an N–N stretching mode. Corresponding ab initio calculations complete this picture with details on the electronic structure and allow us to identify a most adequate density functional to describe the spectroscopic properties of the studied species in a simpler broken-symmetry open-shell DFT context. The theoretical results predict the existence of a metastable product OTi2N2 and correctly account for the observed spectra of the various isotopic varieties.