Transition Metal Sulfide Cations Gas Dynamics Theory Research

Interest in transition-metal sulfides arises from their significance in industrial catalysis and biology. In industry, transition-metal oxides are used as versatile catalysts in many applications, however, for some processes their reactivity is too high and non-specific product formation occurs. In contrast, transition-metal sulfides are less reactive and susceptible to poisoning and can show higher selectivity. Transition metal sulfides also play a particular role in biochemistry in that heterometallic sulfur complexes form the active sites in several metalloenzymes. In fact, the transition-metal-ion chemistry has been an active area for both experimental and theoretical studies. The reactions of transition-metal sulfide cations (MS⁺, M=Sc, Ti and V) with small molecules (CO₂, COS and H₂S) in the gas phase have been studied by using density functional theory (DFT). According to our theoretical calculations, we propose the possible reaction channels as well as the reaction mechanisms, obtaining qualitative information regarding the dynamics and thermochemistry of the reactions, and the calculation results are compared with the experimental data available. The O/S change reaction of ground state TiS⁺ and VS⁺ (Sc⁺) with COX (X=O,S) proceed via a one-and two-step mechanism, respectively, and the ability order to activate C-O bond is: ScS⁺ > TiS⁺ > VS⁺. The S-transfer reaction is characteristic of multi-channel and multi-step, yielding two isomer products (MS₂⁺-1 and MS₂⁺-2) having a three-member-cyclic structure and water molecule (H₂O) structure, respectively. Although the O/S exchange reaction of MS⁺ (M=Ti, V) with COS has a lower barrier in our calculations, the product cross-sections in experiment show that the O/S exchange reaction is much less efficient than the S-transfer reaction. One conceivable explanation for this is that the two reactions are competitive and one of the dominant factors affecting the reaction channels is the probability of the formation of the different collision complexes. The experimental no-barrier energy pathway involved in the S-transfer of TiS⁺ with COS was not found theoretically, we suggest the reaction involves the excited states of the collision complexes along the energy surface with...