Thermodynamic and kinetic properties of scandium (I) ion reacting with SCO in gas phase

Abstract

Theoretical studies on the thermodynamic and kinetic properties of the reactions of scandium (I) ion with the sulfur-transfer reagent SCO via the C-O bond activation pathway have been carried out over the temperature range of 200-1200 K using the DFT/B3LYP method, general statistical thermodynamics, and Eyring transition state theory with Wigner correction. The relevant reactions include reaction 1 ¹Sc⁺ + SCO → ¹IM1 → ¹TS1 → ¹IM2 (Step 1) → ¹TS2 → ¹IM3 → ¹ScO⁺ + ¹CS (Step 2), and reaction 2 ³Sc⁺ + SCO → ³IM1 → CP → ¹IM2 → ¹TS2 → ¹IM3 → ¹ScO⁺ +¹CS in which the spin multiplicity changes from the triplet state to the singlet state in the crossing region. It was concluded that the order of the equilibrium constants (K) and the reaction rate constants (k) are consistent with that of their corresponding exoergic energies, ΔE, and reaction barriers, respectively. Step 2 of reaction 1 is both thermodynamically and kinetically favored over the whole temperature range. Moreover, both Reaction 1 and reaction 2 are exothermic and spontaneous processes in which their entropy increases, and the magnitudes of their thermodynamic values all decrease with increasing temperature.