Spin-flip reactions of Zr + C2H6 researched by relativistic density functional theory

Density functional theory (DFT) with relativistic corrections of zero-order regular approximation (ZORA) has been applied to explore the reaction mechanisms of ethane dehydrogenation by Zr atom with triplet and singlet spin-states. Among the complicated minimum energy reaction path, the available states involves three transition states (TS), and four stationary states (1) to (4) and one intersystem crossing with spin-flip (marked by ⇒): 3 Zr + C 2 H 6 → 3 Zr-CH 3 -CH 3 ( 3 1) → 3 TS 1/2 → 3 ZrH-CH 2 -CH 3 ( 3 2) → 3 TS 2/3 ⟹ 1 ZrH2-CH2 = CH2 ( 1 3) → 1 TS 3/4 → 1 ZrH 3 -CH = CH 2 ( 1 4). The minimum energy crossing point is determined with the help of the DFT fractional-occupation-number (FON) approach. The spin inversion leads the reaction pathway transferring from the triplet potential energy surface (PES) to the singlet’s accompanying with the activation of the second C-H bond. The overall reaction is calculated to be exothermic by about 231 kJ mol−1. Frequency and NBO analysis are also applied to confirm with the experimental observed data.