Abstract
Many chemical reactions of transition metal compounds involve a change in spin state via spin inversion, which is induced by relativistic spin-orbit coupling. In this work, we theoretically study the efficiency of a typical spin-inversion reaction, 3Fe(CO)4 + H2 → 1FeH2(CO)4. Structural and vibrational information on the spin-inversion point, obtained through the spin-coupled Hamiltonian approach, is used to construct three degree-of-freedom potential energy surfaces and to obtain singlet-triplet spin-orbit couplings. Using the developed spin-diabatic potential energy surfaces in reduced dimensions, we perform quantum nonadiabatic transition state wave packet calculations to obtain the cumulative reaction probability. The calculated cumulative reaction probability is found to be significantly larger than that estimated from the one-dimensional surface-hopping probability. This indicates the importance of both multidimensional and nuclear quantum effects in spin inversion for polyatomic chemical reaction systems.
Highlights
Many chemical reactions can proceed through different spin multiplicity states during the course of a reaction, including electronically nonadiabatic transitions induced by spin-orbit coupling [1,2,3,4,5,6,7,8,9,10,11,12,13]
Since spin-orbit coupling is generally large in molecular systems that contain heavy elements, many catalytic reactions involving transition metal atoms occur on multiple potential energy surfaces with different spin multiplicities
The singlet and triplet potential energy surfaces for the H2 + Fe(CO)4 reaction were calculated by density functional theory (DFT) using the Gaussian 09 program [31]
Summary
Many chemical reactions can proceed through different spin multiplicity states during the course of a reaction, including electronically nonadiabatic transitions induced by spin-orbit coupling [1,2,3,4,5,6,7,8,9,10,11,12,13]. Since spin-orbit coupling is generally large in molecular systems that contain heavy elements, many catalytic reactions involving transition metal atoms occur on multiple potential energy surfaces with different spin multiplicities. Such a chemical reaction scheme has been historically called “two-state reactivity” or “multistate reactivity” [8,9,10,11,12,13]. The efficiency of the nonadiabatic spin-inversion transitions should be discussed quantitatively
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