General Discussion of Spin-Uncoupling in Chemical Reactions

2 General discussion of spin-uncoupling in chemical reactions 

Michl et al. [29] have calculated the H4 system and shown that the doubly 

In the text above it is argued that the thermal chemical reactivity often is coded by the triplet excited states of the diamagnetic reagents. The crucial role of electron spin in the control of the reaction channels in the region of the activation complex is easily inferred from the general principles of chemical bonding. The radical-like (or diradical-like) moieties appear in the transition state wave functions [36]. 

Very often the catalyst (unsaturated TM complex) has a low-spin ground state with a high-spin state being very close in energy [23, 36, 37]. This situation is very useful for catalysis it is not necessary to produce a spin-flip and a low barrier is achieved. The metal surface is an ideal catalyst in this sense, since any spin multiplicity can be realized at the local state of the surface, perturbed in the course of the chemisorption process. In other words, a metal cluster which simulates the surface in the course of the chemisorption process has a number of quasi-degenerate state with different spin-multiplicities. 

Theoretical analysis of spin-uncoupling is a useful way to understand catalytic reactions, and to give an illustration of this we discuss how the TM species can 

---