Ground-state, involving bond breaking

Levich et al have extended their low temperature case to include reactions involving bond breaking in which the activation energy arises from internal vibrations as well as solvent fluctuation. In this case a reactant species in an excited vibrational state is supposed to undergo an electron-transfer reaction to form a product species in the ground vibrational state. 

Ground-State PESs Involving Bond Breaking... 

Several attempts have been made to analyse the captodative effect through rotational barriers in free radicals. This approach seems to be well suited as it is concerned directly with the radical, i.e. peculiarities associated with bond-breaking processes do not apply. However, in these cases also one has to be aware that any influence of a substituent on the barrier height for rotation is the result of its action in the ground state of the molecule and in the transition structure for rotation. Stabilization as well as destabilization of the two states could be involved. Each case has to be looked at individually and it is clear that this will provide a trend analysis rather than an absolute determination of the magnitude of substituent effects. In this respect the analysis of rotational barriers bears similar drawbacks to all of the other methods. 

An interesting alternative to the externally corrected MMCC methods, discussed in Section 3.1.1, is offered by the CR-EOMCCSD(T) approach [49, 51,52,59]. The CR-EOMCCSD(T) method can be viewed as an extension of the ground-state CR-CCSD(T) approach of Refs. [61,62], which overcomes the failures of the standard CCSD(T) approximations when diradicals [76,104,105] and potential energy surfaces involving single bond breaking and single bond insertion [49,50,52,60-62,65,67,69,70,72,73] are examined, to excited states. 

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